Updates to the Glazing Requirements under Part L, F and O
With the exponential acceleration of climate change, never before has there been such immediacy to reduce carbon emissions within the construction sector aggressively.
The government’s recent revisions to building regulations included Part L (Conservation of fuel and power), Part F (ventilation) & Part O (overheating) are drivers to further reduce carbon emissions within the residential build sector. The updated Approved Document L (ADL) in the Welsh Building Regs came into force Wednesday 23rd November 2022. Both building regs offer similar requirements in terms of thermal insulation values with glass thermal performance requirements recalculated from the original 1.6 W/m2K rating on glazing to 1.2-1.6 W/m2K as a minimum depending on the building specifics.
Further updates to Part F added improved requirements for natural air flow through a building whilst the brand new Approved Document O created rules and guidelines to combat overheating in house design.
Construction within the UK’s residential sector now stipulates that all new dwellings must produce around 30% less CO2 than previous 27% carbon emissions, a new defining imperative within the specifications market.
All together, these changes saw the biggest update in the requirements from glazing seen in recent time. Read on below for an overview off all the changes brought into effect this year, with more changes due in 2025.
Changes to Building Regulations Part L
Approved Document L1A and L1B were merged to form one section of building regulations, dictating the thermal performance requirements for glazing on any dwelling. The updated Part L offered increased requirements for the energy consumption and insulation of homes with much stricter performance values required from the glazing.
The update has seen the Uw value requirements from glazing improve with a minimum requirement of Uw 1.4 W/m2K (the limiting factor) for all glazing in existing dwellings and 1.6 W/m2K for new build dwellings.
It is highly likely however, that dwellings will need to achieve a much higher level of insulation per window in order to achieve the overall target Fabric Energy Efficiency Rate.
A Uw value is the overall thermal performance of the glazing system as a whole. The unit of the thermal insulation value is given in W/m2K, which means “Watt per square metre and Kelvin”.Read how Uw values are calculated.
The increased Uw demands can present a somewhat daunting task for specifiers having to reconfigure thermal values with building materials which are designed to perform and outlast all others.
However, architects and specifiers will be gratified to learn that large glass elevations or minimal glass designs are still viable with the improved performance requirements.
For in depth details of the changes required for glazing under Part L see our full technical articles below:
Changes to Building Regulations Part F
Part F requirements were updated in 2022 with improved requirements for ventilation in new or replacement windows. Building regulations Part F lists the required minimal ventilation rates for rooms or dwellings (based on the number of bedrooms). Ventilation has to be considered as part of the glazing design to assist with this however, this can be achieved through trickle vents as well as other forms of building ventilation.
Architects and specifiers are required to look at the building as a whole to achieve the requirements under Part F. It has also been reported that there are various contradictions between the updated ventilation requirements in Part F and the improved requirements for air tightness in Part L. You can speak directly to us regarding the requirements for your project and our technical teams can offer advice on the specification of your glazing to achieve both performance elements.
Brand New Building Regulations Part O
Approved Document O was released this year to combat overheating in homes through considered design. Many architects that we work with were already utilising the CIBSE TM59 methodology to design for overheating, but it is now part of the building requirements.
Part O mandates that rooms need to be evaluated in isolation in regards to overheating and adequate means of cooling must be included to maintain the optimum temperature for a healthy living environment.
Within structural glazing, there are several dynamic solutions which prevent overheating, glare and, reduce energy consumption on HVAC systems.
- Solar Control coatings – recommended for south-facing installations, structural glass roofs and large glazing elevations. More can be found in our technical Solar Control Glass article
- Electro Chromic Glass
- Automation of opening glass solutions – Link to ARES modern glass technology
- External shading solutions – Link to Louvre Roof Systems
As the UK’s leading architectural glazing specialists, we pride ourselves in offering a broad range of high-performance structural glazing and thermally broken systems, all supported by our inhouse technical team of experts. From triple glazing to heated glass, there are countless ways to make glass sustainable.
Looking to speak with one of our friendly experts on your next project? Contact us today!