New regulations state window size must be limited amid fears that UK homes are becoming too hot

New regulations state window size must be limited amid fears that UK homes are becoming too hot

You may have heard the news regarding new building regulations coming into play, limiting the size and number of windows on new build residential homes from 2025, in an effort to keep homes cool as the climate warms.

You’ll be forgiven for [quite rightly] thinking that the proposal of new regulations on window size is a little tone death. Rather than tackling any number of the contributing factors to the climate issues we face, such as the impact of peat farming or the burning of fossil fuels for electricity which is the largest source of CO2 in the UK; The announcement seems to suggest that, as a nation, we are instead turning a blind eye. Adopting the attitude that we can’t prevent climate change, we may as well prepare to fry under the heat of the sun. Or shut ourselves away in dark rooms, behind clunky metal shutters.

A spokesperson for the Department of Levelling Up, Housing & Communities stated, “It is vital we adapt as we prepare to face the reality of climate change”. How?

By proposing further controls into, already strict, building standards and regulations. The individuals it will hit hardest are those looking to buy their first homes on New Build help-to-buy schemes, property developers and those looking to build their long-anticipated dream home. Complete with large panoramic views of the beautiful landscape beyond.

The new regulations not only completely ignore the greater issue of climate change but also disregard the numerous benefits of allowing natural light into your home; As not only an energy-saving solution over the winter but also for the mental wellbeing of its inhabitants. They also do not restrict the usage of materials such as uPVC, which almost always end up in landfill after their shorter life expectancy, compared to recyclable & maintainable wooden alternatives.

These regulations are in response to concerns over British houses becoming ‘uninhabitable’ if 40C summers become the new norm. Driven by environmental groups and government officials from the Climate Change Committee, who seek a future of new build homes that make sure people won’t overheat in the summer. Because, in true British fashion, if we aren’t complaining about the snow, we’re complaining that we’re too hot!

What are the new regulations on window size?

In a nutshell, the new regulations on window size are proposed to apply to new-build properties built from 2025 onwards.

They will either require homeowners or developers to place limitations on window sizes to a percentage relating to the floor area of each room and the house, depending on the direction they face.


They will require the homeowner or property developer to conduct a thermal analysis. Modelling the home’s design, including available shade from fixtures such as external shutters, and ventilation to ensure that the internal temperature will not be too high.

Conservatories and orangeries on homes can be exempt if they are unheated and separated from the house with exterior doors and walls. A Westbury French, sliding, or pocket door, would separate your proposed orangery seamlessly.

When will these regulations come into force?

Published as part of a huge overhaul on building standards, (and currently only in consultation), these new regulations are set to come into force in June 2025. However new transitional regulations will come into effect from June 2022, these will only impact U-values in new buildings and eventually replacement windows aswell. A spokesman for the Department for Levelling Up, Housing & Communities said: “These new regulations cover only new residential buildings, not extensions”.

The Exceptions

Exceptions to the rules are that existing homes and extensions on renovation projects, at this stage, need only acknowledge the regulations as ‘guidance’ rather than as a legal requirement. It is stated that “While there may be other buildings where the introduction of an overheating standard is beneficial, we currently do not have strong evidence about the prevalence of overheating risk for buildings in the existing residential stock”.

Before the new regulations on window size come into force in June, transitional arrangements are in place. If a building notice, initial notice or full plans, for building work are submitted to the local authority before 15th June 2022 and building work commences before 15th June 2023 work on that individual building is permitted to continue under the previous standards.

What does this mean for homes being built from June onwards?

When speaking to the Telegraph, Ric Wojtulewicz, Head of housing and planning policy at the national federation of builders said: “We can build heavily glazed buildings but smaller companies who do a number of different housing types on one development may avoid it, due to the potential cost of the Dynamic Thermal Modelling on each home.” (An analysis into the risk of overheating to ensure compliance to the new regulations)

Before continuing, buildings with larger portions of glazing will be considered a more “premium product” as lower-priced and mid-market companies choose to avoid them as a cost-saving measure.

Andrew Mitchell, Director of Energy Services at Stroma said, “We are going to get boring homes across the country because the regulations have got so hard”. He’s not wrong. The illustration provided by the Ministry of Housing, Communities & Local Government in the Consultation, entitled The Future Buildings Standard, leaves less to be desired. With an example of the kinds of sad-semi’s we can expect to see replacing our green landscapes in future.

new regulations on window size

However, these new regulations on window size are predicted to increase the demand for homes with plenty of windows and an orangery or conservatory. Which in turn will increase the value of homes that boast a generous helping of natural light. Particularly if those homes include windows with solar glazing.

This could mean that it will be in the interests of property developers and homeowners to seek thermally efficient (and environmentally friendly) windows, and not sacrifice on fenestration and the architectural glazing that will help their builds fetch a premium; Or those looking to build their dream ‘forever’ home and enjoy the view from their favourite armchair, well into their twilight years. Should now consider simply conducting a Dynamic Thermal Analysis.

How can you be sure that your New-Build home will comply?

Indicated in the consultation are two methods for compliance, known as The Simplified Method and the Dynamic Thermal Analysis Method.

The Simplified Method

The Simplified Method has been developed using a combination of limiting unwanted solar gains and removing excess heat. To reduce the risk of overheating. It will be based on a consideration of the risk in your area, for example, homes in Greater London are considered most at risk, whereas homes in the rest of England are considered at moderate risk. England is then further divided using the external summer temperature data in CIBSE’s weather files.

The property will then be categorised further into Group A or Group B.

Group A will include most houses, being characterised as having openings on opposite facades, whereas Group B will be mostly made up of flats, with windows on facades that are not opposing.

Within The Simplified Method, there will be requirements on minimum shading, from methods such as shutters, low-g glazing, and overhangs. In addition to the maximum area of glazing.

The Dynamic Thermal Analysis method

This method uses CIBSE’s TM59 Design Methodology for the assessment of overheating risk in homes. Similar to The Simplified Method it uses the location of the property, in addition to the materials used, orientation, air change rates and an occupancy scenario to calculate risk. It is also assessed day and night and allows a more thorough and accurate analysis of the building.

This method includes additional guidance to that of The Simplified Method, on limiting the unwanted solar gains in the summer via shading, but also removal of excess heat. For example, the ability to fully open windows, ventilation in external walls, and mechanical ventilation systems. It considers the glazing design such as orientation, g-value, window sizes, building design, such as the placement of balconies and the shade adjacent to the building from structures or landscape.

new regulations on window size

How Westbury meet these regulations

For existing homes, these new regulations on window size should be viewed as guidance only and are not legal requirements. So, it’s business as usual. New build homes from June onwards will be most affected.

The new glazing standards for windows, doors and roof lanterns are a maximum U-value of 1.4. Which Westbury have been working to as a minimum standard and far exceeded for some time. With U-values as low as 1.1, including triple glazing.

It’s important to highlight that not all U-Values are measured the same when it comes to Thermal Performance. Our U-values are recorded from the product in its entirety, glazing and frame, to provide the most accurate performance results possible. Comparatively some companies prefer to only advertise the centre pane, which can produce misleading results. This can result in your windows and doors could experience a great deal more heat transference than expected.

If you are required to conduct a Dynamic Thermal Analysis, we can supply you with the results from our independent testing and all information on our product specification. We can also work with you on ensuring that glazing is finished with Westbury Sun Guard to reduce heat transference.