Performance

Unidek/The Performance

Performance

Thermal Performance

The thermal transmittance (U-value) of the composite roof panel will vary dependent on the thickness of the panel required to accommodate the design span. However, as a guideline a U-value of 0.16W/m²K will require a composite thickness of 244mm, which in turn will provide a free span of 6m.

Fire Properties

The Roofing SIPS elements require a layer of 12.5mm plasterboard to the underside of the panels to secure a Class 1 surface spread of flame, which is normal practice in loft design. When installed correctly, expanded polystyrene products including SIPS roofing do not present an undue fire hazard. The EPS core within the Unidek Condor range of SIPS is manufactured to BS EN 13163:2001 and is made from fire retardant material.

Additional finishes (e.g. tongue and grooved boards) can be supplied for the underside of the SIPS panels, but it will be necessary to provide fire protection to the timber construction.

Air Leakage Characteristics

Roof panels are normally sealed by a layer of plasterboard and finish coat to the underside of the roof, this virtually guarantees negligible air leakage through the finished construction.

The actual air leakage between Unidek roofing panels is 0.43m³/hr/m². If this was replicated throughout the rest of the building, the rate of air leakage would be twenty times better than that required by Building Regulations. Careful consideration should be given to the Accredited Standard Detailing to ensure air tightness at all critical junctions of the building.

Condensation Risk

Provided that the SIPS roof panels are sealed to each other and the surrounding structure, the risk of interstitial condensation under normal domestic or commercial use will be minimal for constructions using a low vapour resistance tile underlay (i.e. breathable membrane). In constructions experiencing high humidity or where traditional felt underlays are used, it is recommended that a full analysis to BS 5250 is carried out to predict the condensation risk. If the predicted risk is high, then a suitably positioned vapour control layer should be used. The Technical team at Unidek can supply a full condensation risk analysis upon request.

Ventilation Requirements

The use of Unidek Condor SIPS roof panel results in a warm roof construction thereby removing the need for ventilation within the pitched roof construction. However, adequate ventilation should be provided within the finished living area of the roof to avoid any risk of Interstitial condensation (e.g. trickle vents or mechanical extraction).