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Important updates to building regulations for refurbishment projects

Long overdue changes are afoot in the UK building regulations, which will have an impact on windows and doors for both new build and refurbishment projects.


The UK Government will introduce, by 2025, the new Future Buildings Standard, which aims to future proof new homes, increasing energy efficiency standards.

In the meantime, in an attempt to transition to the Future Buildings Standard, some interim changes are to be introduced on 15th June 2022.


The changes affecting windows and doors for refurbishment projects are focussed into Building Regulations Approved Document F: Ventilation and Approved Document L: Conservation of Fuel and Power.



Approved Document F: Ventilation

There is starting to be a realisation in the construction industry that ventilation along with airtightness are much more important for the health and performance of buildings, and therefore more consideration should be given to ventilation.


Building regulations, administered via our Fensa certification, previously required that we replace like for like with regards to trickle ventilators. In other words, if we are replacing a window with a trickle vent, the new window should have a trickle vent. Fairly simple. The client also had the option to ‘opt out’ of trickle vents. The new requirements go a bit further and require a bit more thought.


The new requirements specify an equivalent area for trickle vents, depending on the room type:


To habitable rooms and kitchens the equivalent area is 8,000mm2.

To bathrooms the equivalent area is 4,000mm2.


Each trickle vent in our systems typically achieves 2,500mm2, so in a habitable room we would need 4 trickle vents, and in a bathroom 2 trickle vents. This is generally achievable, depending on the size and design of the windows / doors being replaced.


Things are slightly different if your property has a continuous mechanical extract ventilation system. In that case we are only required to have trickle vents with an equivalent area of 4,000mm2 in windows not in wet rooms (i.e. kitchens, bathrooms and utility rooms).

It is worth noting that if it is not technically feasible to adopt the minimum equivalent areas set out, then trickle vents with the closest possible equivalent area can be used. Additionally, other ventilation strategies can be employed if it can be shown that they meet the requirements.



Approved Document L: Conservation of Fuel and Power

The changes to building regulations Part L are where things will really get interesting for the replacement window industry. The minimum thermal performance of windows and doors is increasing, to actually push refurbishment windows and doors ahead of new build windows and doors.


Previously, to comply with building regulations for thermal performance, replacement windows and doors needed to achieve a whole window / door U value of 1.6W/m2K. Our blog post https://www.okohaus.co.uk/post/istripleglazingworthit outlines the importance of understanding relative U values when comparing window and door products. Basically, the lower the U value, the less energy is escaping from the building, and therefore the better performance of the window / door.


The changes, from 15th June 2022 will require that windows and doors must achieve a whole window / door U value of 1.4W/m2K. interestingly, replacement timber windows will only need to achieve 1.6W/m2K, a move which we believe is to allow traditional timber sliding sash windows to be replaced close to like for like.


Many aluminium, UPVC and even aluminium / timber composite window and door systems will struggle to achieve 1.4W/m2K. At the time of writing it seems that much of the industry has their heads buried deep underground and many system manufacturers don’t seem to have products that will genuinely be able to keep up with the changes. Some parts of the industry are actively campaigning to delay the changes.


For our products, we will no longer be able to use the Velfac V200 double glazed system for refurbishment projects, except in exceptional circumstances. For example, where the windows are very simple and large, with a bespoke, project specific U value calculation. Our Rationel and FT-Vilstal systems have no problems meeting the improved thermal performance requirements with double glazing, so should start to become a more attractive value proposition for more of our customers.



Given the UK housing stock is widely reported to be the worst performing in Europe, it’s right that the immediate focus is on improving standards for refurbishment projects. This will at least quickly stop the continued practice of low performance renovation, thereby avoiding making the problem worse. And, we believe it’s right, and long overdue, that government should legislate to push the construction industry to improve performance. Only by raising the already very low bar that has been set will consumers be protected from making poor choices in what is a significant investment in their property.

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