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Ask Pilkington

What are the requirements for glazing for the next Part L?

On 15th December 2021, the Government published the 2021 editions of the supporting Approved Documents Part L (conservation of fuel and power) and Part F (ventilation) of the Building Regulations for new and existing buildings in England, as well as the new regulation (Part O) addressing the risk of overheating in new homes.

The 2021 edition of Approved Document L Volume 1 has introduced changes to the limiting elemental standards for fabric performance – sometimes referred to as 'backstop' values – including a reduction (improvement) in the window U-value from 2.0 to 1.6 W/m2K. However, the expectation is that the U- value will have to be much lower than this to enable new dwellings to achieve their targets for primary energy, carbon dioxide emissions and fabric energy efficiency rates.

For replacement windows in existing dwellings, the minimum standards have been improved to a Window Energy Rating (WER) Band B or better, or window U- value 1.4 W/m2K.

For buildings other than dwellings, the 2021 edition of Approved Document L Volume 2 has made changes to the limiting elemental standards for fabric performance, including a reduction (improvement) in the window U-value from 2.2 to 1.6 W/m2K.

The new regulation aimed at mitigating the effect of overheating in new dwellings could see a greater use of solar control glass, particularly in urban and suburban London and parts of central Manchester. One of the solutions identified in the simplified method of Approved Document O is glazing with a maximum g value of 0.40 and minimum light transmittance of 0,70. This can be achieved by Pilkington Suncool™ 70/35.    

The new requirements will apply from 15th June 2022.

For more details about the new requirements, visit our Part L hub by clicking here.

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