To highlight the energy inefficiency at the heart of the UK’s existing housing stock, Thomas Lane took energy consultant Cathy Hough to inspect a typical south London terraced house, built 100 years before the latest revision to Part L. It wasn’t pretty …

Welcome to the typical British home: no insulation in the walls, very little in the roof, single-glazed windows, wind whistling through gaps in doors and windows and a redundant chimney sucking precious warm air into the sky. An inefficient boiler struggles to keep it warm by burning prodigious quantities of fuel and spewing clouds of carbon dioxide.

There are millions of three-bedroom Victorian and Edwardian terraced houses just like this across the UK. Additionally, there are millions of semis and detached homes built in the great housing booms of the 1930s, 1950s and 1960s, and of course there are millions more built at other times, too. This legacy is responsible for 27% of the UK’s carbon emissions and, according to BRE, these homes will have to last an average of 1000 years before they are replaced because current rates of demolition are so low. So, the only hope we have of reducing these emissions is to get on with insulating the walls, roofs, doors and windows.

To see precisely how the energy efficiency of the typical British home could be improved we commissioned an energy audit on a three-bedroom Edwardian terrace in Peckham, south London, owned by one Jonathan Bell. We used the rating scheme just launched by the Department for Communities and Local Government, which you’ll have to use too if you’re selling a house after next June, when the Home Information Pack becomes compulsory.

Energy consultant ESD carried out the audit. The results are in the diagram & table attached. (See below: "How to put your house in order" & "How Mr Bell could get a B")


We start with how the walls were built because they’re the principal heat conduits. This house was built in about 1905, which means it has solid walls, in this instance 225 mm thick. Cavity walls weren’t introduced until the 1930s. ESD’s senior consultant Cathy Hough checks a newer extension at the end of the kitchen and this too has solid walls.

“If this had cavity walls the first thing I’d do is insulate them – it’s a no-brainer,” says Hough. “There are still 9 million uninsulated cavities in the UK, which is absolutely crazy as it only costs £300. There are grants available and it can save £100 a year in heating bills.”

If this had cavity walls the first thing I would do is insulate them – it’s a no-brainer

Cathy hough, ESD

With solid walls like this, however, the options are either internal or external wall insulation. External insulation means changing the appearance, which is tricky in a period property. Internal wall insulation seems the way to go.

There is some consolation here as the house is terraced, which means there is no heat loss to the house next door, providing it’s occupied. Hough points out there is limited scope for insulating the walls in this home as there are only two external walls, and these contain a large proportion of glazing. So Hough turns her attention to the double doors leading from the kitchen into the gardens. These are relatively new – and single glazed. “We did these on a budget and they were the cheapest doors you could buy,” says Bell. “You can see our lame attempts at draught-proofing, but it really makes a difference.”

The kitchen floor is solid concrete, which earns another black mark. “Ideally you would have ground-floor insulation, which brings the U-value down to 0.25,” says Hough. “But that would raise the floor so it would be a last resort.”

The living room has a bay window with three single-glazed windows that replaced double-glazed ones. “We ripped these out because they were made from aluminium and were horrible,” says Bell. Clearly, budgets can work against thermal efficiency. “We replaced all the windows in the house for £8000. If we’d gone for double-glazing it would have been double that.”

This was before the 2002 version of Part L of the Building Regulations was introduced – if Bell did the same thing today, he would be compelled to install thermally efficient windows. Hough says single-glazed windows are a big source of heat loss in this type of property, simply because they cover so much area. “The U-value of single-glazed windows is over four. Standard double-glazing is two.

In this situation, Hough advocates draught-proofing but warns that damp can be a problem if all the gaps are blocked. She says controlled ventilation is the answer, ideally in the form of a heat recovery unit in the loft as this would bring fresh air in and recover heat from expelled air. The fireplaces have been taken out, which is a plus point. “Uncontrolled ventilation of chimneys can be a massive source of heat loss,” she says.

The floor in this part of the house comes in the form of timber boards fixed onto joists with a void underneath. Of course there are gaps. Hough says filling them with a flexible sealant would help but the best thing would be to insulate beneath the floorboards. Unfortunately this is a big, disruptive job.

Most people don’t even know these grants exist. It’s not enough to leave it up to consumers to do their own research. A well publicised campaign would make a difference …

Jonathan bell, homeowner


Upstairs is a repeat of downstairs with the difference being that heat loss isn’t through the floor but the roof. The roofspace has a typical 100 mm of insulation between the ceiling joists; to bring this up to the current Building Regulations, another 170 mm of insulation is needed. The problem is this roofspace has chipboard fixed across the ceiling joists to allow the room to be used for storage, making it difficult to top up the insulation. According to Hough the options are to make the joists higher by adding lengths of wood to them, fitting insulation between, then putting the chipboard on top, or using special insulating boards on top of the ceiling joists. Bell reckons the roofspace at the rear of the house has no insulation at all because there is no access to it.

Bell fitted large opening roof lights over the bathroom and the hallway. They are double-glazed, but Hough says triple glazing would have been better. Solar gain is a problem, particularly in the bathroom. “It gets incredibly hot in here in the summer so we leave it open all the time,” says Bell.

The house is centrally heated by a gas boiler. The radiators don’t have thermostatic valves, which would help the energy rating because they shut down radiators where there are heat gains, such as in the kitchen. The boiler is a combination type. This means there is no hot water tank to leak heat, but also that a bigger boiler is needed to heat water quickly. As with many houses in the UK, there are no south-facing areas of roof so hot water solar panels are not an easy option.

After some intensive number-crunching Hough pronounces the home to have an E rating, which comes as no surprise to Bell. He says he doesn’t think a low energy rating will put people off buying inefficient houses until energy prices really go up.

He adds that the energy rating would have been useful when buying the house as it would have informed some of his decisions, particularly on buying windows. “If we had been a bit more educated about the benefits of double-glazing we might have tried to get the money together to do that.” He adds that he was unaware of the many grants available (see the “Incentives” box on the opening page). “Most people don’t even know these grants exist. It’s not enough to leave it up to consumers to do their own research. A well publicised campaign would make a difference.” Funny he should say that …

What incentives are there?


Part L of the Building Regulations increasingly compels existing homeowners to upgrade the energy efficiency of their homes. A proposal to force existing homeowners to spend 10% on general energy efficiency improvements when spending more than £8000 on home improvements was dropped from the final approved document. But Part L does demand some energy saving measures for existing dwellings when certain elements are replaced. These are:

  • All new boilers must be of the high efficiency condensing type.
  • All new windows must comply with Part L unless the home is listed or in a conservation area.

Energy efficiency grants

Grants are available to upgrade the energy efficiency of your home, but these depend on your personal circumstances. These include where you live, which energy supplier you have, whether you are on benefits, whether you own your home, and how old you are. This is made more complex as grants are administered by a number of different organisations. For example, the centrally funded Warmfront scheme is only available to people on benefits, with organisations ranging from local authorities to private companies giving the grant in the form of reduced prices for qualifying energy efficiency measures.

Another source of grants is the energy supply companies who are obliged to offer energy saving measures under the Energy Efficiency Commitment. These are usually for quick-win measures, such as cavity wall or loft insulation. Unfortunately, there is little else available to the average homeowner. And, as Jonathan Bell, our homeowner in the energy audit, points out, many energy saving measures are extremely expensive: “There’s a huge leap from spending a very small amount and spending thousands. You are either dealing with simple things like changing the light bulbs, or replacing the windows.” Bell wouldn’t benefit from money towards cavity wall insulation as he has solid walls – and this isn’t covered by a grants scheme.
A simple, nationally administered, well publicised grants scheme could encourage more people to improve the energy efficiency of their homes to the long-term benefit of all.

The 99% Campaign: what we want

Building’s 99% Campaign calls for the energy efficiency of Britain’s
existing building stock to be made a priority.


  • To provide incentives for owners to improve the energy performance of their
    buildings, whether through market incentives, taxation, grants, planning or
    whatever else has a chance of working. Over the next few weeks we will be
    discussing the options.

  • To provide clear guidance on the energy certification of existing buildings.
    The industry urgently needs details of the certification methodology so owners
    can prepare for implementation in 2009. We need a timetable for implementation
    and we need to start training energy audit inspectors.

To register your support for the 99% Campaign, email