Energy Efficiency in British Housing - Historic Building Regulations Energy Efficiency Requirements

Historic Building Regulations Energy Efficiency Requirements

The u-value limits introduced in 1965 were:

• 1.7 for walls
• 1.4 for roofs

Following the 1973 oil crisis, these were tightened in 1976 to:

• 1.0 for exposed walls, floors and non-solid ground and exposed floors
• 1.7 for semi-exposed walls
• 1.8 average for walls and windows combined
• 0.6 for roofs

1985 saw the second tightening of these limits, to:

• 0.6 for exposed walls, floors and ground floors
• 1.0 for semi-exposed walls
• 0.35 for roofs

These limits were reduced again in 1990:

• 0.45 for exposed walls, floors and ground floors
• 0.6 for semi-exposed walls
• 0.25 for roofs
• plus a requirement that the area of windows should not be more than 15% of the floor area.

Like the 2006 changes, it was predicted that the introduction of these limits would result in a 20% reduction in energy use for heating. A survey by Liverpool John Moores University predicted that the actual figure would be 6% (Johnson, JA “Building Regulations Research Project”).

In the 1995 Building Regulations, insulation standards were cut to the following U-values:

• 0.45 for exposed walls, floors and ground floors
• 0.6 for semi-exposed walls and floors
• 0.25 for roofs
• the limit on window area was raised to 22.5%

The 2002 regulations reduced the U-values, and made additional elements of the building fabric subject to control. Although there was in practice considerable flexibility and the ability to 'trade off' reductions in one area for increases in another, the 'target' limits became:

• 0.35 for walls
• 0.25 for floors
• 0.20 or 0.25 for pitched roofs (depending on the construction)
• 0.16 for flat roofs
• 2.2 for metal framed doors and windows
• 2.0 for other doors and windows
• the limit on window area was raised again to 25%

Similar limits were introduced into Scotland in 2002 & 2006, though with a lower limit of 0.3 or 0.27 for walls, and some other variations.

It was claimed by Government that these measures should cut the heating requirement by 25% compared to the 1995 Regulations. It was subsequently also claimed that they had achieved a 50% cut compared to the 1990 Regulations.

While the u-value ceased being the sole consideration in 2006, u-value limits similar to those in the 2002 regulations still apply, but are no longer sufficient by themselves. The DER, and TER (Target Emission rate) calculated through either the UK Government's Standard Assessment Procedure for Energy Rating of Dwellings (SAP rating), 2005 edition, or the newer SBEM (*Simplified Building Energy Model) which is aimed at non-dwellings, became the only acceptable calculation methods. Several commercial energy modeling software packages have now also been verified as producing acceptable evidence by the BRE Global & UK Government. Calculations using previous versions of SAP had been an optional way of demonstrating compliance since 1991(?). They are now a statutory requirement (B. Reg.17C et al.) for all building regulations applications, involving new dwelling/buildings and large extensions to existing non-domestic buildings.