The Code for Sustainable Homes (CSH) came into effect in England in April. There is no doubt that it forms part of the government’s response to concerns about global warming and its commitment to reducing CO2 emissions. Nor is it any surprise to find the construction industry in the front line of its defence. Statistics vary, but the cost of running and heating buildings is estimated to account for more than half of CO2 emissions in the UK and the manufacture and transport of building materials a further 5% each.

Based on many of the principles contained within the Ecohomes scheme, which in the case of new housing it replaces, the Code is voluntary for both public and private housing developers. In practice, however, to access Housing Corporation funding, all social housing will have to achieve at least a three-star rating. This will entail an improvement of 25% on the energy performance requirements of Part L 2006. English Partnerships (EP), too, will lay down minimum requirements, so developers seeking land from EP will find that compliance with the Code becomes necessary.

At first glance it might seem complex, but in other ways it provides an objective tool for defining standards and it does bring together many facets of sustainability. Developers can achieve ratings from one to six stars, calculated on a “points out of 100” basis across nine categories. There is flexibility in how points are achieved, but some performance aspects are compulsory, as the table summarises.

The Code might well be viewed as a stepping-stone for the government to reach its declared objective of zero carbon status for all new homes by 2016. It is mildly worrying therefore that a final definition of ‘zero carbon home’ is not entirely set, although a general impression can be formed. In broad outline, a zero carbon home should be both thermally efficient (at least 100% better in terms of energy performance than the minimum laid down in Part L 2006) and locally generate all its own energy requirements (eg using solar panels on the roof) – but more precise guidelines are not yet to hand.

Gathering points will be painstaking. The maximum points available in any one category – not surprisingly for Energy/CO2 – are 35.6 (leaving two-thirds to be found elsewhere, in very much smaller amounts). Within this, to achieve a five-star rating, developers must demonstrate 100% improvement over the Target Emission Rate (TER) under Part L1A (2006), to notch up 16.4 points, with a maximum of 17.6 available for a six-star zero carbon home.

Houses will have to be airtight – it might be enough to achieve 10m3/hr/m2 to comply with Part L, but to add CSH points, developers will be aiming for a score of less than 3m3/hr/m2.

The Code for Sustainable Homes provides an objective tool for defining standards and it brings together many facets of sustainability

Insulation will have an important part to play and we will probably see new products being developed, based on different physical principles than the traditional materials that we are used to using such as polystyrene and mineral wool. Floor and wall constructions, too, will change. Timber suppliers take note: studs will get bigger, with 140mm and larger likely to replace 89mm as the norm. Solar shading will be another good opportunity for timber suppliers and will force designers to reconsider their use of glass, to balance solar gain with heating and cooling needs. The individual thermal performance of walls, roofs, doors and windows will have an impact on the points score.

As with all legislation the devil is in the detail. While developers wrestle with airtightness and heat loss, they should not lose sight of the fact that they can pick up 2.4 easy points just by providing “safe, secure and weather proof” cycle storage for at least 95% of the properties in a development (and provision of home office facilities is worth another 1.2). Timber shed suppliers equally should take note – it would be well worth considering whether you offer sheds that cycles can be stored in, or custom-made cycle storage.

The Code might well be viewed as a stepping stone for the government to reach its declared objective of zero carbon status for all new homes by 2016

And it would be all too easy to assume that because timber is such an inherently sustainable material it is all up for grabs. To achieve the maximum 4.5 points available in the materials category, the five major building elements – roof, external walls, internal walls, floors and windows – must achieve A+ or possibly A ratings as defined in the new Green Guide (published by BRE in a short-term version at the end of April). Keep an eye on security in the ‘Management’ category and add another 2.2 points by installing Secured by Design tested windows and doorsets (although the whole development need not meet SBD standards).

Proof of responsible sourcing of materials can lead to a maximum of 2.7 points. Timber with chain of custody certification under the FSC, PEFC, CSA or SFI schemes will score more credits and subsequently more points than other schemes. Every point will count, however, so demand for certified timber will grow. It will be harder for other materials to demonstrate their credentials.

Sound insulation will be a key area under ‘Health & well-being’. Up to four points can be achieved if homes can improve on the current acoustic requirements of Part E by 8dB sound reduction. Designers can gain another four points by providing good daylight standards (although the provision of larger windows could conflict with meeting SAP ratings elsewhere) and a further four by catering for reducing mobility as occupants grow older, using all 16 of the features specified in the ‘Lifetime homes’ standard.

To achieve certification of Code compliance, a developer will produce an initial design for appraisal. A trained and certified code assessor – individuals (self-employed or employed) who have been trained, assessed and certified by BRE – will then conduct an initial assessment on the design, recommend a sustainability rating and issue an interim Code Certificate. This is carried out for each house type (but not each dwelling). The assessor will perform a post-completion check on a sample of the development to verify the rating before issuing a final Code Certificate of Compliance.

Bear in mind that this is only happening in England at present. Rumour suggests that Wales will adopt the Code and set an even shorter time-frame for achieving ‘zero carbon’, but nothing is confirmed. Northern Ireland has given no indication at all as yet about it intentions, but it tends to follow England and Wales in time. Scotland has no intention of using the Code itself, although it has incorporated into May 2007 revisions of its own building standards those elements of the Code it considers worth making a mandatory requirement.

Whatever the outcome, it is generally held that the Code will pave the way both for standards to be raised over the next 10 years and for increased regulatory requirements as the market seeks to find improved energy solutions. The government might even in time decide to make it obliga-tory for all housing to declare a Code rating – even if that means a ‘no rating’ declaration. Hardly a good marketing move – but this is still just a rumour.

• Visit www.trada.co.uk and follow the links to Regulations & standards briefings from the home page for further insights into the Code. A full copy of the Code for Sustainable Homes can be downloaded from www.planningportal.gov.uk.