Are housebuilders failing to build to zero-carbon standards - as suggested by minister Andrew Stunell - or is the failure to build due to a flaw in the targets?

You might think the built performance of new homes against energy targets was something of a technical issue. One for the propellerheads at the BRE. Not a bit of it. Last week’s hand-grenade lobbed by junior communities minister Andrew Stunell into the discussion about just how energy efficient today’s new homes are has detonated into a fully-fledged industry-wide debate over the future of new homes.

The UK will fail to meet its carbon reduction targets unless not building to designed performance is tackled

David Strong, David Strong Consulting

Stunell was speaking - or grandstanding, as one unnamed housebuilder described it - to the Lib Dem conference last week when he said the government’s zero-carbon target risked becoming an “empty slogan” because of the industry’s failure to meet designed targets. Based on the evidence of detailed assessments of a small number of homes, and in the teeth of deep frustration from housebuilders over his choice of language, he will now set up a new committee to tackle the issue - despite the fact there are already working groups set up to deal with the problem by the communities department, and meetings between industry figures and the government over the summer. The question is whether Stunell is right, which would mean there’s a problem here, and if so, what can be done about it?

One person who agrees whole-heartedly with the minister is Malcolm Bell, professor emeritus at Leeds Metropolitan University, and lead author of the study Stunell referred to in his speech - an examination of a group of homes built by the Joseph Rowntree foundation in York at Elm Tree Mews. This found that the amount of carbon emitted by the homes would be more than twice as much as expected - 6.4 tonnes a year as opposed to 2.7 tonnes - with heat loss 54% greater than designed. And, despite being carried out in just four houses and two flats, Bell thinks the conclusions have ramifications for the whole industry: in the history of testing built performance of new homes, he says, not one he knows of has reached or exceeded its designed performance. “Yes we haven’t done a large survey yet, enough to know the exact distribution of problems. But enough work has been done, both in Elm Tree Mews and previous studies, to suggest there is significant risk of a gap between design and actual performance.”

His view is backed by the findings of the Zero Carbon Hub, the pan-industry group advising the government on its zero carbon strategy, which published research earlier this year suggesting that making the improvements necessary to ensure built energy performance matched its designs are so complex it will take a decade for the industry to achieve. The Hub advised the government to force builders to build to a higher standard on the assumption that the finished home will miss that performance target but achieve the original standard.

But this view is controversial, particularly for housebuilders. Critics of Stunell’s position point out that the proposed zero carbon target, whereby all new homes must be zero carbon by 2016, is the toughest in the world. Furthermore, a survey by the RICS last week found the UK was in the top three countries in the world in terms of working toward zero carbon in the built environment.

Housebuilders resent Stunell’s description of the problem as one of compliance with standards, which they say implies housebuilders are attempting to get away with not building what they’re supposed to. John Slaughter, policy director at the Home Builders’ Federation (HBF), says: “Andrew Stunell seems to think housebuilders are wilfully not achieving results - well there is absolutely no evidence of that at all. The issue is not one of compliance, it’s about whether the regulations housebuilders comply with are fit for purpose in delivering the results the minister wants.”

Essentially, the HBF’s position is that housebuilders do build to the standards they are supposed to, demonstrated by the fact homes aren’t failing post construction building control tests on this basis. Instead, Slaughter says, the regulations housebuilders are asked to meet don’t lead to the lower emissions they are designed to produce. He suggests that the software used to model how much energy a house emits - known as SAP - contains flaws that if addressed could potentially make a much greater difference than compliance issues. It is a common refrain: Elizabeth Ness, group sustainability executive at housebuilder Crest Nicholson, says: “The fundamental basis of SAP is sound, but actually working with SAP is a real challenge.”

Slaughter says the HBF has offered to help the government work up a more detailed evidence base on the whole issue. “At the moment there’s certainly not enough evidence to base a policy on.”

But here the debate hots up further. Some allege that the reason there is little evidence of homes not meeting current standards is because energy performance isn’t being tested by Building Control. David Strong, former BRE environment boss and director of David Strong Consulting, says the building control system needs root and branch reform. At the moment, he says, officials are more focused on picking up on life and death issues such as fire safety than on whether a building meets energy efficiency stipulations. He says: “I’ve never heard of a building being failed because of energy efficiency failings.

“Unfortunately there seems to be an unholy alliance of vested interests here. With privatised building control officials reliant on housebuilders’ business and competing on cost, it’s not in their interest to rock the boat. But the UK will fail to meet its carbon reduction targets unless the issue of not building to designed performance is tackled.”

Unsurprisingly, Building Control officers disagree with this view. Paul Everall, chief executive of Local Authority Building Control, says the energy performance of buildings is very high up officers’ agenda, and that given the average eight or nine visits officers make to a house, they are well placed to assess whether designed standards are being adhered to. The reason homes don’t fail the system, he says, is because problems are picked up and improvements made along the way. But he doesn’t deny there are commercial pressures which don’t make it easy, and that future improvements in energy efficiency standards in 2013 and 2016 will make things even more challenging. “You would now be hard pushed to find a local authority that doesn’t take this issue very seriously. But competition [with private sector inspectors] doesn’t help, there’s a danger it will drive down standards, and there’s a temptation to cut corners.”

This is exacerbated by the fact it is difficult to test for energy performance. The tests at Elm Tree Mews took weeks, and Bell that says while there are suggestions of how
to shorten this to two or three days, currently there are no quicker options. Everall says his body is working to find a quicker alternative, but the problem remains. “There is very little incentive, if any,” Bell says, “for the housebuilders to invest in processes that will improve the built performance of their homes.”

So how does this mess get sorted out? First of all a degree of openness from housebuilders and standard setters is a prerequisite. The question of how construction products perform, not just in the lab but in the home, will also have to be addressed. For example at Elm Tree Mews prefabricated timber frame panels leaked more energy than suggested because they had to be adapted to bear heavier structural loads. Ness says: “It’s about assured build performance from the beginning to the end of the supply chain.”

Many of the housebuilders are pinning their hopes on a consultation on the revised version of SAP, due in the autumn. However, the limited evidence so far suggests Stunell is right to be worried that this is unlikely to sort out the problem. For real change in the industry to take place companies and trade bodies need to be brave about collaborating and sharing information about how energy efficient homes actually get built in practice.

Why do new homes perform so badly?

Thomas Lane

Thomas Lane, Building’s technical editor 

There are various reasons why new build homes perform so poorly. The first is that SAP, the software used to predict performance, isn’t 100% accurate. It doesn’t account for every condition that affects performance nor can it cope with unusual technologies or designs. It is regularly revised and is improving, but there is some way to go.

The second reason is home construction isn’t up to scratch. In some cases this is down to builders taking short cuts such as installing less insulation than called for by regulations. In theory, this should be picked up by Building Control but if officers are stretched they tend to focus on life safety regulations such as structure and fire. Also it is difficult to tell if a floor has been insulated properly once the concrete has been poured.

In many cases builders aren’t trying to take short cuts but fail to meet increasingly onerous construction standards. Eliminating thermal bridging and building highly airtight homes requires forensic attention to detail, which most housebuilders are not used to doing.

The third issue is system performance. Products are tested in isolation in laboratory conditions but once these are combined into a system onsite performance can radically drop off. For example the Energy Saving Trust tested 89 heat pump installations to see how well these performed. To qualify as a renewable technology the systems must produce 2.9 units of heat for every unit of electricity used to run the heat pump. The tests revealed that three quarters of the installations wouldn’t qualify as a renewable technology. In most cases this was down to poor quality system design and installation, in some cases heat pumps should never have been selected as the heating technology.