How to Insulate Old Homes

Improving the energy efficiency of existing homes is a hot topic at the moment. In February, the Govern ment published its first consultation on the subject – the Heat and Energy Saving Strategy – which suggests that, by 2020, seven million homes (or 27% of the total UK stock) will have received a whole-house energy-saving package, mostly funded by the Government either from the Treasury or via a hidden tax on our fuel bills.

But what if you want to make improvements right now? At present, there are schemes available to help with loft and cavity wall insulation, but nothing for more exacting work, such as solid wall insulation.

Lofts and Cavity Walls

There are two schemes. One is run by the Energy Saving Trust, called the Affordable Energy Scheme (0800 512012); the other is called the Heat Project (0800 093 4050), which is funded by energy suppliers. They both offer subsidised cavity wall and/or loft insulation. Anyone can apply for this grantaided work, which has to be carried out by approved installers, and the rate paid is fixed at £189, which gets you 130m² of cavity wall insulation or 55m² of loft insulation — or twice £189 (£378) if you want both. If your project exceeds these amounts, you are charged pro rata at £4.50/m². If your project is smaller, then the rate is lower.

This represents a considerable saving on the true market rates, especially for cavity wall insulation which might cost you around £800-£1,000 for a detached house. It’s not such a clear-cut bargain for loft insulation, which is easily undertaken on a DIY basis. The downside being that you have to use an installer selected by the scheme, and that you may not be offered a choice of which insulation material you can use.

However, both schemes offer a free survey to assess whether your house has cavity walls and if they have already been filled.

Solid Walls

But what if your house doesn’t have conventional cavity walls? They weren’t common before 1930 and there are many construction forms, such as timber frame, where they have never been used. If you want to improve the U-values of non-cavity structures, at present there is no grant aid.

You have essentially two choices: internal or external. Both involve placing insulation next to the existing wall and then covering over with a new wall finish. While this is not technically difficult, it invariably involves a number of adaptations. Externally, you have to sort out the details around openings, and possibly extend the roof overhang. Internally, you have to move sockets and switches, window boards, skirtings and radiators. And you will have to provide a new wall finish.

Internal solid wall insulation makes sense if it’s being carried out as part of a major refurbishment, but can be too disruptive to undertake on a piecemeal basis. External insulation, which eliminates more cold bridges, can be carried out independently. But, again, it is only a sensible option if undertaken as part of a major upgrading of an existing house, which might already involve altering the external appearance, such as when the windows are being replaced.

Three Homes, Three Different Solutions

ABOVE, clockwise from top left: Part of this Georgian cottage was rebuilt and extended, clad in original bricks. A 75mm cavity of Rockwool is fitted on the inside of 150mm concrete blocks.

100mm insulated dry-lining is fitted inside to protect the brick façade; but on the northfacing rear wall, 150mm rigid EPS wall insulation has been applied externally. (Read more about this renovation...)

Polyurethane rigid foam insulation has been sprayed into the roof of this eco-friendly barn conversion, to help create a usable first floor living space. (Read more about this project...).

NB: The actual costs of the insulation itself are not very different, however it is applied. But the additional works for solid wall insulation make it a much more expensive option.

Further reading:

• The Code for Sustainable Homes: How to get the points
• Solutions for Insulating Walls
• How to Insulate Your Loft
• How to Give Your Home an Eco Makeover