Will Air Gaps Make Reflective Insulation More Effective?

To get the most out of reflective insulation like SuperFOIL, it’s crucial to have an air gap between the foil layer and the surface it’s applied to. This is because reflective insulation works differently from traditional insulation materials.

The reflective surface increases the amount of thermal radiation the surface emits. If you have a reflective surface facing into a closed air gap, it makes the air space work better at stopping heat transfer. This trick works all year round, cutting down on heat loss in winter and blocking too much heat from the sun in summer. That means less need for heating in winter and less sweating in summer, making it a smart insulation choice no matter the season.

Radiant heat moves through the air, so when you install a radiant barrier foil, you need an air space on at least one side of it to work properly. With this setup, the highly reflective foil surface acts as a barrier, bouncing heat back to where it came from and stopping it from seeping through into your living space.This keeps temperatures steady in your home AND keeps you from wasting energy on your heating or cooling at the same time. 

By having unventilated air gaps* next to the shiny outer surfaces, multifoil insulation can reflect up to 97% of the radiant energy back to its source. These air gaps essentially work like an extra layer of insulation, helping to maintain a consistent temperature throughout the house – cooler in summer and warmer in winter. In short, leaving an air gap increases the R-value (thermal resistance) of the multifoil insulation.

Air Gap Depth Guidelines

The depth of the air gap depends on the direction of airflow and remains consistent for every SuperFOIL product, regardless of the project type: be it new build, retrofit, refurbishment, or extension:

  • For roof installations, where airflow is vertical, a minimum depth of 13mm is best.
  • For wall installations, with horizontal airflow, a minimum depth of 20mm is best.
  • For floor installations, where airflow is downward, a minimum depth of 50mm is best.

As important as air gaps are, reflective insulation can still be effective even without one. The key to their effectiveness lies in the reflective surface, which is designed to reflect radiant heat away. Just remember, without an air gap, you can’t achieve the highest possible performance the multifoils are designed to provide. 

We understand that every project is different, that’s why we’re here to answer questions and provide any technical assistance you need to complete your project on time. To get specific recommendations for your upcoming project, you can speak to our technical team; please get in touch by emailing [email protected] or call us on 01636 639900.


Unventilated air gap – improves the thermal performance of the foil and enhances heat reflection. To gain the best thermal value for the air space the air space must be UNVENTILATED. If the airspace is deemed to be slightly ventilated (which is difficult to achieve) a different value applies. If the airspace is well ventilated, no thermal resistance is achieved.


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