THE GREEN FILES
By Sonia Green-Brown, PE
Issue 211- Helping Buildings Perform Better
It is estimated that 40% of the world’s energy is consumed by buildings. This might be surprising to some as we tend to think of them as being passive but their energy usage has gotten increased attention due to the rise in energy costs.
One the biggest contributors to this cost is the air-conditioning load. The good news is that there is a lot you can do about it whether you are starting a new project or renovating an existing space.
As air-conditioning in both homes and businesses have become fairly commonplace, sealing and insulating is ever more important. For an existing home a fairly easy improvement is to add insulation to attic spaces as this has the potential to reduce energy costs as spaces should cool down quicker allowing for higher thermostat settings.
I caution you that before you consider insulation, the issue of moisture control should be examined very closely with your Architect and builder. It is very important that buildings are properly sealed to prevent the intrusion of moisture.
When considering new construction the opportunity is there to weigh the cost benefits of high R values for both walls and roofs. For reference, the US Department of Energy describes a wall with a R Value of 14.6 or higher as having advanced insulation and those with a R value of 11.6 as standard. However many are opting for values as high as 30 or even 40 with the anticipation of realizing energy savings down the line. The R value refers to the resistance to heat flow and a higher R value indicates greater insulation effectiveness.
Windows are critical and should be carefully selected. Added to insulation a window upgrade could make a significant difference to how hard your air-conditioning system has to work. They need to be properly sealed all around to avoid leakage and double paned if budget permits or at the very least tinted to reduce the impact of solar radiation that makes the interior feel warmer. The same rules apply to any glass doors. Interior shading from blinds or sheers for example also helps keep inside cool.
If building new and property size permits, rotate the building so it is not fully east or west facing but rather experiences sunrise or sunset at an angle and not full on.
Roofs add sufficient load to the cooling system to consider making your roof a cool roof. According to the Cool Roof Rating Council (CRRC), a cool roof reflects (Solar Reflectance) and emits (Thermal Emittance) the sun’s heat back to the sky instead of transferring it to the building below.
Trees are also important and provide exterior shading to windows, so resist the temptation to raze the land before building or when landscaping.
These seemingly minor changes go a long in making your building more efficient.
We would like to hear how this article has helped you. Send questions or comments to sbrown@graphitebahamas.com.
Sonia Brown is Principal of Graphite Engineering Ltd and is a registered Professional Engineer.
