Types of flat roof insulation

Insulating your flat roof is important for saving money on your heating bills as well as reducing carbon emissions. Read on to find out about the types of flat roof insulation available.

Insulate your flat roof to save money

Heat rises and will escape quickly through an un-insulated roof. Installing insulation in your flat roof will help to prevent this from happening; keeping your home warm and saving you money on your fuel bills. Flat roofs are made up of a number of layers which are usually: the roof deck, a vapour control layer, a thermal layer, a waterproofing layer and a surface layer.

The layers that make up a flat roof

The roof deck can be made of metal, timber, concrete, composite or plywood and will support your flat roof. The vapour control layer can be made of polymeric foil, bitumen sheet, polyethylene membrane, or a self adhesive sheet. The thermal layer of the flat roof is used for insulation and is made of materials that trap air bubbles and air pockets in order to insulate the flat roof. Common materials used for insulation are mineral wool, fibreglass or polystyrene. The waterproofing layer of the flat roof is commonly made up of single-ply membranes such as thermoplastic or elastomeric; uPVC or resin-surfaces are also an option. A surface layer of stone chippings, hard resin or mineral finish is often applied to protect the waterproofing layer. It can be difficult to know which is right for your roof but your roofing contractor will give you advice on what is needed.

Wood fibre roof insulation

Wood fibre insulation is an organic board made of wood, cane or vegetable fibres mixed with various binders and fillers. It can be asphalt impregnated or coated to improve its water resistance. It has a thermal resistance value per inch of 2.78, making it fairly mediocre as insulation for a flat roof but good value for money.

Perlite roof insulation

Perlite insulation is composed of perlite combined with organic fibres and binders. Air cells are trapped within the perlite, which provides the insulation for your flat roof. The insulation board is treated with an asphalt coating to limit asphalt absorption into the insulation. Like wood fibre, it has a thermal resistance value of 2.78.

Expanded and extruded polystyrene roof insulation

Polystyrene insulation for your flat roof comes in two forms – expanded and extruded. Expanded polystyrene is made up of polystyrene mixed with a foaming agent. When exposed to heat the material expands and traps warmth. It has a thermal resistance value of 3.80. Extruded polystyrene is made of polystyrene that is heated, exposed to atmospheric conditions and then expanded. Its thermal resistance value is 5, making it a good choice for your flat roof insulation.

Polyisocyanurate roof insulation

Polyisocyanurate insulation is sandwiched between organic and non-organic felt within your flat roof. A blowing agent such as pentane is used to expand the foam material which gives it its high thermal resistance of 6.0.

Cellular glass roof insulation

Cellular glass insulation for your flat roof is composed of crushed glass that is placed in a mould and heated to a high temperature. It is available in flat or tapered blocks and provides a thermal resistance of 4.69.

Living, green roofs

A green roof will insulate
your home effectively

Although you may not have considered it before, a flat roof covered in grass and plants is a quirky and very efficient way of insulating and protecting your home. Green flat roofs have increased insulation because of their thickness and also keep your home cool in summer. Although they reduce your energy costs as well as being environmental, they can be expensive to install as the roof may require fortifying to deal with the extra weight. However, they soak up water better and reduce run off by 50%, reducing the chances of leaking from your flat roof. Green roofs are said to be able to last twice as long as a normal roof because of this.

“Cool” flat roof

You may want to consider a “cool” flat roof if you live in a hot area. The dark, heat absorbing materials such as tar and asphalt that are usually used in the construction of a flat roof can soak up the heat from the sun and transfer it down to your home. A cool roof is made by applying a reflective coating and can reduce the summer cooling costs of your home by 70%. You will also get a tax break if your cool roof meets Energy Star standards.

Flat roofs are sensitive to human traffic and are liable to split or crack if they are trodden on, leading to leaks. When having a flat roof installed it is highly recommended that you hire a certified professional because of this which also ensures your roof is safe and efficient.