To support members through the changes that took place to Approved Document L ( AD L ) of the Building Regulations in 2022 , CAB produced a Guidance Note which details the changes in thermal insulation across the devolved Parliaments of the UK , this document has now been made available to non-members via the CAB website . Whilst our members and the wider industry have now got to grips with the 2022 changes to Approved Document L , we need to turn our focus on the next change to AD L where the Government is asking for an even greater leap in thermal efficiency which is planned to be introduced in 2025 .

The Government is keen to ensure we begin to build carbon neutral homes from 2025 , but new homes built now and in the future will only equate to a total of 20 % of our building stock by the governments 2050 target . This means that refurbishment of existing building stock will be crucial to getting more of our buildings carbon neutral by 2050 . But , when replacing just windows and doors , does it make sense to install high performance windows and doors into a structure which does not meet the same standards ? Importantly , does the reveal for the installation offer good insulation as cold bridging at this junction with the structure can have a significant negative effect on a new products thermal performance ?

Whilst we applaud the speed of the move to ensure new buildings are constructed to good , overall carbon neutral standard , does it make sense to ‘ piecemeal ’ the refurbishment of our existing building stock ? LETI emphasises that poor interfaces with the structure will compromise any potential thermal improvement if the building is not treated as a whole . Would it not be better to ensure that any replacement products , such as windows and doors , have a positive building thermal

improvement overall , which in turn will reduce energy consumption ? Should we be tackling the thermal improvement of window and door reveals as part of the ‘ home improvement ’ installation as this will certainly be needed when the building fabric is further insulated to meet carbon neutrality which may mean that the ‘ new windows ’ fitted into the existing structure will need to be removed , or even changed again ?

Several CAB members already have cited examples of building refurbishment using thermally improved window systems , not necessarily of the highest performance , but when linked with structural thermal insulation taking a whole building approach , shows that payback of the improvements can be realised in a few years in energy savings . Could this be an alternative route to achieving carbon neutrality by 2050 ? Looking at the latest Government initiative for improving our existing building

stock , ECO +, the scheme does not include grants to upgrading of old windows ? Whilst a twenty year old boiler should be replaced for improved efficiency , so too must double glazing which is twenty years old . Again , should we not be looking at taking a whole building approach to thermal improvements in our building stock ? Legislation recently announced in Scotland is that the Scottish Government is to push through legislation to ensure that all new homes built in two years time are built to a Passivhaus standard , or a Scottish thermal efficiency equivalent . LETI states that building to a Passivhaus standard increases costs for new build by only 5 % to 10 % over current regulation construction , which should prove affordable as energy savings will cover the increased costs .

Looking even further into the future , should we be satisfied with just building to carbon neutrality ? There is much talk on social media at the moment that we should

be aiming higher for our new build , where buildings should be ‘ carbon positive ’, that is to say to create an environment benefit and intentionally remove carbon dioxide from the atmosphere , which will help to reach the overall carbon neutrality for all our building stock .

Unlike some other materials , aluminium profiles are easily produced , as dies to extrude aluminium are relatively cheap and simple to design . Thermal break technology has also improved greatly in the last few years and high performance windows are already available to meet the most stringent thermal insulation requirements . A simple review of the UK ’ s Passivhaus Trust website shows that of the thirteen Passivhaus certified window systems available in the UK , five are aluminium systems , four are PVC systems , and four are timber based systems . As far as sustainability is concerned , aluminium can perform in use at least as twice as long as other fenestration materials , hence its preferred use in commercial projects and its growing use in residential new build and home improvement projects .

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