Spray Foam vs. Fiberglass, anyone done the math?

vtboy51

I'm building roughly a 2000sq ft home in Vermont, is it worth the extra cost to spray foam the walls vs. fiberglass? How many years roughly to recoup the cost of spray foam?

hammerlane

What kind of costs are you getting for each?

Cost for fiberglass batt about $800??

Cost for spray foam about $6000??

Am I close?

AGWhitehouse

If you are planning on being alive long enough or are going to pass this house down to your kids, I'd stay away from spray foam unless you're doing a flash/batt method. When it comes time to renovate/upgrade that structure, spray foam will only add significant $$...You can't snake, you have to demo. So you'll pay more now and pay more later for a full foam install while flash/batt system will give you the sealing quality at a cheaper price and allow for renovations, etc. in the future.

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vtboy51

I haven't even gotten that far, I just figured someone has already done some rough homework on the extra cost and what the heating cost benefits are.

AGWhitehouse

The talk around the water cooler is that foam is, on average, 3x the cost of fiberglass...

There is more to consider on all this than just what type of insulation. Foam creates an air-tight seal that is not found in "traditionally" built homes. When you seal a house that tight, you now need to introduce mechanical ventilation to achieve the code required air changes and eliminate the risk of "sick house syndrome". These are costs that go above an beyond the additional insulation costs. Not taking into account the air change requirements, could lead to increased health risks and bouts of common illnesses due to airborn pathogens and debris that is not being filtered or exchanged.

The "traditional" home design accommodated the required air exchanges via leaky walls, windows, and doors. You turn on the kit/bath exhaust and it pulled in air through all the cracks. If you seal all those cracks and get nice tight doors/windows, you'll need to provide a source for fresh air intake.

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jklingel

As stated, foam is expensive; over 3x what cellulose would have cost me. On top of that, the environmental impact is significant. If you want to use batts, I would suggest you consider leaving the fiberglass at the store, and get Roxul or one of the other batt products. FG is lowest on the list for overall R value. Too, consider a double stud wall with dense packed cellulose; one of the cheapest, $/R, and most environmentally positive ways to build. And DO build tight, then get an HRV.

AGWhitehouse

Thanks for clarifying. I do agree and also recommend building tight and providing mechanical means of ventilation. The initial cost is quickly paid back through operational efficiency.

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hammerlane

Very hard to calculate with a degree of scientific certainty the cost benefit of when you would recoup the spray foam money.

To do this you would need two identical homes..well almost identical except one has spray foam and one has fiberglass insulation. Home would need to be situated in the same geographic orientation to take advantage of the sun's orientation.

Then you could calculate energy usage on each.

jklingel

Roger that. One thing that surprised me is how "cheap" it is to provide fresh air. Ignoring the trivial cost of the HRV (), it was only going to cost me a few hundred bucks in heat loss to operate it. I have no idea how that compares to what a leaky house costs you, but it made it clear that the HRV was really not a huge difference, and then you get the air moved properly, etc. I think the "build it tight, ventilate right" mantra is a good deal. I hope so, 'cause I'm gonna spend the $$ on one soon.....

AGWhitehouse

That is going to be the future of building when the new energy codes kick in. My uncle is building an "experiment house" and is purchasing HRV's he says have a 95% efficiency rating and only require 1A to operate. He said he was going to get me the cuts, but if he wasn't exagerating, those are some awesome performance specs. I can't imagine a leaky house is better than that considering the added benefit of actually filtered air exchanges.

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NEFoamer

It's generally going to cost around 3x more for closed cell insulation, which is what you would want in vermont. I would NOT recommend flash and batt to anybody unless you're spraying at least 2" of closed cell, and at that point you might as well add the 3rd inch. The average payback is generally going to be around 7-10 years, but that is largely going to depend on your initial costs, heating costs, and future heating costs. You'll generally save 40%-50% on heating and cooling costs. You can usually also reduce the size of HVAC equipment, which can offset some of the cost of an HRV.

NEFoamer

Here is one case study, I'm sure you can find some more out there, hopefully more specific to your location.

http://advancedinsulationla.com/casestudy.pdf

hammerlane

I think that comment is such a crock and a common "talking point" in the window and insulation industry. I wonder how many companies would back that up with a guarantee to pay anything over a 3 year average of your gas bill in the winter.

hammerlane

Interesting reading

NEFoamer

Feel free to google richard rue and energywise. Former nasa scientist who developed a program to do just that.