Reflective Foil Insulation

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Reflective foil is one of the new breed of cleaner, greener and more effective insulation materials available today.

Made from layers of aluminum foil, wadding and air bubbles the material works by reflecting radiant heat when used with an air-space, whereas traditional materials such as fibreglass blankets conducts heat.

Confused? You’re not the only one. But let's try to lift the mist.

Traditional materials like fibreglass reduce heat transfer by trapping air in the mass of the blanket but this does not reduce radiant heat transfer.

Foil insulation on the other hand does reduces radiant heat transfer and does so by up to an incredible 97%.

What this means is that it produces much better results with far less material than would be the case with fibreglass and other kinds of insulation.

And, because, of the high performance of the material, foil insulation reduces vapour and moisture condensation which is usually such a big problem with products like fibreglass.

Like all products there are variations of foil insulation. It is important to check that the material meets the requirements of Section L of the building regulations, some of the products, such as that used in France, will not meet the required standard though it could be used in conjunction with other material.

The best products are made from multiple layers of foil and soft wadding and can contain up to 14 layers of material which amounts to a thickness of around 25mm.

The Benefits

  • Unlike fibreglass there are no health risks when using the material as there are no fibres to irritate the eyes or particles to inhale
  • The material can be fitted without the need to wear protective clothing such as masks and gloves
  • The material can be very easily and cleanly cut simply by using ordinary household scissors
  • Because it does not have the density of fibreglass, foil insulation does not absorb and retain heat
  • It provides a very effective vapour barrier reducing moisture build up and condensation
  • Can be fitted to rafters by using staples, nails or screws
  • The material is non-toxic and environmentally safe and, in most cases, can even be recycled
  • Ultra high performance

Using Foil Insulation

The material must be used with an open air space otherwise all the benefits listed above will be nullified.

To install the material properly and to maximise its moisture barrier the seams of the insulation must be taped.

This kind of insulation should only be used in single sheets. Doubling the thickness of the material by using two or more layers will not improve performance.

It can be used as a stand alone material or as part of a complete radiant barrier system by being used on top of mass insulation material in the roof or floor.


The good news is that the material can be very easily and quickly fitted using the minimum of tools. The material is supplied in rolls which are very easy to handle even when they are removed from their protective packaging.

As with most tasks of this nature it is best to work left-to-right and top-to-bottom. Staple the material to the first rafter or truss and unroll the length of the material stapling to each rafter or truss.

Some manufacturers recommend over-lapping each joint by around 50mm (both vertical and horizontal).

When you have finished the top layer begin the second (lower) layer, again working from left-to-right, remembering to overlap the joint slightly. Excess material can be easily trimmed with either scissors or a knife.

When all the material is fitted all the joints lust be taped with foil tape to control vapour. Counter battens can then be applied (which will provide the necessary air gap) before fixing the plasterboard and finishing off.

Some of the foil based insulation products are designed, or best suited, to be used with other products rather than as a stand alone solution so do check before using the material.

For more info see the related pages below

All About The Thermal Envelope

What On Earth Is Polyisocyanurate Roof Insulation?

Is Foil Insulation The Best Material To Use?

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