20 Dec 2007

Why I don't think Code Level 6 is such a great idea

A thought provoking piece over on Fairsnipe questioning whether the Code for Sustainable Homes goes far enough. Martin’s opinion seems to be based around the fact that Barratt have recently been awarded a contract to develop 200 top Level 6 homes at Hanham Hall in Bristol. “Even failed newspaper baron Eddie Shah is reportedly building low cost homes that meet level 5,” he writes.

His implication being that if an amateur can get to Level 5 at low cost, and a box-basher-outer like Barratt can do Level 6, then the bar has been set too low.

I see a similar reaction to the Code as we did to Egan’s Rethinking Construction - we didn’t need it, we couldn’t do it - it will cost too much and then suddenly with a great coat of whitewash everyone was Egan compliant.

I see where he’s coming from but I think he’s completely wrong on this one. Why? What’s wrong with the Code for Sustainable Homes and, in particular, Code Level 6, the zero carbon house.

1. It demands the use of micro renewables to offset the energy being used. I believe that our future energy needs are going to met by a green grid-based solution. The same logic that brought about the creation of the national grid in the 1930s applies today just as it did then: localized power production is an inefficient use of resources. Micro renewables are expensive and often unsuited to small sites, yet Code Level 6 insists that they are fitted to all new homes after 2016. Far better to build and professionally manage large grid-based renewable power stations.

2. The low-energy side of the Code for Sustainable Homes is based pretty much on the PassivHaus standard. Whilst this is the acknowledged gold standard in the field, it’s not without its critics and no one has yet completed a Passive House in the UK, yet alone lived in one for a few years to find out whether it’s as good as its cracked up to be. Its fans claim that it costs only 5-10% more to build to this standard but I am not convinced about this: in theory, the list of differences may only be marginally more but to build a Passive House with air changes at under 1 q50 (as opposed to the current UK standard of 10 q50) takes a lot of attention to detail. Not “Bodge it up, bush, bush” which is how we build most houses in Britain.

3. Even if we overcame this hurdle, it’s still not clear to me that the PassivHaus standard translates to the UK climate, or our customs. For instance, what is the point of fitting triple glazing inside technically impressive insulated frames (U value 0.8 or under) when over half of us like to sleep in rooms with the window open all year round? I don’t think anyone has thought this through.

4. There is a whole ton of stuff in the Code for Sustainable Homes that has nothing to do with low energy housebuilding. The water restrictions are technically very challenging and will require rainwater harvesting systems to be installed on all new properties. This may be a noble aim in the low rainfall regions of the UK, but what if you are building in the Lake District where they have more water than they know what to do with? Lifetime Homes? Good stuff. Considerate Constructor scheme? Right on. But the crisis facing us is climate change, so what are all these other noble initiatives doing in here, muddying the water?

In summary, I find myself in a strange position. I think the idea of having a road map showing us how we should be building in the future is a great idea and I applaud the DCLG for being bold enough to bring on such a plan – it should have happened years ago. But I just feel that the Code for Sustainable Homes is the wrong plan. It’s all very well it being technically challenging to get to Code Level 6 — it is, despite what Martin seems to think — but the goal has to be rational and workable as well. Getting to the top levels of the Code, as it stands, involves substantial costs for very little benefit: that’s not clever, it’s a waste of precious resources. For every pound spent stretching a house from Code Level 3 to Level 6, you could save twenty times more energy addressing the energy gaps in the existing stock.

Afterthought: I don’t wish to snipe at Barratt for taking on this Code Level 6 project in Bristol. I think it should be built, occupied and monitored for three or four years to see how it works. That would take us to….about 2014. That would be the time to make a final decision about the roadmap.


  1. Mark, I have a couple of comments about your post, I am head of Sustainability and Innovation at HTA, the architects for the scheme.
    Firstly, there is no evidence that building large power stations is more cost effective than microgeneration. I believe that the answer lies somewhere in between the two, lets call it mediumgeneration. By having the 'energy centre' close to the homes and by using it to generate heat and power we can get above 80% efficiency, more than twice the average efficiency of grid based power stations. I also think that microgeneration will work in some cases but not in many cases.

    Secondly, you say that the other aspects of the Code 'muddies the water'.
    What the code does is set some non-negotiable targets and some negotiable targets, and in the short term those negotiable ones can be used to provide the most appropriate scheme to each region. So, if the water targets are inappropriate, then don't go for the highest level in an area of high rainwater. In general, the code requires a detailed design of each scheme, which can only help to deliver better quality and more energy efficient buildings.I agree that there is another level of thinking to be done on how to apply the code to very small sites where some of the requirements will make small sites uneconomic, and and how to apply the code to regions with different rainfall and sunshine in the UK

  2. Rory,

    Green power stations: the only renewable technology that really makes sense at the micro level is the roof mounted solar hot water panel. All the ones that generate electricity are far better concentrated in professionally managed farms. People argue about grid transmission losses but most commentators reckon they amount to less than 10% of the total load: that's small fry compared to the installation losses on, for instance, mounting PV arrays in non-ideal orientation, which will be happening on hundreds of thousands of rooftops.

    Put it another way. What is the advantage in NOT being connected to the grid? And if you do connect to the grid, then location becomes much less important. What is so special about the rooftops of new houses?

    As for muddy water: I think you'll find that the water use targets are not negotiable. Code Level 6 demands a notional water use of less than 80litres/person/day and doesn't make any allowances for where the site is. IMHO, that's nuts.

    You need to score at least 90% of the maximum possible points to meet CL6, so the wiggle room is wafer thin. At a site like Hanham Hall with 200 homes, such a target may be breeze, but it will render many small sites undevelopable. That's also got to be nuts.

  3. AnonymousMay 19, 2009

    Fascinating stuff I am a part time building surveying student at Kingston University, I have an exam on the CSH next week, I note that this article was written in 2007 and the same issues being discussed here have not yet been resolved in the Feb 2008 revision of the CSH.

    Do you know if there is likely to be a further revision in 2009?