Heat Loss - Roof

"The heat lost from the roof of an uninsulated house would typically be of the order of 26% of the total losses."

What's your roof type?


 Common Insulation Method

 Pitched Roof e.g. Sloping with tiles

Mineral/glass wool or similar fibrous material in between joists in loft.

 Flat e.g. Horizontal with felt covering

Various. Rigid foam directly under external weatherproof cover.(Warm roof). Insulation directly above ceiling. (Cold roof).

Insulation Methods

 Loft Insulation

As energy prices increase the recommendations for insulation thicknesses are reviewed. Currently the recommended depth for mineral wool insulation is 270mm (10.5") but see the Energy Saving Trust pages on loft insulation for more detailed information.
Insulation requirements are derived from the maximum heat loss that is considered acceptible. As a result insulation thicknesses vary between materials because they are not all equal in performance. Some offer higher insulation than others and therefore need less thickness to meet the maximum heat loss.

Warm Roof

There are two main methods for insulating a flat roof. The first of these is called a warm roof and involves placing insulation directly under the 'felt' on the outside of the roof. This means that the majority of the roof under the insulation is on the warm side and hence the term warm roof.
The insulation takes the form of rigid sheets and is bonded to the roof surface. Needless to say the existing 'felt will have to be removed and replacing for this solution. Warm roof materials are readily available from most builders merchants and outlets such as Wickes, B&Q etc.

Cold Roof

The second insulation method for a flat roof is the cold roof. This consists of placing the insulation directly above the ceiling. Consequently the majority of the roof is above the insulation and on the cold side.
The insulation can be mineral wool or insulated board whichever is most practical. Some ceiling height may be lost and the existing ceiling will have to be removed and replaced to incorporate the new insulation.


Ventilation has to be considered in all roof constructions. This is to combat possible damp problems created when warm moist air (from the interior of the builing) meets cold surfaces (the external roof surface). A cold roof construction is especially prone to this and so would require ventilation above the insulation. This introduces a requirement for extra space above the insulation and vents for outside air which increases the risk of further heat loss.
A warm roof does not have the above problems but installation requires replacing the outside waterproof covering.


The roof of a building accounts for one of the greatest heat losses and so the government encourage insulation through grants. Further information can be found at the Energy Saving Trust 

Assessment Tools

A hand held temperature gun can be used to survey a roof in order to gauge the effectiveness of insulation.