Ever been in your attic in the middle of a hot sunny day? Even a well ventilated attic reaches temps of 140 degrees which means the interior of the home is sitting under a broiler. A home owner, Justin, whose wife is due to deliver their first child in June called me because the room they chose as the nursery stays very hot all day long. Not a great environment for a new born. A radiant barrier sales person had already quoted them $4,000 and promised a bunch of things that building science proves just aren’t true. (See article Beware the Radiant Barrier Salesman) Luckily he read the article and gave me a call.
The first problem was that the attic was poorly insulated and had a million holes in it that weren’t air sealed (a common issue in many homes). The second problem was that both of the HVAC units and all of the ducts were located in the attic (a typical set up for a two story on a slab). HVAC equipment is not insulated and the ducts are only R-6 so it’s kind of like trying to make ice cubes in an oven.
The easy solution to his issue was open cell spray foam. What is spray foam? It’s a urethane based expansion foam product that when applied to a surface, creates a continuous air and insulation barrier which is much more effective than blowing in insulation or dealing with the gaps left by installing batts. Just imagine the entire underside of your roof deck being covered with Great Stuff.
Why is spray foam so effective? When an attic is encapsulated with spray foam, the temperature inside the attic is never more than 10-15 degrees different from the inside of the house. Now your HVAC equipment runs much more efficiently, which saves you a lot of money and you’re removing the “broiler” effect. It is also completely air sealed which means all the nasty pollutants and allergens that get sucked into your duct systems are kept outside where they belong. BONUS ALERT: the entire attic becomes a semi-conditioned storage unit, a must for a house on a slab.
Are there any negatives to spray foam? Like anything of course there are. The main issue for many is the cost. It’s usually two to three times the cost of air sealing and adding more insulation, but is 10 times more effective, so it’s well worth the investment in my opinion.
Justin and his wife chose to have spray foam added to their attic and they couldn’t be happier. The nursery stays cool, their utility bills have dropped significantly, and they have lots of storage they didn’t have before.