Is anyone using 1/4″ foil/foam/foil insulation in remodeling?
I’ve been using 1/4″ foil/foam/foil insulation on a limited basis in some of my remodeling projects. It is rated R-7 in horizontal use and R-10 in ceilings. This isn’t the stuff with air bubbles in it but has a thin foam encapsulated by aluminum foil on each side. It seems to be a very good insulation option but I never see it even listed as an option in fine homebuildings’ articles on insulation. Is there a reason for this? Is it just not known about or are there some drawbacks that I’m not aware of? I usually use it in conjunction with some fiberglass to achieve a higher r-value.
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Those ratings of R-7 and R-10 are extremely misleading.
The manufacturers get away with it because they test the product in an application where the heat loss is from radiated heat, not conducted heat. It sounds like you put it in places where conducted heat is the problem. In that application, the actual R-value could be less than 1.
As I understand it, as long as the foil insulation has a minimum of 3/4" airspace on either side then the stated r-values will be achieved. I have stapled it to the underside of uninsulated 2by6 rafters in an attic storage area at my home and the results were a dramatic difference in temperature before and after in winter or summer.
radiant barrier performance
Is highly dependent on real world factors ... like dirt. I agree w/ the other poster ... exagerated claims, not real world tested R-values ... when applied e.g. in attics ... as soon as the foil gets a layer of dirt/dust on it, the big ticket benefit begins to rapidly deteriorate.
R-7/R-10 is largely BS ... maybe in the laboratory it can happen under a test, but not in your house. Yeah, you probably saw a big difference and may be impressed ... but put yourself in identical shoes after months or a year after the install ... not quite the same. 1/4" of foam will yield about R-1.75 at the very best (i.e. urethanes or poliso family). R-1.25 in the extruded polystyrene family. Less than one if in the 'bead board' family.
If you could apply a radiant barrier ... e.g. in a vacuum, it would perform well throughout its life ... but we don't do that ... which is why you've never seen any hoopla beyond the sales pitch over these types of products. Even Thermax states the tested, rated R-value of their foil faced products without the affect of the radiant barrier component. They do talk about the benefits of applying their product w/ an air space and the subsequent radiant affect ... but they don't push it and rely on it to sell their product.
Nothing wrong with it per se, but as others have pointed out you probably only get R3 or so in real life, making it hardly worth the effort to install.
If you're insulating an old hunting cabin or some such it's probably a lot better than nothing, but for a home anywhere where you actually NEED the insulation you should look for something better.