What is a building envelope and why is it important?

A building envelope is commonly defined as the separation of the interior and exterior of a building.  It helps facilitate climate control and protect the indoor environment.  Overall it is the entire exterior building system.  It includes doors, windows, roof, foundation, floor, siding and all the components such as structural masonry and insulation. In the past articles we have discussed or you are aware of energy efficient bulbs, energy efficient appliances, and updated mechanical systems such as heating and cooling systems.  If the building envelope is not in good shape all the updates to other systems will not matter.  The reason for this is the building envelope can account for a substantial amount energy loss if not properly attended.

The benefits of a good building envelope include reduced stress, wear and tear on mechanical systems.  This results in turn to reduce energy bills.  This is an attractive benefit to you and the resale value of the house to prospective buyers.

Unfortunately the building envelope is not just one component, but a variety of independent parts that make the system.  Replacing one part of the system will increase your efficiency, but to a minimal degree if you do not address all parts of the system your efficiency will not be as high as it should be with all components operating efficiently.

If you have an older home remember homes were designed in an era where energy was less expensive.  I have mentioned in the past windows and doors are actually one of the highest cost ratio items to upgrade in a home for the return on investment and savings ratio.  However, when it pertains to the building envelope windows and doors are a critical component to the envelope and should be replaced if needed.  While windows and doors are the most expensive item to upgrade the easiest way and least expensive update for this would be caulking and weather-stripping.  The upgrade helps seal what suffers the most wear and tear.  This component is often overlooked, but can have a massive impact on a homes efficiency.  The exterior wall and fascia are often not insulated.  The exterior should be checked to make sure it is performing to the standards of ventilation originally intended for the home.  Technology has advanced over the years to correct ventilation and moisture issues if it is present.  The last component is the wall system.  Wall systems include brick, wood, siding or concrete and the materials that connect these materials.  Wall systems have a very long life expectancy.  However, if there is air infiltration, insects, transfer of temperature, or water intrusion the wall system may need to be addressed sooner rather than later.

The first step before adventuring into any of these components of the building envelope is to contact an energy rater in your area.  The energy rater can perform tests on your home and give you a better starting point to which components need to be addressed.  Having a properly functioning building envelope will benefit you for the life of the home.

-Mr. Green