Warm Roof Insulation Requirements

The below table shows the thickness of insulation required for a typical warm roof construction with insulation fitted above the rafters.

Warm roof insulation requirements.

There are two ways to insulate a roof. Warm loft insulation is used on pitched roofs where you are using the loft space as a room or for storage. How does room in roof insulation work. Installing a warm roof can be extremely straight forward and simple to do.

The insulation boards are placed in the space between the rafters in the loft and act as a protective layer against the cold outside whilst keeping the warm air inside. Insulation is placed in between the joists underneath the roof surface above. Warm roofs offer a superior thermal performance and therefore come with a higher cost. Thermoplastic or elastomeric are the most effective and should extend up adjacent walls at least 150mm from the roof surface.

There are two basic categories of roof design. With a warm roof the usual process is to split the insulation into two layers. Building regulations and standards set the levels of thermal insulation required when carrying out building work either for new build or refurbishment projects. With a warm roof the insulation is installed on top of the existing surface rather than in between the rafters.

If 180mm is to be installed then 100mm board might be introduced between the rafters there has to be a minimum 25mm air gap between the insulation and the underside of the tiles or slates with an 80mm board running across the rafters. Column a is for extensions where the existing dwelling s walls and roof u values are worse than 0 70 w m k in the walls and worse than 0 25 w m k in the ceiling. Cold deck this is where the insulation is placed between the joists rafters or in between the ceiling joists in the case of a pitch roof. The insulation is installed under the roof in the slope.

A warm roof has the insulation above the structural deck which is thus kept warm. The rigid insulation structure provides a complete waterproof barrier and means that the rising warm air can t escape. The waterproof layer is above the insulation and a vapour control layer is placed below the insulation. No ventilation is required for these types of roofs.

You should leave the space under the roof tiles free from insulation to give adequate ventilation so that you don t get condensation or water coming through the tiles. The roof insulation thickness will vary dependent on the required u value. Or else on the interior of the building just. Warm deck this is where the insulation is placed on top of the rafters joists and the roof covering is then placed over the insulation.

A thermal layer of fibreglass polystyrene or other insulating material should be inserted either above the roof decking the warm roof model which is suitable for homes or permanent residences.