The first and biggest is the cost. Spray foam insulation is about $4 per sq ft, and that is not just your attic. Roof space is about 30% more square footage than the attic floor area, that should be taken into account when budgeting. So if your home is 2,100 sq ft single level, your attic roof slope eligible for spray foam would be around ( 2,100 x 30%) + 2,100 = 2,730 sq ft with a cost for adding spray foam of 2,730 x $4 = $10,920! You can get a small solar panel system for that cost or even take a nice vacation to Europe... It's a tough choice, Europe or spray foam in the attic? Spray foam is definitely an investment, and we encourage our customers to do it if it meets our 3 step cost benefit analysis listed below.
3 Step Cost-Benefit Analysis For Spray Foam Insulation
- Are there other energy saving improvements that will give a better bang-for-my-buck?
- What other energy saving improvements will give me the same comfort results as spray foam?
- What is the lifetime value of spray foam vs other energy saving improvements?
Below is a summary table of other energy saving recommendations common for Phoenix homes and their associated cost savings, comfort impacts, and lifetime value considerations... all three cost-benefit analysis in one location. The table shows estimated savings on an average 2,100 sq ft home in Phoenix. The cost effectiveness is rated on a scale of 1 to 10, with 10 being the highest rating. The Average ROI is found by taking the savings / cost, with the higher numbers giving quicker paybacks. The Comfort Factor is also on a scale of 1 to 10, with 10 being the highest rated and having the biggest comfort impact. The Lifetime Value column takes into account the useful lifetime of the upgrade. For example, a pool pump's lifetime is 10 years, shade screens have a lifetime of 10 years and insulation has a lifetime of 25 years. Upgrades like duct work sealing, insulation and air sealing have lifetimes capped at 25 years. The higher the number, the better for the Savings-to-Investment Ratio. Spray foam was estimated to have a savings of $300 a year, over a generous 50 year lifespan with a cost of $11,000.
By looking into all the alternatives, you can see a typical home has multiple options to choose from that are both more cost effective and can fix temperature fluctuations in the home. Yes, it is true that spray foam will put less wear on an air handler located in the attic, but if that air handler is starved for air because of bad duct design or leakage, it's still going to be overworked no matter what the attic temperature is.
One of my favorite facts for homes in Phoenix is the heat gain chart published by SRP which shows that only a minor portion of heat gain in our homes comes from the attic. Simply put, if a spray foam rep sounds like he is over promising savings, he probably is.