1 Insulate your property
You can insulate a traditional building in a various ways to reduce heat loss and save energy. A range of insulation materials are suitable for use with older properties, both listed and unlisted.
Careful thought must be given to the insulation that best suits a building’s original fabric. It must also be installed with care, to avoid damage and to realise the full benefits of the insulation over the long term.
It’s best to begin by making small changes to behaviour and your property as these have the most impact. For example, you must first draught proof your property to feel the benefit of installing wall insulation.
Find more details about insulation in our Short Guide 1: Fabric improvements for energy efficiency in traditional buildings.
2 Roof and attic
About 25% of heat is lost through a typical roof. Fitting insulation in the loft is a good place to begin to improve a building’s energy efficiency.
At least 270mm of insulation is needed for it to be fully effective.
Types of insulation include:
- natural materials such as hemp fibre board or sheep’s wool
- recycled products made from newspaper
- mineral wool
Natural materials should usually be used in traditional buildings, as they’re better able to buffer moisture and prevent condensation.
Insulation can be placed between the ceiling joists in the usual way, to give a ‘cold roof’. Fitting it instead between the rafters gives a ‘warm roof’ (wood fibre board is good in this context).
Coomb ceilings/roof spaces should be effectively insulated while maintaining ventilation throughout the roof space. There should be a gap of at least 40mm between the top of the insulation and the underside of sarking boards.
Insulating the underside of a ground-level timber floor – known as a suspended timber floor – is sometimes possible. This can be carried out from below, where there is sufficient crawl space, or by lifting floorboards to install insulation from above.
Care should be taken to avoid damage if floorboards must be lifted to install insulation. Lifted with care, most floorboards can be re-laid, with new boards added in places to make good any damage.
The benefit of adding insulation should be weighed up against the damage that its installation can cause to the original fabric of the building.
Insulation must allow a degree of moisture movement. You shouldn’t lay non-permeable insulating board on top of a timber floor, for instance: it will trap water vapour, which may cause wood decay.
Solid flagstone floors are best left alone, to avoid damage. But if you need to lift the flags for another reason, think about installing insulation at the same time. An insulated lime concrete floor can be laid under the flags.
Where original floors have been lost, installing an insulated lime concrete floor will give considerable benefits. Such work is often combined with the installation of underfloor heating systems.
4 External doors
You can install insulation in the panels of a door, which are generally thinner than its main body. This helps to reduce heat loss through an otherwise sound door.
A thin layer of a suitable insulation material should be added to the inside of the panels only. This avoids altering the building’s external character.
Thin insulation material is more expensive than other insulation products, because of its higher performance. The finished insulation should be flush with the door framework. New beads may be needed to finish the edge.
You can modify shutters in the same way, to maximise their ability to reduce heat loss.
5 External walls
This won’t be appropriate in all cases, for both technical and aesthetic reasons. But external wall insulation may be a good option to consider where an inappropriate cement render is being removed.
Replacing render with external wall insulation can improve the fabric of the building and reduce heat loss.
An appropriate insulation material might be insulated lime render containing hemp fibre or expanded clay aggregate. A board based material such as wood fibre board can also be installed externally.
Boards and spray-applied materials that don’t allow moisture to move through the building fabric should not be used.
External wall insulation isn’t right for all buildings. For example, it would badly affect the appearance of ashlar work or a masonry façade, and areas such as downpipes and roof verges are likely to be difficult to address.
6 Internal walls
It may be possible to use existing lath and plaster wall linings when insulating a traditional building internally. Often, a material such as bonded polystyrene bead or open cell foam can be placed in the gap between the lining and the masonry wall.
Where internal wall linings have been lost, a range of insulation materials can be applied to walls internally – either directly to the masonry or within a timber frame.
Internal insulation options include:
- hemp board
- wood fibre
- insulated board
- cellulose fibre
Our testing found that all of these materials significantly improved a building’s thermal performance.
These and other products can be applied in a variety of different ways. For example, boards are fitted between existing or new timber strapping and can be finished with a skim coat of plaster, and blown cellulose is sprayed on damp and a board placed over it.
Newer insulating products such as insulated lime plaster result in softer lines and edges.
Make sure your chosen materials have a good degree of vapour permeability. If they don’t, moisture may build up in the wall, leading to damp and decay.