Radiant Barrier vs Bubble Insulation: Which One Do You Need?
Radiant barrier and reflective bubble insulation both stop heat the same basic way, but they are built for different jobs. Picking the right one saves money and gives a better result. Here is how they compare, using the values on IIP’s own data sheets.
How both of them work
Most heat that comes through a hot roof travels as radiant energy. A metallized surface with very low emittance reflects it. Our ReflectaShield Pro, for example, has an emissivity of 0.05, which means it reflects 95% of radiant heat. The reflective face needs an air space next to it to work: the R-values we publish assume an enclosed air space of at least 3/4 in (19 mm).
What makes them different
A radiant barrier is a thin, reinforced sheet: metallized film on a woven polyethylene scrim. Bubble insulation adds one or two layers of closed air bubbles between the faces. That adds thickness, stiffness and a little more R-value, and it turns the sheet into a liner that can span framing on its own.
| ReflectaShield Pro (radiant barrier) | Double Bubble Foil/Foil (bubble) | |
|---|---|---|
| Build | Metallized film, woven scrim, metallized film | Metallized film, two air-bubble layers, metallized film |
| Thickness | 125 µm (0.125 mm, 4.9 mil) | 5/16 in (7.9 mm) |
| R-value, heat flow down* | R-7.57 | R-7.95 |
| R-value, heat flow up* | R-3.67 | R-4.05 |
| R-value, horizontal* | R-5.04 | R-5.42 |
| Fire rating | Class A / Class 1, ASTM E84 | Class A / Class 1, ASTM E84 |
| Roll | 48 in (1,219 mm) × 125 or 250 ft (38.1 or 76.2 m) | 4 to 8 ft (1.22 to 2.44 m) × 125 ft (38.1 m) |
| Roll weight | 14 lb (6.4 kg) per 500 sq ft (46.5 m²) | Heavier, stiffer roll |
*With a minimum 3/4 in (19 mm) enclosed air space, as the FTC R-value Rule requires.
Choose a radiant barrier when…
- You are adding a reflective layer to an attic, on the rafters or over the joists.
- You need it under metal roofing or on a roof deck.
- Light weight and fast coverage matter: a 250 ft (76.2 m) roll covers 1,000 sq ft (92.9 m²).
Choose bubble insulation when…
- The sheet has to span purlins or girts as a liner in a metal or post-frame building.
- You want a vapor retarder: Double Bubble Foil/White tests at 0.01 perm (ASTM E96).
- You want a bright, finished white face inside a barn, shop or poultry house.
- You are insulating crawl spaces, ducts, pipes or water heaters, where a thicker, softer sheet is easier to wrap and fit.
Read the conditions, not just the number
The same product has three different R-values depending on whether heat flows down, up or sideways, and all of them depend on the air space. Under the FTC R-value Rule, sellers must state those conditions. If a reflective product is advertised with one big R-value and no conditions, ask how it was tested.
Questions we get asked
Does a radiant barrier replace regular insulation?
It works differently: it reflects radiant heat instead of slowing conducted heat. In attics it is usually added alongside the existing insulation. Check your local code for the R-value your building needs.
Which way does the shiny side face?
Toward an air space of at least 3/4 in (19 mm). Without the air space, a reflective face cannot do its job.
Which costs less?
Radiant barrier costs less per square foot. Bubble insulation costs more, but it also spans framing as a liner, retards vapor and can give a finished white face.
Not sure which one fits your building? Send us the job details and we will recommend a product and quote it delivered, or compare everything on our products page.