Existing Buildings
Renotherm is a spray-applied, chemically modified polyurethane foam applied to the underside of the roof which bonds slates and tiles to each other and to structural or supporting timbers to replace the anchorage of fixing nails. It is a much less costly alternative to re-roofing and can be applied to slates, tiles, pantiles and other various roof coverings. It permanently cures the problems of nail fatigue and makes the roof much more resistant to storm or impact damage.
Insulation
Because it is liquid when it is applied it seeks and seals any unwanted air leakage that may occur, preventing the ingress of wind-driven rain, snow and dust and dramatically reduces heat loss.
The foam has a 'K' Value of 0.02W/m2K and when applied to an average depth of 40mm the 'U' Value of a roof (with 100mm of mineral fibre at ceiling level) is reduced from 0.35W/m2K to 0.20 W/m2K. The foam can be applied to thicker depths to surpass the most stringent Building Regulations. To achieve 0.16W/m2K for instance, only 85mm, including the batten depth is required.
Installing the insulation at rafter level keeps the loft void warmer and prevents condensation build up which otherwise occurs whenincreasing insulation at ceiling level. The warmer, drier, cleaner roof space eliminates the risk of pipes and tanks from freezing.
Wasteful ventilation in roof spaces is no longer required and the unventilated roof void complies with ISO 13788:2002 (and BS 5250: Appendix D) Code of Practice for Control of Condensation in Buildings with no occurrence of surface or interstitial condensation. VAT is charged at only 5% for installations in homes to encourage energy efficiency.
The water vapour resistance of Renotherm 600MNs/g is sufficient to prevent interstitial condensation but allows the battens, which are covered on three sides by the foam, to 'breathe' and by preventing wind-blown rain and snow the battens stay dry.
Renotherm meets Class 1 Surface Spread of Flame when tested to BS 476 Part 7: 1997.
Renotherm slows the deterioration of tiles and slates by frost. On the underside of the covering frost damage is eliminated. On the weather side the frequency of the freezing/thawing cycle is reduced. Slates and tiles will be less prone to damage by impact as the foam distributes the forces. Where slates and tiles are damaged after installation, they may be replaced by cutting away the foam from the underside, replacing the slate or tile and re-treating the affected area. Aerosol cans are suitable for small areas.
Test data confirm that although Renotherm adds only 2kg/m2 total weight to the roof, roofs treated with Renotherm have sufficient cohesive and compressive strength to transfer the loads imposed by the roof covering should the battens be deficient.
Renotherm contains no nutritional benefit and is not attractive to vermin or pests and closes off common access routes. Tiles and slates adhered in place prevent theft. It has been found to be particularly suitable for historic and listed buildings where it is important to maintain the original character of the roof.
