Tin foil on steroids. Originally called Multi-Layer Insulation by NASA who invented it for the Apollo missions, it is typically 2 sheets of foil with a scrim in between. They reflect radiant energy. Sunlight is the best example of radiant energy, campfires are another example. Our bodies also produce a lot of radiant energy which is why emergency road kits often include a foil blanket.
- Reflects 97-98% of radiant energy.
- High fire rating, so it can be left exposed in many areas.
- Inexpensive option for covering fiberglass in knee walls and attics.
- Great to use with radiant floors.
- Not very effective in cold climates.
- Need an open air space on each side to reach its full R-value.