A short while ago, I received a flyer promoting some turn-key residential properties that allege to be energy efficient.
The units boasted energy efficient appliances, but beyond that, they were silent. When we talk about efficient or high performing buildings, it is certainly important to ensure that we carefully examine the building envelope.
Although we may not think of them that way, collectively buildings are big consumers of energy.
Indeed according to an article by Alan Macklin published in the August 2011 issue of Modern Building Systems, it is estimated that 40 percent of the world's energy is consumed by buildings, making the management of energy used by buildings a key component in reducing greenhouse gas emissions and frankly reducing the cost of doing business.
This increased emphasis on the performance of buildings worldwide is due in part to legislation.
In fact, in the same article by Macklin he cites the directives by the European Council for 2020 to reduce greenhouse gas emissions by 20 percent, increase the share of renewable energy by 20 percent and improve energy efficiency by 20 percent. The other major factor in this drive is of course money. Because of the rise in energy costs, building management, once the domain of the engineer, has now become a central focus for financial leaders and company CEOs.
The performance of homes is of course just as important to the homeowner who has to grapple with increased spending on energy as well.
Over the years, I have heard numerous persons lament the fact that as hot as it is outside, the inside of their homes is even hotter. This problem can be blamed on poorly sealed, un-insulated homes - a matter that has increasingly been seen as a problem because air-conditioned homes are now commonplace.
From the standpoint of the mechanical engineer, when we look to design an air-conditioning system for a business or home, the projected performance of the building itself is a critical factor in the design process. If we start from the outside, the orientation of the building on the property is important, in that assuming you have sufficient land area to do so, it is better to rotate the building so it is not fully east or west facing but rather experiences sunrise or sunset at an angle.
Avoid the temptation to raze the property before building. Instead, keep some of the trees, as this will reduce future landscaping costs and potentially provide exterior shading to windows.
To improve the performance of your building you need to consider the "R value" of walls and roofs, and to do so, effective insulation is often necessary.  The R value refers to the resistance to heat flow and a higher R value indicates greater insulation effectiveness.
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.
Walls should be well constructed with all openings properly sealed.
With reference to home construction, for example, the U.S. Department of Energy describes a wall with an R value of 14.6 or higher as having advanced insulation and those with an R value of 11.6 as standard. Windows should 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 reduce the load on the air-conditioning system.
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.  Solar reflectance and thermal emittance are measured from 0 to 1 and the higher the number the cooler the roof.
A lot of cool roofs are white and we can relate to this from feeling the difference between wearing white or black clothes.
Many of us are also familiar with Bermuda roofs that are white. However according to the CRRC there are many cool color products that have dark pigments but are highly reflective. They further predict average energy savings on cooling costs can range from 7 percent to 15 percent.
Therefore, with your building envelope designed and making sure it's outfitted with high efficient lighting and appliances, you will be well on your way to achieving a truly energy-efficient building.
 
Challenge for this week: If planning to build a new office or home, discuss building performance with your architect before plans are drawn.
 
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

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