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Originally Posted by FF_T_Warren
What's better spray foam or blown insulation? What's the cost difference?
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well from working in attics for 30 years I can tell you I hate blown insulation and think its crap.
my reasons are, it never stays put, and it moves with little effort like a pile of leaves in that its prone to blow around, so any drafts from attic vent areas can and do often leave areas within a foot or two of that area, devoid of insulation after a few months by slowly moving the insulation away from the drafty area.
second, as you walk move or work in the attic it gets shuffled around and matted down and is never the same again so if you have anyone working in your attic (no matter how much you trust them) you better go up there behind them and "rake the leaves" as it were to evenly and uniformly spread it out again.
lastly is its prone to leave too much dead air space between the tuffs so if its 6" deep its no better then a 3" solid bat because of all that air space mixed in.
now all that being said, its better then nothing, and its often the only reasonable alternative to insulate areas that are hard to get to, so it has its uses, but I wouldn't put it in a new house just to save money because in the long run its no where near as good as regular bat insulation.
spray foam is the best choice for insulation but you always want to use a bat for the ceilings so its not completely foam. if its all foam you need special considerations to handle the stale inside air and trapped moisture so the a/c system must draw in outside air to replace the inside air and then this diminishes the a/c system efficiency and raises its initial as well as running costs all because when you have too much foam everywhere, you get moisture issues and stale air factors. the main problem with foam is its a great insulator but its also a moisture barrier that doesn't allow the house to breathe so having it in the walls is good but don't "seal the box" by doing the ceilings with it, that's too much "sealed" air and moisture in the house. its like what happens to an ice chest or unplugged refrigerator you leaved close for a while, the air gets funky as hell and mold starts growing in it.
this is why I am foaming my walls and floors but using regular bat for the ceilings to avoid moisture and stale air issues.
hope that helps