Green houses

What makes a zero carbon house?

The quest to build zero-carbon homes is plagued by controversy, but as Tony James discovers it is vital to a low-carbon future.

When people think of making reductions in carbon dioxide emissions, it is customary to look at power generation, heavy industry and transport - especially planes and cars. However, buildings contribute half the carbon dioxide emissions from the UK, and homes make up a significant part of that. Over 27 per cent of all carbon dioxide emissions in the UK are from family homes. “It’s been recognised for a few years now that we need to make some changes to the way homes operate,” Neil Jefferson, chief executive of the Zero Carbon Hub says. “Going forward with new homes, we will begin to make significant reductions in carbon emissions. It’s been a real drive of people to get engaged with thinking about how buildings can contribute towards the UK’s carbon targets.”

Back in 2006, the housing industry got together with Yvette Cooper, then the UK housing minister, with the aim of setting standards for new homes. A ten-year plan was laid out for getting to zero-carbon homes from 2016. “People really rallied around that,” Jefferson adds.

That was an era of optimism for the building industry with record new builds going hand in hand with booming profits. But since those halcyon days the housing sector has suffered along with the rest of the economy, with only half the number of expected new homes being built.

One of the most contentious issues has been to agree on the definition of a zero-carbon home. Current and previous housing ministers have had to tackle the fact that, until recently, there has not been a practical and workable definition for zero-carbon new homes. “Many critics would say that there wasn’t a definition, but that’s not strictly true,” Jefferson explains. “The definition that was set in 2006 was in the Code for Stable Homes, code level 6.”

At its most basic, a code level 6 zero-carbon home is a home which, in itself, produces no carbon emissions over the course of a year. “People can get their heads around that, but the code also includes the carbon emissions from the appliances used within the homes and the emissions relating from consumer-use within the homes,” Jefferson says.

“Assumptions can be made, but it varies from family to family, it depends whether the home is occupied much of the time, or any part of the year.”

In a previous role, Jefferson was involved in collaborating with Barrett Homes to build a zero-carbon home in Watford - the first code level 6 zero-carbon home being built by a volume builder in the UK. “It required multiple technologies to achieve zero carbon, because even once you have significantly reduced the heating requirements by having a very high fabrics standard and double glazed windows, you still need to generate zero-carbon electricity for powering all of those appliances,” he says.

Target standards

It was in building those prototypes that there was the realisation that for reasons of technical feasibility and financial viability, it maybe wasn’t making the right sense. The answer was a change in emphasis for the 2016 target with a minimum fabric standard, a minimum on-site carbon compliance standard and a framework in the building regulations for making carbon savings away from the site - or allowances or offsets.

Critics of the standard point to the fact that it is often easier and more cost effective to use offsets rather than meet the standard, a sentiment that Jefferson rejects. “What I would say about the hierarchy that we are working to is that there is a minimum fabric standard and a minimum carbon compliance standard to be achieved on sites, and both of them have been set in a way that is challenging, very challenging, but achievable,” he says. “So in terms of what is called offset, which is the allowable solutions, I guess we are trying to create a competitive market where allowable  solutions will be cheaper than doing more on site.

“It’s still too early to tell you exactly how the offsetting and allowable solutions scheme will work, but we’ve proposed a framework to government and we’ll have a better idea later in the year. Within the proposal the issues are tackled such as how long credits are good for. If developers are paying into a pot, that credit can only be good for so long. What you don’t want is for private sector organisations or local authorities just to be sat on those funds - we want them to put them to life immediately and to create opportunities.”

Zero Carbon Hub

The quest for the holy grail of carbon-free housing will forever be out of reach, and pursuit of this impossible target appears to be something of a millstone around the neck of the sustainable housing sector. “Enough people have said to me, aim for the Moon and you will end up in the stars, but generally people have been impressed with the progress that has been made,” Jefferson says. “There were a lot of people who said that the 2016 task force on Zero Carbon Hub has been kicked into the long grass, but we are still here and significant progress has been made in building regulations. I do accept the point that zero carbon means different things to different people.

“At the moment I would say ‘Yes, you can build zero-carbon homes now’. It is a challenge all the way through. The fabrics will be a bit different because you are building to a higher fabric standard, the walls are going to have more insulation in them, you are going to be using higher spec windows, and you are potentially going to be thinking about using mechanical ventilation and heat recovery for the first time.

“In terms of the technologies, you have to start thinking again. If your job is to manage the trades on site, you are thinking, ‘who is going to put those technologies in?’. It’s integration of the whole supply chain and building trade coming together; that is the big challenge.”

Local planning authority

To further the cause, the Zero Carbon Hub has been putting a lot of effort into educating upstream stakeholders, talking to people at the highest level in the local planning authority. “We are saying to planners, ‘if developers are coming to you with proposals to build zero-carbon homes, they are going to need to do this and that’. Maybe it is low-carbon infrastructure or maybe it is solar or whatever, just to make sure that the planners are aware of it.

“At senior level we are engaged with house builders so they are thinking about how they are reacting to it, and they really are thinking about it. Some of the work that we have done on the cost side is almost like a new key performance indicator for house builders to say, ‘how much are we paying for solar PV?’, because previously it was the odd site that were incorporating renewables. Increasingly it is becoming a more regular feature.
“In the same way that they are focused on how much they pay for bricks and mortar, they are thinking how much they are paying for this and is that the right solution? It certainly is becoming more the norm. So the challenges are not necessarily the existence of the products required, but about managing the integration of the whole design and build process.”

Planning policy guidance

Policies within the housing sector have been fraught with difficulties, including well-intentioned initiatives such as density guides and car parking. “It’s probably worth learning lessons from past policies,” Jefferson adds. “The interpretations of policies set by the previous government are historical, going back to John Prescott in 1999 and 2000. It was the advent of planning policy guidance, which became PPS3, which quite rightly said Brownfield first. That policy had to be interpreted at local level by planning authorities.  

“There was also guidance on density, which lead to increased density. You only have to look at homes built from 2000 onwards to clearly see that they were built to increase density. In fact from the middle of the last decade and before the recession, more than half the new homes in the UK were flats and that was because the market was booming. Local planning authorities were welcoming the idea of building to high densities on Brownfield sites, which led to more flats, and then bad times came and the producst were left unsold. Flats were built in the wrong locations; cities and towns like Leeds and the towns in Essex.”

The underlying message is that the housing market is volatile, as are the regulations and policies that guide builders. Density targets have gone; targets relating to the number of homes we build have gone. “Previous governments have said we will build two million extra homes by 2016 and three million by 2020, at an average of a quarter of a million a year,” Jefferson says. “We are building barely half of that now. And the new coalition government has got a very different views about the way that we will build more homes in the UK.”

Size matters

In terms of the size of homes, it seems as though there is a greater demand for smaller households because people are living longer, along with the increase in separation and divorce. “So arguably there’s a greater need for smaller homes,” Jefferson says. “People tell me about another issue, which is that people tending not to move out of their bigger family homes if the market is not great. Rather than selling your home for less then you think it’s worth, just sitting on it.”

With the 2016 deadline fast approaching, there is no doubt that the industry is on a fast learning curve, but the intervening five years are likely to see further tinkering with the regulations and even the definition of zero carbon - either due to political expediency or the parlous state of the house building sector.

Recent articles

Info Message

Our sites use cookies to support some functionality, and to collect anonymous user data.

Learn more about IET cookies and how to control them