Inspiration and advice for your building project
ABOVE: Eco homes don’t need to break the bank — as Nicky and Robin van der Bij proved when they designed and built their stunning coastal cottage for just £115,000. Even better, it costs just £270 a year to heat.
Recent research carried out by English Partnerships (englishpartnerships.co.uk) suggests that hitting the new building standard for UK homes – the Code for Sustainable Homes Level 3 (CSH 3) – will cost 12-15% more than meeting the current Building Regulations requirements. This research assumes an ‘average’ 120m² UK home with three bedrooms, but is not specific on where the money will be spent.
The CSH will assess the drawings and specifications for the planned house and award points (out of a total of 100 points, based on a percentage system) in nine design categories: Level 1 requires 36 points; Level 2 – 48 points; Level 3 – 57; Level 4 – 68; Level 5 – 84; and Level 6 – 90. The categories are:
These nine categories break down into two groups: ‘Mandatory’, and what can be called ‘Other’. The Mandatory elements are Energy and Water. Within the Other group is a subgroup comprising Surface Water Run-off, Waste, and Materials, where minimum standards must still be met.
Bear in mind that the CSH assessment is carried out at the design stage, prior to construction. And it is design that is the key.
Also consider that the Mandatory elements account for only 10.3 points. The other 46.7 points come from the Other group. And there are some fairly soft targets in that group. A few examples include:
It is possible to gain half the needed 46.7 points with little impact — simply by making those small, cheap changes to the design and correctly labelling things to bring them to the CSH assessor’s attention.
Water consumption (internal and external) needs to be limited to 105 litres per person per day. The way this is calculated is fairly complex but the ‘standard’ UK house uses around 150 litres per person per day — so it’s about a 30% reduction.
There are two ways to achieve this: make provision for a greywater recycling system (at a cost of around £2,000) which will effectively achieve the target on its own. Alternatively you need to think about things like aerated taps and reduced-flow showers.
The Energy requirement is to achieve a 25% improvement on Building Regulations 2008 Part L standard and there are a few ways to do it. A construction system like SIPs, for instance, that is highly insulated and relatively airtight, with a solar thermal system on the roof, will achieve it by default. Other construction systems (brick and block for instance) will need more thought as to the heating and hot-water systems. A SEDBUK (sedbuk.com) A-rated boiler or a heat pump will be essential but insulation levels will still need to be upgraded. It is in this area where the majority of the extra cost will be used.
The requirement is to hit a minimum standard for surface water run-off, site waste management and sustainable materials.
There are two options for dealing with surface water run-off: a rainwater harvesting system (at a cost of around £3,500) makes the problem go away (and also helps achieve the 105 litres per person requirement), or you need to think about water-permeable hard surfaces like drives and patios and perhaps a rainwater soakaway.
Site waste management can be tricky as you are reliant on your contractors to comply. An organisation called WRAP (Waste & Resources Action Programme; wrap.org.uk) will provide a free scheme template to help you deliver best practice and hit the target.
Achieving CSH 3 means using materials with at least a D-rating from the BRE Green Guide (bre.co.uk) on at least three of the key elements of the build (walls, roof, floor, windows and doors, etc.). The majority of ratings in the guide are A, some A+. It is really only concrete that gives a problem. Masonry cavity walls and timber frame are both A-rated.
Assessment is a bureaucratic process and the more paperwork you provide, the better. Drawings, site plans, specifications, manuals, instruction books, invoices, experts’ reports, anything and everything relating to the construction and use of the home needs to be assembled in an orderly fashion and delivered to the assessor. The devil is, as usual, in the detail.
Interestingly, research carried out in 2007 by the Richard Hodkinson Consultancy shows that PassivHaus (the German standard generally accepted as the most energy-efficient construction system) would not meet CSH 3. The CSH assessment uses the Standard Assessment Procedure (SAP) test to calculate energy performance, and for many years there have been questions over the efficacy of the SAP test, especially with more thermally efficient buildings.
If you can’t afford to increase your build cost by 15% then time spent studying the Code, and perhaps a knowledgeable architect, can still get you there. Good luck.
There are a possible 100 points (which is based on a percentage system) that can be gained overall, but confusingly there are also a maximum of 103 credits to be won. The official Code Level rating is worked out in points, but to achieve this score, everything must initially be worked out in credits before being converted to points. However, bafflingly, some credits earn more percentage points than others, with Water achieving the highest number of points per credit (1.5); and Materials the lowest (0.3). So while there are 24 Materials credits to be gained, you can only make 7.2 points; and while there are only 6 Water credits to be gained, these make up 9 points.
Code Level 3 aims for a 25% (5.8 points) ‘dwelling emissions’ improvement on Building Regulations, but Level 4 aims for 44% (9.4 points), while Levels 5 and 6 aim for 100% (16.4 points) and zero carbon (17.6 points). But a further 18.8 points can be earned in the Energy category by other measures including incorporating 75% energy-efficient lighting, a drying space, energy-labelled white goods, a home office and cycle storage. With regard to water consumption, Levels 5 and 6 require a maximum usage of 80 litres per person per day (7.5 points) compared to Levels 3 and 4 requiring 105 (4.5 points). Although the Energy and Water sections of the Code have Mandatory levels for achieving a higher rating, the rest can be earned over of a variety of categories; for example, there are a maximum of 14 points to be easily earned in the ‘Health and Well-being’ category. See communities.gov.uk for a full guide of where points can be earned. Level 6 is likely to be incorporated into the new national Building Regulations in England and Wales by 2016.
The Energy Saving Trust has devised a package of scenarios for homebuilders to save 25% in energy and CO² reductions against Building Regulations. The guidelines it suggests for a typical 104m² detached house are as follows.
|Exposed floors U-value||0.25||0.20|
|Mechanical ventilation||Extractor fans||MVHR 85% efficiency|
|CO² DER (Dwelling Emission Rate)||23.22||17.59|
Requirements can very depending on heating type.
*A U-value measures how well a building component keeps heat inside a building, while the Y-value is the heat loss factor for thermal bridging within the dwelling. The lower each value the better.
Update: Whilst most LAs currently only insist on the achievement of Code Level 3, some are now asking for Code Level 4 - for information on how to achieve level 4 click here.