Reflective insulation and radiant barriers

Radiant barriers (often known as RFL: Reflective Foil Laminates) are in most cases a shiny aluminum foil laminated onto paper or plastic. Radiant barriers main goal is to prevent the heat of the sun (namely in attics) and is mostly used in hot and warm climates as a form of reflective insulation.

Energy savings For hot and cold climates

In hot climates, radiant barriers can lower cooling costs significantly. Savings between 5%–10% in cooling bills are often reported.

In cold climates, this form of reflective insulation in attics/roofs is rather dispensable. In these climates, it’s usually more cost effective to install higher levels of common insulation (fiberglass, sprayed foam, cellulose, mineral wool materials) than to apply a radiant barrier in an attic (usually on the underside of the roof).

Reflective insulation materials

There are three main forms of radiant barriers materials:

- RFL sheets (sarking)
- RFL concertina-type and
- RFL bubble-form.

Bubble-form is mainly used in irregular or obstructed places. RFL sheets and concertina-type materials are used in more standard spaces and frames, typically between studs joists and beams of ceilings, or walls and floors.

Uses

Reflective insulation (through radiant barriers) is mainly used in attics, but it may also be used in cavity walls and around door openings, water heaters and pipes.

A do-it-yourself job?

Reflective insulation is fairly simple to install either in new or existing homes. Materials are lightweight and easy to handle, clean and non-toxic.

There are, anyway, some particularities that you should take into account, namely the manufacturer’s instructions and basic safety precautions. You should also check fire and building codes. And do not forget that a poor installation means a low performance…

Warranties

Warranties involving reflective materials vary a lot by manufacturer, but you shouldn't worry too much about that: radiant barriers are resistant to harsh conditions and very durable.

Costs

radiant barriers costs in the 15–70 cents per square foot are common. Some products combining insulation and reflectivity are more expensive.

Installation of reflective insulation in attics (Roof-ceilings)

The simplest way to install reflective insulation is to lay the radiant barrier directly on top of existing attic insulation, with the reflective side up. But this isn’t a good option, due to moisture problems (even if products are perforated) and dust accumulation, that will strongly reduce the performance of the system.

A much more efficient alternative is to apply the reflective material between the roof sheathing and the attic floor insulation. Many radiant barriers are placed at the top cord of trusses or draped over them.

The schemes below, from RIMA (Reflective Insulation Manufacturers Association), show two common and efficient methods of installation.

Reflective Foil Reflective Foil Insulation

In the case of foil-type barriers, it's important – for efficiency and ventilation goals - to introduce a minimum air space between (1.0 inch/2.5 cm) between the material and the bottom of the roof.