Minimum Recommend Requirements

Fabric specification for Timber \ Steel Frame Insulation

The fabric of this method of construction is determined by the Scottish Accredited Construction Details for Timber \ Steel Frame, the y factor calculated when the measurements for each psi value are taken and calculated individually can vary between 0.06 W/m2K and 0.08W/m2K, when the Foresite typical details for the head, jamb and sills are added to these ACD’s the y factor can range between 0.02 W/m2K and 0.04W/m2K. The psi values for these Foresite details have been calculated by recognised software to a BR497 standard so that they can be used to calculate the as designed DER and the as constructed DER.

The design details for the Timber \ Steel Frame ACDs determine the Floor, Wall, Roof U values; and the probable air permeability result. The typical details shown are generic and the U values are determined by the insulations thermal conductivity and their depth. The design information calculator provides the assessor with U value calculators and design options which are suited to the 2005, 2010 building regulations and Level 4 in the code of the sustainable homes. Here are the recommended minimum performances for each element of the Part L1A specification for the 2005, 2010 building regulations and level 4 for the code of sustainable homes.

The Floor U value0.2 W/m²K
The Wall U value0.2 W/m²K
The Roof U value0.18 W/m²K
Air Permeability6 m³(h.m²)
The Thermal Bridge0.08 W/m²K
The Floor U value0.18 W/m²K
The Wall U value0.18 W/m²K
The Roof U value0.13 W/m²K
Air Permeability4 m³(h.m²)
The Thermal Bridge0.06 W/m²K
The Floor U value0.1 W/m²K
The Wall U value0.1 W/m²K
The Roof U value0.1 W/m²K
Air Permeability2 m³(h.m²)
The Thermal Bridge0.03 W/m²K

Fixed building specification of this model

the emphasis when designing a specification should always be the Fabric First approach, through good construction detailing and workmanship. Optimising the performance of the fabric limits the need to use more expensive fixed building specifications to make a dwelling compliant. The options that are provided in the Foresite design information calculator for the fixed building specification are uncomplicated and cost effective.


There are three elements that effect the compliance of a dwelling, the Fabric specification; the fixed building specification; and the design criteria of a building. The energy assessor inputs these three elements into the SAP software and a Dwelling Carbon Dioxide Emission Rate (DER) is calculated which is the measure of the performance of the dwelling, if the DER is equal to or better than the Target Carbon Dioxide Emission Rate (TER) or level of Code required in the code for sustainable homes then the building is compliant.

  • (1) The fabric specificationwhich is determined by the method of construction is the most important element because it is the most cost effective means of making a building energy efficient.
  • (2) The fixed building specification which can be expensive and complicated and are used in our models to help the fabric become compliant.
  • (3) Design of a building, there are different design criteria that determine if a building is compliant: the size of the building; how many sides are exposed; the orientation; how complicated the design of the building is with the length and number of construction junctions

Each dwelling is individual and needs to have a specification tailor made. The energy assessor uses the design information calculator which will provide recommended minimum requirements for each elements of the specification specifically for the fully filled cavity ACD, the Designer uses their version of SAP 2009 to prove the specification is compliant, if not compliant the Designer uses the suggestions from the calculator on how to cost effectively improve the specification and make the specification compliant.

© Copyright Foresite 2012. | Designed by Spintech IT ltd. | login