Radiant Barrier Installation – Part 2

The next step in installing a foil radiant barrier is to figure out what you are looking for in a foil.

Different vendors sell their foil in different configurations (i.e. lengths). The most common size in bulk seems to be a 4 foot long roll at either 500sqft or 1000sqft long. How you install the foil makes a difference in what you buy. . Installation can be horizontal or vertical. I install the foil horizontally, but I have seen how a vertical installation can be very beneficial for certain areas. if you intend to install vertically, then you need to measure the width of your rafters (mine were 24" apart). That means it is extremely helpful to buy the foil in a roll that is 24" +2" of overlap to staple on the rafters. Buying the foil in a 26" width roll will give you the overlapping foil to make a solid attachment and give a margin of error for when you don't get the foil 100% straight. Since I install the foil horizontally, I asked the distributor to cut the 4 foot roll in half. This makes for a much lighter roll to carry and it is much less cumbersome to maneuver a 2 foot roll in a tight crawlspace. I've done both, so I avoid having to repeat that mistake.

The most important tip i can give for buying foil is to get the good stuff. This is not limited by brand, but by grade. Most brands have different grades of foil. Each grade is a measure of how tough they are, not a measure of the actual reflectivity. The bonded aluminum is usually the same in each grade, but the cheaper foil will rip and tear much easier than the higher grade foil. The cheaper grade can actually be torn with your bare hands. I started out using this grade because I was told that it was all I needed. They were partially correct. I would staple one side and then try to pull it taut and staple to the other side. When I pulled on the foil to make it straight and tight, it would rip and I would have to go staple it again. Accidently touching the foil after it was installed would produce similar results. It got to be very frustrating. Once I tried the good stuff, which feels closer to armor plating than foil, I will never go back. It is simply not worth the time and hassle.

The two types of regular foil tend to be either polyethylene or polypropylene with aluminum bonded to either side. There is also what is referred to as "bubble foil". This is a layer (or two) of bubble wrap (the same as used in packaging) with aluminum bonded to either side. The bubble wrap (single layer or double layer) holds its shape and can be used in places where there is not a lot of good stapling points. The bubble wrap also provides a thermal break that the regular foil does not have. The bubble wrap is more expensive (about double the price) so I only use it in specific places where the regular foil would not hold as well (i.e. foiling a metal garage door) or where a thermal break would be beneficial (i.e. wrapping a water heater).

So regardless of what the vendor uses as a grading system (premium, ultima, super, woweekazowee) all you really need to ask is what do they consider their strongest material (sometimes referred to as "contractor grade"). I'm not saying that you can't or shouldn't use the cheaper material. I'm simply trying to save you the frustration I had to go through.

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