Part L and SAP (England)

The Building Regulations, part L, is the section which covers energy conservation for new buildings (with part L1A covering new buildings and part L1B covering existing ones)

At present there is a period of transition which is well explained in an NHBCThe National House-Building Council describes itself as being "the leading warranty and insurance provider and standards setter for UK house-building for new and newly converted homes"  Technical Extra publication.

The regulations are mandatory and have gone through a series of revisions over the last 40 years or so which have progressively increased the degree of insulation required. The latest changes have also included air tightness, along with the testing of it (at least in some cases).

It is intended that the regulations will be tightened up every couple of years or so until by the year 2016 all new homes will be zero carbon. We can probably expect that these high ambitions will be eroded away, mainly by the big players in the building industry itself. Ringside seats please!

The heat loss calculations which are necessary to satisfy the regulations are based on something called the TERTarget emission rate. The minimum energy performance for a new dwelling as defined in the Building Regulations. in the case of a new dwelling and this is calculated using a SAPStandard Assessment Procedure - the method used in the building regulations for calculating the energy use of a house. see Part L and SAP rating which estimates the annual space and water heating needed for a house. The house size, heating system and a standard occupancy assumption are used for the calculation, along with many other factors including insulation and air tightness.

This calculation gives the CO2Carbon dioxide is a gas which is given off when carbon based materials such as fossil fuels (coal, oil, and natural gas) are burned. It is called a greenhouse gas because it works like the glazing of a greenhouse and causes global warming emissions for the house. (So it is not just about the energy used by the house but also includes factors for the type of fuel used. This is why a wood burning stove rather than an oil boiler will affect the calculations).

What gets a little bit confusing is that the energy efficiency of a dwelling (which is a mandatory standard) has been incorporated into a separate standard called the Code for Sustainable Homes (CSH Code for Sustainable Homes. A standard for eco-houses developed by the Building Research Establishment. It covers a wide range of criteria ) which covers a lot of other aspects of the house’s sustainability but which are mainly voluntary.  CSH is not without its critics, partly because it is not a firm standard but rather a mixed basket of features for collecting greenie points.

The current SAP scale ranges from one to 100, with 100 being the best. Anything over that indicates a house which is a net exporter of energy. SAP ratings are often carried out by a specialist consultant, but may also be undertaken by some designers and package suppliers. Even a quick glance at the methodology for calculating heat loss according to SAP reveals an awesome complexity which can only be handled by a spreadsheet and someone working it who knows what they are doing.

The 2009 edition of the Standard Assessment Procedure (SAP 2009) was introduced from October 2010 and will be used for compliance with building regulationsThese are the legal regulations which govern how a house is constructed. (not to be confused with Planning Permission which is about whether you are allowed to build the house at all or what it might look like) see Building Regulations) in England & Wales (Part LThe Building Regulations, part L is the section which covers energy conservation for new buildings (with part L1A covering new buildings and part L1B covering existing ones)) and in Scotland (Section 6) and for the generation of Energy Performance Certificates for new dwellings. Similar provisions will be made in Northern Ireland at a later date. The actual SAP calculation details are available to download from here.  (and here be dragons!)

after 2010

The UK seems determined to green its building process and reach a very high standard of energy efficiency. However it does also seem to be backing (or riding) two horses at the same time, the horses being the German PassivhausSee more on the Passivhaus standard. The PassivHaus Institute has pioneered a standard for low energy buildings. It includes very low energy usage and ways of achieving this. The word is derived from the idea of buildings which are fundamentally low energy and passive solar heated rather than using extra gadgets to heat them. See Passivhaus for the UK branch of the organisation. standard and the English staged development of Part L of the  building regulations. Although they are not intended to cover quite the same ground and may well be harmonised in some way in the future, it does seem to be a bit like trying to reinvent the wheel.

The UK also seems to have a confused plan to implement a complicated, pick and mix (Ecohomes) policy. At the same time the intention is to bring all new houses to code level 6 by the year 2016. Level 6 is higher than the  Passivhaus standard! Don’t hold your breath.

The continental northern European thinking does seem to be better. Have one clear, very high but attainable standard for energy use and then have other more organic and developing (often local) standards for building materials and healthy construction techniques.

Why not take the lead from Germany and head towards the Passivhaus standard for 2016? It offers:

• a clear approach to massively reducing energy consumption to the minimum, sensible, realistic levels
• a well proven model with thousands of certified examples
• a well established accreditation system
• a popular and growing certification system for component manufacturers (which is almost completely lacking in the UK)
• ongoing development of methods for bringing older housing up to the Passivhaus standard.