Achieving Fabric Energy Efficiency Standards

Building to 2013 standards, Code level 4 or 5, or looking
towards 2016 and Zero Carbon, CavityTherm in a traditional
brick wall with a reasonable cavity width will get you there!

Achieved U-values

ElementU-values (W/m²k)
Thermal BridgingY=0.05
Air Permeability5m³/hr/m²

FEES Targets (Conducted in a range of dwelling types)

U-valueUnit (W/m²k)
Walls0.15 - 0.18 W/m²K
Roofs0.13 W/m²K
Floors0.13 - 0.15 W/m²K
Windows1.2 - 1.4 W/m²K
Doors1.0 - 1.4 W/m²K
Thermal Bridging0.04 - 0.07 W/m²K
Air Permeability5.0 - 5.2 m³/hr/m²@50Pa

CavityTherm is not unique amongst Xtratherm products
in delivering thermal performance beyond simple U-values.

The Xtratherm product range that includes walls, floor and roof products deliver not only the U-value requirements
for Passive standards, but are also critical in the detailing required to reduce thermal bridging heat loss.

Floors - 0.12 W/m²K
Walls - 0.15 W/m²K
Roof - 0.15 W/m²K

Below we show a self-build project (simplified to allow junctions to be identified).
Let’s look at how the specification needs to be improved to compensate for poor detailing.

y = 0.03 (Thermally Modelled Junctions)
The equivalent of an open ‘Window’ 1.25m x 1.25m (1.56m²) opening.
y = 0.08 (Accredited Details)
The equivalent of an open ‘Patio
Door’ 2.1m x 1.8m (3.78m2)
y = 0.15 (SAP Default)
The equivalent of an open ‘Garage
Door’ 2.1m x 3.3m (6.93m2) opening.
Y-value 0.03 using Xtratherm products with approved PSI values - within Accredited details and calculated.Y-value of 0.08 based on the use of Accredited Details but not calculated by the Assessor.No particular detailing specified or witnessed
Default value
Details UsedAccredited DetailsAccredited DetailsUnspecified / or Witnessed Details

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Accredited Details for Construction (ACDs).

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