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Future Building Standard – Proposed Requirements for Change of Use Projects

16 Mar 2021


When the Future Homes Standard was published in 2019, it didn’t consider work to existing buildings.

This omission has now been rectified with the Future Building Standards. It proposes new targets and requirements affecting three different Approved Documents when it comes to creating a dwelling within an existing building. In other words, barn and office conversions.

At time of writing, the Future Buildings Standard is still open to public consultation, so the following details are all subject to change. We’re expecting the requirements to be finalised in the later half of 2021.

Starting with U-Values and Part L.

Insulation levels will need to be increased compared to the thresholds used today. The U-Value targets vary depending on whether you’re renovating an element or completely rebuilding it, and whether you’re in England or Wales, but the common factor is that the maximum allowed U-Values are being improved.

Approved Document Part L also sets minimum standards for heating efficiencies, heat losses from pipework and energy saving devices. A newly installed heating system should meet the name standards as if it were being fitted in a new building, and should be designed to a maximum flow rate of 55 degrees.

You do not need to meet a Target Energy or Emission Rate for a change-of-use project, but you do need to be mindful of the EPC rating, as there are proposals (separate to the Future Buildings Standard) to set tougher targets in the coming years to make house sales illegal if the building falls into the lowest EPC categories.

Ventilation and Part F.

Under the proposed new AD F, a change-of-use scheme is treated very similarly to a brand new building. Suitable ventilation systems will be required, and new windows should come with background ventilation as standard.

But more emphasis is being placed on the location of extraction fans and intakes… the design must ensure ventilation outlets face away from polluted roads and noisy areas. This is to reduce the risk of poor air quality and lower the noise levels that leaks into a dwelling.

And finally, overheating requirements:

Code name AD X (or AD S) is a new Approved Document to target the risk of overheating, and will apply to new dwellings created through change-of-use.

The glazing ratio (glazing area compared to floor area) and the free area (area of openable windows, external doors and louvres) need to meet proposed new targets, otherwise additional steps will be required to mitigate the overheating risk.

This may include the use of tinted windows, adding balconies or external shutters, or completing a detailed thermal dynamic review to take into account site specific details such as the precise angle of the sun and shadows caused by neighbouring buildings.

We will publish a follow-up article later this year when the various targets have been finalised, and what that means in terms of real-world compliance.

The above applies to change-of-use projects only. We have separate articles that cover proposed changes regarding domestic extensions and renovations.

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Jon Ponting

Energy & Sustainability Specialist


Jon Ponting

Energy & Sustainability Specialist