On April 6th 2014 a new version of the regulations relating to Energy Efficiency of Buildings came into force in England. These regulations are Part L1A (new dwellings) and Part L2A (new industrial buildings.) A new version of SAP was introduced replacing SAP 2009 with SAP 2012.
- Building Control have told me that my new house only needs to comply with SAP 2009. Why is this?
The regulations apply to any project for which a planning application was made after that date, or for which building work commences after 6th April 2015. Houses completed before April 6th 2014 have to comply with SAP 2009 and if a planning application was made before April 6th 2014 and work begins before 6th April 2015 the house will still have to comply with SAP 2009. Different rules apply in Scotland, Wales and Nothern Ireland. In Scotland, a new version of Section 6 is to be introduced in 2015, when new homes are expected to have to achieve a 21% reduction in CO2 emissions from current standards. Wales will have its own version of Building Regulations, to be introduced in July 2014, requiring an 8% reduction in CO2 emissions from current standards. In Northern Ireland an update is generally introduced a year after the English version.
- I thought that this new house was really quite good and it failed SAP 2012. How?
SAP 2012 demands a higher standard of design and there are some major technical issues.
- The Target Emission Rate (TER) is reduced by 6% compared with Part L 2010, which raises the bar a little higher. It is more difficult to achieve a compliant dwelling without renewable or low-carbon energy technologies. I would advise that the initial design of the house should be attempted with a conventional gas boiler and solar panels or heat pumps should be added later if passing the SAP test becomes too difficult.
- Some of the “fuel factors” which determine how much CO2 emission is attributed to each fuel type were adjusted. The fuel factor for LPG was reduced 4%, making LPG a slightly more attractive choice under SAP. The fuel factor for grid electricity, already the worst choice, was increased by 5.44%. I wouldn't advise using ordinary electric heating in a new house at all. I can't recall any project in which this has actually worked in SAP 2012. Electric heating would still work in a Part L1B refurbishment but not in a Part L1A new building. Using an electric heat pump will give you a bit more of a margin than a gas boiler as it still gives you a higher TER (Target Emission Rate.) Your CO2 has to be below the TER to pass the SAP test. A heat pump doesn't give you the same fantastic advantage that it gave you in SAP 2009 but it does give some. It might be worth considering.
- Design Fabric Energy Efficiency (DFEE) must beat Target Fabric Energy Efficiency (TFEE). In practice this is the most frustrating thing about SAP 2012. Normal designs for modern day insulated buildings will fail. Ordinary brick and block walls with 50 mm partial cavity insulation, accredited construction details and ordinary double glazing fail spectacularly and will not respond to the usual suggestions by the SAP assessor to add a heat pump or a small solar panel to your design. It makes no difference. What you need is a better fabric energy efficiency. One way of achieving this is highly insulated walls, for example, a 150 mm cavity with 100 mm of Kingspan or Celotex or a good quality timber frame wall. It may also be necessary to use glass with a low U value and high solar gain (G value) in order to maximise the heating effect of the sun. Another approach is to improve the thermal bridging (see 5.) Average DFEE and TFEE can be calculated for and applied to a block of flats. DER and TER (CO2 emissions) can be averaged in the same way. With flats it can be easy to get the whole block to pass if only one or two fail.
- Appendix R of SAP 2012 provides a specification of U values for a notional dwelling which meets the new standards. Some of these are much stricter than in SAP 2009. It is possible to offset shortcomings in one area with improvements in another, so the Appendix R values are not hard-and-fast limits.
- External wall U-value 0.18 W/m²K
- Floor and Roof U-value 0.13 W/m²K
- Solid door U-value 1.0 W/m²K
- Semi-glazed door U-value 1.2 W/m2K
- Windows and >60% glazed doors U-value 1.4 W/m²K, solar gain (g-value) 0.63
- Air permeability 5 m³/hm² at 50 Pa
- 100% Low Energy Lighting
- The new SAP model takes a more stringent approach to thermal bridging, and adds a few more junctions to the ones that already existed in SAP 2009. Advanced thermal bridging schemes can be used that go beyond normal ACDs. The Scottish building regulations have their own booklet of thermal bridges which are excellent and can be used in any part of the UK, not just in Scotland. Some insulation companies also have their own advanced thermal bridges but the calculations may only work with their products.
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- Thermal Bridging
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