Previous post: Part I
I thought now might be a good time to bring some technical stuff again to this blog, and thus, the second part of STACEY 1.0; Energy & Carbon.
LEED gives a lot of attention and weight to credits related to “Energy & Atmosphere”. The reason behind that is its large contribution to human comfort and the environment. We also believed that doing such thing would contribute to humanity and the environment and would result in a good building that wouldn’t need as much resources to run – which is always good.
But one very important thing that most architects forget about or, rather, don’t want to do (because they will lose their reason for existing if they did) is to have a sustainable shape for these buildings that they claim to be sustainable. Certain shapes require a lot of resources to make and also produce a lot of carbon due to their engineering, how they stand up, and how they are constructed.
The shape of our building has been decided solely by quantifiable criteria such as solar gain, daylight to regularly-occupied spaces, natural ventilation, and water consumption. Unlike other “sustainable” buildings that we see, the result is that the shape – the basic building configuration – uses less energy than other shapes. Guess why? Because it was not the result of an starchitect’s inspiration, but rather the result of combining all these factors together to determine what was optimal.
I just included that as an introduction in case you were wondering … Now lets get to the numbers.
Reduce the Energy Used – 43% less
One good thing to do before you even start thinking about producing your own energy is to reduce the energy used in the 1st place. One basic thing that contributes to that before you even begin the planning and detailing your building is to decide its basic shape and orientation. Certain shapes minimize the exposure of facades to east and west sun which are the least desirable and the hottest in the UAE, and can make a big contribution to decreasing solar gain and therefore minimize the cooling load.
The building has been oriented along the east-west axis to achieve the optimum for minimizing the cooling loads as well as give better year-round illumination levels as all windows face true north or south. This decreases the energy required for lighting and also enhances the indoor quality since natural daylight is more desirable and more healthy for people anyway.
As you begin detailing the building, there are several strategies to help further reduce the energy demand. Selecting the best construction for exterior walls, windows, slabs, and doors is important. For the slabs, exterior walls, interior walls, and doors, we selected constructions that had the lowest u-value (overall heat transfer rate) to minimize the amount of heat that gets into the building.
For windows, it was a bit harder than just selecting low u-value windows because windows have another important variable called the VLT (Visible Light Transmittance). This expresses the amount of visible light that is transmitted and a higher VLT means that more light passes through the window. Another factor we had in mind was the SHGC (Solar Heat Gain Coefficient) which is a measure of how well a window blocks the heat from the sun. We had to find the optimum balance between the u-value, the VLT value, and the SHGC value to get the optimum result. Doing this minimized the heat gain from the windows, and this reduced the cooling load and meant lower energy consumption. On the other hand, maximizing the amount of daylight passing through these windows meant that we provided the occupants with a better indoor environment and, at the same time, reduce the energy load by lessening the need for artificial light.
Another thing that helped reduce the energy demand was the use of absorption chillers. The absorption chiller uses a heat source (in this case, methane from the anaerobic digester on the water purification level) to provide the energy needed to power the cooling system. The absorption chiller uses much less electricity and produces less noise and without the vibration of the usual electrical chillers. Moreover, they do not use any CFC- or HFC-based refrigerants, and thus there is no risk of harm to the ozone layer.
Producing On-Site Energy – 70%
The building is able to produce 70% of its electricity using the PV roof it has. The building needs 1,648 MWh of energy annually, 1216 MWh of which are produced annually. This has been achieved through having a 20 degrees inclined roof supported by a space frame that, in turn, is supported by cross-braced steel columns. On top of that, are approximately 600 PV cells mounted on a single, planar array that avoids self-shading that otherwise results. The PV cells have dimensions of 3×2 meters and have an efficiency level of 19%. They can be safely cleaned every 4 months or as necessary using a gantry system as shown in the render below.
All of this goes a long way towards reducing the carbon emissions by 95% when compared with a building of the same size and location.
That was all about energy and carbon. Until my next post, have a great life.