7 New Confirmed changes to Part L of the Building Regulations (Dwellings)

7 New Confirmed changes to Part L of the Building Regulations (Dwellings)

After nearly 10 years, the existing building regulations for Approved Document Part L, Conservation of Fuel and Power, have now finally been updated. Now, after a lengthy consultation process, the 2021 update has been published.
These changes will be coming into force on 15^th of June, 2022.

There have been radical changes to Part L along with part F (Ventilation), as well as the addition of a brand-new set of regulations pertaining to overheating entitled Part O. It is estimated that these regulations will reduce the emissions for new homes by 31% compared to the previous regulations.

For the most part, the changes focus on the fabric performance of the building,
with standards for U-Values, thermal bridging calculations, and air-testing all being tightened. Sections have also been added with the intention of future proofing homes. The changes have also been made to bridge the gap between 2022 and the introduction of the Future Homes Standard, due for release in 2025.

So, what do these changes involve? And what impact will they have on our work at ERS Consultants? The following hopes to explain these questions:

1. Enhanced U-Value Standards

One of the most obvious changes from the old regulations to the new is the improvement in U-Value standards for new building elements. These are the minimum requirements for the average U-Value of various elements in the building fabric.  These values are also used to ensure that new build dwelling elements meet an improved minimum standard in comparison with the standards of previous regulations.

This table shows the limiting U-Value standards for new building elements:

Along with this, the notional dwelling will still use a mains gas boiler with a minimum efficiency of 88%, along with a minimum of 75% L.E.L in all outlets. For the first time though, the notional dwelling will have Waste Water Heat Recovery (WWHR) as standard.

2. Changes to Air-Testing

Previously, air-tests were only required on a sample of dwellings in a development, and units that were not based on a sample were penalised by two points in the air test result. Following the changes, every dwelling will need to be air tested. This is intended to improve the construction standards of new build properties.

3. Changes to Thermal Bridging

Perhaps the most significant change to our work comes in the form of new methods of calculating thermal bridging; previously, we have used Approved Construction Details (ACD’s) in almost all cases, occasionally changing these where necessary, depending on the junction. This is a change that has been expected for some time now, as the current Accredited Construction Details, published in 2002, are significantly outdated and a more detailed calculation is now required.

With the introduction of the new regulations and SAP 10, ACD’s have been removed, and architectural designers will need to detail their drawings to a certain specification such as those from manufacturers, or bespoke calculations will have to be made for each junction. Many insulation manufacturers publish details specific for their products. There is a very comprehensive set of details freely available from LABC. This is specifically referred to as an example in the new Part L Approved Document.

4. Changes to Thermal Mass Parameters (TMP’s):

The thermal mass of a building construction was, in most cases, previously done by selecting a generic calculation of low, medium or high, depending on the construction, with precise calculations very rarely being done. This option has been removed from SAP 10.  This means that we will need information about the construction of all internal partitions and intermediate floors.  We then have to measure the areas of both sides of all these internal elements and assign a thermal mass (or ‘kappa’) value to them.

A building with high thermal mass construction (e.g., solid masonry) will take longer to warm up when the heating is turned on from cold than a low thermal mass construction (e.g., timber frame).  The high thermal mass building will also take longer to warm up on a very hot summer’s day.

Manipulating thermal mass at design stage will not solve energy use or summer overheating problems.  External fabric, fuel type and heating efficiency will still determine the outcome of a SAP calculation. 

5. Updated Carbon Factors  

Recently, the government introduced a grant scheme encouraging homeowners to install heat pumps into their home to lower carbon emissions. Heat pumps use grid electricity to power the compressor which produces heat for the home from the outside air. In Part L1 2013, the carbon factor for grid electricity assumed that it produced 2.4 times more emissions than mains gas. At the time this was calculated, the UK still had a reliance on coal-fired power stations, whereas it no longer does, nor has it for several years. With the carbon factors now being updated to reflect the current emissions from grid electricity, heat pumps are now a far more attractive option for a new build home.

6. New Rules for Extensions

Previously, for an over-glazed extension to pass an analysis, the total CO₂ emission rate was the only metric from the ‘as designed’ dwelling required to gain a pass. Now though, a primary energy metric has been introduced to the whole house calculation method for extensions. This metric will look at the sources of energy into the home and how it was produced and delivered to the dwelling.

As the grid electricity is progressively decarbonised, the CO₂ emission rate becomes a less useful metric to drive down the energy demand of buildings, and the primary energy rate was originally selected under the Energy Performance of Buildings Directive (EPBS) as the more appropriate metric to achieve this aim.

7. Future Proofing

Part S is an all-new building regulation document that requires all new homes to have facilities for electric vehicle charging. Whether this be charging points, or just making it easy to have future connections installed.

Gas and oil boilers will also be phased out and banned in new build homes in 2025. This is in favour of more low-carbon technologies such as heat pumps. Both of these aims ensure that buildings being built today suit the needs of its future occupants, as well as addressing environmental concerns.

In conclusion, these updates to Part L and the introduction of SAP 10 are there to improve the environmental performance of all new dwellings in the UK. There will be a 31% reduction in emissions when compared to the standards in the previous regulations. This reduction is set to be achieved by the enhanced standards used to calculated the TER, TFEE and also the new primary energy metric. Changes to air-testing, now to be done in all new dwellings rather than samples, and the method of calculating thermal bridging will both encourage better building standards across all new builds as well as make clients and builders more aware of schemes relating to good practice in environmentally friendly construction.