Part L 2022 Current Thinking

Part O - What to do about Manchester?

Solar control glass is anticipated to increase in demand driven by the new requirements for Part O (overheating) of the Building Regulations and the supporting Approved Document for new dwellings in England. It is recognised as one of the shading solutions when using the simplified method of assessment, but there is some doubt about how projects in Manchester should be treated.

Strictly speaking, it is only urban and some suburban parts of London that are considered high risk locations, with the rest of England categorised as moderate risk. However, Appendix C of Approved Document O provides guidance for some parts of central Manchester, even listing postcodes for which guidance for high risk locations should be considered.

An FAQ issued by the government on 15^th June, clarifies that the minimum standard for buildings in central Manchester is to use the moderate risk values when applying the simplified method. However, it then goes on to advise that designers may want to consider following the guidance for higher risk locations in central Manchester as there may be elevated night-time temperatures in these locations.

With this apparent 'grey' area, it may be prudent for the designer to consider new residential buildings in the listed Manchester postcodes to reduce the risk of subsequent complaints about overheating. One of the acceptable shading solutions is glazing with a performance of maximum g value of 0.40 (or 40%) and minimum light transmittance of 0.70 (70%), which can be achieved by Pilkington Suncool™ 70/35. Specifying a product such as this would be expected to help mitigate the risk of overheating on residential buildings in central Manchester as well as high risk locations in London.

For more information on the Pilkington Suncool™ 70/35, please click here.

Phil Brown. Date: 19^th July 2022

Transitioning to the new Part L

Now that the new Approved Documents for Part L in England have been published, we also know what the transition arrangements will be.

As cited in the documents, they will take effect from 15^th June 2022. However, they will not apply to work subject to a building notice, full plans application or initial notice submitted before then – provided the work commences on site before 15^th June 2023.

This is a clear attempt by government to tighten up transitional arrangements for building regulations. As identified in the consultation, there were reports of housing developments being built to old requirements introduced in 2010 and even 2006.

Where work has not commenced on a specific building covered by the building notice or plans within that period, transitional arrangements would not apply and instead the latest requirements would apply. This should be considered a positive move by housebuyers, knowing their new homes have been built to the latest energy efficiency standards and not those that were in place ten or more years ago. As limiting and notional building U values have been tightened up in the 2021 edition of Approved Document L, it also should help to ensure high performance glass and glazing products are installed in those homes.

With the clock ticking, it will be interesting to see if the next few months see a proliferation of Part L applications from developers before 15^th June.

Phil Brown. Date: 5th January 2022

O is for overheating but it’s not as easy as ABC

Published as an early Christmas present to take effect on 15^th June 2022, we now know the new regulatory requirements for mitigating overheating in new residential buildings in England. We know that this is Part O of the building regulations – the letter 'S' has been assigned to infrastructure for charging electric vehicles - making it easy to remember: 'O' for overheating. However, the supporting Approved Document is a little more complicated than the proposals from the consultation stage.

For starters, as well as more clearly defining Greater London, parts of Manchester have been incorporated into the higher risk category for the simplified method. This will not surprise commuters travelling into Manchester and looking out of the train window at the many towers popping up to fill the skyline. It remains to be seen whether other urban areas of England will be viewed as higher risk in the future and captured by the next iteration of Approved Document O.

Another change in the simplified method is the shift in focus to the maximum glazed area in the most glazed room, recognising that a 'one specification fits all' approach may not be appropriate. From a glazing perspective, this could result in solar control glass being installed on a large glazed south-facing room, but low emissivity glass on a North-facing room with smaller windows. The requirements will also be affected by the presence or absence of cross-ventilation, i.e. openings on opposite elevations.

With the simplified method focused on ‘high risk’ areas of London and central Manchester, all other areas of England will be considered as ‘moderate risk’. No shading will be needed for these locations, but there could be restrictions on glazed areas. If the maximum glazed areas in Approved Document O are exceeded, even for moderate risk areas, then housebuilders and developers will need to apply the detailed method, taking into account the g value of the glazing, among other factors. They may need to decide on whether to restrict glazed areas or introduce shading solutions.

One of acceptable shading solutions is glazing with a 70/40 performance, which can be achieved by Pilkington Suncool™ 70/35.

Any solution proposed for mitigating overheating in new residential buildings also needs to consider impact on other functions, such as noise at night, pollution, security and protection from falling.

So, Approved Document O is here. It's more complicated than originally proposed, but one thing is certain – the risk of overheating in new residential buildings can no longer be ignored.

For more information on the Pilkington Suncool™ 70/35, please click here.

Phil Brown. Date: 4^th January 2022

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: 4^th 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: 2^nd 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: 28^th 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: 28^th November 2019

Part L 2022 Current Thinking

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