Green buildings with Ecotect

There is a lot of talk about green building design and many architects are coming up against design-related criteria of Part L. WIth building performance becoming key, Martyn Day evaluates a low-cost solution that could be the answer to better building design.

I originally came across Ecotect when evaluating the last release of GraphisoftÝs ArchiCAD. Graphisoft has managed to gain the distribution rights to the program and has also integrated the two products to speed up geometry import. This month, IÝve had a more in-depth exploration of Ecotect and itÝs really a swiss-army knife analysis tool with great visual feedback to quickly analyse a buildingÝs performance in a number of key areas.

The building in red is being analysed for overshadowing in a city environment.

We usually leave the price of the software to the end of the review but at ú850 per seat, I think itÝs worth mentioning at the start, for as we work through its capabilities I am sure many will assume that the software will cost thousands of pounds. At this price, I donÝt see any reason why even the smallest of practices couldnÝt justify a copy. That said, the software covers areas that are highly technical and specialist knowledge would be of some advantage but this isnÝt something that couldnÝt be overcome with a little training.

The beauty of Ecotect is that it can be used at every stage of the design process, from defining the maximum site envelope or testing the conceptual model, to nailing the details and refining solar performance and acoustics. The more information you can give the system, the better the results. It also provides an environment with which to test out the impact of material variations, should that be thermal or acoustic. In the case of glazing the software will even generate an ideal case, Part L compliant model from the original design - showing just how far you are out.

Geometry

If you were having trouble justifying a move to 3D, performance analysis and Ecotect are the very reasons that designing in 3D makes sense. The first part of the job is to get your model into Ecotect. The software has its own basic modelling environment that you can have a crack at but it really isnÝt as intuitive as a CAD system and is best used for generating basic layouts. Although, you can switch between different views of the model, such as orthographic or axonometric projections, and a nice visualise feature shows the model in OpenGL, the issue is that the views arenÝt in sync, so model view manipulation is on a per window basis.

EcotectÝs natural daylight analysis results are very visual and offer instant assessment of a design.

There are a number of import options including 3DS but this just imports dumb geometry and all the areas still have to be defined and zoned. This is where ArchiCAD has the advantage as its models come in automatically zoned - with the exception of overlapping geometry conditions which have to be resolved for the analysis engine. Here, if a window runs between zones or there are multi-storey components, these have to be identified or altered. For instance a ceiling on the first storey is a floor to the 2nd storey.

The Ecotect modelling environment can make element selection difficult on complex zoning, and using ArchiCAD for the original model definition speeds up this process. It may even be worth owning a copy to generate the concept models to feed into Ecotect and cut the prep work. Once these have been identified you are ready to start building up the material definition of the building, whatÝs it made out of, where it is on the planet, its orientation, what time of day it is and what month you are interested in.

Materials and environment

The most important part of analysis is making sure the software has enough information to carry out a meaningful calculation. For instance, the walls, glazing, and partitions all need to be assigned materials for any thermal analysis and the software comes with a big library which prove all the U values and numerical characteristics that the analysis equations need. Cooling systems and plant should be added here too, providing Ecotect with any man-made environmental measures that have been anticipated. This can be a laborious process but itÝs just a case of selection and allocation in the dialogue. If the materials arenÝt present or a value needs tweaking, itÝs easy to go in and edit. I suspect at this stage, a little knowledge goes a long way as errors here can skew the result. ItÝs best to start learning the software on simple models and guesstimate the results. ItÝs always good to have a certain expectation of the output before you start so the end result is logical. Never take computer analysis output as gospel.

Ecotect does have some 2D output as well. Here the 2D rays from the sun hit a cross section of a building with louvres. The resultant light entering the building is shown.

The site conditions matter too and here you carry on building data for your model analysis. Enter the modelÝs orientation and position on the planet (by latitude and longitude, time zone), thereÝs a built-in weather data file which provides yearly average environmental conditions against which the design should be tested (you can import your own too). This is used for thermal and ventilation calculations.

Now with your model zoned, materials allocated and environment and global position assigned, itÝs possible to start running some calculations to get a wide range of performance characteristics, including solar radiation, right to light, over-shadowing, conformance to Part L, light penetration, ventilation and many others.