Roof insulation in progress at Greys Court, Oxfordshire
Greys Court, Oxfordshire © Historic England
Greys Court, Oxfordshire © Historic England

Insulating Roofs in Historic Buildings

This page provides advice on improving the thermal performance of various forms of roof by adding insulation. Older buildings can have a wide variety of roof forms and materials, often within a single building, each of which may require a different technical solution.

Insulating roofs at ceiling level

For most roofs placing insulation above the ceiling of the top floor can be cheaply and easily achieved without significant modification. High levels of ventilation can usually be achieved which reduces the possibility of any condensation occurring within the cold roof space. 

Insulating roofs at rafter level

For buildings with rooms in the roof space, insulation can be added above, between or beneath the rafters or as some combination. However, the design of the building may restrict some of these options.

Adding insulation above the rafters can change the position of the roof covering in relation to abutments and eaves so this needs to be carefully considered. 

Insulating flat roofs

Many older buildings have areas of flat roof, typically over extensions or porches. Insulating these areas can in many cases be relatively difficult so care is needed to make sure the work is effective and does not cause problems.

If insulation work is being carried out to the main areas of roof it is important that flat roofed areas are not forgotten.

Insulating dormer windows

Older buildings often have dormer windows which come in a variety of shapes, sizes and materials. If the main roof is being insulated then it is advisable to consider insulating any dormer window which is a part of that roof.

Insulating thatched roofs

Thatch has a much greater insulating value than any other traditional roof covering and therefore adding insulation may not be appropriate or necessary. However, if insulation is added it is important that the material and detailing are compatible with the highly permeable nature of this material. 

Open fires, chimneys and flues

Whether used or unused, fireplaces and chimneys can have an important role in improving the energy efficiency of a building. Open chimneys can be sources of useful ventilation but they can often let too much warm air out and cold air in.

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