As mentioned last month, the Cambridgeshire local authorities have been awarded funds by the Department of Energy and Climate Change (DECC) to assist privately owned houses, and rented houses, with the cost of the insulation of houses with solid walls. An event that was planned by SPEP on Wednesday 23rd postponed. Grants are available towards the cost of external insulation. See details on the website www.actiononenergy.net.
Measurement of heat losses through exterior walls:
For solid walls, 45% of the total heating costs are due to heat losses through the exterior walls.
Houses of the same size, but with cavity walls are better insulated than for solid walls, and the total heating costs will be correspondingly lower. Even so, for cavity walls, 35% of the total heating costs are due to heat losses through the exterior walls, but see below for insulation benefits of cavity insulation.
The measurement of heat loss through buildings is the "U-value", the units of which are "watts/square metre" (i.e. the amount of heat passing through an area of a square metre).
Approximate values for different external wall constructions are:
Solid 9" (225mm) brick wall – U-value 2.0 w/sq m
Cavity brick wall 11" (280mm) – U-value 1.6 w/sq m
Cavity brick wall with cavity insulation – U-value 0.6 w/sq m
Modern cavity wall with insulated 150mm cavity – U-value 0.2 w/sq m
New house in Primrose Hill built in 2013 – U-value 0.1 w/sq m
As can be seen from these figures, a house with solid brick walls will lose 10 times as much energy through the exterior walls as a modern house with an insulated 150mm cavity. The new house in Primrose Hill used SIPs (Structural Insulated Panels) to give a quicker building method that is even better insulated than most new houses built today. This is likely to be the building method of the near future.
A Passive House, or a Zero Energy house, would normally have a U-value of around 0.15 w/sq m.
It is possible with external, or internal, insulation, to improve the insulation of solid 9" brick walls to a U-value of around 0.3 to 0.5 w/sq m. Again, for more information, refer to www.actiononenergy.net.
An example of external wall insulation has been installed at 15 Main Road, Little Gransden in 2002. The cost of this extra insulation has now paid for itself through savings in oil useage, as well as giving increased comfort. An example of internal wall insulation was installed in the Committee Room and the kitchen of Little Gransden Village Hall in 2013.
Trevor Brown on telephone number 01767 677285, or email firstname.lastname@example.org