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Future Homes Standard 2025: What are the F, L and O regulations?

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By Ruth MacEachern

Product Manager

Jun 21, 2022

The Future Homes Standard is a criteria linked to energy efficiency that comes into play in the UK in 2025. The key purpose of the standard is to significantly reduce carbon emissions, with properties being built with 75% less carbon compared with existing regulations. This is in line with the end goal of Net Zero by 2050.

What is the main objective of this regulation?

The standard is split into two areas, with the first concentrating on changes and implementation of new regulations, with the second in the form of a consultation document that was completed in 2020. Through this, guidance for both new build dwellings and for retrofitting of properties, and as a result will then produce zero-carbon ready homes which require no additional energy efficiency measures. The standard encompasses several areas, including a reduction in carbon producing appliances such as gas heating systems and fuel appliances utilising fossil fuels, increased thermal efficiency and air tightness levels within dwellings and also the consideration of embodied carbon via the materials used within the construction of properties and over their lifespan.


Both Approved Document F: Means of Ventilation and Approved Document L: Conservation of Fuel and Power have recently been modified to be able to provide both the innovation and infrastructure to carry this into the future. There has also been the introduction of Approved Document O: Overheating Mitigation, which will all fully come into force on 15th June 2022.

The approved document F

There has been an increase in ventilation rates and a shift towards mechanical ventilation systems for Approved Document F, as well as the inclusion of the previous standalone Domestic Ventilation Compliance Guide, and a separate volume containing non-residential guidance. There is a change in terms of the compulsory use of background trickle vents when utilising Continuous MEV with a requirement of 4000mm² in each habitable room.


This, coupled with a substantial increase in the whole dwelling ventilation rate, which has seen the minimum ventilation rate for a two bedroom property shift from 17l/s to 25l/s leans itself towards continuous C-MEV and MVHR becoming the norm as we edge further towards 2050 and the Net Zero target. These systems also produce sustainable methods of ventilating both new and existing dwellings.

The approved document L

Approved Document L has been reduced from four documents to two, with residential and non-residential volumes. Standards have been set high with a fabric first approach, concentrating on the materials used to build the dwelling to provide the required levels of energy efficiency without immediately resorting to mechanical alternatives such as was often seen in previous versions of the document.


A 30% reduction in carbon emissions for new dwellings is required as an interim target up to the commencing of the Future Homes Standard in 2025, and, and also provides a more stringent methodology for energy modelling. This has resulted in a minimum performance tolerance for elements of a dwelling such as walls, doors and windows which will increase energy efficiency and prevent poor standards of construction.

The approved document O

The new Approved Document O provides guidance for mitigating overheating. This is something that has been present as an issue within construction for some time, and with the increased energy efficiency methods and requirements of achieving the Future Homes Standard, the new publication is welcomed. The document concentrates on two main methodologies, the Simplified Method and Dynamic Thermal Modelling which look at many variables to determine whether further action is required to reduce the risk of overheating. Essentially, the key point from Approved Document O is that any potential overheating issues should be identified at the design and pre-construction stage, rather than via a mechanical ventilation and cooling focused option once the property is built.

Main changes of the regulation

The changes and introduction of these Approved Documents will bring a significant shift in working practices across the whole of the construction sector. The level of innovation and research required to be able to bring these new heating and fuel sources to both our new build and existing properties is extensive and requires those with specialist skills to be able to develop the necessary technologies to futureproof construction processes.


Part of this research has seen an increase in alternative fuel sources such as air or ground source heat pumps, hydrogen, hydroelectricity and wind, that are often used within vehicles and for remote dwellings, but time will tell to see how these can be shaped and developed to be robust enough for properties to provide the levels of energy efficiency needed to meet the Future Homes Standard.


As well as including the three approved documents, elements such as the Government’s Standard Assessment Procedure or SAP, have also been modified to provide a more stringent method of both selecting and manufacturing suitable products to meet the requirements set by the SAP assessor in terms of optimal sustainability and performance.


The changes highlighted within the standard will come into force in 2025, with the consultation having closed in 2020. However, between now and then, there are plans to have interim documents produced that cover a variety of areas. England is looking to produce a technical consultation relating to specification for the Future Homes Standard in 2023/2024, Wales are producing a review of Part L under the new standard and Scotland are looking to provide additional guidance around Covid-19. Wales, Scotland and Northern Ireland are yet to publish their interim variants of Approved Documents L and F plus any further guidance on overheating mitigation, though Wales have confirmed that Approved Document S will be their named overheating document.


The Future Homes Standard will really set the precedent for the development of energy efficient dwellings in the UK, leading the way towards the Net Zero goal in 2050. The fabric first focus, and clarity of the key features of the documents including thermal efficiency, alongside the shift in ventilation suitability and mitigating overheating provide sustainable and realistic goals that will be able to significantly reduce the percentage of greenhouse gas emissions in the UK- and provide a stable base for future practices.


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