SEI Passive House2008.qxd:Layout 1 - MosArt · 2017. 5. 27. · 1.1 Passive House and the...

Passive homesGUIDELINES FOR THE DESIGN AND CONSTRUCTION OF PASSIVE HOUSE DWELLINGS IN IRELAND

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Sustainable Energy Ireland (SEI)

Sustainable Energy Ireland was established as Ireland’s national energy agency under the Sustainable Energy Act 2002. SEI’smission is to promote and assist the development of sustainable energy. This encompasses environmentally and economi-cally sustainable production, supply and use of energy, in support of Government policy, across all sectors of the economyincluding public bodies, the business sector, local communities and individual consumers. Its remit relates mainly to improv-ing energy efficiency, advancing the development and competitive deployment of renewable sources of energy andcombined heat and power, and reducing the environmental impact of energy production and use, particularly in respect ofgreenhouse gas emissions.

SEI is charged with implementing significant aspects of government policy on sustainable energy and the climate change

abatement, including:

• Assisting deployment of superior energy technologies in each sector as required;

• Raising awareness and providing information, advice and publicity on best practice;

• Stimulating research, development and demonstration;

• Stimulating preparation of necessary standards and codes;

• Publishing statistics and projections on sustainable energy and achievement of targets.

It is funded by the Government through the National Development Plan with programmes part financed by the European

Union.

© Sustainable Energy Ireland, 2008. All rights reserved.

No part of this material may be reproduced, in whole or in part, in any form or by any means, without permission. The material contained in this publica-tion is presented in good faith, but its application must be considered in the light of individual projects. Sustainable Energy Ireland can not be held

responsible for any effect, loss or expense resulting from the use of material presented in this publication.

Prepared by MosArt Architecture, UCD Energy Research Group and SEI Renewable Energy Information Office


Table of Contents

Preface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ii

Foreword . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . iii

SECTION ONE

The ‘Passive House’ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

1.1 Passive House and the Passivhaus Standard . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

1.1.1 Definition of the Passivhaus Standard . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

1.1.2 Technical Definition of the Passivhaus Standard for Ireland . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

1.2 Applications of the Passivhaus Standard in the EU and Ireland . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

1.2.1 Evolution of the Passivhaus Standard in Europe . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

1.2.2 Application of the Passivhaus Standard in Ireland . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

1.3 Dwelling Energy Assessment Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

1.3.1 Dwelling Energy Assessment Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

1.3.2 Compliance with the Building Regulations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

1.3.3 Building Energy Rating . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

1.3.4 PHPP and DEAP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

SECTION TWO

How to Design and Specify a Passive House in Ireland . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

2.1 Building Design Process for a Passive House . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

2.2 General Principles: Heat Energy Losses and Heat Energy Gains . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

2.2.1 Passive House Building Envelope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

2.2.2 Passive House Building Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

2.3 Energy Balance Calculations and Passive House Specification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

2.3.1 PHPP Software and Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

2.3.2 Passive House Certifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

SECTION THREE

Passive House Prototype for Application in Ireland . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31

3.1 Design and Specification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31

3.1.1 Combining Aesthetic and Energy Performance in House Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31

3.1.2 Decision Support using Passive House Planning Package (PHPP) Software . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31

3.1.3 Prototype Passive House External Wall Sections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38

3.1.4 Prototype Passive House Design including Mechanical and Electrical Services . . . . . . . . . . . . . . . . . . . . . . . . . . . 38

3.2 Cost Considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39

ihttps://www.mosart.ie/

PrefaceBy Dr Wolfgang Feist, Founder of the Passive House Institute, Germany

Energy Efficient Passive Houses – Reducing the Impact of Global Warming

The February 2007 report of the Inter-Governmental Panel on Climate Change(IPCC) has shown that climate change is already a very serious global issue. Thenegative effects it will have on the ecosystem, the world economy and on livingconditions are anticipated to be on a massive scale.

Climate change is caused largely by human behaviour due mainly to the use offossil fuels as our main source of energy generation. The magnitude of futureclimate changes is closely linked to worldwide CO2 emissions into the earth’satmosphere. The worst effects of global warming, such as a thawing of the entireland-borne ice in Greenland and Antarctica, can still be prevented. However, thisrequires a substantial reduction in worldwide CO2 emissions far below thecurrent level.

There is hardly any doubt that an energy system ready for the future will have tobe sustainable. Sustainable development is economic development that can becontinued in the future without causing significant problems for other people,the environment and future generations.

Passive Housing can play a major role in reducing the impact of global warming.The energy requirement of a passive house is so low that a family will never againneed to worry about energy price hikes. Passive Houses are virtually independentof fossil sources of energy and can be fully supplied with renewable energy if acompact heat pump unit is used in combination with an ecological electricitysupplier. Due to the low energy requirement of passive houses the regionallyavailable renewable energy sources are sufficient to provide a constant supply ofenergy for everyone.

Ireland’s mild climate puts it in a favourable position to introduce Passive Housesto mainstream construction compared to the more severe climates prevalent incentral Europe.

ii https://www.mosart.ie/

Foreword

Sustainable Energy Ireland is Ireland’s national energy authority, set up to support Irish government energy

policy objectives. Following the introduction of new legislation, most notably the European Community

Directive on the Energy Performance of Buildings and the recent announcement of the intent to regulate

and require the use of renewable energy systems in new buildings, we are seeing the emergence of

extraordinary standards of energy performance for building construction in Ireland, as well as a rapid

increase in the uptake of renewable energy technologies for building services.

Ireland is facing a number of serious challenges includingrising energy costs and meeting our emissions obligationsunder the Kyoto protocol. These and other factors havegiven rise to a fundamental rethink in the way we design,construct and operate buildings. it is becoming clear thatbuilding ‘green’ has evolved and is fast becoming thepreferred choice, providing high quality, high efficiency,dynamic and cost effective solutions for consumers andbusinesses. The passive house is the ultimate in low energybuilding and is recognised in Europe as the most advancedin terms of energy performance of buildings. Interestingly,the European Commission is set on implementing morestringent requirements for the refurbishment of existingbuildings and moving towards the passive house standard.

Today, the passive house offers one of the most desirabletechnological and economical solutions for comfortableliving and working. It can be applied to new and existingbuildings in the commercial, industrial, public and residen-tial sectors. With over 6,000 passive houses built in Europe,this well proven and tested innovative standard is nowattracting significant interest in Ireland with pioneers likeMosArt and Scandinavian Homes leading an emergingmovement in the construction industry.

In response to the need to educate professionals and theirclients on how to design, specify and construct passive

houses and facilitate the further development of thisstandard here in Ireland SEI commissioned ‘Guidelines forthe Design and Construction of Passive House Dwellings in Ireland‘. These detailed guidelines for self-builders andarchitects focus on new build houses and cover bothconventional block construction and timber frameconstruction methods. They will ultimately become part ofa suite of guidelines to cover, for example, multipledwellings, non-residential buildings, extensions, renova-tions etc.

The guidelines cover the rationale and definition of thepassive house standard, how to design and specify a passivehouse along with, construction options, associated services,cost considerations and lifestyle issues. SEI hopes they willbe useful in increasing awareness and understanding of thekey principles and techniques in designing, constructingand operating the ultimate low energy building – thepassive house.

Brendan HalliganChairman, Sustainable Energy Ireland

iiihttps://www.mosart.ie/

SECTION ONE

The ‘Passive House’


1.1 Passive House and thePassivhaus Standard

A passive house1 is an energy-efficientbuilding with year-round comfort andgood indoor environmental conditionswithout the use of significant activespace heating or cooling systems. Thespace heat requirement is reduced bymeans of passive measures to the pointat which there is no longer any need for aconventional heating system; the airsupply system essentially suffices todistribute the remaining heat require-ment. A passive house provides a veryhigh level of thermal comfort and provi-sion of whole-house even temperature.The concept is based on minimising heatlosses and maximising heat gains, thusenabling the use of simple buildingservices. The appearance of a passivehouse does not need to differ from aconventional house and living in it doesnot require any lifestyle changes. Passivehouses are naturally well lit due to largeglazed areas designed to optimise solargains, as well as healthy buildings inwhich to live and work due to fresh airsupply through the controlled ventila-tion system.

The Passivhaus Standard is a construc-tion standard developed by thePassivhaus Institut in Germany(http://www.passiv.de). The standard canbe met using a variety of design strate-gies, construction methods andtechnologies and is applicable to anybuilding type.

This publication outlines the require-ments in applying that standard inIreland, and in all cases when referring toa passive house is describing a housebuilt to the requirements of thePassivhaus Standard.

1.1.1 Definition of the PassivhausStandard

The Passivhaus Standard is a specificconstruction standard for buildings withgood comfort conditions during winterand summer, without traditional spaceheating systems and without activecooling. Typically this includesoptimised insulation levels with minimalthermal bridges, very low air-leakagethrough the building, utilisation ofpassive solar and internal gains andgood indoor air quality maintained by amechanical ventilation system withhighly efficient heat recovery.Renewable energy sources are used asmuch as possible to meet the resultingenergy demand (Promotion of EuropeanPassive Houses (PEP) 2006), includingthat required for the provision of domes-tic hot water (DHW).

It should be noted that the primaryfocus in building to the PassivhausStandard is directed towards creating athermally efficient envelope whichmakes optimum use of free heat gains inorder to minimise space heating require-ment. While there are also limitations onthe amount of primary energy that canbe used by a dwelling for such demandsas DHW, lighting and household appli-ances, this will not be the primary focusof these guidelines. That is not intendedto imply that such energy uses areinsignificant, however. In fact, a passivehouse may have similar DHW require-ments as would apply to any typicalhouse in Ireland and given the lowenergy required for space heating theenergy demand for DHW will thus repre-sent a relatively high proportion of theoverall consumption. In order to addressthis, some guidance is provided on

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The ‘Passive House’

Passive house in Ghent, Belgium (2004).Source: Passiefhuis Platform vzw.

Passive house in Oberosterreich, Austria (2000).Source: IG Passivhaus Osterreich Innovative Passivhausprojekte.

Interior of passive house in Oberosterreich, Austria(2000). Source: IG Passivhaus Osterreich InnovativePassivhaus projekte.


strategies to ensure that renewableenergies are employed as much as possi-ble for production of DHW.

Structural air-tightness (reduction of airinfiltration) and minimal thermal bridg-ing are essential. A whole-housemechanical heat recovery ventilationsystem (MHRV) is used to supplycontrolled amounts of fresh air to thehouse. The incoming fresh air is pre-heated, via a heat exchanger, by theoutgoing warm stale air. If additionalheat is required, a small efficient backupsystem (using a renewable energysource, for example a wood pellet stove)can be used to boost the temperature ofthe fresh air supplied to the house.

The energy requirement of a house builtto the Passivhaus Standard is:

� Annual space heating requirementof 15 kWh/(m2a) treated floor area(TFA), and

� The upper limit for total primaryenergy demand for space and waterheating, ventilation, electricity forfans and pumps, household appli-ances, and lighting not exceeding120 kWh/(m2a), regardless of energysource.

Additionally, the air-leakage test resultsmust not exceed 0.6 air changes perhour using 50 Pascal over-pressurisationand under-pressurisation testing.

In order to maintain high comfort levelsin any building, heat losses must bereplaced by heat gains. Heat losses occurthrough the building fabric due to trans-mission through poorly insulated walls,floor, ceiling and glazing as well as fromuncontrolled cold air infiltration throughleaky construction and poorly fittedwindows and doors. In a typical olderdwelling, such heat losses have to bebalanced by heat gains mostly

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Air-leakage (or infiltration) is theuncontrolled penetration of outsideair into a building. It takes placethrough openings, primarily throughinadequate and imperfect sealingbetween window frames and walls,between the opening sections of thewindows and along the joints of thebuilding.

Thermal bridging refers to a material,or assembly of materials, in a build-ing envelope through which heat istransferred at a substantially higherrate (due to higher thermal conduc-tivity) than through the surroundingmaterials. Junctions betweenwindow or door and wall, wall andfloor, and wall and roof should bedesigned carefully to avoid orminimise thermal bridging. A thermalbridge increases heat loss throughthe structure, and in some extremecases may cause surface condensa-tion or interstitial condensation intothe construction. Surface mouldgrowth or wood rot may be the conse-quences of a thermal bridge.

Measure/Solution Passivhaus Standard for the Prototype House in the Irish Climate

1. Super Insulation Insulation Walls U < 0.175 W/(m2K)Insulation Roof U < 0.15 W/(m2K)Insulation Floor U < 0.15 W/(m2K)Window Frames, Doors U < 0.8 W/(m2K)Window Glazing U < 0.8 W/(m2K)Thermal Bridges Linear heat Coefficient Ψ < 0.01 W/(m2K) Structural Air Tightness n50 < 0.6/ air changes per hour 2. Heat Recovery/ Air Quality Ventilation counter flow air to air heat exchanger

Heat Recovery Efficiency > 75%

Minimal Space Heating Post heating ventilation air/ Low temperature heating

Efficient small capacity heating system Biomass, compact unit, gas etc. Air quality through ventilation rate Min 0.4 ac/hr or 30m3/pers/hr Ventilation Supply Ducts Insulated Applicable

Applicable

Window Glazing Solar energy transmittance g > 50% Solar Orientation Minimal glazing to north Thermal Mass within Envelope Recommended

A rated appliances

Hot water connection to washing machines/ dishwashers

Recommended

Recommended Regular maintenance ventilation filters Recommended

Recommended

Biomass system Recommended Photovoltaics Application in a case by case basis Wind Turbine Application in a case by case basis Other including geothermal Application in a case by case basis

DHW Pipes Insulated

3. Passive Solar Gain

4. Electric Efficiency Energy Labelled Household Appliances

Compact Fluorescent or LED Lighting

Energy Efficient Fans/Motors

DHW Solar Heating5. On-site Renewables

Area to be dictated by house size and occupancy

Table 1. Technical Definition of the Passivhaus Standard for Ireland.

Passive house in Hannover, Germany (2004).Source: IG Passivhaus Deutschland InnovativePassivhaus projekte.


contributed by a space heating system.The internal heat gains from occupantsand other sources such as householdappliances as well as passive solar gainscontribute a relatively small proportionof the total overall need in a conven-tional older dwelling. In a passive house,the heat losses are reduced so dramati-cally (through better insulation andairtight detailing) such that the sameinternal gains and passive solar gain

now contribute a relatively high propor-tion of the total need. As a result of this,a smaller space heating system isrequired compared to that needed in aconventional older dwelling.

A new built semi-detached, two storeyIrish house built to comply with therequirements of Building RegulationsTechnical Guidance Document (TGD)Part L 2005, Conservation of Fuel andEnergy), uses approximately 75kWh/(m2a) energy requirement for spaceheating and 156 kWh/(m2a) primaryenergy. The equivalent house built to therequirements of TGD Part L 2007 wouldbe liable to use 40-50 kWh/(m2a) deliv-ered / useful energy for space heatingand 90-95 kWh/(m2a) primary energy.The Passivhaus Standard requirement forspace heating is 15kWh/(m2a). Whencompared, and having regard toconstraints imposed by other require-ments in the Building Regulations Part L,a passive house thus represents a savingof around 70% on space heating demandrelative to a typical house built to theBuilding Regulations 2005, and around60% relative to a typical house built tothe Building Regulations 2007.

1.1.2 Technical Definition of thePassivhaus Standard for Ireland

In Table 1 a range of U-values is specifiedin order to meet the Passivhaus Standardof annual space heating requirement of15 kWh/(m2a) for the Irish climate.Specifying U-values is dependent uponmany variables and can only be verifiedthrough testing the performance of thedwelling design in the Passive HousePlanning Package (PHPP) software. TheU-values included in Table 1 have beentested for the prototype passive housepresented later in Section 3. This proto-type house is a semi-detached twostorey house of compact form. Adetached bungalow house of sprawlingform would require much lower U-valuesto meet the Passivhaus Standard. Due tothe mild Irish climate, it is possible tomeet the standard using U-values forwalls in the prototype house that arehigher than those typically recom-mended by the Passivhaus Institut forcolder central European climates.

A sensitivity analysis was undertakenusing different U-values for the proto-type house in order to see whether itwould be possible to relax the buildingfabric requirements e.g. in relation toglazing, in Ireland and still achieve thePassivhaus Standard. The results of thisanalysis are included in Section 2.

1.2 Applications of thePassivhaus Standard inthe EU and Ireland

1.2.1 Evolution of the PassivhausStandard in Europe

The Passivhaus Standard originated in1988 by Professor Bo Adamson of theUniversity of Lund, Sweden and Dr.Wolfgang Feist of the Institute forHousing and the Environment. Theconcept was developed through anumber of research projects and firsttested on a row of terraced houses by Dr.Wolfgang Feist in 1991 in Darmstadt,Germany. The Passivhaus Institut(http://www.passiv.de) was founded inDarmstadt, Germany in 1996 by Dr.Wolfgang Feist as an independentresearch institution. Since then, it hasbeen at the forefront of the PassiveHouse movement in Germany and hasbeen instrumental in disseminating thestandard throughout Europe and

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Illustration of comparative heat losses and heat gains in older dwellings and in dwellings built to PassivhausStandard. Source: Passivhaus Institut. http://www.passiv.de.

1

0

10

20

30

40

50

60

70

80

Part L 2005 Part L 2007 Passivhaus Standard

kWh

/m2 /

y

Space heating energy comparison, Building Regulations (TGD) Part L 2005 and 2007 and the Passivhaus Standard .Source: Sustainable Energy Ireland

OLDER DWELLINGS PASSIVHAUS STANDARD

Primary energy, in kWh/year: Thisincludes delivered energy, plus anallowance for the energy “overhead”incurred in extracting, processing andtransporting a fuel or other energycarrier to the dwelling. For example,in the case of electricity it takesaccount of generation efficiency atpower stations. SEI, Dwelling EnergyAssessment Procedure (DEAP), 2006version 2, pp. 28.

Delivered energy, in kWh/year: Thiscorresponds to the energy consump-tion that would normally appear onthe energy bills of the dwelling forthe assumed standardised occupancyand end-uses considered.


overseas. The Institut provides a numberof services including: "PassivhausProjektierungs Paket" (PHPP - PassiveHouse Planning Package), a worksheetused to determine the energy supply /demand balance for passive buildings(available in Ireland from SEI RenewableEnergy Information Officeemail:[email protected]); consultancydesign of passive buildings and buildingcomponents; and certification of qualityapproved passive houses (more detailsin Section 2).

Over 6,000 dwellings built to thePassivhaus Standard have beenconstructed all over Europe in recentyears. This includes 4,000 in Germanyand Austria,2 where the PassivhausStandard was first applied as well asNorway, Sweden, Denmark and Belgiumand numbers are continuing to grow.CEPHEUS3 (Cost Efficient Passive Housesas European Standards) was a researchproject (1998-2001) that assessed andvalidated the Passivhaus Standard on awider European scale. The project wassponsored by the European Union aspart of the THERMIE Programme of theEuropean Commission, Directorate-General of Transport and Energy. UnderCEPHEUS, 14 housing developmentswere built, resulting in a total of 221homes constructed to the PassivhausStandard in five European countries.Another project supported by theEuropean Commission DirectorateGeneral for Energy and Transport is PEP,which stands for ‘Promotion of EuropeanPassive Houses’ (http://www.europeanpassivehouses.org). PEP is a consortiumof European partners aiming to spreadthe knowledge and experience on thepassive house concept throughout theprofessional building community,beyond the select group of specialists.

1.2.2 Application of PassivhausStandard in Ireland

The Kyoto Protocol was ratified in 2005and the proposed targets of reducinggreenhouse gas (principally CO2)emissions by 8% compared to 1990levels by the period 2008-2012 becamelegally binding for EU Member States(UNFCCC, 1997). Within the EU burdensharing agreement in this regard,Ireland's target limit of 13% above 1990levels had been reached in 1997, and it is

likely that the limit will be overshot byup to 37% (74Mt CO2) by 2010 (O’Learyet al, 2005). The EC Green Paper onEnergy Efficiency (EU, 2005), states that itis possible for the EU-25 Member Statesto achieve energy savings of 20% by2010, and sees the greatest proportionof these savings (32%) coming from thebuilt environment.

In Ireland the residential sector accountsfor 25% of primary energy consumptionand energy related CO2 emissions(11,896 kt CO2), the second largestsector after transport at 35%. Theaverage dwelling is responsible forapproximately 8.1 tonnes of CO2emissions, 4.8 tonnes from direct fueluse and 3.3 tonnes from electricity use.Irish dwellings have a higher averagelevel of fuel, electricity and energyrelated CO2 emissions per dwellingcompared to the average of the EU-15(SEI, 2008).

Following the Government White Paper‘Delivering a Sustainable Energy Futurefor Ireland’ (DCMNR, 2007), and thesubsequent Programme for Govern-ment, the Building Regulations Part L inrespect of new dwellings have beenstrengthened to bring a 40% reductionrelative to previous standards in respectof primary energy consumption andassociated CO2 emissions arising fromspace heating, water heating, ventila-tion, associated pumps and fans, andlighting energy usage. These provisionsapply from July 2008. This policy hascommitted to a further review in 2010with the aim of extending that improve-ment to 60%.

It is clear that the performance of bothnew build and existing housing stockmust be addressed if we are to achievethe objectives set out both at Europeanand national level. The energy require-ment of a house built to PassivhausStandard goes beyond the 40%improvement that applies from July2008.

The Passivhaus Standard was first intro-duced in Ireland by the Swedish archi-tect Hans Eek at the ‘See the Light’conference organised by SustainableEnergy Ireland (SEI) in June 2002. TomásO’Leary of MosArt Architects, a delegateat the conference, was so enthused byMr Eek’s presentation that he decided on

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Passive house in Guenzburg, Germany (2006)Source: UCD Energy Research Group

Passive house Eusenstadt, AustriaSource: Construct Ireland Issue 2, Vol 3

Multi-family dwelling ‘ Hohe Strasse’ Hannover,Germany Source: UCD Energy Research Group

Kronsberg Passivhaus Complex Hannover, Source: UCD Energy Reseach Group


the spot to sell his townhouse, buy a sitein the countryside in Co. Wicklow andbuild a passive house. The O’Leary familyhas been living in the “Out of the Blue”house since Spring 2005. This house isthe first Irish passive house to be certi-fied by the Passivhaus Institut inGermany, and has been the focus of aresearch, demonstration and energymonitoring project funded by SEI.MosArt Architects, the PassivhausInstitute of Dr Wolfgang Feist and theUCD Energy Research Group arepartners in the project. The project hasbeen instrumental in establishing thebasis for the deployment of thePassivhaus Standard in Ireland in differ-ent ways:

� it has provided a learning experiencefor professionals involved in thedesign, specification, constructionand servicing stages

� it will provide a scientific basis forperformance assessment throughmonitoring and evaluation

� it is an excellent demonstration tooland has been the focus of manyvisits, presentations and journalarticles.

1.3 Dwelling EnergyAssessment Procedure

1.3.1 Dwelling Energy AssessmentProcedure

The Dwelling Energy AssessmentProcedure (DEAP) is the Irish officialprocedure for calculating and assessingthe energy performance of dwellings.The procedure takes account of theenergy required for space heating,ventilation, water heating, associatedpumps and fans, and lighting, lesssavings from energy generationtechnologies. The DEAP calculations arebased on standardised occupancy andthe procedure determines annualvalues for delivered energy consump-tion, primary energy consumption, CO2emissions and costs. These values areexpressed both in terms of annual totalsand per square metre of total floor areaof the dwelling.

As the national methodology, DEAPserves two primary functions. The first is

to demonstrate compliance with certainprovisions in the Building Regulationsand the second is to produce a BuildingEnergy Rating for a dwelling.

1.3.2 Compliance with the BuildingRegulations

The DEAP methodology is used todemonstrate compliance with certainaspects of Part L of the Irish BuildingRegulations (The Conservation of Fueland Energy - Dwellings: 2007). In partic-

ular, it is used to calculate the primaryenergy consumption associated withthe space heating and ventilation, waterheating, associated pumps and fans, andlighting requirements of a dwelling andto determine the amount of CO2emissions associated with this energyuse.

If both the energy consumption and theCO2 emissions are below the limits set bythe regulations (determined relative towhat would arise for a “reference

page 5

Building Energy Rating Label. Source: Sustainable Energy Ireland.

The EU Energy Performance of Buildings Directive (EPBD) was transposed into Irishlaw on 4th January 2006. This states that when a building is constructed, rented orsold a Building Energy Rating (BER) certificate and label must be made available toprospective buyers or tenants. The BER is expressed in terms of KWh of primaryenergy/m2/year. A passive house has the potential to achieve an A2 or even an A1rating as shall be demonstrated in Section 3(MosArt).


dwelling” of the same dimensions) thenthe dwelling is deemed to be compliant.

1.3.3 Building Energy Rating

A Building Energy Rating (BER) is anobjective scale of comparison for theenergy performance of a buildingranging from A1 to G (see graphic onprevious page). Essentially a BER is anasset rating, based on a standardisedoccupancy and usage pattern, and iscalculated for a dwelling using DEAP.The rating is the annual primary energyconsumption of the dwelling expressedin terms of kWh per m2 of floor area. TheCO2 emissions associated with thisenergy consumption are also reportedon the BER certificate and expressed interms of kg of CO2 per m

2 of floor area.

1.3.4 PHPP and DEAP

Whereas DEAP is the mandatory methodfor both producing a Building EnergyRating and for demonstrating compli-ance with certain aspects of the IrishBuilding Regulations, the PassivhausStandard and the associated PHPP is avoluntary design standard for achievinglow levels of total energy consumptionwithin a dwelling.

While it is to be expected that a dwellingconforming to the Passivhaus Standardwill comply with Irish BuildingRegulations Part L, a separate calculationusing DEAP will be required to demon-strate both this and to determine its BER.

The Passivhaus Standard can be metusing a variety of design strategies,construction methods and technologies.In general, the low energy consumptionrequired to meet the standard will resultin a dwelling achieving a favorable BER,provided that attention is paid to theadvice outlined in later sections of theseguidelines.

page 6

References

European Commission (EC), 2005.“Green Paper on Energy Efficiency”.[Internet] EC. Available at:http://ec.europa.eu/energy/efficiency/index_en.html

European Commission (EC), 2006. “Promotion of European Passive Houses(PEP)”. [Internet] PEP. Available at:http://www.europeanpassivehouses.org/html

Government of Ireland, Department ofCommunications, Energy and NaturalResources (DCMNR), 2007. Government“White Paper Delivering a SustainableEnergy Future for Ireland”. [Internet]DCERN. Available at:http://www.dcmnr.gov.ie/Energy/Energy+Planning+Division/Energy+White+Paper.html

O’Leary, F., Howley, M., andO’Gallachóir, B., 2006. “Energy inIreland 1990-2004, Trends, issues,forecast and indicators”. Dublin.Sustainable Energy Ireland.

O’Leary, F., Howley, M., andO’Gallachóir, B., 2008, “Energy in theResidential Sector: 2008 Report”.Dublin. Sustainable Energy Ireland.

United Nations Framework Conventionon Climate Change (UNFCCC), 1997.The Kyoto Protocol. [Internet]. UNFCCC.Available at: http://unfccc.int/resource/docs/convkp/kpeng.html

1 A passive house is a building, for which thermal comfort (ISO 7730) can be achieved solely bypost-heating or post-cooling of the fresh air mass, which is required to fulfill sufficient indoorair quality conditions (DIN 1946) - without a need for recirculated air. Source:http://www.passivhaustagung.de/Passive_House_E/passivehouse_definition.html

2 See http://www.passiv-on.org/

3 See http://www.passiv.de/07_eng/ news/ CEPHEUS_final_short.pdf

Ireland’s 1st Passivhaus, Wicklow Source: Tomás O’Leary, MosArt Architecture


SECTION TWO

How to Design and Specify a Passive House in Ireland


This section introduces the passivehouse building design process as well asexplaining the balance between energylosses and gains. It also provides anoverview of the various building systemsand technologies typically employed ina passive house and presents the PHPPsoftware used for energy balance calcu-lations. The design and specification ofthe example prototype passive house inthe Irish climate developed as part ofthese guidelines will be covered ingreater detail in Section 3.

2.1 Building Design Processfor a Passive House

Client’s BriefThe design of a passive house willtypically commence with developing abrief with the client, whether this is afamily wishing to build a single ruraldwelling, a Local Authority progressing ahousing scheme or a commercial devel-oper proposing a mixed residentialproject. The brief would typically outlinethe client’s practical requirements interms of space functions and densityand also their preferred image orconcept for the building(s). Clients inter-ested in building a passive house willoften have carried out some research onthe subject and so may already berelatively well informed regarding thebenefits of living in a passive house.

Site VisitA site visit is important to identify thepresence of structures, landform orevergreen trees which might castshadows on the house during the shortwinter days when the sun is low in thesky (thus reducing the potential forachieving a glazed south facing façade).It may happen that the best views from

the site are to the north suggesting theplacement of large glazing areas on thenorthern façade in order to exploit thatview. All orientation options must beconsidered by the designer at this stage– the house must not only function wellin terms of energy efficiency but also interms of optimising the potential of thesite and its surroundings.

Sketch DesignThe next phase of the design process isto develop a sketch design for the house.The basic principles of passive housedesign will greatly inform the develop-ment of the initial design. An idealapproach would be to have the longestfaçade of the house facing south, a biasof glazing towards the southern eleva-tion with reduced glazing area on thenorthern elevation and a compact formin order to minimise surface to volumeratio. Shading devices may be requiredin order to protect against the risk ofoverheating in summer and theaesthetic integration of this is essential.In terms of internal layout, it is preferableto organise, where possible, familyrooms and bedrooms on the southernelevation with utility room and circula-tion spaces on the northern elevationwhere availability of sunlight is not socritical.

Initial Evaluation of Energy Performance Once the sketch design has beenapproved by the client, it is important totest the energy balance of the housedesign using the Passive House PlanningPackage (PHPP). The essential elementsof the design are entered into thespreadsheet, including U-values of walls,floors, roof and glazing as well as orien-tation, volume, and size of the house.This will provide an early indication of

whether the Passivhaus Standard isbeing achieved.

If the space heat requirement is signifi-cantly above the threshold of 15kWh/(m2a) then the building will have tobe modified whether in terms ofimproved U-values, reorganisation ofglazing or adjustment of form. Thedesigner should intuitively know howimprovements can best be achievedwhile broadly remaining true to theagreed sketch design. If the space heatrequirement is significantly less than thethreshold level, then it might be possibleto increase the U-values and thereforesave on insulation costs.

Care should also be taken to note otherperformance indicators calculated bythe software, such as frequency ofoverheating, for example.

Detailed Design and SpecificationThe design of the house is next devel-oped to the level of detail required toapply for planning permission. Typicallythis would not require all constructiondetails but it is wise to consider thevarious technologies at this stage inorder to avoid difficulties later on.

The type of construction will need to beconsidered, whether timber frame,masonry, externally insulated masonry,insulated concrete formwork, steelframe or straw bale as well as the spacerequired for services such as solarpanels, large domestic hot water tank,mechanical ventilation equipment withsupply and exhaust ducting. The specifi-cation of such services might be outsidethe expertise of the house designer andit may be required to commission theservices of a Mechanical and ElectricalEngineer.

How to Design and Specify a Passive House in Ireland


It is also critically important to planahead in terms of airtightness and coldbridging detailing as these often repre-sent the most challenging aspects ofpassive house design.

The detailed design should be re-testedin the PHPP software to ensure that thePassivhaus Standard is achieved. At thisstage all the required data fields have tobe completed as accurately as possible(details of the PHPP tool datasheets areoutlined in section 2.2.1). The result of thisdetailed test might suggest that minoralterations are required to the initialhouse design in order to meet thepassivhaus standard. The client should bekept informed at all times of the decisionsbeing made by the design team and havethe opportunity to suggest alterationsshould the need arise.

Tender Documents and Drawings Once planning permission has beengranted, a more detailed set of technicaldrawings will be required in order toenable the construction of the house. Ashighlighted above, the emphasis will beon detailing of junctions between differ-ent elements of the building, practicalrequirements for minimising heat lossthrough cold bridging, planning forairtightness and the location androuting of services. The sizing of theventilation equipment, backup spaceheating, solar domestic hot watersystem, as well as details of controls forspace and water heating and ventilation,will have to be specified at this stage.The detailed drawings and specificationcan then be issued for tender to compe-tent contractors.

Site OperationsThe detailed design of the passive housemust now be realised on-site and qualitycontrol is paramount to achieving thestandard envisaged in the PHPPsoftware. The most challenging aspectwill typically be achieving the requiredlevel of airtightness, as this is greatlyaffected by the quality of craftsmanshipon site. The challenge becomes all themore difficult if the building contractorhas no prior experience of building tothe Passivhaus Standard. More challeng-ing again is the common practice of thehouse built by ‘direct labour’ andwithout an experienced supervisor withoverall responsibility to achieve the highstandards set.

It will usually be necessary to engagespecialist sub-contractors to supply andinstall such elements as the ventilationequipment, solar system, back upheating systems and controls.

Post Construction TestingThis is the final stage to determinewhether the constructed dwellingactually meets the airtightness require-ments of the Passivhaus Standard. Theair-leakage must not exceed 0.6 airchanges per hour using 50 Pa (0.6ac/h @50 Pa) overpressurisation and under-pressurisation testing. An independentinspection and testing body shouldconduct the testing activities. It is impor-tant to undertake this test as soon as theairtight layer is complete so that anyleaks can be rectified. Where thedwelling does not meet the require-ments further testing may be required.

2.2 General Principles: HeatEnergy Losses and HeatEnergy Gains

2.2.1 Passive House BuildingEnvelope

The building envelope consists of allelements of the construction whichseparate the indoor climate from theoutdoor climate. The aim of the passivehouse is to construct a buildingenvelope that will minimise heat lossand optimise solar and internal heatgain to reduce the space heatingrequirement to 15 kWh/(m2a).

Roof Loss 30%-35%Flue Loss

Ventilation Loss 25%

Window Loss 15%

Floor Loss 7%-10%

Loss through Walls

25%-30%

Areas of Heat Loss in Homes

Comparison typical building fabric heat loss patternsin a detached dwelling, excluding ventilation and infil-tration (Source: UCD Energy Research Group)

Comparison of energy rating between differentGerman construction standards and the passivehouse. (Source: Passivhaus Institut, Germanyhttp://www.passiv.de

Comparison between PHPP and DEAP

The dimensions used in PHPP arealways external dimensions (Figure2.2.1.1). DEAP calculates with internaldimensions.


The following building envelope param-eters are fundamental in this process:

1. Well insulated building envelope

2. High energy performing windowsand doors

3. Minimised heat loss through thermalbridging

4. Significantly reduced structural airinfiltration

5. Optimal use of passive solar andinternal heat gains

Building Envelope Insulation Many building methods can be used inthe construction of a passive house,including masonry, lightweight frames(timber and steel), prefabricatedelements, insulated concrete formwork,straw bale and combinations of theabove. The prototype passive housepresented in this publication (details inSection 3) illustrates both masonry andtimber frame construction as represen-tative of the most typically used buildingmethods for dwellings in Ireland.

Continuous insulation of the entirethermal envelope of a building is themost effective measure to reduce heatlosses in order to meet the PassivhausStandard.

A thermographic image can be used toillustrate the difference between goodand poor levels of insulation in a house.Heat loss through the building envelopeis highlighted by the green, yellow andred colouring. The green areas representthe best insulation whereas the redrepresents the warmest outer surface(hence the worst insulated). The amountof thermal radiation emitted increaseswith temperature, therefore warmobjects stand out well against coolerbackgrounds. In the passive house some

heat is lost through windows but heatlost through external walls is very low. Inthe conventional building, on the otherhand, there can be significant heat lossfrom the entire building envelope,especially through windows.

Insulation of the building envelope canbe divided into four distinct areas: exter-nal wall, floor, roof and windows.Existing passive houses in Central andNorthern European countries have beenachieved with U-values for walls, floorsand roofs ranging from 0.09 to 0.15W/(m2K) and average U-value forwindows (including glazing andwindow frames) in the region of 0.60 to0.80 W/(m2K). These U-values are farbelow (i.e. better than) the limitscurrently set under the Irish BuildingRegulations, with the most markeddifference pertaining to windows, walland floor.

A sensitivity analysis using the PassiveHouse Planning Package (PHPP), v.2007, was undertaken using a range ofU-values for the timber frame andmasonry constructions of the prototypehouse using climatic data for Dublin. Inall options tested, the same data inputwas used for airtightness 0.6ac/h@50Pa,ventilation and minimised thermalbridging. Various parameters weretested in order to determine, forexample, the required level of U-valuesfor the building envelope in the Irishclimate, and to ascertain whether itwould be possible to use double glazingand still achieve the PassivhausStandard in Ireland. The results asoutlined below are: Option 1 being themost energy efficient house and Option8 being the least energy efficient. An

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Irish Building Regulations, ElementalHeat Loss Method (BuildingRegulations Technical GuidanceDocument L, Conservation of Fuel andEnergy TGD Part L 2007).

Maximum average elemental U-valueW/(m2K)

• Pitched roof, insulation horizontalat ceiling level 0.16

• Pitched roof, insulation on slope0.20

• Flat roof 0.22• Walls 0.27 • Ground Floors 0.25• Floors with underfloor heating

0.15• Other exposed floors 0.25 • Windows and roof lights 2.00

Thermal transmittance (U-value)relates to a building component orstructure, and is a measure of the rateat which heat passes through thatcomponent or structure when unittemperature difference is maintainedbetween the ambient air tempera-tures on each side. It is expressed inunits of Watts per square metre perdegree of air temperature difference(W/m2K).

Source: Building RegulationsTechnical Guidance Document,Conservation of Fuel and Energy (TGDPart L) 2007.

Calculation of building element areas using externaldimensions. Source PHPP 2007 Handbook, pg 37

Thermographic image illustrating difference in heatloss through building envelope in a conventional andpassive house building.Source:http://upload.wikimedia.org/wikipedia/en/f/f2/Passivhaus_thermogram_gedaemmt_ungedaemmt.png


outline description of each of the eightoptions analysed is provided. Only thefirst three achieve the PassivhausStandard set for annual space heating of15 kWh/(m2a) treated floor area:

� Option 1 – U-value 0.10 W/(m2K) forall building elements combined withtriple glazed windows with averageU-value (including glazing andwindow frames) of 0.80 W/(m2K)results in space heating requirementsignificantly below the standardlimit required of 15 kWh/(m2a).

� Option 2 – U-value 0.15 W/(m2K) forall building envelope elementscombined with triple glazing. Theresults show space heating require-ment below the Passivhaus Standardlimit.

� Option 3 – this is the option that hasbeen used in the design of theprototype passive house in Irelandas part of these Guidelines, with U-value of 0.175 W/(m2K) for externalwalls and U-value 0.15 W/(m2K) forall other building envelopeelements, coupled with triple glazedwindows.

� Option 4 - U-value for all buildingenvelope elements of 0.10 W/(m2K)combined with an efficient doubleglazed unit with low U-value of 1.5W/(m2K ) which does not achieve thePassivhaus Standard.

Note: Advantages and disadvantages ofusing triple glazed windows are discussedin detail in section ‘Windows & Doors’)

� Option 5 – U-values for walls, roofand floor employed at the limits ofthe individual elemental heat lossrequirements in the Irish BuildingRegulations, (Building RegulationsTGD Part L, Conservation of Fuel andEnergy 2005 and 2007) combinedwith triple glazed windows, failing toachieve the required standard.

� Option 6 – also a failure is the combi-nation of U-value 0.10 W/(m2K) forbuilding fabric in combination withstandard double glazed units.

� Option 7 – U-values 0.15 W/(m2K) forwalls, roof and floor as the prototypehouse but with standard doubleglazing U-value 2.0 W/(m2K) whichcomes way above the limits set forthe Passivhaus Standard.

� Option 8 – U-values for walls, roofand floor employed at the limits ofthe individual elemental heat lossrequirements in the Irish BuildingRegulations, (Building RegulationsTDG Part L, Conservation of Fuel andEnergy 2005 and 2007) and standarddouble glazed units, failing toachieve the Passivhaus Standard.

Note: Results presented here are indicativeonly and should be used as starting pointfor specification of a passive house

dwelling in Ireland. Meeting thePassivhaus Standard must be tested andverified with the PHPP software for thespecific dwelling design.

Thermal ConductivityThermal conductivity (λ-value) relates toa material or substance, and is a measureof the rate at which heat passes througha uniform slab of unit thickness of thatmaterial or substance, when unittemperature difference is maintainedbetween its faces. It is expressed in unitsof Watts per metre per degree (W/mK),(Building Regulations TechnicalGuidance Document Part L,Conservation of Fuel and Energy 2007).Insulation materials for walls, roofs andfloors vary in terms of thermal conduc-tivity. Typical conductivities for differentinsulation materials are included belowas well as the approximate thicknessesrequired in order to achieve a wall (orroof ) U-value of 0.15 W/(m2K) and 0.10W/(m2K)

Typical insulation materials used inIreland include mineral/rockwool,polystyrene, polyurethane, polyisocya-nurate, sheep wool and hemp. Differentinsulation materials may suit differenttypes of construction application and it isimportant to consider the material bestsuited for the situation and pay attentionto detail in its proper installation. Forexample, quilted or loose fill insulation isgenerally suitable for use on the floor of

Option

U-values of ext. wall

U-values of roof

U-values of

floor

AverageU-value of

windows and doors

Space heating requirement

1 0.10 W/(m2K) 0.10 W/(m2K) 0.10 W/(m2K) 0.80 W/(m2K) 7 kWh/(m2a)








Sensitivity analysis of the prototype passive house in Ireland outline test results for eight options. Source: MosArt Architecture


an open attic space where it will fillcompletely between ceiling joists, butcare needs to be taken in ensuring venti-lation in the attic whilst avoiding risk ofwind displacement of insulation neareaves. In contrast, rigid insulation maybe at lower risk of displacement by wind,but would need to be cut perfectly to fitsnugly between the joists, to avoid a riskof thermal looping or leakage. As afurther example, a high density rigidinsulation tends to be better suitedunder a floor slab compared with insula-tion that easily compress or are affectedby moisture.

The U-value of the construction is deter-mined by the conductivity of materialsand components used from the internalsurface to the external surface of thethermal envelope. Examples of typicalconstruction methods and materialsused for the prototype passive house inIreland are illustrated later in Section 3.

Windows & DoorsThe recommended approach to thedesign of a passive house is to haveavoid an excessive area of north facingglazing and place relatively largewindows facing south or due south. Thisis in order to minimise heat lossesthrough the north facing elevation,which receives no direct sunlight duringmost of the heating season, whilemaximising ‘free’ solar heat gains on thesouth. An advantage of large windows isan increase in interior daylight levelswhich in turn reduces the need for use ofelectricity for artificial lighting and alsoensures a more pleasant natural light-filled living environment.

There is, however, a balance to beachieved between heat losses throughthe glazing and solar heat gains throughthe south/east/west facing windows.When designing a passive house, thePHPP software should be used to calcu-late the heat losses and heat gains

taking into account building orientation,areas of glazing and specific types ofglazing so the optimum balance ofglazing for each passive house designcan be reached. Also, as highlightedfurther below, there is a need for thedesign to ensure that the risk of solaroverheating is minimised.

It has been illustrated above that the useof windows and doors with average U-values of 0.8 W/(m2K) can be combinedwith U-values for opaque elements of0.15 W/(m2K) to comfortably achieve thePassivhaus Standard in Ireland. There are

a number of advantages in usingwindows with average U-values of 0.8W/(m2K) as well as highly insulateddoors, principally the assurance of acomfortable indoor climate due to thelower cold radiation heat transfer at thesurface of the glass. One will not sense adrop in temperature standing immedi-ately adjacent to this standard ofwindow, unlike the experience of stand-ing next to a conventional doubleglazed unit with U-value, for example of2.0 W/(m2K). An added benefit of usinghighly energy efficient windows anddoors includes significant draughtreduction due to the fact that they havetypically two seals or gaskets (comparedwith conventional double glazed unitswhich often have only one) as well asexcellent sound insulation. Finally,

natural convection which is driven bytemperature difference between theinside face of the glass and the roominterior is much reduced, thereby avoid-ing this source of cold air flows andthermal discomfort.

The sensitivity analysis for a passivehouse dwelling in Ireland showed that inthe case of Option 4 above thePassivhaus Standard yearly spaceheating requirement could not beachieved with efficient double glazedwindows with a U-value of 1.5 W/(m2K).

Typically triple glazed window units areused in passive houses in Central andNorthern Europe. The Passivhaus Instituthas certified a range of glazing and doorunits suitable for use in passive housebuildings. Although it is not a prerequi-site to use certified passive houseproducts (http://www.passiv.de) in apassive house, choosing approvedproducts means the validity of technicaldata has been tested and verified by anindependent certifier. The principalcharacteristics and advantages of usingtriple glazed windows in a passive houseare listed below, for both glazing and theframes:

page 13

Insulation Material Type

Thermal conductivity W/mK

Thickness for U-value of 0.15

W/(m2K)

Thickness for U-value of 0.10

W/(m2K)

Polyisocyuranate or polyurethane 0.023 145mm 220mm

Polystyrene, sheep wool 0.035 220mm 340mm

Cellulose, Hemp and Rockwool

0.04 250mm 400mm

Wood 0.15 825mm 1,250mm

Conductivity of insulation materials and approximate thickness to achieve specific U-value for external walls (kvalues will vary according to density). Source: MosArt Architecture

Light filled room in a passive house.Source: MosArt Architecture.

Comparison of the interior surface temperature depending of the type of glazing. Source: Internorm, fenster – Lichtund Leben catalogue 2007/2008, pp.91.


Glazing:� Three panes of glass separated by

special low-conductivity spacerseliminates the risk of condensationat the bottom of the glass in coldweather (which could lead to rottingof timber frames over time);

� High solar energy transmittance (g ≥50), referring to the amount of solarradiation which can penetrate theglass and thereby contributetowards heating of the dwelling;

� A low emissivity (low-e) coating onthe inside of the outer two paneswhich reduces thermal re-radiationback out through the glass. It shouldbe noted that a ‘soft coat’ has slightlybetter U-value but a ‘hard coat’glazing has higher solar transmit-tances.

� Insulating gases between the glasspanes, typically argon or krypton,which help to reduce heat escapingthrough the glass.

� With triple glazing the solar energytransmittance (gs), i.e. the amount ofsolar energy entering through thatglazing is somewhat reducedcompared to double glazing due tothe effect of the additional layer ofglass. A requirement of thePassivhaus Standard is to use glazingwith minimum solar transmittanceof 50% or higher.

Frame:� The frame must be well insulated

and also have a thermal barrier (be“thermally broken”). Even woodconducts heat and a thermallybroken timber window frame willresult in much lower heat losses thana solid one.

� There will typically be two weathergaskets on triple glazed windowsused in a passive house dwelling, theprimary function of the outer onebeing for weathering with the innerone serving to improve airtightness.The majority of these types ofwindow open outwards which iscommonplace in ContinentalEurope; however, there are modelsof inward opening windows beingdeveloped which will be availablesoon in the Irish market. One advan-tage of outward opening windows isthat they don’t intrude in the roomspace which might be important inmore compact dwellings.

� Triple glazed window frames aretypically much wider and strongerconstruction than their conventionaldouble glazing counterparts.

The use of larger areas of glazing on thesouth elevation is helpful in maximisingthe amount of sunlight available in theshort days of winter. It must be remem-bered, however, that highly energyefficient windows allow less daylight(visible light transmittance) into a build-ing than normal double glazed windowswithout e-coating. Light transmittance isan optical property that indicates theamount of visible light being transmit-ted through the glazing. It variesbetween 0 and 1 (0 to 100% light trans-mitted), representing the proportion oflight transmitted. A double glazedwindow with low-e coating will typicallytransmit 72% of visible light. A tripleglazed energy efficient window will

typically transmit 65% of visible light(these are indicative values only - actualvalues depend on the manufacturer’sspecification).

In a conventionally constructed olderhouse in Ireland radiators are typicallypositioned under windows in order toheat the cold air entering through thesingle or double glazing. In a passivehouse, locating a heat source beneathwindows is simply not required as theheat load is transferred throughout thehouse via the mechanical ventilationsystem. This has the added benefit ofenabling unobstructed use for placingfurniture against all external walls.

Thermal BridgingThermal bridging (i.e. un-insulated jointsbetween walls, floors/ walls, ceilings/adjacent walls, windows/walls etc) areweak points of thermal resistance in thebuilding envelope and cause unwantedlosses of energy which should be elimi-nated or significantly reduced to adegree that the associated heat lossesbecome negligible.

A thermal bridge increases heat lossthrough the structure, and in someextreme cases this may cause surfacecondensation or interstitial condensa-tion in the structure. Surface mouldgrowth or wood rot may be the conse-quences of a thermal bridge. Typicaleffects of thermal bridges are:

� Significantly increased heat losses;

� Decreased interior surface tempera-ture (cold spots) which may alsoresult in high humidity in parts of theconstruction; and

� Mould growth cause by warm inter-nal air condensing on cold surfaces.

All of the above situations can beavoided in houses built to thePassivhaus Standard. The PassivhausStandard for linear thermal transmit-tance (Ψ) should not exceed 0.01 W/(mK).This requires the building designer toidentify and locate all potential thermal

page 14

Cross section though a triple glazed insulated windowand frame. Source: MosArt Architecture.

The quantity which describes the heatloss associated with a thermal bridge isits linear thermal transmittance (ψ).This is a property of a thermal bridgeand is the rate of heat flow per degreeper unit length of bridge that is notaccounted for in the U-values of theplane building elements containingthe thermal bridge.

Source: SEI, Dwelling Energy Assess-ment Procedure (DEAP) 2005 edition,version 2, pp.55


Thermal bridges are calculated in PHPPon the external face of the thermalenvelope whereas in DEAP the thermalbridges are calculated on the internalsurface of the envelope.


bridging in the construction, applyingcareful specification and detailing ofthose elements providing where possi-ble a continuous layer of insulation, aswell as taking care to execute thoseelements on site as per design details.

Designing and building a passive housein Ireland requires the development ofconstruction details that go far beyondguidance provided (to avoid excessiveheat losses and local condensation) inBuilding Regulations Technical GuidanceDocument Part L, Conservation of Fueland Energy. Building practitioners couldrefer to the accredited constructiondetails specifically developed for passivehouse building published in Germany“Thermal Bridge-Free Construction”(PHPP 2007, pp.96). Thermal bridgingcan be tested and verified in the PHPPsoftware as the design of the passivehouse building is being developed.

Structural Airtightness and Draught-Proofing Building an airtight or leak-free structureis imperative to achieving the PassivhausStandard. If there are gaps in the build-ing structure then uncontrolledamounts of cold external air can infil-trate the building. Achieving a high levelof airtightness eliminates cold draughtsand associated comfort losses. It alsoprevents condensation of indoor moist,warm air penetrating the structure, andpossible structural damages due todecay, corrosion and frost.

Air tightness is achieved in masonryconstruction by careful application ofappropriate membranes and tapes orwet plastering within the buildingenvelope. A great deal of attention mustbe paid to detailing and workmanship inorder to ensure that the airtight layer iscontinuous all round the building,especially around junctions betweenwalls and floors, roof, windows, doors,etc. Penetrations of the airtight layer bymechanical and electrical services mustbe properly sealed.

The air tightness of a building can beaccurately measured by carrying out ablower-door test. The test involvesplacing a powerful fan suspended in asealed canvas sheet within a dooropening and operating the fan at veryhigh speeds thereby creating eithernegative or positive pressure within the

house. By sucking air out of the house,for example, a negative pressure iscreated with the result that external airwill be sucked in through any gaps orcracks in the building envelope. Thepressure used for such tests is 50 Pascalwhich can be accurately set by theblower door equipment.

When undertaking the test it is usuallyquite easy to identify any major leaksdue to the presence of a strong draughtwhich can be felt by the hand or, forsmaller leaks, can be detected by athermographic camera. The cause ofthese draughts can then be sealed withappropriate materials as the test is ongoing. It may also happen that the leaksin the envelope are very minor andtherefore difficult to locate. In thesesituations it is typical to reverse thedirection of the fan and blow air into thehouse putting it under positive pressure.Odorless smoke can then be releasedinto the building and leaks can beobserved from the outside where thesmoke appears through the envelope. Itis important to notify the fire service ifyou are carrying out such a test in case itis mistakenly reported as a house fire bypassers by.

The Passivhaus Standard is reachedwhen there are less than or equal to 0.6air changes per hour @50 Pa pressure.

The most critical issue regarding testingfor airtightness is timing during thebuilding process. It is important thatremedial measures can be carried out inorder to remedy any leaks or cracks. Thetest should be carried out before secondfix carpentry, for example, where thereare no skirting boards or window boardsfitted and where the junctions coveredby such materials are still accessible andcan be sealed. The test should also becarried out after all mechanical and

page 15

Infrared image of the interior of a passive housewindow. All surfaces (wall structure, window frame,and the glazing) are pleasantly warm (over 17 °C). Evenat the glass edge, the temperature does not fall below15 °C (light-green area) (Source: Passivhaus Institut, http://www.passiv.defrom the passive house Kranichstein)

For comparison, a typical older double glazed windowis shown. The centre of glass surface temperature isbelow 14 °C. In addition, there are large thermalbridges, particularly where the window meets theexternal wall. The consequences are significant radianttemperature asymmetry, drafts, and pooling of cold airin the room. (IR-photography: Passivhaus Institut offices,http://www.passiv.de )

Timber Frame I-Beam construction reducing thermalbridging. Source: Passivhaus Institut, Germany.


In the ventilation sheet of PHPP the airchanges @ 50 Pa have to be entered.The DEAP calculation uses air changes@ normal pressure for its inputs.

The results of the blower door test @ 50Pa have to be divided by 20 to enterthe correct value in DEAP

Example: 0.6 ac/hr / 20 = 0.03 ac/hr

Input PHPP: 0.6, Input DEAP: 0.03


electrical services that need to penetratethe building envelope have beeninstalled. Otherwise, installing suchservices after the test could severelycompromise the airtightness of thebuilding.

In a typical Irish house built in accor-dance with TGD Part F 2002 the methodin which habitable rooms are ventilatedhas usually been via a hole in the wall orventilator in the windows of 6,500mm2

fitted with a controllable grille. Suchmeans of ventilation can result in largeamounts of cool external air infiltratingthe building depending on wind speedand pressure. The same is true for openchimneys or flues in conventionalhouses.

In a passive house, on the other hand,the supply of fresh air is provided by awhole house mechanical ventilationsystem with heat recovery whichnegates the necessity for openings inthe wall or windows. Thereby draughtsare eliminated and structural air tight-ness is not compromised.

In developing the building design it isvery important to anticipate differentialmovement and decay of adhesives andchemical bonds by detailing junctionswhich will assist in maintaining anairtight layer for the life of the building.Many excellent details, for example, canbe found at the website of the ScottishEcological Design Association(www.seda2.org/dfa/index.htm). It canalso be important to use membranesand plasters that are both airtight butalso vapour diffuse which allow thestructure to “breathe” to its cold side.This means allowing moisture within thestructure to escape to the outsidethereby reducing the risk of interstitialmoisture and the threat of rot and decayover time.

Passive Heat Gains

Passive heat gains in a passive house area result of the combination of solar gainsand internal gains.

Solar Heat GainsPassive solar gain is optimised by provid-ing an east-west alignment to the build-ing, if possible with the site, resulting inthe longest façade facing south, and byplacing the majority of the glazingtowards the south. Very high qualitywindows (average U-value ≤ 0.8W/(m2K)) facing south will have apositive thermal balance – they will havemore heat gain than heat loss through-out the year. Results of a recent paramet-ric study by J. Schnieders of thePassivhaus Institut “Climate Data forDetermination of Passive House HeatLoads in Northwest Europe” illustratesthe relationship between the area ofsouth facing glazing and the space heatdemand for a passive house dwellinglocated in Ireland (measured climatedata for Birr used). The parametric studyuses the first passive house built by Dr.Wolfgang Feist of the Passivhaus Institutas a case study building, shown below. Itcan be seen that the space heatingdemand initially decreases quite steeplywith increasing south facing glazing.There are diminishing returns fromincreasing the area of south facing glass,however, and there eventually comes apoint where there is little or no benefit inproviding more south facing glass as thenet heat loss is greater than the heatgains over the year.

There is no optimal ratio of glazing tofloor area that can be used as a rule ofthumb in deciding what proportion of agiven façade should be glazed. The areaof glass has to be determined as part ofthe design verification procedure usingthe PHPP software.

Internal Heat GainsA passive house is very efficient at utilis-ing ‘free’ internal heat gains from domes-tic household appliances, kitchen andutility equipment, electronic equipment,artificial lighting, and occupants. Heatlosses from stoves or boilers alsocontribute towards the overall spaceheating requirement as long as they arepositioned within the building envelope.Occupants of the building alsocontribute to meeting the heat load; a

page 16

Correctly insulated house avoiding thermal bridge.Source: Passivhaus Institut, Germany

Timber frame house pre-cladding fitted airtightmembrane. Source: Passivhaus Institut, Germany.

Continuous Airtight Membrane. Source: Passivhaus Institut, Germany

There are two measurements used to define airtightness, namely cubic metres of airper square metre of exposed fabric per hour (m3/m2/hr) or air changes per hour (ACH).While the measured result for the former is generally 20% greater than that of thelatter, the difference is practice greatly depends on the building form.

Example to convert:

The prototype house in section 3 has a volume of 503.40 m3 and a total envelope areaof 324.21 m2.

The blower door test result is assumed, with 0.6 ac/h @ 50 Pa

503.40 m3 x 0.6 ac/hr / 324.21 m2 = 0.47 m3/m2/hr


typical adult human continuously emits100W of heat when stationary. A familyof five persons, therefore, can emit up to0.5 kW of heat. This may seem like asmall amount but it equates to approxi-mately one third of the total space heatload for the prototype passive housepresented in Section 3.

Risk of OverheatingPlacing extensive areas of glass on thesouth facing façade in a well insulatedand airtight dwelling might lead tooverheating in warm sunny days. ThePHPP software will alert the designer toany risk of overheating by calculatingthe frequency of overheating andexpressing this as a percentage of theyear in which the internal temperature inthe house rises above 25˚C. If thefrequency of temperatures over thiscomfort limit of 25˚C exceeds 10% of theyear (measurement referring to hoursrather than days), additional measuresfor reducing overheating should beincluded in the dwelling. To preventuncomfortable indoor temperatures in apassive house dwelling it is recom-mended to specify shading devices(blinds, overhangs or awnings, etc.)which will let the low sun enter thehome in winter but prevent the high sunentering in summer.

In the first Irish passive house in Wicklowshading was not in place on south facingglazing during the first summer and thehouse did overheat. A balcony wasinstalled ahead of the second summer,which significantly reduced thefrequency of overheating. In mid-summer when the daylight hours are

long the sun only enters the building inthe middle period of the day whileduring winter when the daylight hoursare short the low sun completely illumi-nates the entire interior of the building.

In the temperate climate in Irelandwhere external temperature rarelyexceeds 25˚C, the risk of overheating canbe easily avoided by careful considera-tion of shading devices and provision ofopenings for natural ventilation incombination with thermal mass insidethe dwelling (exposed concrete floor;masonry wall, etc.). In some cases themechanical ventilation system could beused to distribute fresh air throughoutthe building by switching to a ‘summerbypass’ setting. This however should beavoided where possible as the ventila-tion system will consume electricityresulting in increased primary energy. Itis preferable that the dwelling designershould employ ‘passive’ cooling strate-gies to minimise overheating.

2.2.2 Passive House Building Systems

As indicated earlier a passive housedoes not need a conventional spaceheating system of radiators or under-floor heating to maintain a comfortableindoor climate. Instead, typically, thefollowing building services are requiredin a passive house:

� Mechanical ventilation system withheat recovery which provides mostof the space heat requirement

� Backup system capable of heatingthe air passing through the dwellingvia mechanical ventilation to meet

Source: Climate Data for the Determination of Passive House Heat Loads in Northwest Europe, J. Schnieders,Passivhaus Institut, pp.17.

No more than 0.6 air changes/hour at 50 Pascalpressure should be observed in accordance with thePassivhaus Standard. This should be checked forcompliance with a blower-door test which willimmediately highlight leaky areas. Airtightness can beachieved through the use of membranes, roofing feltsand plasters combined with sealants and vapour diffu-sion resistant materials.Source: UCD Energy Research Group

Location of overhang and balcony. Source: MosArt Architecture.

Lighting contributes towards internal heat gains.Source: MosArt Architecture.

02468

1012141618202224

0 10 20 30 40 50 60

Area South Facing Windows [m2]

Spac

e H

eat D

eman

d / H

eat L

oad

Space Heat Demand [kWh/(m2a)]

Heat Load [W/m2]

Ireland - Birr

U-Value Wall = 0.175 W/(m2K)U-Value Window = 0.85 W/(m2K)

Deep roof overhang shadesupstairs windows

Balcony shades downstairs windows


any auxiliary space heating needs,expected to be small. Typical fuelsources for the back up systeminclude biomass, gas, and in someinstances electricity (for example‘green electricity’ from renewablesources). The back up system is alsoused to provide hot water, eitherthroughout the year or duringwinter if a solar water heatingsystem is used during summer.

Each of these items is dealt withseparately in greater detail below.

Given the lengths to which the designerand builder must go to in terms of ensur-ing a highly insulated building envelope,excellent airtightness and minimalthermal bridging, it is important that thebuilding services in a passive house areas energy efficient as possible. This isespecially critical in the case of themechanical ventilation heat recoverysystem. Therefore, the requiredefficiency of the mechanical ventilationsystem with heat recovery for a passivehouse dwelling is at least 75%. It is alsovery important to consider comfort,health and safety issues in the design ofthe building services for a passive house,ensuring for example that the backupheating system is adequately sized todeal with extreme weather conditions,that filters in the ventilation equipmentare replaced regularly and that there isan independent fresh air supply for anycombustion devices such as a boiler.These and other issues are dealt with ingreater detail below.

Mechanical Heat Recovery Ventilation(MHRV)An airtight house requires a well-designed mechanical ventilation systemto provide good indoor air quality. Apassive house is ventilated using amechanical system which incorporatesair to air heat recovery (mechanical heatrecovery ventilation, or MHRV). Exhaustair is extracted from rooms that typicallyproduce heat, moisture and unwantedodours such as kitchens and bathrooms.Before this air is expelled to the outsideit passes through a heat exchangerwhere the heat is transferred to theseparate stream of incoming fresh air,thereby eliminating the need tocompletely heat the fresh air as it entersthe building. It is important to appreci-ate that the stale exhaust air and clean

fresh air do not mix in the heatexchanger and therefore there is no riskwhatsoever of what might be referred toas ‘sick building syndrome’. Rather, thestale air and clean air is channelledthrough closely spaced but separatenarrow sleeves in the core of the heatexchanger.

Ventilation systems use electric powerand therefore have a slightly negativeimpact on the primary energy consump-tion. This will have affect the BuildingEnergy Rating. In our example in Section3, the energy used by the MHRV is about10% of the annual primary energydemand.

The benefits of having a whole-housemechanical heat recovery ventilationsystem (MHRV) are many, including:

� Constant supply of the correctamount of fresh air to all habitablerooms thereby reducing indoor CO2levels and removing the cause ofstuffiness and tiredness;

� Simultaneous extraction ofmoisture-laden air from bathrooms,utility rooms and kitchens as well asventilating noxious gases andunwanted smells if present; and

� A lowering in humidity levels reduc-ing mould and fungus that mayappear over time and decreasingdust mite levels.

There are databases (SAP Appendix Q orwww.passiv.de) in which various MHRVproducts are listed in terms of efficiencyand performance.

MHRV System EfficiencyThe efficiency of the heat exchanger inthe MHRV determines the amount ofheat that can be recovered from theexhaust air and, therefore, has a verysignificant influence on the additionalspace heating that may be required in apassive house. The aim is to use thewarm exhaust air to raise the tempera-ture of the cool fresh air to provide forthermal comfort all around the house.On a night where outside temperaturesare below freezing, the fresh air might beraised to, for example, 18˚C havingpassed through the MHRV. Theefficiency of sensible heat recoveryshould exceed 75% for the nominalrange of flow rates specified for the unitwhen measured in terms of the supply-

Photo depicting how the low winter sun enters theroom below the overhang/awning/balcony. Source: MosArt Architecture.

Schematic of the supply air ducts, the extract air ductsand the heat exchanger within mechanically venti-lated house. Source: Passivhaus Institut.

The sommer-bypass can be used for cooling in thesummer if needed. Source: MosArt Architecture.

Photo depicting how the house is shaded from the highsummer sun by the overhang/awning/balcony.Source: MosArt Architecture.


air side temperature ratio as described inEN 13141-7:20041. Specifiers and design-ers should be wary of products claimingextraordinary efficiency rates of 95% orhigher. The safest route is to installequipment that has been independentlytested and verified by such bodies as thePassivhaus Institut.

The graph below is based on actualtesting of the first Irish passive house inWicklow. It illustrates, for example, howmechanical ventilation ensures goodindoor air quality by removing the highconcentrations of a tracer gas that wasdeliberately released into the house aspart of the test procedure. In less than1.5 hours the air quality in the house hadreturned to normal.

Recommended Ventilation RateAccording to the Passivhaus Institut, theappropriate air change rate for dwellingsis between 0.3 and 0.4 times the volumeof the building per hour, with a generalrecommendation of leaning toward thelower rate. This maintains high indoor airquality while ensuring a comfortablelevel of humidity and maximizingenergy savings.

Compliance with the Irish BuildingRegulations Part F might require more airchanges per hour than the PassivhausInstitut recommends. It is possible toenter a higher air changing rate into thePHPP which consequently leads to a slightincrease of the energy consumption.

The PHPP software suggests that 30m3

per person per hour should be providedto dwellings to ensure good air quality.These two measurements can be used tochoose an appropriately sized machine

for different dwelling designs. Taking theprototype house presented later inSection 3 as an example, an occupancyof five persons would require 150 m3 offresh air delivered to the house per hour.In terms of extract, the PHPP softwareuses the following rates for differentroom types as default values, kitchen =60m3/h, bathroom = 40m3/h , shower =20m3/h and WC = 20m3/h. In the proto-type house these total 140 m3/h which isclose to the supply volume which willensure that the whole house system willbe balanced. The supply and extractvolumes can be accurately set by using adigital anemometer and adjusting thevalves on the vents in each room asrequired. A photograph of this process isshown below.

Adjustment of Fan Speed and ExchangeRateMost MHRV machines have differentsettings for different circumstances.These are often referred to as a ‘party’setting, where there are a lot of peoplein the house and where additional freshair is required, and ‘holiday’ setting,where the house is being left vacant andthe flow of air is reduced. Under normaloccupancy, the former of these settingswill use more energy and also decreasethe level of humidity whereas the latterwill use less energy and perhaps lead toan increase in humidity.

It is not advisable to constantly run theequipment on the lower setting just tosave energy when the house is occupied.MHRV machines uses surprisingly littleenergy given the important role thatthey play in the passive house. The PHPPsoftware uses a standard value of

0.45Wh for every m3 transported air inthe calculation of electricity (due toMHRV). When designing a passive housein Ireland the specific fan power shouldbe carefully considered as the electricityconsumed for fans has direct impact interms of primary energy performanceand hence the Building Energy Rating(BER). Therefore, specific fan power forfans should be less than 1 W/l/s .

Winter and Summer ModeThere are generally two ventilationmodes in a passive house: SummerMode and Winter Mode. In winter, theMHRV uses the heat in the exhaust air towarm the incoming fresh air. In summer,a bypass in the equipment can be set toopen automatically (controlled bythermostats) such that the incomingfresh air is not heated. Alternatively insummer natural cross ventilation may beused and the MHRV system can beswitched off.

Insulation and Positioning of Duct Workand VentsIt is very important to adequatelyinsulate the supply air ducting so thatthere is minimal loss of temperature indelivering warm air around the house.The thickness of insulation generallyused in passive houses is between 6 cmand 10 cm for ductwork. It is also prefer-able to locate the ducting within thethermal envelope and to keep pipe runs

page 19

Ceiling air supply vent. Source: MosArt Architecture.

Graph depicting how mechanical ventilation ensures a good indoor air quality by removing the high concentrationsof tracer gas that were inserted into the house under test conditions. Source: UCD Energy Research Group.

IR C

once

ntra

tion

Hours

Using a digital anemometer. Source: MosArt Architecture


as short as possible by ideally position-ing the MHRV unit in the centre of thehouse. This requires careful planning at avery early stage of building design.

Vents are normally placed in the ceilingbut can also be placed in the wall ifnecessary. The air inlets are typicallydesigned to spread the air horizontallyacross the ceiling, minimising downwarddraughts. There should be a gap eitherunder or over the door of each room toenable the easy movement of air fromone room to the next. If doors are fittedtight without such a gap, rooms withexhaust vents would be under negativepressure and rooms with supply airwould be under positive pressure.

Noise Fan and valve noises can be almostcompletely eliminated by sound controlmeasures (e.g., vibration isolationmounts, low air speed and acousticlining in ducts). The grilles on ventsgenerally guide incoming air along theceiling from where it uniformly diffusesthroughout the room at velocities thatare barely perceptible. If the ventilationequipment is operating on a highsetting (‘Party Setting’) the noise of theequipment and the air flow may be more

noticeable. MHRV machines are gener-ally housed in a well insulated casingand noise should not be a critical issue.

Maintaining Good Air QualityIt is import

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