ROOFING PHENOLIC INSULATION BOARDS

Phenolic roof insulation boards are the most productive type of rigid phenolic core, foil-composite insulation presently accessible for use in domestic buildings of new and existing warm pitched roof constructions where the ceiling follows the pitch of the roof and encloses a habitable space. The product is also good to be used as an insulation above the rafters and as a thermal insulation board between and below rafters, in tiled and slated pitched roofs. The product has a declared thermal conductivity λ value ranging from 0.018 to 0.021WmK and is light to handle and can be cut easily. However, care must be taken to prevent damage, particularly edge damage. Panels are very often associated with brands such as Kingspan® and Xtratherm®. Kingspan® offers Kooltherm K107 manufactured with a blowing agent that has zero ODP and low GWP. On other hand Xtratherm® offers a high-class rigid phenolic foam insulation board with a low emissivity foil facings called SR/PR Safe-R with thermal conductivity of 0.021W/mK. However, Kingspan® offers a slightly lower R-value by a minimum of 0.03W/mK. Phenolic range includes the following readily available product thicknesses: 25mm ǀ 40mm ǀ 50mm ǀ 60mm ǀ 75mm ǀ 80mm ǀ 100mm and 120mm. 

PHENOLIC BOARD PRODUCTION PROCESS

Boards are manufactured from closed-cell phenolic foam, faced with a (perforated) bilaminate aluminium foil, bonded to glass tissue on both sides, with the sizes 2400mm x 1200mm. Raw materials are injected onto the lower foil-facer on a conveyor belt. The exothermic reaction expands the foam, which then comes into contact with the upper foil-facer. An automated process cures and cuts the product to the required size.

PITCHED ROOF PHENOLIC BOARD INSTALLATION

Phenolic insulation material, when used in pitches of greater than 70°, should not be used on buildings in England and Wales that have a storey at least 18m above ground level and which contain: one or more dwellings, an institution, a room for residential purposes (excluding any room in a hostel, hotel or boarding house), student accommodation, care homes, sheltered housing, hospitals or dormitories in boarding schools.

OVER RAFTER INSTALLATION

When installing over rafters, the product must not be walked on except over supporting roof timbers. The product has insufficient nail-holding ability to be considered as an alternative to timber sarking. When installing over the rafters, it is not necessary to tape the product joints; a preservative-treated stop rail should be secured to the rafters at the eaves. The phenolic material is laid on to rafters, starting at the stop rail and working towards the ridge so it covers the whole roof area. The product should be tightly butted and fixed in a staggered pattern. Product joints should be butted over rafters, not mid-span. It is important to ensure a tight fit between the product, product and rafters and other detailed elements. At ridges and verges, the material should be cut to achieve a close-butt joint. Treated counter battens are fixed above the insulation boards down the line of each rafter, run from eaves to ridge using the helical fixings at a minimum spacing of 300mm centres. A minimum 37mm fixing penetration into the rafter should be maintained. Short lengths of counter batten should be tightly butted.

BETWEEN RAFTERS

When installing between rafters, small gaps between the rafters and the product should be filled with expanding foam. A ventilated air space of minimum depth 5mm may be required between the underside of the roof tile underlay and the upper face of the product, dependending on the specification of the roof tile underlay used. When a suitable vapour permeable roof tile underlay is used over the insulation it may be installed without a ventilated air space underneath it. When a high resistance (type HR) underlay is used, the space below it, must be ventilated in accordance with BS 5250 : 2011 Annex H. The product is cut to fit tightly between rafters and is supported on stop battens or galvanized metal angles using nailable sarking clips. The product is secured to counter battens running down the length of the rafters, and fixed at a minimum spacing of 300 mm centres through the counter batten and insulation. The product may be attached to the underside of rafters, either as a single layer or in conjunction with an insulation product between the rafters.

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Video credit:https://www.youtube.com/watch?v=wpEzX69YrYg