Bubble-foil insulation

I've worked with this stuff a lot, and I think it's a great and useful product- but I agree the R-value claims are mostly BS. It's value is not as insulation, but as a highly versatile and easy to work with air-sealing product:

- It's flexible but not flimsy, kinda semi-rigid. This makes it much better for many uses than either plastic sheeting or rigid foam board
- It's lightweight, easily cut with scissors or a blade, and clean- no gloves or respirator needed, makes no mess.
- It can be stapled, and is more resilient to punctures than plastic sheeting.
- The insulation value is minimal, but is a slight bonus, along with the radiant barrier.

There are two main things I've used this for:
- In attics, sealing large or irregular holes such as chases and dropped soffits (as an air-sealing measure and also to prep for cellulose insulation);
- As a backing/support/air barrier for insulation in walls and skylight shafts: i.e. Stapled to the back of attic knee-walls, or around skylight shafts in attics. This keeps the fiberglass from falling down, and also establishes an air barrier on both sides of the vertical insulation, which is necessary.

Bottom line, the marketing may be full of BS, but it's still a really handy product for some uses. Brand name doesn't matter in my experience, just make sure it's the kind with a double layer (not single layer) of bubbles.

Seems like a descent radiant barrier and some insulation value. I stuck some behind my radiators to
Reflect more heat towards the interior, less to the masonry exterior wall. Although the wall has an air gap so probably not as bad as it seems. The wall adds thermal mass.

An aluminum sheet might have done the same and looked a little better.