There has been a lot of awareness raised with the new foam insulation products over the last 10 years but I still have homeowners ask me from time to time, “is foam really worth the money?”
A few things come into play when insulating your attic. Since we are in Atlanta, we all know how hot an attic can be on 90-degree day in August – it’s like a steam room. The cost with cooling our homes in Atlanta typically exceeds the cost of heating our homes (this winter was a little unusual), so a very hot attic can affect the number of times your cooling system cycles to keep your home cool if the attic is not well insulated. This of course consumes more energy. If you have an air handler (furnace) and ducts in the attic, the high level of heat reduces the effectiveness of the system putting more stress on the system.
When you install batts or blown insulation over the ceiling area of your home to the standard R-30 level (R=insulations ability to resist the flow of heat), the insulation acts as a barrier between the hot attic air and the cooled area below the ceiling. Batts, when installed properly and expanded, provide a little more R value than loose insulation due to the inconsistent levels that is experienced with blown.
Blown does work well at filling hard to reach areas or voids that are usually a little more difficult with batts. As fiberglass and cellulose is less expensive than spray, I recommend that you insulate to at least an R-40 to R-49 level if you want to see some cost savings in cooling. Remember that walking on your insulation or allowing it to get wet reduces its R-value.
When spray foam insulation, which typically has twice the R value of batt insulation, is directly applied to the bottom of your roof decking, filling the voids between the rafters and overhangs, you increase the size of the envelope to include the attic. Even though the attic is not mechanically conditioned (that is open ducts dumping warm or cool air into this area), the attic will be substantially cooler than one that is insulated with batts or blown.
This product reduces the radiant heat moving through it and since all eaves and openings are sealed it also reduces the convection heat. The 35 to 40 degree cooler attic temperatures above your drywall ceilings keeps the living areas below cooler longer. Also, if your heating and cooling system is in the attic, the system will not experience the high levels of heat thus will perform better.
When using foam insulations insure that you use an open cell product when applying to surfaces that may experience water intrusion. A leaking roof may not manifest itself with a closed cell material. Closed cell products are great in floor joist cavities in crawlspaces or vertical wall areas.
If you are planning on remaining in your home for any length of time, you may want to consider increasing the insulation in your attic, insulating floor cavities over any unheated basements or crawlspaces, and if replacing siding, upgrading the insulation in wall cavities. I recommend that homeowners have an energy audit or home performance assessment done to better understand how insulating your attic or crawspace affects other systems or components in your home.
The energy you save will put a smile on your face and reduce carbon footprint which is good for everyone, so weatherize!