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Design Guidelines Multifamily

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  • 8/9/2019 Design Guidelines Multifamily


    EDR Multifamily DesignGuide for Energy Efficiency

  • 8/9/2019 Design Guidelines Multifamily


    This report was prepared by Paci c Gas and Electric Company and unded by Cali ornia utility customers under the auspices o the Cali ornia Public Utilities Commission. Neither Paci cGas and Electric Company nor any o its employees and agents:

    1. Makes any written or oral warranty, expressed or implied, regarding this report, including,but not limited to those concerning merchantability or tness or a particular purpose.

    2. Assumes any legal liability or responsibility or the accuracy, completeness, or use ulness o any in ormation, apparatus, product, process, method, or policy contained herein.

    3. Represents that use o the report would not in ringe any privately owned rights, including,but not limited to, patents, trademarks or copyrights.

    November 2009

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    Introduction ................................................................................... 2Unique Challenges and Solutions for Multifamily Energy Efficiency ..3Impact of Title 24 Code Requirements on Building Energy Use .........5Energy Efficiency Measures for Multifamily Buildings .....................9Non-Energy Benefits of Multifamily Energy Efficiency ............... .... 20Special Opportunities for Affordable Housing ........ ......... ......... ....... 22Resources for Designers and Product Specification ......................... 24

    List of Figures, Graphs, and TablesFigure 1: Multifamily Construction as Percentage of Total ResidentialConstruction in CA.............................. .......................... ....................... 2Figure 2: Time Dependent Valuation Graph ........................ .................. 5Figure 3: Diagram of Integrated Multifamily Design Process ................ 9Figure 4: Example of 15% Compliance Options AnalysisWeighing Windows, Duct Testing, and Hot Water Controls for aSample Project ....................... ......................... ......................... ......... 18Figure 5: Simple Payback Cost-Benefit Analysis Process .................... 19Figure 6: Average Percentage of Monthly Income Spent on Utilities 20Figure 7: Impact of an EEBUA ........................ ......................... .......... 23

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    According to the Cali ornia Department o Finances Economic Forecast, the number o multi-amily new construction units permitted in Cali ornia has grown rom 26% o all residential

    permits to around 40% between 2005 and 2007. Assuming this trend continues, Cali orniacould save an average o 1,155,521 kWh annually i just 10% o the newly constructed unitsexceed 2008 Title 24 standards by 15%.1

    This Multi amily Design Guide For Energy E fciency provides a summary o resources, methods,and tools to assist the design community in building more energy e cient multi amily build-ings. Energy e ciency in multi amily buildings is measured, regulated, and evaluated in Cali-

    ornia by both the Title 24 Building Energy Standards and the Title 20 Appliance Standards.

    This document ocuses on multi amily energy e ciency in an e ort to better understandappliance e ciency metrics and the various mechanisms or exceeding the minimum Title 24building standards.

    Architects, engineers, energy consultants and owner-developers with a basic knowledge o building science undamentals will learn how these subjects apply and are speci cally relevantto multi amily housing projects.

    1 Based on PG&E projections or estimated kWh savings or Cali ornia Multi amily New Homes program.

    D a t a f r o m t h e

    C a l i f o r n i a

    D e p a r t m e n t o f

    F i n a n c e s E c o n o m i c

    F o r e c a s t s h o w s

    t h a t o v e r a l l h o m e -

    b u i l d i n g i s d o w n ,

    b u t t h e p r o p o r t i o n

    o f m u l t i f a m i l y

    t o s i n g l e f a m i l y

    u n i t s p e r m i t t e d i n

    C a l i f o r n i a i s g r o w i n g .

    F i g u r e 1 :

    M u l t i f a m i l y

    C o n s t r u c t i o n a s

    P e r c e n t a g e o f

    To t a l R e s i d e n t i a l

    C o n s t r u c t i o n i n C A








  • 8/9/2019 Design Guidelines Multifamily



    There are several challenges unique to multi amily housing that owner-developers must over-

    come or energy e ciency to make economic sense. They can all be addressed, however, throughproper planning, good decisions, and early investment in energy e ciency.

    Various Multifamily Building Types

    Title 24 de nes a multi amily building as one that contains three or more attached dwellingunits. This de nition spans various multi amily building con gurations including low-rise,high-rise, mixed-use, and attached town homes, each o which require di erent approaches

    when making energy e ciency decisions. For example, the energy use pro les and energy e -

    ciency options or high-rise and mixed-use buildings di er rom those o single amily residen-tial construction. High-rise multi amily projects ( our or more habitable foors) are regulated by the non-residential energy code or envelope and Heating, Ventilating, and Air Conditioning(HVAC) measures and the residential code or water heating and lighting. Also, mixed-usespaces, such as o ces, retail, and recreational acilities, which are o ten included in multi amily buildings, are covered by non-residential code and construction practices.

    Split Incentive

    Multi amily developers o ten overlook investing in energy e ciency i they do not directly bene t rom the resultant monetary savings. When the tenants bene t nancially rom energy e ciency decisions paid or by the owner, it is called a split incentive. What many owners anddevelopers o ten ail to realize, however, is that an energy e cient building with documentedlower utility costs and higher occupant com ort levels can provide indirect bene ts such asdecreased vacancy rates, reduced turnover, an edge over the competition, and, in some cases,higher than average rent.

    An investment in energy e ciency is more likely to occur in cases where the owner-developermaintains control o the property and pays or the utilities, since it typically proves to makegood economic sense. There ore, both the eventual ownership structure and the utility bill

    payment system play a signi cant role in equipment and system selection during design.

    Shared Systems vs. Individual Systems

    Multi amily buildings o ten have a combination o shared and individual systems serving theHVAC and domestic water heating (DHW) needs o the dwelling units. It is common to have acentral boiler provide hot water and sometimes space heating as well. At the same time, cooling


  • 8/9/2019 Design Guidelines Multifamily



    may be provided through local an-coil units. For large multi amily buildings, the decisionabout which systems to choose is dependant on several actors such as rst costs, maintenancecosts, and allowing tenants local control over their indoor environment.

    Energy Use Schedules

    Energy use schedules in multi amily buildings are not as predictable as, say, an o ce building, where one can assume people are working between certain hours o the day and that the spaceis unoccupied outside those hours. In residential buildings, the uncertainty o occupancy timesmakes it di cult to estimate peak demand or energy use. Within a given dwelling unit, it isdi cult to predict how much energy occupants will use, both in terms o duration o energy use and operation o systems. Occupant behavior impacts the building energy use independento the technical e ciency o the system.

    Water Heating as a Higher Percentage of Total Energy Budgets

    Another key aspect o multi amily buildings is that, when considering the combined elec-tric and gas budget or space heating, cooling, water heating, lighting, and process loads, theenergy used to heat water is typically a higher percentage o the overall energy use than inother building types. While water heating is a standard necessity in both single amily andmulti amily residential buildings, it is a larger portion o the total energy bill in multi amily buildings due to increased occupant density and reduced building envelope areas. In areas

    where there is not a signi cant heating or cooling load, such as Cali ornia climate zones 3 and5, the dominance o the water heating energy use over the other energy uses becomes even

    more signi cant.

    For these reasons, it is important to take an integrated approach to the complex multi amily building and system design so that incremental rst costs are minimized and the long-termenergy e ciency o the building is maximized. This document provides in ormation on strate-gies to achieve this integrated design while maintaining cost savings.

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    The multi amily building sector was not included in Cali ornias Building Energy E ciency Standards (Title 24, Part 6) prior to 1998. Between 1998 and 2005, several loopholes incode provisions signi cantly reduced the e ectiveness o Title 24 regulations or multi amily buildings. By correcting and clari ying most o these loopholes, the 2005 code change signi -cantly raised the bar or energy e ciency in multi amily buildings. Overall, the 2005 standardsincreased the energy e ciency o a minimally compliant multi amily building by about 24.3%

    or electricity usage, 25.8% or electric demand usage, and 15.7% or gas usage over that o aminimally compliant building under the 2001 standards.

    The 2008 energy code, e ective August 1, 2009, urther raises the bar with new roo ngper ormance requirements, more stringent minimum per ormance requirements or enestra-

    tion, and additional HERS measures. The changes require new multi amily buildings to useapproximately 19.7% less electricity, 7.4% less demand electricity, and 7.0% less gas than wasstandard or a home compliant with 2005 standards.

    Time Dependent Valuation (TDV)

    Time Dependent Valuation (TDV) was introduced with the 2005 Title 24 standards. TDV changed how energy is valued based on the time o day, the time o the year, and the build-ings climate zone. It plays an integral role in the energy budget calculation or the per ormancemethod by assigning high values or on-peak electric savings (e.g. summer a ternoons) and low values or o -peak electric savings (e.g. nighttime).

    In the 2008 Title 24 code, the di erence in valuation o electricity on-peak versus o -peak is larger.

    F i g u r e 2 :

    G r a p h i c a l

    I l l u s t r a t i o n o f

    Ti m e D e p e n d e n t

    Va l u a t i o n G r a p h

    Time DependentEnergy Value in 2008Standards

    Flat Energy Value used in2001 standards

    With at energy value a kWh saved isvalued the same for every hour of the day

    TDV places a higher value on a kWh saved during a high-cost peak hour than that saved during an off-peak hour

    E n e r g y

    V a l u e

    Monday Friday

    Time DependentEnergy Value in 2005Standards

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    Consequently, there is greater Title 24 compliance credit given to peak electric energy savingmeasures, like high energy e ciency ratio (EER) air conditioners and low solar heat gaincoe cient (SHGC) windows, versus measures that save energy o -peak. Conversely, TDV results in greater Title 24 compliance penalties or building eatures that cause increased energy consumption during on-peak periods, such as a disproportionately higher percentage o glazing

    on west- acing acades and oversized, un-shaded windows or skylights.

    Home Energy Rating System (HERS) Measures

    Each new cycle o the Title 24 Standards increases the emphasis placed on site veri cationper ormed by a certi ed HERS Rater. HERS Raters provide a valuable quality assuranceservice, ensuring that the equipment or envelope measure speci ed in the energy calculation isactually installed in the building.

    The 2008 code includes a list o new HERS veri cation measures. For example, the standardsno longer acknowledge a thermal expansion valve inspection in place o a re rigerant charge test.The presence o a re rigerant charge light indicator display, however, may now be veri ed in placeo the re rigerant charge test. Other new HERS veri cation measures include testing air handlers

    or air leakage, veri ying cooling coil airfow, and exchanging quality insulation installation orspray polyurethane oam, all spin-o s o HERS measures included in past codes.

    The ollowing graphic illustrates changes to those measures requiring HERS veri cation.

    2005 HERS Measures

    Reduced Duct Leakage

    Supply Duct Location and Deeply Burried Ducts

    Duct Sur ace Area and R-value

    Improved Re rigerant Charge

    Thermostatic Expansion Valve

    Air Handler Fan Watt Draw

    High EER

    Maximum Cooling Capacity

    Adequate Air ow

    Building Envelope Sealing

    Quality Insulation Installation

    New or Revised Measures or 2008

    Low Leakage Air Handlers

    Re rigerant Charge Indicator Light Display (CID)

    Verifed Cooling Coil Air ow

    Evaporatively Cooled Condensers

    Ice Storage Air Conditioners

    Quality Insulation Installation or Sparay Polyurethane Foam

    PV Field Verifcation Protocol

    Measures Removed rom HERS Testing in 2008

    Thermostatic Expansion Valve

    Adequate Air ow

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    Envelope Measures

    2008 Title 24 revisions tightened envelope e ciency requirements by adding per ormancerequirements or roo ng materials and increasing window e ciency standards.


    The 2008 Title 24 requirements are more stringent or glazing U- actor requirements inall climate zones, while SHGC requirements have been lowered in some climate zones. A new National Fenestration Rating Council Component Modeling Approach (CMA) is now allowed or modeling o site-built enestration without physical testing.

    Other 2005 Title 24 prescriptive requirements remain unchanged in the 2008 Title 24 stan-dards, including:

    West- acing window-to-foor ratios exceeding 5% result in a compliance penalty or low-rise buildings. In high-rise buildings, west- acing window-to-wall ratios exceeding 40%

    result in a compliance penalty.For both low-rise and high-rise buildings, window area o the proposed building iscompared to a standard design with identical window area.


    In 2008 Title 24, maximum prescriptive U- actors or high-rise residential envelope assemblies were revised in certain climate zones. Consequently, metal- ramed walls and screw down metalroo s without thermal blocks now require continuous insulation to meet the new requirements.

    The 2005 Title 24 regulation de-rating the e ective R-value o an envelope assembly by approx-imately 13% or standard insulation installation in low-rise residential buildings remains in

    orce with the 2008 standards. This addresses the poor quality o typical insulation installationand the resultant decrease in overall R-value o the assembly.


    Under the 2008 Title 24 code, there are new prescriptive standards or the thermal emittanceand refectance o roo ng products. The most signi cant change includes speci cations orsteep-sloped roo s, making them similar to the previous requirements or low-sloped roo s.The refectance or the roo ng product must now be aged-refectance, which is the refectanceestimated a ter three-years o eld use o the product, rather than refectance o a new roo .

    For high-rise buildings, these requirements apply to:

    Low-sloped roo s in climate zones 10, 11, 13, 14, and 15 For low-rise buildings, they apply to:

    Low-sloped roo s in climate zones 13 and 15Lighter weight steep-sloped roo s in climate zones 10 through 15Heavier weight steep-sloped roo s in all climate zones

    In addition, a new Solar Refective Index (SRI) calculator allows some trade-o s betweenrefectance and emittance lower than 0.85.

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    Central Domestic Water Heating

    In the 2008 Title 24 standards, additional requirements or central water heating systems ensuremore e cient operation. They include new mandatory requirements or either the installationo an air release valve on a riser immediately upstream rom the pump or the attachment o the

    pump on a vertical section o pipe to avoid pump ailure rom air pockets in the recirculationloop. A hose bib must also be installed immediately downstream o the pump to allow thepump to be primed a ter maintenance and isolation valves must be provided to allow or easy removal o the pump. In addition, 2008 Title 24 includes a new mandatory requirement toinstall a check valve on the cold water make-up line into the heater to minimize crossover fowsbetween hot and cold water pipes.2


    HVAC requirements or the 2008 code are designed to reduce peak load. These include:

    Credit or high Energy E ciency Ratio (EER) with HERS eld veri cation A mandatory minimum Seasonal Energy E ciency Ratio (SEER) o 13.0 or small airconditioners and heat pumps based on the 2007 ederal appliance standardsIncreased prescriptive duct insulation R-values (except climate zones six through eight)Prescriptive duct testing in high-rise buildings

    Since the residential standards are requiring a tighter building envelope, there must also bea way o ensuring healthy air changes within a home. Consequently, 2008 code additionsinclude mandatory whole-house mechanical ventilation. Mechanical ventilation requirements

    also include proper sealing o walls between garages and the house and exhausting bathrooms,clothes dryers, and HVAC combustion to the outdoors.

    The 2005 code option or HERS veri cation o a thermal expansion valve in place o a re rig-erant charge test in split system air conditioners was traded or the presence o a re rigerantcharge light indicator in the 2008 prescriptive standard.


    Mandatory lighting measures require that general lighting xtures in bathrooms, garages,laundry rooms, and utility rooms are either high e cacy or controlled by occupancy sensors.

    Additionally, the total wattage rom installed high-e cacy xtures in kitchens must equal orexceed that o the installed wattage rom low-e cacy incandescent xtures.

    2 2008Title 24, section 113(c)5

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    Mandatory Minimums, Prescriptive, andAbove Code Performance

    Cali ornias energy code sets orth mandatory minimum requirements or building envelope,mechanical equipment, and lighting that applies to all residential projects, regardless o climatezone, statewide. In addition, a project must meet the appropriate prescriptive minimumrequirements or each o the sixteen Cali ornia Energy Commission (CEC) de ned climatezones to receive a building permit. I a building deviates rom the compliance constraints o theprescriptive approach or shows per ormance beyond code minimum, the whole building mustcomply with the per ormance approach. When a project intends to go beyond code with theper ormance approach, it is measured in terms o percent better than standard. From 2001 to2011, statewide utility residential new construction programs and the ENERGY STAR orHomes Program and have set 15% better than standard as the next incremental step towardsachieving energy e ciency. Regardless o whether or not a project is participating in a utility-sponsored energy e ciency incentive program, each high-e ciency multi amily project mustutilize the whole building per ormance approach to demonstrate compliance with their better-than-code goal.

    In Cali ornia, EnergyPro and MICROPAS are the so tware tools approved by the Energy Commission to model buildings or per ormance compliance with residential Title 24 require-

    ments. An energy consultant typically uses these so tware programs to prepare documents thatdemonstrate the building design meets or exceeds Cali ornias Title 24 Building Energy Standards.

    Integrated Design Process

    F i g u r e 3 : D i a g r a m

    o f I n t e g r a t e d

    M u l t i f a m i l y D e s i g n

    P r o c e s s

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    Integrated energy design is an approach that looks at building components as part o an inte-grated and interactive system rather than stand alone components. Since the building designand construction o multi amily buildings involves numerous trade disciplines in the decisionmaking process, integrated design requires close collaboration between the owner-developer,architect, mechanical engineer, electrical engineer, energy consultant, and a utility or energy

    e ciency program representative. Energy e ciency objectives and decisions also need tobe conveyed to contractors, purchasers, construction superintendents, nancing teams, andleasing agents.

    Design charrettes, brainstorming, and decision-making sessions are an e cient and e ective way to gather the expertise o the projects contributors, encourage them to establish the scopeo the project, and acilitate them in creating an integrated solution. With common energy e -ciency goals established in an early design phase charrette, an energy consultant can calculatea rough model o the expected building energy consumption. Per orming a building simula-tion early in the design phase establishes the buildings basic energy e ciency pro le withinits climate zone and site. Additionally, these models in orm the building geometry with theoptimal speci cations or essential parameters, such as window orientation and area, which aidsin decreasing the need or mechanical systems and per ormance elements, like HVAC sizingand windows. Upon making some intuitive decisions about the interaction o these systems,the design team will use the building simulation tools to assist in the decision-making processduring design development. To evaluate the options produced by the building simulation tools,cost-bene t analyses are also used to make nal decisions about design and speci cations.

    Following are essential topics to cover during a charette to help ensure that energy e ciency isanalyzed comprehensively:

    Optimize long-term energy cost savings through energy e ciency Establish unding and nancing criterion, such as LIHTC, to be included in the projectIdenti y measure combinations that result in optimal energy e ciency Consider utility and other incentives and rebates to reduce rst costsUse cost analysis tools to evaluate the cost-e ectiveness o measuresConsider on-site generation to complement energy e ciency Identi y green marketing opportunitiesDont orget the non-energy bene ts o energy e ciency

    Energy Efficiency Measure Selection

    There are various means to cost-e ectively achieve whole building energy e ciency. Using apackage o measures speci c to each building, its respective climate zone, and site layout is o tenthe most practical mechanism to go beyond the Title 24 requirements. While certain energy e ciency measures have predictable per ormance in speci c climates and building prototypes,no two buildings are exactly the same. Each building needs its own customized set o measuresthat meet both the energy e ciency and cost-e ectiveness criterion. Cost-e ectiveness is a

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    simple comparison between two economic elements rst costs and long-term energy savings. A cost-e ective solution is one that uses a combination o measures that provide com ortto the occupants, reasonable up- ront costs or the owner-developer, and lowered long-termenergy usage.

    Designing the most cost-e ective high-e ciency buildings requires the project team to eval-uate packages o measures by comparing their up ront costs against their energy savings overthe li etime o the building, rather than selecting individual measures in isolation. Per ormingmultiple building simulation runs with di erent combinations o measures establishes thesensitivity o particular measures in that building. This parametric analysis gives the designteam an understanding o the most cost-e ective measures to achieving greater energy e -ciency. The resultant building will include a package o climate-appropriate measures whereeach individual measure per orms optimally and acts in synergy with the others.

    Next we will look at some o the common measures used to increase energy e ciency in multi-amily buildings and how to choose an appropriate package o measures or a speci c project.

    Site ConsiderationsEvery building site comes with a unique set o climate conditions. The two main site aspectsthat impact energy per ormance are sun and wind, which directly a ect the orientation andexterior envelope o a building. Creating a building design that responds optimally to siteinfuences should be considered early in the design process so as not to miss this opportunity

    or cost-e ective energy savings.

    Optimal shape and building orientation decrease the need or heating, cooling, and electriclighting. Although there is some additional time required in the design phase, these measurescan yield the most cost-e ective energy savings because there are no associated material orinstallation costs, as there are with mechanical measures, and the consequent savings accumu-late over the li etime o the building.

    The general idea is to maximize solar gains in winter and minimize them in summer, especially in the a ternoons. Orienting larger sur aces to the north or south and shading windows on thesouth are the most common mechanism o ensuring energy savings through this method. Toprovide protection rom wind and reduce ambient temperatures, one can also take advantageo natural shading eatures on site, such as trees, hills, and surrounding buildings.

    Building envelope

    Building pro essionals call the outer layer o a building the building envelope because itenvelopes the interior living space. This outer layer includes walls, roo s, foors, windows,doors, and skylights. The building envelope is the primary source or solar heat, light, and airto enter and exit the building. Thus, envelope e ciency is a principal determinate o heatingand cooling loads in a building.

    A n e x c e l l e n t

    r e s o u r c e

    f o r C l i m a t e

    R e s p o n s i v e

    D e s i g n i s t h e E D R

    p u b l i c a t i o n t i t l e d

    D e s i g n F o r Yo u r

    C l i m a t e

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    Quality Insulation

    Insulation is used in combination with building materials that readily trans er heat, such asbrick, concrete, or wood, because o its ability to resist heat fow. The energy per ormancespeci cation or insulation in low-rise residential buildings is the R-value, a measure o a mate-

    rials resistance to conductive heat trans er. The minimum prescriptive R-values (see Section151, Table 151-C o the 2008 Title 24 standards or detailed speci cations) vary by climatezone and are highest in those with extreme temperatures, such as climate zone 1 and 11-16.Installing insulation with a higher R-value than what is prescriptively required by Title 24 canbe a cost-e ective method to achieve a per ormance credit.

    For high-rise residential buildings, the metric used or insulation per ormance is the U- actor, which is the metric or how much heat is transmitted through the construction assembly. Thus, while higher is better or R-value in terms o energy per ormance, lower is better or U- actor.The maximum prescriptive U- actors vary by climate zone and by construction assemblies(wood- ramed vs. metal- ramed vs. heavy mass).

    When calculating the overall R-value o the construction assembly, the R-values or each indi-vidual envelope components are added together to calculate the overall resistance to heat fow o the assembly. When calculating the overall U- actor o the construction assembly, the inverse

    or each individual envelope component is added together. The overall U-value is then thereciprocal o the result (ie. 1/Ua + 1/Ub = 1/Utotal). This resistance can be compromised,however, and is much lower than the speci ed level o insulation when insulation is not prop-erly installed. The most common faws that degrade thermal per ormance in insulation instal-lations are:

    The insulation is not in contact with the air barrier, creating air pockets through whichconvective air movements allow additional heat trans er, bypassing the insulation andreducing overall energy per ormance. On the exterior envelope, the air barrier is gener-ally the back o the drywall.The insulation has voids or gaps, resulting in portions o the construction assembly thatare not insulated.The insulation is compressed, creating a gap near the air barrier and/or reducing thethickness o the insulation.

    For low-rise residential buildings, these common problems o sub-standard insulation installa-tion are addressed with the Quality o Insulation Installation (QII) HERS measure or wood

    ramed walls, ceilings, and roo assemblies (foor assemblies are not included). A standardR-value calculation method is applied or the e ective value used in Title 24 compliance. I the insulation on a building is not to be inspected by a HERS rater, then this standard value isreduced by 13%. I the insulation is to be inspected by a HERS rater ollowing the procedureso the QII HERS measure, a Title 24 compliance credit is available that restores the e ectiveR-value to the standard calculation value.


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    The QII measure veri cation is similar to the process set orth by the EPA in their ThermalBypass Checklist (TBC) requirement. This checklist identi es the sixteen areas where heatmost commonly bypasses the insulation. These must be veri ed by a HERS rater in order or abuilding to meet the minimum requirements or certi cation as an ENERGY STAR home.

    Air Sealing (Reducing Infltration)

    In ltration is the unintentional exchange o conditioned air with unconditioned air throughcracks and leaks in the building envelope. Loss o conditioned air and the subsequent need tocondition the newly in ltrated air represents a signi cant loss o energy. HERS veri cation by a blower door test ensures that cracks and other leakage sources are sealed. Additionally, airsealing produces non-energy bene ts by preventing undesirable moisture in ltration, makingliving spaces dra t ree, and greatly improving com ort.

    Radiant Barrier

    A simple and cost-e ective solution to block the suns heat rom penetrating the roo andheating the attic is a radiant barrier. A radiant barrier can reduce attic heat by up to 30% andblock up to 97% o radiant heat gain, saving energy and increasing com ort.3 Additionalenergy savings are achieved in homes where the HVAC and ductwork are within an attic space

    with a radiant barrier because it reduces heat gain otherwise incurred by this equipment. Theessential characteristic o radiant barriers is that they are high refectance and low emittancematerials. A radiant barrier can have refective sur aces on one or two sides. I a one-sidedradiant barrier is installed, it must ace an air space to be e ective.

    Radiant barriers are most e ective in hotter climate zones and low-rise buildings. When incor-porated into a well-thought-out energy e cient design (i.e. with a whole building approach)that can be documented through a building energy simulation program, air conditioners canbe down-sized, which signi cantly reduces rst costs.

    GlazingWindows, Doors and Skylights

    Windows, doors, and skylights transmit daylight, which brings health and a sense o well-beinginto our homes. They also bring a connection to the outside world and the cycles o day andnight, winter and summer. However, a single pane glass window, commonly ound in oldermulti amily buildings, has insulation properties that cause it to lose heat ten to twenty times

    aster than a well-insulated wall. The introduction o dual-glazed windows was a great improve-

    ment, almost doubling the insulating value.

    The overall size o the window itsel is a key energy per ormance metric. Larger window areae ectively means larger heat fows between the indoors and outdoors, even when using the best

    windows possible or a given climate (since insulated walls are better than the best windows interms o thermal per ormance).

    3 Radiant Barriers. ToolBase Services. 8 July 2008http://www.toolbase.org/Technology-Inventory/Roo s/radiant-barriers


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    The orientation o windows also impacts energy usage in a building. Windows acing southand west have more solar gains than those acing north and east. Large west- acing windowsare the least energy e cient window design. To this e ect, Title 24 has limitations on total

    window area as a percentage o total foor area or low-rise and o total wall area or high-risein the prescriptive approach.

    The National Fenestration Rating Council (NFRC) provides comprehensive ratings o window,door, and skylight thermal e ciency. Their enestration evaluation system identi es three basicproperties to consider or energy per ormance calculations:

    Insulation value (U- actor): a measure o conductive heat trans er that results rom adi erence in air temperatures between the outside and insideSolar Heat Gain Coe fcient (SHGC): a measure o heat trans er rom direct or indirectsolar radiation that is independent o air temperature

    Visibility (Visible Transmittance or VT): although not a measure o energy per or-mance, it is an important consideration when selecting a window; the choice o U-Factorand SHGC will usually a ect the VT o the window

    Adjusting the U- actor and SHGC has signi cantly di erent e ects on the energy per ormancedepending on whether the building is in a heating-dominated or cooling-dominated climate.

    In cooling-dominated climates (inland hotter regions), reducing the SHGC will providelarger energy savings than lowering the U- actor. This is because the heat rom direct solarradiation coming through windows is a magnitude larger than the heat rom conductionthrough windows.

    In heating-dominated climates, on the other hand, a reduced U- actor has a relatively largere ect on reducing heating energy. This occurs because any heat gains rom solar radiation are

    welcome in cold climates, whereas heat losses due to heat conduction rom the warm interiorsto the cold outdoors contribute to higher energy use.

    Window selection is not as simple as selecting a window with the best, i.e. lowest, per or-mance values. Each climate zone and building will have its own characteristic mix o heatingand cooling days throughout the year and the best energy e ciency measures will vary accord-ingly. Only computer simulation, either with specialized window programs like RESFEN and

    Window5 or whole house simulation programs, can provide climate- and building-speci cguidance or the optimal SHGC and U-value.

    Heating, Ventilation, and Air Conditioning (HVAC)

    Purchasing a heating and cooling system or new and existing multi amily homes represents amajor cost decision. More o ten than not, the owner-developer needs to rely on pro essionalexpertise or guidance. Since the li etime cost o running heating and cooling equipment cansurpass the cost o the home itsel , it pays to get the selection right the rst time.

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    Improving energy e ciency with high-e ciency equipment and distribution systems doesnot have to result in unacceptably higher rst costs. When combined with e cient buildingenvelope measures and an accurate building load calculation, mechanical equipment can beproperly sized and the resulting cost savings can help pay or other energy e ciency measures.Common techniques or HVAC energy e ciency are the use o higher e ciency equipment,

    correct sizing o air conditioners, proper duct system design and installation, reduced airhandler an power, and adequate airfow over the indoor coil.

    Selecting the right system is o ten based on prior experience and rst costs, not a rational energy e ciency decision. Do not allow your project to all into this de ault. Not all systems are equalenergy users; central air conditioners, such as split or packaged systems, and heat pumps areavailable in higher e ciency ratings than smaller, room air conditioners. Heat pumps, orexample, tend to be 40-50%4 more e cient than electric resistance baseboards because 1) theheat generated is immediately trans erred to the air stream and delivered (presumably) to thecorrect location and 2) the heat trans er takes place in an enclosed environment, so more heatis trans erred to the air stream.

    High-e fciency HVAC Equipment

    The simplest approach to improving equipment e ciency is to choose ENERGY STARlabeled equipment. Higher e ciencies can be attained by consulting online resources such asthe Consortium or Energy E ciencys (CEE) Directory o ARI Veri ed Equipment, whichgroups equipment in e ciency tiers above and beyond those provided by ENERGY STAR.

    Also use ul is the Energy Commissions Appliances Database, which lists equipment certi edor use in the State o Cali ornia in a simpler spreadsheet ormat.

    SEER vs. EER Ratings Although the ederal standards look at the Seasonal Energy E ciency Ratio (SEER) rating,in Cali ornia, it is more important to select an air conditioner based on its Energy E ciency Ratio (EER) rating, especially in the hotter, inland regions. The test conditions or the EER rating are more like Cali ornias hot, dry climate than the SEER rating, making it a bettermeasure o energy e ciency per ormance in our area. The Energy Commission recognizes thisby rewarding high EER equipment with a much higher Title 24 credit than high SEER equip-ment. This credit is only available when a HERS Rater veri es that the system consists o theproperly matched components necessary to achieve the high EER rating.

    Correctly Sizing an Air Conditioner

    Using a rule o thumb approach or past experience to ballpark the equipment size typically results in an oversized air conditioning unit. Oversizing is common because it ensures against

    uture customer complaints that the equipment cannot adequately cool or heat one or morerooms. Oversizing, however, is a costly mistake, both in the infated rst cost o equipment

    with unnecessary capacity and in the long-term cost to run the oversized unit.

    4 As with any energy using system, savings will vary depending on climate and particulars o the building.

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    Heating and cooling equipment e ciency is based on properly sized equipment. When anHVAC unit is oversized, there is a signi cant e ciency cost because the equipment is shortcycling, i.e. cycling on and o o ten. This short cycling can increase wear and tear on theequipment, which reduces li e expectancy and increases maintenance costs. In addition, theoversized ans that blast hot or cold air creates uncom ortable dra ty conditions and unneces-

    sary noise in equipment that short cycles. Conversely, right-sized systems provide even heating,cooling, and quiet operation.

    The main bene ts, however, are cost and energy savings. Properly sized equipment can reduceenergy usage by as much as 35%.5 The bonus is the superior com ort that properly sized anddesigned systems can provide.

    Proper Duct Design and Installation

    HVAC equipment e ciency is only part o the equation or an energy e cient HVAC system.No matter how e cient the equipment is, i the distribution system is not also well designed

    and operating properly, the HVAC system as a whole will not be e cient.

    The rst step towards an e cient air distribution system is to include an ACCA Manual D ductdesign, or equivalent, as part o the construction documents. This will tell the HVAC installer

    where to install the supply and return registers and what sized ducts should be connected tothem. It will also provide critical external static pressure in ormation so the air blower canbe sized correctly. There is so tware available that can automatically calculate duct sizes andairfow requirements.

    Ducts in Conditioned Space When the duct design process starts early enough, providing time to negotiate duct locations with the architect and structural engineer, it is possible to locate ducts entirely within theconditioned space. This can be particularly cost-e ective as there are little to no incrementalcosts, apart rom advanced planning, detailing in the design stage, and coordination betweenthe trades during the installation stage. In multi amily construction, this strategy is best accom-plished by locating the duct system within a central dropped ceiling (so ted) area. The equip-ment is located in an adjoining closet or in the dropped ceiling itsel . One o the most impor-tant details o this approach is to maintain the so tted area within the thermal and air barrierso the conditioned space, which is o ten a required detail or re protection purposes. Ductsin conditioned space can also be accomplished by running the ducting in the structural spacebetween foors. This approach requires early consultation with the structural engineer because

    they generally require open web foor trusses.

    Sealed and Tested Ducts Duct systems that are not sealed can leak 20% to 40% o their conditioned air in new homesand as much as 40% in existing homes, wasting energy and increasing the cost to the consumer.

    When ducts are located in unconditioned space (e.g. attic), leakage o conditioned air rom

    5 Residential HVAC. Consortium or Energy E ciency. 8 July 2008http://www.cee1.org/resid/rs-ac/rs-ac-main.php3

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    supply and return ducts cause signi cant energy losses because there is less conditioned airreaching the intended space. The situation or leaky return ducts is urther complicated by thepotential risk to the health o the inhabitant. The air that is sucked in rom attics, crawl spaces,or other building cavities can be contaminated by dust, mold, chemicals, and/or airbornepathogens rom animals. It is there ore especially important to make sure that the return ducts

    are sealed.

    Sealed ducts save energy and money and improve indoor air quality. Duct sealing is assumed inthe baseline low-rise Title 24 building model or every climate zone. Buildings that do not havesealed and tested ducts are assumed to leak 22% o their conditioned air and receive a penalty in the code calculations. I a proposed building does not include sealing ducts, other measuresmust be used to o set the penalty.

    Water Heating

    Because a multi amily projects water heating energy budget o ten represents a signi cantportion o the overall energy budget, water heating systems have a disproportionately largeimpact on a projects overall energy per ormance. There are various system options andcomponents that can improve per ormance, and there ore several layers o decisions. Formost large multi amily buildings, a central water heating system with a recirculation loop isan e ective method o delivering hot water in a reasonable amount o time. A central systemallows maintenance to be carried out at a single location, whereas having individual waterheaters in units multiplies the number o locations requiring maintenance, creating many more locations within the building where leaks and water damage could occur. Addition-ally, central water heaters are typically more e cient than individual water heaters. In orderto increase the e ciency o the central hot water system, it is important to consider the


    E fciency o the boiler/heater: The ederal minimum and Title 24 standard or largegas boilers is 80% thermal e ciency. Simple atmospheric boilers can reach a maximumo about 82% thermal e ciency. Condensing boilers can attain thermal e ciencies upto 98% by capturing the sensible and latent heat rom the fue gases.Controlling energy use in recirculation loop pumps: Continuous pumping o hot

    water wastes energy by using electric energy when hot water is not needed. Installingcontrols, like demand and temperature modulation controls, that turn the pump o

    when hot water is not needed is an e ective energy e ciency strategy.Pipe location: Similar to ducts in unconditioned spaces, pipes (especially when un-in-

    sulated) can lose a signi cant amount o heat to the surrounding air or ground whenexposed to the outdoors or buried underground. The best location or pipes is within thebuilding envelope so that heat losses are minimized.Pipe insulation: It is important to insulate pipes, especially in unconditioned andsemi-conditioned locations. Underground pipes can cause massive heat loss due to thehigh conductivity o ground moisture, so they require special watertight insulation.In large hot water distribution systems, heat loss rom piping accounts or 15-25% o total domestic hot water gas consumption, so pipe insulation is an important means o reducing energy waste.

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    Combination of Measures

    By per orming multiple building simulation runs with di erent combinations o measures, thedesign team can determine the sensitivity o particular measures in that building. This kindo parametric analysis becomes use ul in later stages o design because the team as a whole hasa shared knowledge o where to expect the most cost-e ective measures or achieving greaterenergy e ciency.

    One o the things that building simulation so tware can accomplish, which is almost impos-sible without the calculation power o a computer, is to accurately evaluate the e ectiveness o multiple measures and compare those results with alternate combinations. For example, it is

    well known that a signi cant amount o the cooling load enters the living space through theroo /attic/ceiling areas in hot climates. One might think that by simply adding insulation, thecooling load could be controlled to any desired level. Insulation, however, is subject to the lawso diminishing returns. Building simulation models show that combining a radiant barrier

    with a comparatively lower level o insulation urther reduces cooling loads and is a more cost-e ective solution or a particular climate zone than maximizing insulation alone.

    It is important to remember that the goal o the integrated design process is not to use the moste cient measure or any given building element, but rather to seek the most cost-e ectivecombination o energy e cient measures. Economics is always a prime consideration whenselecting any set o measures. Only by balancing the elements o rst cost and energy savingscan one achieve a combination o measures that will provide com ort to the occupants, costsavings to the owner-developer, and low energy usage.

    As seen in this example, the same measure or combination o measures can result in widely divergent energy savings or di erent buildings having di erent envelope, HVAC, and sitecharacteristics.

    Conducting a parametric analysis that explores various options is the best way to determine themost e cient measure(s) or a given project.

    F i g u r e 4 : E x a m p l e

    o f 1 5 % C o m p l i a n c e

    O p t i o n s A n a l y s i s

    We i g h i n g Wi n d o w s ,

    D u c t Te s t i n g ,

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    Option 4 = DHW Temperature ControlsOption 3 = Tight Ducts Only

    Option 2 = High Eff Windows + Tight DuctsOption 1 = High Eff Windows

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    Cost-Benefit Analysis

    There can be multiple combinations o measures that will achieve similar levels o energy e -ciency or a building. However, this does not mean each combination is equally cost-e ective.

    A basic payback analysis is the simplest way to compare di erent energy e ciency options.

    The simple payback compares the initial purchase price ( rst cost) o the energy e ciency measures to the projected dollar savings the rst year the measures are in place. In most new construction projects and those where lower-e ciency equipment is installed without anenergy e ciency analysis, the rst cost is the incremental price di erence between the energy e cient measure and the code minimum or less e cient measure.

    For larger projects, or those where long term cost-e ectiveness is more important than rstcost savings alone, a Li e Cycle Cost (LCC) analysis is the best approach. Although energy e ciency rst costs can exceed those o conventional construction, the LCC o an energy e cient building is typically much lower. Generally, the energy savings in an e cient building

    will o set any up ront construction or installation costs.

    LCC = First Costs + Operational Costs + Maintenance Costs + Replacement Costs +

    Tenant/Occupancy Considerations Salvage Value

    Just as one should compare energy savings rom a combination o measures, one should analyzethe costs associated with the measure combinations and analyze the cost-bene t ratio or energy savings measures.

    Where Incremental LCC = LCC o Energy E fciency Measures LCC o Baseline Design.

    Incremental LCC ($)Energy Savings ($)Cost-Beneft Ratio =

    F i g u r e 5 : S i m p l e

    P a y b a c k C o s t -

    B e n e f i t A n a l y s i s

    P r o c e s s

    Incremental Measure Cost ($)Predicted First Year Energy Savings ($)

    Simple Payback (Years) =

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    Energy e ciency not only provides direct energy savings and lower energy bills, but also non-energy related bene ts such as:

    Greater Marketability or Market-Rate Housing: Market-rate multi amily builderscan di erentiate themselves by marketing their homes as energy e cient, whether by participating in a utility new homes program or meeting the ENERGY STAR labelingrequirements. According to a National Association o Home Builders (NAHB) survey,homebuyers are were willing to pay a median o $5,000 more up ront in the purchaseprice o their next home to save $1,000 every year in utility costs.ENERGY STAR or Homes Partnership Marketing Benefts: As ENERGY STARpartners, builders can use the US Environmental Protection Agency (EPA) produced

    marketing resources and technical resources at no cost. Some examples include:ENERGY STAR logos, partner locator listings, consumer brochures, act sheets, salestoolkits, outreach partnerships, awards, and recognition. For more in ormation on thesebene ts, visit www.energystar.gov/homes.Greater Opportunity or Increased Revenue: Energy e cient eatures can help toincrease revenue; the projected energy and utility cost savings may allow a homebuyer topurchase additional upgrades, thereby increasing builder pro t.Greater A ordability or A ordable Housing:The cost o housing includes both rentand utilities. On average, middle-income households spend about 5% o their monthly income on utilities, low-income households about 20%, and one out o every our low-

    income older person spends about 20% or more o their total income on home energy bills.6 Simply put, energy e ciency saves energy, lowers utility bills, and enhances long-term home a ordability.Increased Com ort and Enhanced Customer Satis action: Energy e ciency eaturesmake homes more com ortable; com ortable homes reduce customer complaints andcallbacks and improve customer satis action. High per ormance heating and coolingequipment help provide consistent temperatures, balance humidity, create proper airfow,improve indoor air quality, and run more quietly. High per ormance windows conductless heat and reduce dra ts to keep the homes temperature more consistent. They alsohelp to reduce the ading o carpets, foors, urniture, and drapes as well as reduce

    unwanted outside noise.Lower Maintenance: Energy e cient products are associated with higher per ormanceand lower maintenance.Quality Construction: Energy e ciency implies quality and high per ormance. Becausemany eatures in an energy e cient home, such as quality insulation installation or tightduct veri cation, require a third-party inspection, builders, tenants, and homeownerscan be con dent that the energy e ciency measures are installed properly.

    6 Karen Brown, Ex Dir, Colorado Energy Assistance Foundation. James Ben eld, Ex Dir, Campaign or HomeEnergy Assistance.

    F i g u r e 6 : Av e r a g e

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    A ordable housing and energy e ciency both o er solutions to some o Cali ornias, and thenations, most pressing social and environmental problems. While technical challenges remainin both areas, nancing mechanisms o ten prove to be the determining actor or success ul proj-ects. Many a ordable housing unding sources encourage energy e ciency in their nancingrequirements, o ten going as ar as o ering higher incentives or rebates or those projects thatincorporate energy e ciency. This convergence o public policy goals has resulted in a range o special unding rewards and opportunities or energy e cient a ordable housing projects.

    State and Federal Financial AssistanceTax Credits

    Low Income Housing Tax Credit (LIHTCs): One o the most important sources o unding

    or a ordable housing in Cali ornia, LIHTCs, are awarded to new construction and rehabilita-tion projects on a competitive points basis by the Department o the Treasury, The Departmento Housing and Urban Development (HUD), and the Department o Justice. O the 155 totalpoints required or eligibility, there are currently a maximum o eight points available or incor-porating sustainable measures, including energy e ciency. O those eight maximum points,there are six available or energy e ciency. In addition, there is discretionary unding, up to5% o the projects basis limit, or distributive energy technologies.

    Federal Energy E fciency Tax Credits: Federal Tax Credits or New Homes are available orsite built homes, excluding rental properties and non-pro ts.

    The builder receives $2,000 or each home whose per ormance is calculated to exceedHeating and Cooling Use o Section 404 o the IECCs 2004 Supplement by 50%.Homes must be built a ter August 2005 and purchased between January 1, 2006 andDecember 31, 2009.

    New Solar Homes Partnership: The Emerging Renewables Program (ERP), administeredby the Energy Commission, was created to stimulate market demand or renewable energy systems that meet certain eligibility requirements. The ERP o ers rebates to reduce the initialcost o the system or the customer in single and multi amily home new construction.

    Housing and Urban Development (HUD)Public Housing Authorities

    Public Housing Authorities (PHAs) play an active role in promoting energy e ciency ina ordable housing. When a ordable housing projects are unded through tax credits, the local

    I n a b i l i t y t o p a y

    u t i l i t i e s i s s e c o n d

    o n l y t o i n a b i l i t y t o

    p a y r e n t a s a r e a s o n

    f o r h o m e l e s s n e s s . 7

    7 Karen Brown, Ex Dir, Colorado Energy Assistance Foundation. James Ben eld, Ex Dir, Campaign or HomeEnergy Assistance.

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    housing authority sets the total housing burden, including rent and utilities, at 30% o thetenants income. The utility portion is determined based on an average level o e ciency ormulti amily buildings in the area, which includes those built be ore the introduction o energy e ciency standards. Rent is then calculated as the total housing burden minus utilities. Thisstandard Utility Allowance is arti cially high when applied to energy e cient projects.

    In July 2008, the IRS authorized the use o an energy consumption so tware model to deter-mine project-speci c utility allowances or new construction. This allows the owners o moreenergy e cient buildings to charge more rent without a ecting the total housing burden o the tenant. Thus, the owner-developer has a mechanism to recover some, i not all, o thecost to implement the energy e ciency measures. Additionally, the tenant receives a smallbene t since the Energy E ciency Based Utility Allowance (EEBUA) is only partially reduced,compared to the estimated energy savings (see Figure 7). In example below, owners rent incomeincreases $10/mo and tenants net utility costs decrease $2/mo without changing total calcu-lated housing burden.

    HUD Energy Action Plan

    The overall goal o the HUD Energy Action Plan is to reduce energy use in HUDs inventory o public and assisted housing and HUD- nanced housing by at least 5%. Public Housing

    Authorities, community planning associations, the Federal Housing Association, and otherregional and local partnerships are also involved in this plan.


    This Multi amily Design Guide For Energy E fciency is part o our new construction resourcematerials and tools the Heschong Mahone Group, Inc. is developing to assist designers andowner-developers o multi amily projects. These guides include:

    Multi amily Design Guide or Energy E ciency Case Study on Energy E cient Multi amily BuildingDesign Brie on E cient Central Water Heating in Multi amily BuildingsMulti amily Energy E ciency Training Slides

    F i g u r e 7 : E x a m p l e

    o f t h e P o t e n t i a l

    I m p ac t o f a n E E B U A

    Energy E fciency-Based UA

    Total Housing Burden $500/moUtility Allowance $90/moDeveloper Rent $410/moTenant Utility Costs $88/mo


    Standard UA

    Total Housing Burden $500/moUtility Allowance $100/moDeveloper Rent $400/moTenant Utility Costs $100/mo

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    Program Information

    US EPA ENERGY STAR Programwww.energystar.gov/homes

    Cali ornia Multi amily New Homes Program: SCE and PG&Ewww.h-m-g.com/multi amily

    Cali ornia Multi amily Energy E ciency Programswww.cali orniaenergye ciency.com

    www. yppower.com

    General Information

    Cali ornia Association o Building Energy Consultants (CABEC)www.cabec.org

    Cali ornia Multi amily Housing Consortium

    www.seiinc.org/m consortium.htmlHousing and Urban Development (HUD)

    www.hud.gov/o ces/cpd/energyenviron/energy/index.c mCali ornia Housing and Community Development

    www.hcd.ca.gov/Partnership or Advancing Technology in Housing (PATH)

    www.pathnet.orgUS Green Building Council (USGBC)


    Verification and HERS Rating

    Cali ornia Home Energy E ciency Rating System: www.cheers.orgCalCERTS: www.calcerts.comResnet: www.natresnet.org/herseems/ratingmethod.htmBuilding Commissioning Association: www.bcxa.org


    Energy-E cient Mortgages: Home buyers looking to buy energy-e cient homes can

    quali y or mortgages with more avorable loan terms www.pueblo.gsa.gov/cic_text/housing/energy_mort/energy-mortgage.htmSolar and Wind Financial Incentives & Tax Credits

    www.cali orniasolarcenter.org/incentives.htmlCali ornia Housing Finance Agency (CalHFA)

    http://www.calh a.ca.gov/multi amily/ nancing/index.htmUS DOE Building Technologies Program