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The importance of Software to calculate the ability of
Architecture to reduce energy demand in buildings
Abstract: The directive 2010/31 /EU determines that after December 31, 2018 , new buildings occupied
and owned by public authorities will be net zero energy buildings and after 31 December
2020 all new buildings.
We will reach this target using various energy calculation softwares , but how many tools are
there that enable us to meet the demands of building in a truly accurate way?I will try to
answer this question in the following paper.
Once energy building simulation approximates the real behavior of buildings it will be easier
to achieve the EU Directive.
It is important that this aproximation occur first at the demand level of the building , knowing
in depth all the architectural parameters and using tools capable to exploit to a maximum the
ability of architecture to reduce energy demands.
architecture, demand , efficiency, energy, software
Introduction
The entry into force of the core document HE , March 13, 2014 , allows the use of alternative
methods of calculating the energy consumption different from the Software established by the
Ministry (Lider-Calener).
According to these regulations, the calculation method used should enable us to break down
the energy consumption in primary energy (fuel or electricity) to meet the energy
consumption of each of the technical services (heating, cooling , ACS and , if necessary ,
lighting ) .
In parallel, the directive 2010/31/EU determines that after December 31 of 2018 , new
buildings occupied and owned by public authorities will be net zero buildings and after 31
December 2020 all new buildings, whether public or not.
This situation opens the door to the use of various energy calculation softwares, but how
many tools exist that enable us to calculate buildings demands in a trule accurate way?
When energy building simulation approximates the real behavior of the buildings, the faster
the fulfillment of the objectives set down by law will be.
It is important that this alignment occur first at building demands level, knowing in depth all
the architectural parameters and using tools capable to exploit the ability of the architecture to
reduce energy demand.
I try to work in this way using a case study of a real building (a residence) to determine how
far we can reduce the energy demand of the building, and then apply the results to buildings
in general.
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Image of the residence
To perform this study, at the same time monitor the residence, the residence has been
simulated with energy calculation tools (with an advanced energy calculation engine) and
finally the energy consumption of the residence has been compared with the model
simulation.
We need to add an extensive amount of information into the software to reduce the input
variables to provide information so that these programs can simulate reality and validate the
future projection of net zero buildings.
Information to calculate the demand
A proper balance between the cost of high-tech materials and equipment and the reduction of
whole-building energy consumption is critical when designing affordable low-energy
buildings. The most effective way to optimize the building envelope is to carry out parametric
analysis of all components.
To calculate energy demand in buildings, we naturally need information about the building.
First at all, we need to know the climate archive of the site. It is very important to use recent
weather data as near as possible to the site, together with air data, humidity, temperature from
the same year that as case study was made.
There are a number of architectural parameters that influence energy demand limitation. The
following architectural and material components and building characteristics will be
considered during this process:
- geometry and orientation of the building
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- overall thermal characteristics of the building shell
- application and configuration of thermal mass
- colour an type of the surfaces
- size and location of glazing
- solar gain control systems
- inherent air leakage characteristics of main building envelope
- natural ventilation
- infiltration of air into main building envelope
- solar protections, inside and outside
- internal loads, caused by human, lighting and equipment
- location of air ducts, etc.
There are some sure parametres, geometry and orientation, colour and type of surfaces, size
and location glazing….but there are other parametres that we don’t know with accuracy,
natural ventilation, inherent air leakage, internal loads, so we need to adjust the simulation
model to make one assumption, and to test the simulation model with the existing model.
Lider-Calener
Lider-Calener, includes a single platform unification of official general programs used to date
for the assessment of energy demand and energy consumption and adapting these applications
to the changes introduced by the Basic Document (DB) from 2013.
This software tool provides the verification requirements for the Basic Document of the
Technical Code. The requirement established for new buildings for use other than private
residential in section 2.2.2 of the HE0 section can be verified using this tool, as provided DB-
HE, according to the basic procedure for energy certification of buildings. Other requirements
of sections HE0 and HE1 can also be verificated by this Software.
We need to know that this Software will be the Software most used to calculate the thermal
balance of buildings in Spain over coming years, so it is important to know the limitations of
the tool:
The current version of Leader-Calener unified has the following limitations:
1) No special geometrical interior structure can be defined if it is neither vertical nor
rectangular (except being horizontal floors)
2) No inclined slabs or floors can be defined
3) No non rectangular windows can be defined
4) In spaces of non constant height, the height will be introduced by adding an exact cubic
volum to the original space
5) By joining spaces vertically, the volume of the resulting space is not correct.
6) There are only two solar radiation maps for all the Spanish sites.
This Software (Lider-Calener) still uses DOE 2 methodology. In the paper “EnergyPlus
Analysis Capabilities for Use in California Building Energy Efficiency Standards
Development and Compliance Calculations” by Tianzhen Hong, Fred Buhl, Philip Haves, say
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“EnergyPlus inherited most of the useful features from DOE-2 and BLAST, and more
significantly added new modeling capabilities far beyond DOE-2, BLAST, and other
simulations tools currently available.” (2008)
So, we are using an old methodology to calculate thermal balance of building in Spain. Lider-
Calener can’t help us to calculate buildings demands in a trule accurate way.
Different Softwares
To know all the different options that architecture can provide to reduce energy consumption,
we need first to validate our simulation model with the real building behavior, we need to
adjust the unknown values of our simulation, creating different scenarios, until the demand
value is the same in the real building and our simulated model.
Nowadays, we have different softwares to calculate the energy demand of buildings but we
have seen we need a different software to Lider-Calener.
Energy Plus is the software that I use to calculate the simulation model. It is a building energy
simulation program that builds on the most popular features and capabilities of BLAST and
DOE-2. EnergyPlus includes innovative simulation capabilities including time steps of less
than an hour, modular systems simulation modules that are integrated with a heat balance-
based zone simulation, and input and output data structures tailored to facilitate third party
interface development. A few of the features in EnergyPlus Version 8.0.0 include: modelling
of ventilated photovoltaic roof and other cladding systems, natural cross ventilation,
simplified definition of HVAC systems, refrigerated casework, variable speed cooling towers
and speed improvements throughout.
We can use a lot of design Software that uses Energy Plus as an energy calculator to estimate
energy consumption.
On the one hand, Design Builder is a fully featured EnergyPlus user interface suitable for use
at any stage of the design process. It enables a wide range of building types to be simulated
using the latest version of EnergyPlus. Advanced design options such as natural ventilation,
daylight control, double facades, chilled beams, and heated floors can be assessed for their
impact on the building environmental performance, comfort, cost, and daylight availability.
DesignBuilder applications include:
- Building design analysis from early architectural stages through to HVAC design
- LEED and EQ prerequisite and credit assessment
- BREEAM credit assessment. DesignBuilder complies with the requirements set out in
A10 of the BREEAM documentation. It can be used for carbon, comfort and
daylighting credits.
- Detailed design through CFD with links to load EnergyPlus temperatures and airflow
such as CFD boundary conditions.
- Assess daylight illuminance effectiveness through Radiance ray tracing simulation.
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DesignBuilder also offers a full-featured user interface to EnergyPlus HVAC. Both air and
water can be treated by placing and connecting components in a graphical environment. The
HVAC interface is integrated with the building model and provides access to most HVAC
component types. All of the ASHRAE 90.1 baseline system types are included.
BIM models created in Revit, ArchiCAD or Microstation can be loaded into DesignBuilder
through a gbXML import process. Revit users can access DesignBuilder while working on
their BIM models through a plugin, which allows the model to be checked and analysed
without leaving Revit.
Alternatively building models can be assembled quickly and easily within the DesignBuilder
modeler by drawing and positioning 3-D blocks. Blocks once drawn can be cut, stretched,
merged with other blocks etc then partitioned into zones. Realistic 3-D elements allow correct
room areas and volumes to be used in daylighting and CFD simulations and add to realism in
rendered views.
Image of the residence simulation (Design Builder)
On the other hand, OpenStudio Plug-in enables us to use the standard SketchUp tools to
create and edit EnergyPlus zones and surfaces. It is possible to explore the EnergyPlus input
files by using all of the native SketchUp 3D capabilities to view the geometry from any
vantage point, apply different rendering styles, and perform shadowing studies.
The plug-in adds the building energy simulation capabilities of EnergyPlus to the SketchUp
environment. We can launch an EnergyPlus simulation of the model we are working on and
view the results without leaving SketchUp.
Highlights of Legacy OpenStudio Plug-in include the ability to:
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- Create and edit EnergyPlus zones and surfaces
- Launch EnergyPlus and view the results without leaving SketchUp
- Match interzone surface boundary conditions
- Search for surfaces and subsurfaces by object name
- Add internal gains and simple outdoor air for load calculations
- Add the ideal HVAC system for load calculations
- Set and change default constructions
- Add daylighting controls and illuminance map
- Get help from tutorials and documentation
This plug-in makes it easier to work with EnergyPlus. The Legacy OpenStudio Plug-in does
not yet handle all critical input objects. Some editing of the input file will usually be required
outside of SketchUp. It is possible to use a text editor, a third-party interface/tool, or other
program (for example, the IDF Editor) to edit EnergyPlus input files. The Legacy OpenStudio
Plug-in for SketchUp was created by the National Renewable Energy Laboratory for the U.S.
Department of Energy.
Image of the residence simulation (OpenStudio)
This study tests both Softwares Simulations, and chooses wich is better for energy demand in
buildings.
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How do we carry out the study?
To do the work accurately, we need to have all the specific information about the site and also
about the building, not only architectural information, but also human behaviour and
functioning installation systems.
It is very important to know whether there is one thermal sensor or on the other hand the
system functioning is always manual or hourly. This means that in the building energy
consumption there is a relation between outside temperature or whetter it is independent.
We need to know the installion function to validate the analysis model. Later on, we will only
be acting on the architecture, on the skin of the building to carry out some proposals to reduce
the energy demand of the building. All this information will be introduced in the simulation
model.
Results of the study
Once the simulation calculation of the building is completed, and the present building was
checked then consumption values could adjust in a very specific way to actual design values.
Building simulation is very similar in OpenStudio and Design Builder, there are not
significative differences between the final calculation because it is possible to use the idf
editor, I will not explain the small differences in this paper.
A priori, we might think that building simulation is correct because the consumption data of
the residence both, monthly and annually is consistent with the calculated data, is very close.
Real consumption similar to simulation model
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The end result shows how ever when the model aproximation results are initially thought to
be correct, because the real consumption is similar to simulation model.
But, the values are far from real, because the indoor temperatures do not match, so somehow
the thermal inertia and heat fluxes calculated by software are incorrrect. The Software is not
creating a perfect simulated reality and it is possible to know because we are using thermal
sensors in the building.
Simulated temperatures
Approximation is still far away and shows that we have still a long way to go even with the
most sophisticate software. In this case the results thought near do not match, but we need to
carry on the same as in the initial study of other buildings at this level of approach.
Now we can make the necessary architectural proposals for improving energetic behavior, but
we must know that the results will have a margin of error associated with the different indoor
temperatures. We need to check this differents results to propose any percentage improvement
will have to take into account the variation between the values.
Conclusions
For this reason the simulation Software is so important, because until now the percentatge of
error calculation was nearly 20%. We need to propose improvements for the existing
buildings, and control the cost and efficiency of the proposal. We need to perfect energy
simulation to make real proposals 100 % reliable and useful for technicians.
Energy Plus contains a fully-integrated network model for calculating air flows and air
stratification, we need to test it with real studies and validate it. We also need to know the
infiltration and ventilation in buildings (doing blower door test), this is an other important
point to take into consideration.
That is very important in the design of passive architecture. It is necessary to incorporate
more passive information into the simulation design to achieve and exploit to a maximum the
ability of the architecture to reduce energy demands
To improve the energy simulation Software, we need to do more studies in real buildings, but
it is necessary to control the indoor air temperature because studies like this, show that the
comparation with monthly energy consumption is not enough, because the behaviour of a
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building is very different to a real one, so if we want to carry out an real analysis of an
existing building we need to put thermal sensors inside the building. This kind of study
enables one to adjust future thermal calculations.
Author: Licinio Alfaro
References
ASHRAE. 2001a. 1989. 1989 ASHRAE Handbook—Fundamentals. Atlanta: American
Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc.
ASHRAE. 2001b. 2001. Modeling Two- and Three-Dimensional Heat Transfer Through
Composite Wall and Roof Assemblies in Transient Energy Simulation Programs.
ASHRAE Project 1145-TRP. March 2001.
Carpenter, S.C., and C. Schumacher. 2003. Characterization of framing factors for wood-
framed low-rise residential buildings. ASHRAE Transactions 109(1).
Christian, J.E., and J. Kosny. 1996. Thermal performance and wall ratings. ASHRAE Journal,
March.
DOE. 2003. Building Energy Databook. U.S. Department of Energy. Available at
<http://buildingsdatabook.eren.doe.gov/>.
Kosny, J. 2003. Testing air-sealing techniques. Home Energy Magazine, January/February.
Kosny, J., and A. O. Desjarlais. 1994. Influence of architectural details on the overall thermal
performance of residential wall systems. Journal of Thermal Insulation and Building
Envelopes, Vol. 18, July.
Kosny J., J.E. Christian, A.O. Desjarlais, E. Kossecka, and L. Berrenberg. 1998. The
performance check between whole building thermal performance criteria and exterior
wall; Measured clear wall R-value, Thermal bridging, thermal mass, and airightness.
ASHRAE Transactions104(2).
Kosny, J., and E. Kossecka. 2000. Computer modeling of complex wall assemblies—Some
accuracy problems. Presented at International Building Physics Conference, Eindhoven,
The Netherlands.
Kossecka, E., and J. Kosny. 1996. Relations between structural and dynamic thermal
characteristics of building walls. Presented at the Conseil International du Batiment
Symposium, Vienna, Austria, August 1996.
Kossecka, E., and J. Kosny. 1997. Equivalent wall as a dynamic model of complex thermal
structure. Journal of Thermal Insulation and Building Envelopes, Vol. 20, January.
Kusuda, T. 2001. Building environment simulations before desk top computers in the USA
through a personal memory. Energy and Buildings 33: 291-302.
Jan Kos´ny, Ph.D. Syed Azam Mohiuddin. Interactive Internet-Based Building Envelope
Materials Database for Whole-Building Energy Simulation Programs.
EnergyPlus Analysis Capabilities for Use in California Building Energy Efficiency Standards
Development and Compliance Calculations” by Tianzhen Hong, Fred Buhl, Philip Haves