Part L 2021 Current Thinking

Part L 2021 Current Thinking

More solar control glass in new dwellings
New building regulations proposed in both England and Wales are likely to increase the use of solar control glass and other shading devices in new residential buildings.

Referred to as Part S in Wales, but not yet assigned a letter in England, the proposed new building regulations are likely to see a change of glass specification in new homes, with low emissivity glass being upgraded to solar control glass in some cases.

To be published in December 2021 and in force from June 2022, the proposals for England separate Greater London from the rest of the country.  A simplified method can be used to demonstrate compliance, taking into account location, dwelling type, glazing and floor area.

If using this method for residential buildings in Greater London with more than two fabric elements and openings on opposite facades, the maximum glazing area should be 13% of floor area and shading should be provided on glazing between North East and North West (turning clockwise via South).  For residential buildings with two or fewer fabric elements and openings on facades which are not opposite, then maximum glazing area should be 15% of floor area.  Where shading is required, glazing with a maximum g value of 0.40 and a high light transmittance of 0.70 is one of the accepted solutions.

Intriguingly, outside of Greater London, there is no requirement for shading up to a maximum glazing area of 21% of floor area.  This suggests that it is only in London that residential buildings are likely to suffer from overheating, which is surprising given the number of tall apartment buildings being developed in cities such as Manchester and Birmingham.  Maybe the proposals will be changed upon publication to recognise this.

Likely to be applicable from Spring 2022, the corresponding requirements in Wales do not differentiate between different parts of the country, but simplified mitigating approach number 2 identifies solar control glass as a means of controlling the risk of overheating by minimising summer solar gains.  More precisely, the requirements can be met by using low g value glazing (maximum 0.40) up to a maximum glazing area of 20% of floor area in a single aspect dwelling and maximum glazing area of 35% of floor area in a dual aspect dwelling.

Although out of scope of the new building regulations, through enquiries to our Customer Contact Centre, we are already seeing an increased awareness among householders of the benefits of solar control glass in domestic glazing applications.   This is particularly noticeable in the interest in products such as Pilkington Suncool™ One 60/40 for use in bi-fold doors and large, South-facing windows.  Of course, this does mean that replacement windows and doors with solar control glass will need to use window U value rather than Window Energy Rating to demonstrate compliance with Part L.

Fortunately, glass manufacturers already offer a wide range of solar control products with high light transmittance such as Pilkington Suncool™ 70/35 to help meet these new requirements and the anticipated increased demand for solar control glass in residential buildings.

For more information on the proposed new building regulation for overheating in England, click here.

For an overview of the proposals for Wales, click here.
 Phil Brown. Date: 18th May 2021

Daylighting and Part L
As expected, energy savings and carbon emissions reductions have dominated the discussions on the current Part L 2020 proposals, as well as debates about 'fabric first' vs renewable technologies.  Perhaps surprisingly given the increasing awareness of its importance in terms of health, well-being and productivity, daylighting has featured very little during industry meetings about the consultation.

In fact, in the consultation for new dwellings in England, there is a proposal that the supplementary guidance on daylighting from Approved Document L be removed, suggesting a demotion in its contribution to low energy buildings.  With an emphasis on reducing the risk of overheating in residential buildings – anticipated to be subjected to a separate consultation - there is a real concern that developers could be tempted to reduce glazed areas without considering the implications.  This could have a detrimental effect on the health and well-being of occupants.

As daylighting is important to both energy use, through the reduction of artificial lighting requirements, and occupant comfort, the glass industry should call on Government to retain the essential guidance on daylighting in the Approved Document.

Furthermore, in order to improve natural daylighting within new dwellings, a requirement should be introduced to Approved Document L.  This could be via a minimum glazed area of, say 25% of the total floor area, or an average daylight factor of 2% determined through calculation or modelling.

Among the noise around the Part L 2020 consultation, we should not lose sight of the important role that daylighting can make to delivering healthy and energy efficient buildings.
 Phil Brown. Date: 4th February 2020

The battle for Part L
Following on from the Part L consultation in England, the Welsh Government has initiated a consultation that sets out the plans to improve the energy efficiency requirements for new homes in Wales in 2020.

Like in England, the proposals for new dwellings in Wales includes two options.  Option 1 – favoured by the Welsh Government – would be expected to deliver a 37% reduction in CO2 emissions compared to current standards (based on a semi-detached home), whereas option 2 -utilising mechanical ventilation with heat recovery – targets a 56% reduction.
By comparison, the corresponding proposals for new dwellings in England include option 1 based on a high performance 'fabric first' approach and estimated to bring a 20% reduction in CO2 emissions compared to current standards.  The Government's preferred option 2 for England is based on a less ambitious fabric but with the introduction of renewable technologies, aiming for a 31% reduction.

While we wait to hear about proposals for changes to the Technical Handbooks in Scotland, we should be prepared for a Part L 'Battle of Britain' over which country is the most ambitious in terms of energy efficiency and reducing carbon emissions.  This could be important for the glass and glazing industry, particularly for companies selling products into the different countries of the UK, where the required performance of windows may be different.
Phil Brown. Date: 2nd January 2020

Loophole closed to housebuilders 
Government proposals on Part L mean that housebuilders will no longer be able to build homes to old building regulations during the transition period when new regulations are introduced. There is anecdotal evidence that, under current rules, some developers may still be building to 2010, or even 2006, editions of Approved Document L.

From 2020, any new building will have to meet the updated Part L requirements - if work has not already commenced on a specific dwelling covered by planning permission within a 'to-be-determined' reasonable period. This must be welcomed and will help to ensure the latest energy efficient glass and glazing products are installed – a win for homeowners and a win for the environment!
 Phil Brown. Date: 28th November 2019

Missed opportunity for glazing
The Government's consultation on Part L for new dwellings in England is undoubtedly a missed opportunity. Option 1 adopts a 'fabric first' approach to ensure that there is a high performance building envelope, thus 'locking in' energy savings and carbon emission reductions now. The Government's preferred option 2 is based on a less ambitious fabric but with the introduction of renewable technologies. Is this a missed opportunity?

The frustration is that the glass and glazing products to deliver the fabric first approach are already available; new technology is not necessary. Other countries such as Germany and Poland are already at this level in terms of glazing. Through recommending option 2, the Government is encouraging the UK to continue to lag behind our European neighbours.
Phil Brown. Date: 28th November 2019