Up until now, housebuilders have responded to demands that they improve the energy efficiency of new homes by simply adding insulation. Next year, they are going to have to do much more …

Will it still be possible for developers to put electric heating in apartments in 2006? How much insulation is going to be required? And what on earth is a heat pump? The draft version of Part L of the Building Regulations has got the housebuilding industry pondering a lot of questions.

Although the draft, which is out for consultation until October, is more than 300 pages long, it does not have all the answers, and the housebuilding industry has been left in some doubt about how to respond to the government’s drive to increase the energy efficiency of new homes. The doubts have arisen because the draft sets out a new basis for compliance with the regulations. The standard solution to improving energy efficiency in new homes has been to put another jumper on – that is, to simply increase levels of insulation and thereby hit target U-values. Instead, the new draft is basing compliance on the overall level of carbon dioxide emissions.

breaking with tradition

That shift gives housebuilders greater flexibility on how they build energy-efficient homes. Instead of relying entirely on insulation, housebuilders may choose to reduce CO2 emissions by incorporating renewable energy technology, such as photovoltaic panels and heat pumps, into homes. But that flexibility makes the job of designing new houses more complex, and more risky. Then there are the problems of dealing with unfamiliar technology: how much do they cost, where do you get them from and what do you do if they go wrong.

Before the industry can get down to debating the niceties of heat pumps, however, it has to deal with a slightly more fundamental problem: how do you analyse the full impact of the regulations when the accompanying methodology is not yet published? The standard assessment procedure (SAP), provides the essential methodology to measure the CO2 emission level of a new home. The updated 2005 version of SAP, which takes into account the draft of Part L, shows housebuilders how their designs score and where they need to improve energy efficiency – but that will not be finalised until next spring. As Homes went to press, a spreadsheet version of SAP 2005 was expected imminently.

“There’s an awful lot of new stuff to get to grips with,” says Neil Smith, group technical manager with NHBC. “Housebuilders need to be running their housetypes through the SAP spreadsheet as soon as possible. Only when they do that will they get a feel for what it means to them.”

“We’re still a bit in the dark until we have SAP 2005,” says Ian Hornby, national technical adviser at the House Builders Federation. “Previously, we could say that a wall construction would have a certain U-value; now there are too many unknowns. SAP 2005 is an absolute requirement.”

Once the industry is equipped with SAP 2005, it faces choices in finding the best solution using insulation and renewable energy technology. “It will be challenging for housebuilders,” says Hornby. “It will push the structure to its probable limits for domestic construction, and promote modern methods of construction, whether masonry, modular or framed.”

The NHBC’s Smith foresees two immediate changes in the way housebuilders work: “Housebuilders are already going through the SAP process, but the new Part L will mean that they will need to run SAP at an earlier stage, and they will need more input from specialist energy consultants.”

“I can see builders creating a shopping list of ingredients and putting a cost against each one. We have to balance cost and efficiency,” says James Wilson, development director with David Wilson Homes.

We have to balance cost and efficiency. It's such a minefield. I guess it will be a case of trial and error for a number of years

James Wilson, David Wilson Homes

“But it is such a minefield. There are so many different ways of getting to the same answer. I guess it will be a case of trial and error for a number of years.”

technology’s timescale

In the short term, Wilson expects housebuilders to opt for the familiar solution of adding yet more insulation to the structure rather than adopting renewable energy technology. It is only in the medium term, as demand increases and costs come down, that housebuilders expect renewable energy technology to become financially attractive to them.

In truth, housebuilders may not be able to wait too long. The new PPS22: renewable energy, published last month, paves the way for local authorities to demand more renewable energy resources within their area.

Specifically, local planning authorities will be able to demand that a percentage of energy used in new developments comes from on-site renewable energy.

Housebuilders may find themselves forced to consider renewable energy as a way of heating apartments, as Part L threatens to make extinct the ubiquitous electric panel heater. The NHBC’s Smith says that draft Part L makes electric heating in apartments “a very undesirable option”. The HBF estimates that housebuilders that want to fit electric heating will have to improve the insulation in the fabric of the building by about 11% in order to keep CO2 emissions within acceptable limits. As a result, housebuilders could be forced to look at alternatives that they have rejected up to now, such as gas, which is unpopular, or combined heat and power, which is unfamiliar. “We’re scratching our heads to come up with a solution,” admits Wilson, whose company’s internal environmental working group is looking at such unconventional options as biomass-fuelled centralised boilers.

Not many housebuilders know about biomass fuel, or any other renewable energy for that matter. “A lot of this isn’t familiar to housebuilders, but the role of the regulations is to bring about change,” says Richard Hodkinson, director of innovation consultant Hodkinson Consultancy and a member of FaberMaunsell’s Nectar group, which is assessing the feasibility of complying with Part L.

Hodkinson admits that it won’t be easy for housebuilders to increase their understanding of renewable energy technology. “The issue is, how strong is the supply chain, and who’s going to advise housebuilders on what equipment to install,” he says. Housebuilders are likely naturally to look to providers of technology for help, but Hodkinson says the number of companies that can provide that help and interpret housebuilders’ requirements is limited. “Manufacturers have mainly worked on big buildings so far so what language will manufacturers and housebuilders talk? A very different relationship needs to emerge and it will have to be driven by housebuilders,” he says.

The regulations will get tougher year on year ... Housebuilders should focus more on renewable energy equipment

Richard Hodkinson Hodkinson Consultancy

learning curve

The experience of London developer DPS Holdings illustrates the problem. The company has for the first time applied BRE’s EcoHomes environmental assessment system to a 13-unit conversion and new build scheme at St James’ Church in Greenwich, east London. To help achieve its very good score, the company dropped the electric underfloor heating it originally planned and fitted an A-rated boiler, energy-efficient lighting and high-efficiency white goods. It was hardly employing cutting edge technology, but Colin Yates,

business manager with DPS says:

“We had to gather much of our information from third parties. We were very reliant on suppliers providing information about their product ratings, as stipulated by BRE’s guidelines on energy efficiency and environmental quality, which were difficult to obtain.”

Although the draft Part L gives the costs of implementing the regulations as ranging from £300 for an apartment to just over £1000 for a detached house, renewable energy solutions would drive costs higher. The best renewable energy option for housing at the moment is solar water heating, which costs £3000-4000 for a family house, says Andreas Biermann, senior policy analyst at the Energy Saving Trust. “It is what’s most sensible at the moment for housebuilders wanting a renewable add-on at relatively low cost,” he says.


However housebuilders opt to meet the regulations, some costs are inevitable. There are fears that the cost burden could be particularly onerous for smaller housebuilders, who don’t have repeat designs and large-scale sites.

“There’s a need to get rules that are simple,” says John Garbutt, marketing manager of Kingspan, an insulation and timber building system maker. “The examples given at the end of Part L need to be developed so that they are robust. That is critical for the smaller housebuilders.”

Big and small housebuilders will also face the added cost of pressure testing for air leakage. Under the draft document, housebuilders can have fewer homes subjected to testing if they build with RSDs, but are not able to eliminate the cost of testing completely. “We hope that if the Part E RSDs prove successful on site that maybe the ODPM will allow us to avoid the need for testing. The industry has to prove that RSDs work first,” says the HBF’s Ian Hornby.

With so many issues to deal with, what is Richard Hodkinson’s advice to housebuilders? “The first thing they should be doing is interpreting the standards as accurately as they can, not only in terms of their existing product, but in terms of what their supply chain is and what’s required from them. They need to accept that the regulations will get tougher year on year, and if the regulations are driven by CO2, then housebuilders should maybe focus less on insulation and more on equipment.”

The overall message, says Hodkinson, is that this is for real, and that housebuilders will have to do their homework before Part L comes into force. You’ve been warned.

Part L in brief

Part L of the Building Regulations is about to be changed so that homes are assessed on the basis of their "dwelling carbon emissions rate" (DCER) using the government's standard assessment procedure (SAP). The DCER of every new home should not exceed a set rate. Housebuilders can use a combination of insulation and green technology to achieve their DCER target.

Housebuilders won't, however, be able to pack homes with green gadgets and gizmos and disregard U-values. Each element of the building fabric will be assigned a lowest acceptable U-value (see below).

Part L also places emphasis on improving the build quality of homes to minimise energy loss through air leakage. Housebuilders must either apply robust standard details (RSDs) and subject a sample of output to air-pressure testing, or carry out pre-completion testing of a larger proportion of their output.

If housebuilders opt for the RSD route, a pressure test should be carried out on each housetype on a site. If they opt for the alternative, they will have to test 5% of each housetype; the proportion is reduced to 2% if the first five homes meet the standard.

Before Part L comes into force, housebuilders will have to switch to condensing boilers with an A or B energy efficiency score under the Sedbuk rating. That is due to come into force next April. Part L comes into force by December 2005.

Reinventing masonry construction

Reports that the new Part L will signal the demise of masonry build are premature. Taylor Woodrow and Redrow Homes are taking part in a research project to prove that masonry has a future in energy-efficient house building. The project is being conducted in a 25 ha corner of the National Trust's Dunham Massey estate in Cheshire. There the housebuilders are working with Leeds Metropolitan University to build a new breed of masonry homes.

All 710 homes on the Stamford Brook scheme will be built to the new Part L. After that comes into force, the homes will have to meet more demanding standards, and feedback from them will influence the 2010 revision of Part L. The first homes are under construction and their external walls have a 142 mm fully filled Rockwool cavity and an inner leaf of dense concrete blocks. This gives a nominal U-value of 0.22.

To reduce cold bridging, glass-filled polyester wall ties are being used instead of heavy gauge steel. Leeds University recommended further measures to minimise cold bridging, notably installing double lintels: one for the internal wall and another for the external.

To minimise air leakage, the project team initially looked at returning to wet plaster, a far from ideal solution on many counts. Since then, they have found that a thin parging coat of about 4 mm produces equally good results. An air tightness level of 4.5 m3/h/m2 has been achieved. To maintain air quality, a low-energy mechanical extract ventilation system is being used, while some homes will be fitted with mechanical ventilation with heat recovery.

The homes will be monitored once they are complete, but expectations are high. "Trials and modelling have shown that there should be a 30% improvement in the energy efficiency of the homes," says Joe Isle, strategic projects director with Taywood. "The build is costing a small percentage more, but what we are achieving is new standards of masonry construction that will compete with off-site manufacturing and will use local labour."

For the trial, the housebuilders have partnered with specialist contractors and undertaken special training programmes to explain the objectives of the exercise to the operatives. "This uses standard skills, but it is a question of maintaining high quality," says Isle.

The Stamford Brook scheme has not added renewable energy into the mix. "We've concentrated on creating a building envelope to the best quality we can," says Isle. "Then we'll go on and look at renewables."

Six ways to improve the energy efficiency of your homes and what they will cost for a family house

1 - Adopt off-site construction
Changes to Part L could drive housebuilders towards modern methods of construction, experts believe. Even without the definitive SAP 2005, some systems manufacturers say their products can beat the new regulations. "We get the numbers from looking at the home holistically," says John Garbutt, marketing manager of Kingspan, maker of the TEK Haus timber structural insulated panel system (shown below). Modelling carried out for Kingspan by energy consultant XCO2 Conisbee shows that a standard housing association family semi built using TEK Haus would have space heating carbon dioxide emissions of 417 kg/yr, which is comfortably below the 563 kg/yr anticipated in the new Part L.

What’s the cost? This varies according to the system, but for the TEK Haus, the present cost is about 5% more than conventional timber frame. The new Part L will make it more competitive.

2 - Get a grant to fit a photovoltaic panel
If you want to take advantage of government grant aid for photovoltaics, you'll have to hurry as the deadline for applications for the last tranche of £2m to be given away under the four-year Energy Saving Trust programme is the end of October. Over the three years of the programme, EST has seen the number of suppliers of photovoltaics grow from 10 to about 45, but the sector is suffering short-term supply problems, because of high levels of demand from Germany. Taylor Woodrow and Persimmon Homes have installed photovoltaics on homes at their Newcastle Great Park scheme in Newcastle (shown below). "The system can be installed easily and is very user friendly," says Jeremy Speke, project manager for Taylor Woodrow.

The latest products are designed to integrate easily with conventional roofing. For example, Lafarge Roofing's PV 800 system fits flush with five of the company's slate or tiles, while the PV 80 incorporates universal fittings to integrate with almost all slates and tiles.

What's the cost? £10,000 for a standard supply. "We've seen costs come down by 30-40% in the three years of our programme. It has reached a plateau because of the constraints on supply," says Kirk Archibald, EST's photovoltaics programme manager. "The step change will come from the increase in quantity of applications. That is not far away."

3 - Be an early adopter of new micro combined heat and power
"Large-scale CHP has not had a great reputation, because early schemes were not well cared for," says Andreas Biermann, senior policy analyst at the Energy Saving Trust. Another disadvantage of CHP for new housing sites is that the gradual increase of new homes on phased schemes is incompatible with the steady power supply from CHP. The Taylor Woodrow/Countryside Properties joint venture got round this problem at Greenwich Millennium Village in east London by peppering the site with smaller CHP plants, but micro CHP eliminates the problem completely. Micro CHP plants are washing-machine sized units to supply single homes, and earlier this year the Micropower Council was formed to promote them.

Powergen began marketing its WhisperGen micro CHP unit (shown below) earlier this year. BSRIA is running a half-day seminars next month on micro CHP as part of its Barriers to innovation in housing seminar series (www.bsria.co.uk).

What's the cost? Powergen's micro CHP units are priced at £3000, fully installed.

4 - Get more familiar with heat pumps
Heat pumps may rate a mention in draft Part L, but nobody expects housebuilders to take them up in a big way. "They are more common in places like Scandinavia where the population is not dense enough to warrant mains power connection," says Andreas Biermann, senior policy analyst at the Energy Saving Trust. As far as the technology is concerned, heat pumps are relatively straightforward: "It's just a fridge in reverse," says Biermann. But installations tend to be bespoke. Powergen has worked with affordable housing providers, including Metropolitan Housing Trust, to install what it calls heat plants.

What's the cost? About £3000-4000, but that is for a new-build installation. Prices could be as much as £10,000 when retrofitting a building.

5 - Fit a condensing boiler (you'll have to do it soon anyway)
High-efficiency A- or B-rated boilers will be a must in new homes before Part L comes into force as their adoption is being required under a separate amendment to the regulation. Boiler manufacturers are already gearing up for the change, and introducing new products, like Ideal Boilers' extended family of high-efficiency boilers (shown here). Such boilers offer central heating bill savings of up to 30%, says Paul Massey, managing director of Ideal.

What's the cost? It should add £100 to the boiler bill.

6 - Get environmentally conscious with EcoHomes
The EcoHomes measurement system goes beyond energy efficiency, taking into account such diverse factors as water use, ecology and the environmental friendliness of building materials. The requirement for housebuilders to gain an EcoHomes rating on English Partnerships sites and a belief that the rating system could be used as a measurement for a broader sustainable building code to be announced next January have increased housebuilder interest in the system. Responding to this interest, NHBC is running a series of courses in understanding EcoHomes. "Like everything new, there's a lot of mystery to it," says Christine Smith, energy and environmental manager with NHBC. "Housebuilders are all looking for advice on how to achieve things cost effectively."

What's the cost? That depends on what score you aim for. Smith says: "Achieving an EcoHomes pass score on a standard volume housetype is relatively easy, but once you get to the "very good" score that English Partnerships asks for, there are quite considerable costs involved."