English Heritage Climate change & your home — Frequently asked questions

Frequently asked questions

Frequently asked questions

Q: I know old buildings need to breathe what does that mean for lofts?

A: Old buildings do need to allow moisture to move in and out of the fabric to keep dampness below the levels at which decay can set in. This means that impervious materials, like metal foil backed insulation, plastic foams, and waterproof paints, should never come into contact with permeable fabric such as roof timbers and lime ceilings. There are lots of good alternatives which are ‘breathable’.

Q: What kind of materials should I use to insulate my loft?

A: There are several types of materials available that are suitable for use as insulation in traditional buildings. These should have good thermal insulation properties, but should not impair evaporation of moisture or cause it to be held against the building fabric. Mineral wools are acceptable in most situations. Natural fibre based insulation, such as sheeps wool or hemp/cotton fibre mixes, may be preferred on environmental grounds.

Cellulose insulation (cellulose fibres derived from newsprint) is an alternative material to fibreglass and mineral fibre, but its performance can be compromised if it comes into contact with moisture. Loose fill cellulose insulation can be installed between ceiling joists as a DIY improvement. Where blown or vertical insulation is required this must be carried out by an approved specialist contractor.

Q: What kind of materials should I use for sarking insulation?

A: Because sarking insulation is in contact with timber rafters it is important that it is breathable. There are a number of suitable products on the market, most of which are based on wood fibres.

Q: Is insulating foam suitable for roofs of traditional buildings?

A:Insulating foam (isocyanurate) is sometimes sprayed directly onto the underside of slates and tiles and sets into a hard layer with strong adhesion. Foams are claimed to improve insulation and waterproofing, preventing tiles or slates slipping and avoiding condensation. Sprayed foams are not recommended for historic buildings. They prevent the slates and tiles being salvaged during the next re-roofing, the tiling battens and the upper parts of the rafters are sealed in, which may lead to rotting. Such insulation can also restrict the normal flow of air into the roof space.

Q: What thickness of insulation will I should I install?

A: Different insulation materials have different properties so it is always worth checking with the manufacturer or supplier if you have a target standard you want to meet. Also the Building Regulations change from time to time (and are different in the different countries of the UK), so it is worth checking the current regulations.

To meet the current Building Regulation standards in England approximately 225 mm of sheeps wool insulation would be required above a lath and plaster ceiling. For inhabited lofts a total thickness of around 200 to 225 mm of insulation above, between and below the rafters is normally enough to meet the standards. There is flexibility within the Building Regulations to vary the targets if installing large thicknesses of insulation would spoil the character or appearance of an historic building, or if it would dramatically reduce the usable space of a room.

Q: Do I have to upgrade my roof to meet Building Regulation standards?

A: No. The Building Regulations only apply to new building work, so there is no need to upgrade an existing roof to meet the standards if you are not doing work to it. However, installing insulation will help save money on fuel bills and increase the comfort of your home.

Q: My old ceilings are in a poor condition should I replace them?

A: Old ceilings, particularly those made of lath and plaster, are important, distinctive parts of traditional buildings and are worthy of conserving. Suitable laths and lime plaster mixes are now readily available, though as with any plastering, skill is required to achieve a good finish. Remember that spending a little extra to conserve the unique historical feature of your home will increase its attractiveness to prospective future purchasers and repay your investment when you come to sell. Remember also that consent would be required to replace a ceiling in a listed building.

Q: When Ive insulated my loft, will I still be able to use it for storage?

A: Yes, but its worth planning this before you install the insulation so that crawl boards or walkways can be fitted. Even lightweight stored goods can compress insulation causing it to lose some of its effectiveness. Walkways will reduce the risk of damage to ceilings and of injury caused by stepping between joists: they are essential if a second layer of quilt insulation laid over the joists has concealed their position. For most roofs it is a good idea to at least provide walkways to give access to the roof space for routine maintenance of tanks, wiring, aerials etc.

Q: Do I have to change my loft hatch?

A: Not necessarily, though the access hatch to the roof space in many buildings is not insulated and is poorly sealed. This can undermine some of the benefits made in insulating the roof space. Insulating and draught-sealing the loft hatch are relatively simple tasks that are very worthwhile. The effectiveness of the draught-seal is significantly improved if the loft hatch is secured and held firmly in position with bolts or catches.

Q: I think I have bats living in my loft, can I still insulate?

A: Yes, it is normally possible to plan and install insulation without disturbing the bats. Bats are a protected species under the Wildlife and Countryside Act (1981). It is an offence to intentionally kill, injure or take a bat and, with regard to sites used by bats, it is an offence to intentionally damage, destroy or obstruct access to any place used by bats, even when bats are apparently absent, or to disturb bats while roosting. If you do think that you have bats in your roof contact your local Natural England office for free advice before you begin work.

English Heritage Climate change & your home - Frequently asked questions

Q: Should I remove any old insulation before adding new?

A: Not necessarily. If the old insulation was well installed without any gaps, if it is in good condition and most importantly if it is dry, then it can be left in position and added to.

Q: My rooms are draughty but thats nothing to do with the loft is it?

A: It might be. Lots of draughts enter or leave via the ceiling. There are often cracks and holes in ceilings, particularly around pipes and cables where they pass through the ceilings, and around recessed light fittings. The sealing of such cracks and joints as part of an insulation package can reduce the levels of draughts significantly. The cracks should be sealed to prevent moist air from the habitable accommodation entering the roof space and adding to the risks of condensation, especially from areas of high humidity such as bath and shower rooms-look for spiders webs, spiders like to build their webs in areas of air movement.

Q: What should I do about the cold water tank?

A: It is important that all plumbing and water tanks are insulated in a cold roof (where insulation is placed at ceiling level), as the loft insulation will make the roof space colder increasing the risk of freezing. The cold surfaces of tanks are also prone to condensation that can run off and over time lead to decay in the nearby timbers. The area below water tanks should be kept free of insulation, unless the water tank is raised well above the joists.

Q: Should I insulate beneath the parapet gutter and valley gutter in my roof its very awkward to get to?

A: To be effective insulation must be laid to the same depth throughout the roof space, even in awkward areas such as below central valleys and parapet gutters, otherwise cold-bridging and associated problems such as damp and timber decay may occur. Inserting insulation under valley and parapet gutters may require the stripping of the roof coverings and the lead that forms the gutters. This is quite a substantial and costly undertaking.

Q: My house is a listed building. Will I need consent to install insulation?

A: Check with your local planning authoritys conservation officer as every building is different. Simply installing insulation in a loft is unlikely to require permission, but any alterations to the ceilings themselves are likely to need consent. Insulating above the rafters, resulting in a change in the roof line, should never be undertaken without permission.

Q: I live in a Conservation Area; do I need permission to insulate my roof?

A: Check with your local planning authoritys conservation officer as rules vary from area to area. Purely internal work is unlikely to require consent, but altering the roof to accommodate insulation would require planning permission in most conservation areas.


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