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L1A – Conservation of fuel and power in new dwellings

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

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 was the government’s intention that the regulations would be tightened up every couple of years or so until by the year 2016 when all new homes would be zero carbon. This has, since July 2015 been scrapped.

The heat loss calculations which are necessary to satisfy the regulations are based on something called the TER in the case of a new dwelling and this is calculated using a 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 CO2 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).

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 2012 edition of the Standard Assessment Procedure is used for compliance with building regulations in England & Wales (Part L) 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 here.  (and here be dragons!)

future directions

The UK seems determined to eventually 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 Passivhaus 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 did also seems to have a confused plan to implement a complicated, pick and mix (Ecohomes) policy. This has now been scrapped. 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?  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.
While the Passivhaus standard is essentially about ‘fabric first’ it does not preclude bolting on developing technologies such as solar PV, CHP etc. at a later date.

The Approved Documents are ‘standard’ ways of getting Building Regulations approval. There are other ways. see more

If you follow the principles and rules given in the documents you can be sure that they will be approved. Of course you don’t have to use the Approved Documents, as the Regulations make clear:

Approved Documents are intended to provide guidance for some of the more common building situations. However, there may well be alternative ways of achieving compliance with the requirements. Thus there is no obligation to adopt any particular solution contained in an Approved Document if you prefer to meet the relevant requirement in some other way.

In fact the Approved Documents are a bit of a mishmash of traditional ‘rules of thumb’ and technical standards and they have gaping holes in them. Whereas, for instance, there are many pages on how to construct traditional masonry walls, there is nothing about timber frame construction except the odd reference to British standards.

They are also struggling to keep up with the times. If the Passivhaus Standard or zero energy new house building is introduced at some point then whole swathes of the Approved Documents will need rewriting because many of the constructional principles are based on quite low levels of insulation.

There are other ways of satisfying the regulations. For instance they make copious references to BS, BS EN and BS EN ISO standards which may be another way of fulfilling the criteria. It is even possible in some very rare cases to prove that something works by building it first and then testing it afterwards (though this is not for the faint hearted).

Although a self builder cannot be expected to understand all the building regulations, it often pays to have a grasp of what is involved, especially if last minutes changes need to be made to construction details.

The full official set of Aproved Documents is available HERE.

See also: Saving Energy,  How much Insulation,  Wall Insulation,  Insulation Properties,  Air Tightness, Thermal Mass.

Below is a direct link to the Gov.UK Approved Document, L1A – Conservation of fuel and power in new dwellings (England) along with the Domestic building services compliance guide – 2013 edition

These ar large PDF files and may take a moment to load


Download (PDF, 350KB)

Download (PDF, 612KB)