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Thermal Performance

SIPCO are able to provide various thicknesses of panel thus allowing us to achieve very low U-values ranging from 0.35W/m²K down to 0.09W/m²K. Please download our U-value table for different performances.

Use of the structural insulated panels and bespoke jointing systems can create an airtight structure that will meet and comfortably exceed the requirements of Building Regulations. Such is the effectiveness of the SIPCO system that positive ventilation methods should be considered. At the same time positive ventilation systems can be linked to heat recovery that can save energy costs.

A U-value is the amount of heat energy in Watts that can pass through a square metre of element per degree Kelvin of temperature difference (W/m²K). Building Regulations specify minimum U-Value performance criteria for building elements. SIPCO SIPS offer a solution to the strict requirements of Building Regulations, BREEAM and Passivhaus standards, giving system U-values as low as 0.09 W/m²K, with minimal heat loss via thermal-bridging (Y-value).

Thermal bridging occurs in all construction types and is caused by areas of reduced insulation or where an element passes though the insulation. Timber has a lower thermal resistance than the insulation materials placed between the framing members. Therefore, greater heat flow occurs through studs, plates, rails and joists than in other areas of the external wall or roof structures. This increase in thermal conductivity is referred to as thermal bridging. In general, thermal bridges can occur at any junction between building elements or where the building structure changes.

The Y-value is a measure of the total heat loss expected from all of the thermal bridge losses in all of the junctions in the building. The SIPCO system has a typical Y-value of 0.025 W/m²K exceeding the accredited and enhanced construction details values of 0.08 and 0.04 W/m²K respectively.

The additional heat flow resulting from repeating thermal bridges is included in the calculation of a particular building element U-value that contains these thermal bridges, such as studs in timber frame walls. SIP walls and roofs contain solid timber around window and door openings, and may contain solid timber at panel junctions. The proportion of solid timber within a SIP element will be entirely dependent on the building type and size and should be considered on a site by site basis, but the timber content can be as low as 4%, versus an average of 15% for timber framed buildings.

Insulated structural joints and connections combined with the exacting panel tolerances make SIPS one of the easier ways to achieve low levels of air leakage - as low as 0.6 m³/m²hr@ 50 pascals air pressure as standard. Additional tape can be used to reach even tighter Passivhaus standards.      

Note: Building Regulations and British Standards should be consulted for the size of the ventilation voids required in flat and pitched roofs. These regulations and standards also may pose limits on the size/spans of flat roofs for ventilation requirements. SIPCO can conduct U-Value calculations based on our system and client specifications.

Additional information can be found within the Structural Timber Association SIPS Technical Bulletin 4 and SIPS Pocket Guide.

The SIPCO U-value table provides different performances for varying thicknesses of panel - see below:

0.38 w/mk
Max 1.2m x 6.2m
0.35 w/mk Max 1.2m x 6.2m OSB / CPB / MGO / PLY
0.26 w/mk Max 1.2m x 6.2m OSB / CPB / MGO / PLY
0.21 w/mk Max 1.2m x 6.2m OSB / CPB / MGO / PLY
0.17 w/mk Max 1.2m x 6.2m OSB / CPB / MGO / PLY
0.15 w/mk Max 1.2m x 6.2m OSB / CPB / MGO / PLY
0.13 w/mk Max 1.2m x 6.2m OSB / CPB / MGO / PLY
0.12 w/mk Max 1.2m x 6.2m OSB / CPB / MGO / PLY

NB1: Thermal performance figures are unbridged values

NB2: BBA accredited panels apply to OSB facings used structurally (CPB / MGO / PLY facings are non-structural)