Super-low Energy Building Design with BIM

Super-low Energy Building Design

40% of global raw material consumption, as well as carbon pollution, is related to the building industry. As the conductors of building activity, it is the architects’ responsibility to design more energy-efficient buildings.

Building Energy Design Tasks

The European Union Directive 2010, 31 on the energy performance of buildings defines the future building energy design tasks of architects, in addition to their existing responsibilities.
First of all, they must provide correct information about the energy performance of their building design, which – obviously – can become a rather complex task in the event of large-scale developments as shown on the illustrations.

Architects must also be able to consider the optimal combination of energy efficiency improvements, meaning that they need to judge and compare several design variations before deciding on the ultimate one and following through with the more detailed design.

Finally, the use of renewable and district energy sources must also be considered. These are, of course, specific for each and every building location and, therefore, need to be discussed and evaluated for each project individually.

These main guidelines were extracted from the 2010 European Union directive, according to which all new buildings must achieve zero energy level by 2020. In order to be able to design such energy-efficient projects, architecture must be revolutionized.

Sustainable Design Today

According to the present practice, architects hand over the nearly finalized design documentation to the sustainable design expert – usually an engineer – to carry out the building energy design. At that stage of the design process, it is very hard and costly to implement changes based on his findings, so they have little effect on the end result.

Furthermore, engineers apply separate software from the CAD or BIM tools the architects use. This means that the energy expert has to re-enter the building geometry into the energy calculation software. In case of large, complex projects, handling the building geometry twice becomes extremely time-consuming and error prone.

Building Energy Design Solution

EcoDesigner – the energy evaluation add-on application by GRAPHISOFT – on the other hand, is integrated within ArchiCAD. Architects do not need to leave the familiar BIM environment to access advanced technology for building energy calculation. The dialogs have been designed to be easy to use for architects from the early design phase, when 80% of important decisions are made. EcoDesigner is the architects’ software solution for performing building energy design tasks, as required by the European Union Directive 2010 31.

Pic 1 - Energy Balance Evaluation

Pic 1 - Click to enlarge

Pic 1 - Energy Balance Evaluation

Pic 1 - Click to enlarge

The Energy Balance Evaluation report [Pic.01] provides performance information that includes the building envelope’s thermal characteristics, the heating and cooling demands, as well as the monthly energy balance. The energy consumption serves as the basis of the carbon footprint and operation cost calculation, which is displayed both by sources and targets, while primary energy demand is derived from the source consumption but includes the energy required for the manufacturing, transportation and processing of the energy source to the construction site.

The quick energy evaluation enables architects to compare the performance of design variations until energy efficiency is optimized. The final architectural decision made this way is based not only on aesthetics or functional considerations but also on scientific data generated by the energy calculation module.

The utilization of renewable energy is supported in EcoDesigner with a vast array of specific functions. Orientation and sizing of the fenestration can be optimized according to the building geometry and on-site conditions using the BIM. Afterwards, fixed or mobile shading devices can be assigned to glazed surfaces. MEP solutions – such as mechanical ventilation with air-to-air energy recovery, solar collectors or heat pumps – are also available separately or in combinations, from the easy-to-use EcoDesigner dialog.

The Hadlow College

Pic 2 - UK College Building

Pic 2 - Click to enlarge

Pic 3 - BIM

Pic 3 - Click to enlarge

In case of this Tornbridge, UK College building [Pic.02], the target energy performance level was set according to the Passivhaus Standard, a design directive developed by the Darmstadt Passivhaus Institute. Its strict yet straight forward guidelines enable designers to realize extremely low energy projects with virtually no heating or cooling need, in the conventional sense of the word.
The directive sets stringent threshold values for the specific annual net heating and cooling demands (15 kilo watt hours per square meter, year maximum) and the total annual specific primary energy demand (less than 120 kilo watt hours per square meter, year).

The Hadlow College was nominated for the Sustainable Building of the Year 2010 award. Mr. Anwyl, the designer used ArchiCAD with GRAPHISOFT MEP Modeler to create the BIM [Pic.03], and EcoDesigner together with PHPP (the official Passivhaus certification Excel spreadsheet) to turn it into Britain’s first Passive communal building.

Let’s investigate this example to illustrate how BIM-integrated energy simulation can be used to create buildings with extremely low energy consumption and carbon footprint. As the first step, a version of the building with mediocre building physics performance (just good enough according to current mandatory energy regulations) is evaluated, in order to create a baseline design, compared to which the performance improvements can be evaluated.

Summer

Reducing the annual cooling demand below15 kilo Watt hours per square meter – as required by the Passivhaus standard – is not difficult in the Kent, UK climate. Careful design of the shading on the external fenestration and facades together with proper window orientation and sizing, however, is necessary in order to maintain sufficient daylight conditions in the interior of the building and eliminate the chances of overheating of the internal air in the summer.

The Hadlow College is designed in such a way that no mechanical cooling equipment needs to be installed if the natural night cooling strategy – prescribed in detail in the design documentation – is properly implemented by the users of the building.

Sufficient internal heat storage mass also reduces summer peak temperatures – just think of the heat inside a tent vs. the cool interior of a medieval church in the summer. Thermal mass also helps maintaining stable interior temperatures in the winter and preventing possible overheating in spring and autumn conditions.

Pic 4 - Monthly Energy Balance

Pic 4 - Click to enlarge

The summer operation improvements detailed above result in lower solar gain and less cooling demand [Pic.04].

Winter

Composites and construction details with various infiltration heat loss characteristics had been compared using EcoDesigner, before the timber panel construction system was selected for the external walls. It lets less than 0.6 of the building’s total air volume through at 50 Pascal internal-external pressure difference. By achieving such high level of airtightness, the infiltration through the building envelope has been minimized.

By adding certain other skins to the timber panels – most importantly thick layers of thermal insulation material – winter heat loss through the external walls has been significantly reduced compared to everyday buildings. In the flat roof of the Hadlow College, for example, there is 40 cm of thermal insulation.

EcoDesigner obtains the necessary building material properties directly from the BIM model, the user only needs to specify the underground insulation thickness. This makes the comparative evaluation of several different solutions for the external building envelope composites particularly fast and effective.

By installing high-tech windows with triple thermal insulation glazing and equivalent frame construction, transmission heat loss is minimized through the fenestration as well, yet solar gain can be utilized during the heating period.

Superinsulation and superior airtightness has made it possible to construct the Hadlow building with less than 15 kilo Watt hours per square meter annual specific space heat demand, as required by the Passivhaus standard.

Pic 5 - Monthly energy balance

Pic 5 - Click to enlarge

After optimizing the building for winter operation, the infiltration and transmission heat losses have become significantly less, which result in a much lower heating demand [Pic.05]. Note that the differences between the total energy currents in the summer and winter months have decreased and therefore the overall appearance of the monthly energy balance bar chart has become ‘flatter’.

Electricity and Renewable Energy

The target air change rate is provided precisely by the mechanical ventilation with an air-to-air heat recovery, which regains significant amounts of energy from the exhaust air, while the carefully planned artificial illumination consumes significantly less electricity than the interior lighting of similar buildings created to satisfy less rigorous design directives.

According to the Passivhaus design guidelines, however, fresh air heating must be enough to maintain the sufficient internal air temperature. This means that all the required heat must be transported by the ventilation air volume. For this building, the necessary heating energy is provided by a ground water source heat pump. Typically, a 1000 – 2000 watt system (equals the power-output of a hairdryer) is capable of satisfying the heating needs of such a project. The same ground water source heat pump is used for hot water generation as for heating, in order to further reduce fossil fuel consumption and CO2 emission.

Pic 6 - monthly energy balance

Pic 6 - Click to enlarge

The up-to-date ventilation system with air-to-air energy recovery results in less heat loss via the exhaust air [Pic.06]. The significantly lowered heating demand, as well as the energy needed for hot water generation, is satisfied by the renewable (‘green’) energy provided by the heat pump. This ground water source heat pump has an electrical engine, but its additional electricity demand is successfully counter-balanced by the savings achieved by the custom artificial illumination design.

The Necessary Sustainable Building Performance Data

The primary energy value gives a great overview of the building’s energy consumption. Not only does it indicate the net energy source consumed, but it also incorporates the energy needed for the manufacturing, transportation and the raw material processing of the energy source, as well as its transportation to the place of use. Minimizing the specific primary energy demand is a great way to improve the designed buildings’ overall performance.

The improvements in building performance can be summarized by comparing the building performance data of the baseline version and the super-low energy version of the Hadlow College, that contains all the sustainable design enhancements detailed above [Pic.07].

Pic 7

Pic 7 - Click to enlarge

The specific annual net heating demand has decreased by 85%. The specific annual net cooling demand, on the other hand, has doubled in case of the Passivhaus solution, which highlights the greatest disadvantage of super-insulated and airtight buildings: the tendency of overheating. This, however, is only a problem in hot, sunny climates, where the majority of energy is consumed by mechanical cooling. In case of the Hadlow College, the specific cooling demand remains below the 15 kWh/m2a threshold value and can be successfully be solved by natural nighttime cooling.

Finally, the primary energy consumption and the operation cost of the super-low energy alternative is one third of the average design, which shows how using an energy evaluation tool within the BIM environment can make a real difference in the efficiency of buildings.

Calculation Accuracy

In order to verify EcoDesigner’s calculation accuracy, let’s compare the most important result data generated with EcoDesigner and PHPP [Pic.08]. Latter is the official software created to monitor Passivhaus projects and is known for its extreme accuracy. In fact, the PHPP Excel charts are adjusted to reflect the energy consumption and overall performance of certified Passive Houses, after they are built.

Pic 8 - PHPP Energy Calculation Results

Pic 8 - Click to enlarge

In case of the Hadlow College, the calculation results are almost identical. Generally speaking, the EcoDesigner output is within the +-5% percent error margin compared to the respective PHPP results.

Due to the speed of the evaluation process, EcoDesigner can successfully be used for large-scale projects and city planning, as well, when the energy efficiency upgrade of entire neighborhoods or business parks are planned. Dynamic simulation, furthermore, has the advantage of accuracy under all weather conditions, as opposed to stationery calculation methods, which are only applicable within a narrow climate range.

More information about GRAPHISOFT EcoDesigner is available on the official website:
http://www.graphisoft.com/products/ecodesigner/
For a more in-depth explanation of low energy building design with the product, please watch the movie available here:
http://www.graphisoft.com/ftp/marketing/ed/ed-2011/index.html

About the Author

After working as a freelance architect, building constructions and building physics specialist for nine years, Miklos Sved is currently the Product Manager of Sustainable Solutions at GRAPHISOFT. He is also a building constructions teacher at the Faculty of Architecture of the Budapest University of Technology.

This article was published in the 1/2011 issue of ArchiMAG

About the author - Miklós Sved

Comments
24 Responses to “Super-low Energy Building Design with BIM”
  1. Thanks for this article 🙂

  2. Great content and great layout. Your blog deserves all the positive feedback it has been getting.

  3. Colleges will play a huge role in our future energy endeavors as a country. It’s very important that our universities contine to train students for a greener future

    • Ritika says:

      Por otro lado creo que a Autodesk tampoco le fue nada bien pues ignmiaense que estos reporteros haciendo un reportaje que evidentemente beneficia a Revit de Autodesk el profesional que encontraron que mejor representanta a esta revolucion industrial BIM en Texas, fue uno que utiliza ArchiCAD, ironico!On the other hand I think that Autodesk also neither fared well so imagine that these reporters doing a story that evidently benefits to Autodesk Revit, the professional found who best represents to the industrial revolution BIM in Texas, was one using ArchiCAD, ironic!

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    • Rohit says:

      I agree completely, and I blame the media and mekrating. So many case studies have focused on the building model and not much on the information aspects of BIM. We almost have to redefine the term and emphasize the use of the data for more than just design validation.

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  8. Colleges will play a huge role in our future energy endeavors as a country. It’s very important that our universities contine to train students for a greener future, that will include solar power.

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  19. Mohammad says:

    A very rosy picture, ieednd, but one in which some will hear some darkness in the statement All WILL participate. Also, I would consider circulating this, but doubt that I have convincing answers for a number of the questions the piece raises, including: How? (adding new elements easily), Where (the standardized object library), and What (free open standard by which all our tools can contribute to the BIM). By the way, I am as aware of buildingSMART, IFC, IFD, etc. both their successes and their shortcomings as anyone who is not directly involved with their development.

  20. Jerry says:

    Daniel, I don’t have that file set up yet. Now with the switch to ArchiCAD I need to resive my templates again. And more importantly my template over the last few months was tweaked and geared towards a specific client of mine. So I also need to generalize it again. Shouldn’t take long, but it’s a matter of where it falls on the to do list!Also I believe BIMES is the reseller for much of the Middle East, so it’s not surprising that they focus on larger scale projects

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