Appendix A – Insulation guidance
This information has been taken from the CIEH guidance on enforcement of excess cold hazards in England 2011.
(1) Dry lining (solid walls)
Thermal insulation to solid walls can be improved by dry lining external solid walls with a proprietary thermal barrier/layer/vapour check dry insulated lining system installed strictly in accordance with the manufacturer’s instructions. The thickness of the insulation shall be such as to comply with the requirements set out in Building Regulations - Approved Document L1B (Existing Buildings) for Renovation of Thermal Elements.
Special care should be taken during the fixing process to minimise piercing of the barrier/layer/vapour check; the insulation shall be continuous at edges, corners and salient features such as beams, columns and window heads/reveals so as to reduce local paths of high heat loss.
(2) Cavity wall insulation
Thermal insulation to cavity walls can be improved by providing cavity wall insulation using a proprietary method, in accordance with relevant British Standards/Agrément Certificates as appropriate (urea formaldehyde foamed insulant should not be used). The resultant U value of the walls shall be as close as is practical to 0.35w/m2˚C.
Prior to installation an assessment of the wall for suitability for cavity fill shall be carried out in accordance with BS 8208 and best practice guides from the Cavity Insulation Guarantee Agency (CIGA). Carry out repairs as necessary to the external leaf of the wall, including cracks, spalled masonry, defective mortar joints and pointing to leave in good condition to receive the cavity fill. The cause of any moisture ingress should be identified and remedied.
Holes in the inner leaf and open cavities at wall heads should be sealed. Services, ventilation ducts and flues should be sleeved through both leaves of the wall and precautions taken to isolate polystyrene and polyurethane insulation from hot flues.
(3) Insulation to pitched roof (between ceiling joists)
Thermal loss through the roof can be reduced by installing insulation between the ceiling joists in the roof space. It is recommended that all roof timbers are checked for damp, rot or infestation and remedied as necessary. Proprietary quilted or loose fill insulation material to BS 5803 should be installed. The insulation shall be applied between and across the top of the ceiling joists.
The depth of insulation to comply with the Building Regulations 2010 is around 270mm. Electrical cables shall be kept above the insulation to avoid overheating.
Ensure that adequate ventilation (including cross ventilation) is provided to the roof space; the amount determined by the angle of the roof pitch. Where loft insulation is installed, any cold- water storage tanks in the loft shall be fitted with a lid and sides and top to be insulated, omitting insulation to the underside of the cistern.
Insulate the rising main and all cold-water pipes to the loft, including overflows, with materials conforming to BS 5803 and BS 5422. Regard shall be had to BS 5803 and BS 6700 regarding installation of pipe insulation which shall be continuous over all pipes and fittings including junctions.
(4) Insulation to pitched roof (between rafters – e.g. where there is a loft room)
Thermal loss through the roof where there is a room in the roof space can be reduced by installing insulation between the rafters in the roof space.
Proprietary quilted insulation material should be installed to the main roof between and below the rafters. The depth of insulation to comply with the Building Regulations 2010 is around 270mm.
Purpose-made eaves vents that provide the equivalent of a 25mm continuous ventilation gap should be installed, as well as ventilation at the ridge in order to maintain cross ventilation of the roof space and prevent condensation.
A vapour control layer of 500-gauge polyethylene should be provided on the warm side of the insulation to prevent moist air passing through.
(5) Insulation to flat roof (concrete deck)
To minimise heat loss through an otherwise sound concrete deck flat roof, a proprietary high-density mineral wool (or equivalent) can be installed along with an inverted roof board system.
System shall be installed onto the existing waterproof membrane strictly in accordance with manufacturer’s instructions. Thickness of board is to comply with the maximum U-value in the current Building Regulations.
Allowances should be made for increased height of upstands and for preparation of the roof surface to accept boards in accordance with manufacturer’s instructions and to ensure adequate drainage.
Where a concrete deck is not sound, it should be repaired or replaced before undertaking improvement of the insulation.
Proper notice of this work shall be given to the council’s Building Control Officer and a full assessment of the existing roof shall be undertaken by a competent person, including any structural and wind loading calculations recommended by the manufacturer, prior to start on site.
(6) Flat roof (wooden deck, insulation from above)
To minimise heat loss through a wooden deck flat roof, insulation can be installed above the deck.
Thermal insulation should comply with the maximum U-value in the current Building Regulations and be fitted using a proprietary method strictly in accordance with the manufacturer’s instructions. The required thickness of insulation to achieve the above value should be confirmed with the manufacturer.
The existing waterproof layer should be repaired or prepared to receive thermal insulation and act as the new vapour barrier. If required, the waterproof layer should be stripped, decking repaired as necessary and new high-performance vapour barrier bonded or mechanically fixed to the deck using approved methods before insulation is bonded to the deck.
Bond insulation material to vapour control layer using only method specified by the manufacturer.
Allow for increasing height of upstands as necessary.
Provide a new waterproof membrane and ensure a solar reflective finish such as white chippings or solar reflective paint to prevent solar deterioration and leave whole sound and watertight.
Adequate ventilation should also be included in the schedule of remedial works.
(7) Flat roof (wooden deck, insulation between/below joists)
To minimise heat loss through a wooden deck flat roof, insulation can be installed between/below the joists.
Thermal insulation should comply with the maximum U-value in the current Building Regulations, installed using a proprietary method strictly in accordance with the manufacturer’s instructions. The required thickness of insulation to achieve the above value is to be confirmed with the manufacturer.
The existing ceiling should be taken down complete. Proprietary insulation should be installed between joists, and a thinner layer below the joists to prevent cold bridging, using fixings supplied by manufacturer. Leave a 50mm air gap between the top of the insulation and the timber roof deck and provide ventilation to this space.
Provide a new plasterboard ceiling incorporating a vapour barrier.
(8) Insulation to ground floor (suspended timber)
Mineral wool insulation can be provided to a ground floor which has access from below. Insulation should be supported by netting between the floor joists strictly in accordance with the manufacturer’s instructions to comply with the maximum U value in the current Building Regulations.
Gaps between floorboards and skirting boards should be filled with sealant (care must be taken not to block under floor air vents).