How to insulate rafters

Types of insulation

Under-rafter insulation is usually installed in buildings that are already inhabited, rarely in new buildings. It primarily serves to reinforce the insulation layer and thus the insulation effect. It also helps to avoid thermal bridges - i.e. the interruption of the insulation by non-insulated rafters.

Insulation under the rafters is less suitable as an individual measure. However, it makes a lot of sense if there is functional insulation between the rafters and the building is to be brought up to EnEV standard or, in general, better use of the heating energy is to be achieved.

This type of additional insulation is particularly efficient, as a significant improvement in the existing thermal insulation between the rafters of up to 27% can be achieved at low cost and effort. The usable living space is not reduced by the interior insulation, as the under rafters clamping felts are only clamped between the substructure required anyway for the interior cladding (usually plasterboard or wooden panels) and therefore no additional space is required. The additional insulation layer can also be used sensibly as an installation level - for power lines, for example.

A prerequisite for the under-rafter insulation to deliver the desired result, however, is a 100% intact existing insulation between the rafters. A thorough check by a specialist is worthwhile here - it makes little sense to add an intact insulation to a possibly damaged insulation. If in doubt, completely renewing the insulation is the safe way to go.

How exactly insulation works on a pitched roof, which modern materials are available and which advantages they have in detail can be read here.