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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

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