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Making insulation reflective can often be useful.

One of the types of insulation used in building construction and retrofitting is reflective insulation. Other types of insulation, like fiberglass wool, rock mineral wool, and polystyrene are also available. Some polystyrene insulation is backed with reflective foil to combine the advantages of both. Each has its own advantages and disadvantages, but we're going to focus on reflective insulation.

Reflective insulation (also known as foil insulation) is usually made from aluminum foil or aluminized polyester. It is commonly used in two main areas:

This type of insulation reflects radiant heat and works best with a still air layer of at least 25mm/1 inch. It is most effective when kept clean and dust free. The layer of still air itself gives it a degree of extra insulation—provided it is still, otherwise it will be taking heat away through convection.

To understand how insulation works, some knowledge of how heat is transferred is required. Heat is transferred in three ways: radiation, convection, and conduction.

This article is accurate and true to the best of the author’s knowledge. Content is for informational or entertainment purposes only and does not substitute for personal counsel or professional advice in business, financial, legal, or technical matters.

Question: Would you recommend reflective insulation?

Question: When using reflective foil, which side should face the inside and outside?

Answer: It depends on which way you want the heat to go. Put it on the side where you want the heat to radiate away from. If you want to keep a room warm, put it on the inside. If you want to cool a room, then put it on the outside.