Roof Insulation

What Is Roof Insulation? 

Roof insulation is a crucial factor in improving a property's energy efficiency; experts estimate that up to 35% of the heat in a building is lost through its roof. 

Quality roof insulation ensures the heating and cooling systems within a property won’t expend as much energy to maintain a comfortable temperature, meaning lower heating bills and a reduced carbon footprint.

There are a variety of different types of roof insulation available on the market, so it's important to choose the right one for your project. 

The most common method is installing roof insulation boards between the rafters and then installing plasterboard on top of the insulation boards. This process is most common when the loft space is converted into a room. 

Alternatively, you can have foam insulation sprayed between the rafters by professional insulation specialists.

What Are The Four Main Materials Used in Roof Insulation? 

• Fibreglass insulation
• Insulation boards/insulation panels
• Glass mineral wool insulation
• Spray foam insulation (PUR)

Pitched Roof Insulation

When insulating a pitched roof you have a couple of options; you can either install standard loft insulation that sits on top of the joists (a method which can limit overall roof space) or warm-roof insulation, which insulates the entire loft area.

Pitched roofs are generally insulated by laying insulation boards, polystyrene insulation panels (backed with foil) or rolls at rafter level.

When tackling warm pitched roof construction, we recommend investing in a rigid insulation board such as 100mm Celotex GA4100 PIR Insulation Board, which is suitable for application between and over the rafters.

If you're looking for a more cost-effective solution, Loft Roll can be used between the rafters, with the option of installing PIR Insulation or Insulated Plasterboard over the rafters for thermal enhancement.

Please note pitched roof insulation costs will vary depending on the material and method you use. 

Warm Deck Insulation

The most common type of flat roof build-up in the UK is a warm roof deck, where the insulation sits below a waterproof membrane and above the structural deck. 

Because the insulation is above the structure, warm flat roofs do not require ventilation. A warm flat roof is typically the most simple option for ensuring that the construction meets Building Regulations.

Cold Deck Insulation 

Cold roof insulation sees thermal insulation placed beneath the structural deck, allowing it to remain cold. This design requires a vapour control layer to function effectively, in conjunction with adequate ventilation to allow water vapour to escape before it condenses on the cold deck.

Flat Roof Insulation 

Unlike pitched roofs, flat roofs don't have loft space, so the insulation must be installed between the ceiling and roof membrane. Flat roofs are often insulated with rigid insulation boards that are then covered with a weatherproof layer.

The insulation boards work to prevent heat transfer, thereby inhibiting heat from escaping in winter and entering in summer. If you're looking to install flat roof insulation, it's best to do so from the outside.  Flat Roof Insulation can also be installed from the inside, but condensation issues may arise if it is not installed correctly.

Preferably, a flat roof should be insulated from above. Install a layer of rigid insulation board either directly on top of the roof's weatherproof layer or above the timber roof surface, with an additional weatherproof layer placed on top of the insulation board. 

Flat roof insulation costs will depend on which insulation method you choose and the amount of roofing insulation required. 

Inverted Roof Insulation 

Inverted roof systems (otherwise known as 'upside down' roofs) place thermal insulation above the waterproof layer instead of below it. Keeping the waterproof membrane at an even temperature and away from damaging UV radiation or weather conditions are key advantages of this method. 

The amount of insulation used will determine how well the inverted roof performs thermally.

What Are The Benefits Of Roof Insulation? 

• Heat retention/prevention - Roof insulation controls heat transfer to help a building stay warm in the winter and cool in the summer. This, in turn, reduces energy bills and optimises the overall energy efficiency of a building. 
• Sustainability - A byproduct of energy efficiency is sustainability. The less energy a building uses, the less pollution you emit into the environment. 
• Longevity/durability - Multiple structural issues can present themselves in an uninsulated roof such as rot, damp and condensation. Installing roof insulation is a preventative measure to ensure the durability of your build.