Go to Top

How Long Does Roof Insulation Last?

There are many ways to insulate a roof, from the classic pink fibreglass pillows to wood fibres and perlite boards. Which works the best, and lasts the longest? The truth is, each type of roof insulation can be a great, long-lasting choice so long as it is installed properly and not directly exposed to extreme weather conditions. In fact, most modern insulation products are expected to last the lifetime of the house in which they are installed. In Canada, every flat roof should be properly insulated to prevent the loss of heat from the top of the building. Flat roofs whose insulation is installed under a breeze-way are called “cold roofs,” while those with solid insulation at the top of the structure are referred to as “warm roofs.”

Warm Roofs Versus Cold Roofs

Cold roofs are not designed specifically to be cold, however the name isn’t exactly a misnomer. This type of roof does have insulation, but there is ventilation space between the insulation and the ceiling. The reason for this placement is to prevent any snow on the top of the roof from melting, therefore protecting the roof and not wasting heat from the lower section of the roof. Cold roof construction is considered out-dated by most roofers and builders today. These roof types can cause such intense heat loss that cold roofs have actually been made illegal in Scotland.

On the other hand, warm roofs are designed so that the layer of insulation is directly above or below the weather-proof layer of roofing. This immediately caps the heat of your home or commercial building, and bypasses the need for ventilation space within the roof itself. Although warm and cold roofs still exist side-by-side, modern construction is based on the warm roof design.

Despite differences in design, both types of flat roofs have something in common: their insulation lasts up to 100 years.

Types of Flat Roof Insulation

While the most common type of home insulation is fibreglass, it takes a slightly more solid material to insulate a flat roof properly. The most popular kinds of flat roof insulation, ordered worst to best for effectiveness, are wood fibre, perlite, polystyrene, glass cells, and polyisocyanurate.

Wood fibre boards and perlite are some of the most inexpensive insulations that you can buy, but their heat rating isn’t fantastic. Wood fibre boards are made from a composite of small wooden fibres and other binding compounds, and the result is roughly as effective as adding extra layers of chip-board to your roof or loft area. Perlite is a compound of volcanic glass whose manufactured counterpart is much more effective.

For a very cost-effective flat roof insulation, glass cells – also called cellular glass – are a great choice. Made by crushing glass and reheating it in a mould, this insulation is both affordable and effective at keeping in heat or cold. Polystyrene is slightly more expensive. This effective insulating material is a type of foamed plastic with a myriad of applications in the building and manufacturing industries.

Polyisocyanurate is the most effective flat roof insulation material on the market today. These insulation sheets are crafted from foam and layered between organic and non-organic felt.

The Longevity of Roof Insulation

Most modern insulation materials are built to last up to 100 years. Therefore, the choice you need to make as a builder or homeowner is not which will last the longest, but which will be most effective for your budget.

Photo courtesy of Wikimedia.