Originally Published: October 28, 2016 6 a.m.
Question: We have completed leakage testing and sealed our home the best we can; what else can we do to improve our comfort and reduce energy use?
A: The main areas for home energy loss are air infiltration or air leakage and a lack of envelope insulation. Together these parameters determine if you have a tight, average or leaky home and how much energy and money you are losing.
We addressed the effects and importance of air leakage through gaps in the envelope in the previous article, now we look at the other main heat and cooling loss preventer; insulation. Effective insulation conserves energy by slowing heat transmission; increasing comfort by reducing rapid temperature variations, and lowering noise levels; it also reduces the size and cost of heating and cooling equipment. However, it must be reiterated that air leakage severally impacts the effectiveness of insulation, so sealing should be addressed before insulation.
Fortunately heat loss and heat absorption are based on the same basic physical effects; that of conduction of heat through materials, convection of heat through air and gases and radiation from the suns rays in the form of infrared and ultra violet heat. Heat always travels toward cold, so in winter heat moves from inside the home to the outside and in summer from the outside inside. The insulation barrier must work in both directions, preventing heat leaving in winter and blocking heat during summer.
There are two parameters that the energy industry uses to evaluate insulation materials; R-value, which is the thermal resistance to heat transfer through a material, and U-factor the thermal conductance of heat transfer through a material; U being the reciprocal of R (1/R). The higher R the better and the lower U the better; R is usually specified per inch of material thickness.
For a comprehensive list of materials, go to www.greenhomeenergyadvisors.com/articles-and-technical-information/r-value-table/
As an example, the Prescott building code for attic insulation stipulates a minimum R49; therefore, dividing R49 by the R-value of the material selected determines how many inches will be required. For instance, R49 using standard fiberglass batting would be 49/2.8 = 17.5”, for open cell foam 13” and for closed cell foam 7”. Closed cell would seem a no brainer until you consider that closed cell foam is twice the cost of open cell; so, cost is also a factor in material selection.
For an existing home the current insulation material must be determined and more importantly establish how well it is installed. If leakage has been a problem then moisture may have degraded the insulation effectiveness, or the insulation may have shifted leaving major gaps that are not insulated at all, and where convection currents bridge the insulation. Many of these issues are behind drywall and not visible. This is where a thermal diagnostic test using an infrared camera that detects and highlights changes in hot and cold areas behind the drywall and other covered locations come in useful. However, expertise is essential when interpreting these results.
In older buildings where fiberglass insulation has been used and needs repair the removal of drywall is required. If; however, the infrared test shows there is no insulation fitted you may consider using a blown material that doesn’t require drywall removal.
Retrofitting insulation can be a dirty and unpleasant job. These challenges can affect the installation quality, which is essential for performance. For this reason, it is important to use a reputable energy and insulation specialist who is familiar with the multiple insulation materials and the correct installation techniques.
For more information, contact: Paul Scrivens Green Home Energy Advisors, www.greenhomeenergyadvisors.com