Spray Foam Insulation

Spray Foam Insulation

When it comes to energy efficiency, many of my Homeowners ask, Mike, how much "Green $$$" can you put in my pocket?

I respond, how much money are you willing to invest today for a potential payback sometime in the future? They usually respond, I'm willing to invest $10,000-$20,000 for energy saving features that have a payback period of 10 years or less.

Eventually, our conversation centers upon various insulation systems and the topic of spray foam attic insulation comes up.

Scenario 1:

Spray foam insulation applied to the underside of the roof sheathing in the attic, 5 inches thick, R- 15.

The attic space is sealed, soffit and roof vents are not required.

The attic becomes semi-conditioned air space instead of an over heated attic that reaches 150 degrees in the summer.

The air conditioning ductwork is installed in the attic that is now semi-conditioned air space.

Semi-conditioned because the attic is conditioned by air that leaks from the homes living space into the attic not by supply vents.

No insulation is installed on the attic side of the ceiling drywall.

An ERV (energy recovery vent) is installed in the attic to eliminate moisture build up.

System costs $10,000 more than installing R-30, fiberglass insulation.

Scenario 2:

Blown in fiberglass insulation is installed on the attic side of the ceiling drywall to the depth of 10" for an R-30.

The attic space is ventilated, soffit and roof vents are required.

Even with ventilation the attic space can reach 150 degrees in the summer months.

The air conditioning ductwork is installed in this hot attic space.

An ERV is not required.

Evaluation:

Scenario 1's foam insulation seals better against air infiltration, the ductwork in run through semi-conditioned space, requires an ERV, its R value is lower and it costs $10,000 more that scenario 2.

When both scenarios are evaluated by a Independent Certified Energy Rater taking into account all the various factors, they are considered equal.

Summary:

So you can pay $10,000 more for scenario 1 and the payback period is never. 

I'm not a proponent of spray foam attic insulation due to its cost and payback period but I do install spray foam if my homeowners request that we do so. After all, it's their home and my job to provide information and assistance but they make the final decisions.