15th June Building Regulations changes - Heating and ventilation

min read time
2023-06-08 15:06:52

With uplifts to building regulations, affecting heating and ventilation, developers will need to consider how they will meet the new standards. Engineers and specifiers will need to balance requirements for energy efficiency, air tightness and ventilation, which will require a combination of design improvements and the use of ‘alternative and renewable’ all electric and low carbon technologies.

The Department for levelling up, housing and communities has introduced these changes as an important step on the journey towards a cleaner, greener built environment supporting the target to reduce the UK’s carbon emissions to net-zero by 2050. They form interim measures to the government’s Future Homes Standard and Future buildings standard which is planned for 2025. In addition, they aim to improve the quality of homes and buildings with benefits to quality of life, economic activity and the levelling up of deprived regions across the UK.

Revisions to building regulations came into force on 15th June 2022, with a transition arrangement of one year for the plot build to commence, where a building notice or full plans had been submitted to local authorities. From 15th June 2023, the new building regulations will apply to all new home builds which haven’t started construction. SAP assessments will be used to produce BREL (Building Regulations Part L) reports both before any building work starts and ‘as built’ with copies available for homeowners.

Key changes to be aware of for domestic new builds

•    31 per cent less carbon emissions for all new build homes (than the requirements in previous building regulations) 
•    ‘Primary energy’ was introduced as a new metric for measuring energy efficiency. This will be used to measure the efficiency of a building’s heating as well as the energy required to deliver fuel to a building (including the efficiency of the power station supplying the electricity)
•    In all new domestic builds, the new U-value for walls will be 0.26 W/m2, 1.6 for windows and roof lights and 1.2 for doors. Improve fabric, airtightness and thermal bridging performance (futurehomes.org.uk)
•    New and replacement heating systems in both domestic and non-domestic builds must have a maximum flow temperature of 55°C
•    The newly Approved Document O to limit excess solar gain and remove excess heat, enforces new levels of cross-ventilation

Paving the way for the Future Homes Standard

The Future Homes Standard will require new build homes to be future-proofed with low-carbon heating and world-leading levels of energy efficiency and will be introduced by 2025. Air tightness and triple glazing (fabric first) will take us part of the way to meeting the new requirements but from 2025 onwards, it will be very difficult to heat new homes with gas. In its Heat and Building Strategy, the government has set out the following key features of future homes: 

•    Improved insulation
•    Ventilation with heat recovery
•    Smart controls
•    Energy storage
•    Low carbon heat sources (heat pumps for houses and district heat for apartments)

Read more: Sustainable Heating and the future homes standard


Building regulations part L

Approved document L covers the conservation of fuels and power and sets standards for the energy performance of new buildings. All new buildings will need to generate 31% fewer CO2 emissions than the current regulations allow. 

Part L requires a minimum CoP of 3.0 for space heating supplied by a heat pump. This is the ratio between energy out and energy in and is a measure of the efficiency of a system. This means for every 1 kW of electricity in, the heat pump must provide 3 kW of heat out. 

New build houses with air source heat pumps should be designed to a maximum 45ºC flow temperature. This change will have an implication on the type of heating appliances that are used with radiators being required to double in size to achieve the same outputs as a previous flow temperature of 70°C. Underfloor heating will become a more attractive option offering greater energy efficiency, heat distribution and easier space planning.

The new legislation also means the thermal regulations for windows and openings are changing. The current U-values for the thermal transmittance of windows and openings into all settings (new and existing buildings) have been upgraded. A new dwelling should achieve airtightness of 10m3/hr as a minimum. 

Part L1a acknowledges that airtight buildings don’t allow for natural air changes to occur and toxins can build up quickly affecting the health of occupants. It identifies the need for approved ventilation solutions which are detailed in part F.

Building Regulations Part F

Changes to approved document part F place greater importance on air tightness combined with the right ventilation. It has reduced the recognized ventilation strategies with the aim of simplifying and making them easier to follow.
The following ventilation systems are recognised in part F:

System 1 – background ventilators and intermittent extractor fans
System 3  - continuous mechanical extract (MEV)
System 4 – Continuous mechanical ventilation with heat recovery (MVHR)

Note that positive heat input has now been removed as a recognised method of ventilation and minimum airflow through these systems is increased to 6 l/s. There is also an increase in the requirements for background ventilation (window vents) from 2500m2 to 5000mm2 in extract-only systems. 

Part F requires control to enable operation without occupant intervention, but where manual control from the occupant is available and also indicates humidity sensors may be installed in moisture-generating rooms.

Building Regulations Part O

Approved document part O is a new uplift to the building regulations which sets standards for overheating in new residential buildings. It states that excess heat should be removed from the residential building by any of the following means:
a.    Opening windows (the effectiveness of this method is improved by cross-ventilation). 
b.    Ventilation louvres in external walls. 
c.    A mechanical ventilation system. 
d.    A mechanical cooling system 

Although passive means should be used as far as is reasonably possible, ventilation is impacted by the following:

•    Noise – should allow for windows to be closed during sleeping hours in locations where external noise may be an issue
•    Pollution – in areas near significant local pollution, approved document part F should be followed to reduce the intake of pollutants. 
•    Security – must account for the security risk of leaving windows open during sleeping hours

Mechanical ventilation with heat recovery (MVHR) can help to mitigate all of these issues.

Anthony Croke, Territory Product Manager for Indoor Climate Solutions at Wavin commented “No single heating or ventilation product can solve all of these issues. The smart developer is looking at this as a whole, so they can hit the sweet spot of sustainable, energy efficient heating combined with health-giving ventilation. This is critical to meeting regulations, keeping home buyers comfortably warm and creating efficient, future-proofed homes.”

Integrated indoor climate solutions for residential new builds

At Wavin, we offer a range of market-leading systems which can be combined to create tailored solutions to meet requirements for energy efficiency, indoor air quality, ease of use and installation on residential new builds. Our systems are designed to work together to provide a single source, integrated solution with low maintenance, more space and design freedom, compatibility with different floor types and coverings and full zone control. With our extensive experience in residential projects, we can provide support at every stage of your project from design and system selection with value engineering to aftersales and installation support.  

Martyn Neil, Commercial Director for Indoor Climate Solutions at Wavin UK commented “the new regulations are a pathway to the 2025 Future Home Standards and Wavin are ready to support developers to achieve the requirements now and for the future. Indoor climate solutions bring together heating, cooling, ventilation, with smart controls, to achieve a homeowner friendly system, which reduces carbon emissions and meets modern building standards.”

Heat sources

The selection of heat sources will play an important part in the move to sustainable homes with an alternative to gas boilers being required from 2025. Heat pumps are likely to play a key role but other solutions could also play a part.
As set out in the Heat and Buildings Strategy, the government believes that heat networks will be an important part of our net zero strategy. This is supported by the Climate Change Committee’s suggest 18% of UK heat could come from heat networks by 2050 as part of at least a cost pathway to meeting net zero. Heat sources for new networks are likely to be heat pumps and for existing networks, CHP although there may be other ways of capturing or generating heat locally. For residential apartments especially in high-density urban areas, heat networks often offer the lowest cost low carbon heating option. 

Read more: Can district heating networks help support green heating across the UK

Heat interface units for space heating & hot water 

Specifying electronic HIUs gives greater accuracy of settings and temperature control, improved commissioning, fault finding and diagnostics and user control of hot water temperatures. A range of bypassing (keep warm) options can be included but auto bypass learns the users' patterns of heat and hot water and generates a bypass to meet the users' schedule reducing waste energy through excessive bypassing.

CP1 best practice is to specify a HIU unit with VWART (volume weighted average return temperature) less than 33ºC. VWART is the key output of the BESA test standard which was introduced for Heat interface units in 2016. 

A heat interface unit is expected to provide instant hot water in a new build with CIBSE CP1 and NHBC standards requiring that an HIU must deliver 50ºC at the HIU with 45ºC achieved at the taps within 45 seconds. 55ºC should be an achievable network supply temperature. In a new build a good HIU will be able to deliver 50ºC hot water from 55ºC primary temperature with underfloor heating able to operate at 35ºC in new build applications with low heat losses. 

Read more: Benefits of heat interface units

Wavin Calefa HIU features an auto mode, the electronic control unit monitors the usage of the domestic hot water and then uses this insight to learn the specific usage patterns for that home. With this intelligence, the system can make sure that the hot water is always ready to use at these specific times. Thanks to the specially designed 4-option bypass control, the Calefa, which already delivers a very low VWART will reduce the energy used by even more during low demand periods. The auto function makes Calefa truly unique and sets a completely new standard for domestic hot water delivery in the UK. Find out more about Wavin Calefa HIU

Underfloor heating

Wavin has commissioned a whitepaper written by LCP Delta on the impact of using underfloor heating in new build dwellings. It shows that radiant vs convection heat saves 10% of the energy used. Appliance efficiency through using underfloor heating saves a further 3000 kWh per year for heat network applications. Overall this would mean an underfloor heating saving of up to 4800 kWh per year for consumers on heat networks. Read the whitepaper. 

Traditional radiators use convection to heat a room and underfloor heating uses radiation. With underfloor heating a larger surface area than a radiator means that they can operate with a lower heat input. Radiant heat allows a more even distribution, concentrating on the floor or lower levels where the heat is needed the most, than convection with radiators can result in draughts of hotspots. Underfloor heating is also ideal for heating open-plan spaces where radiators would struggle to distribute heat evenly.

At Wavin, we offer a range of underfloor heating systems which can accommodate a number of different installation needs. The three most popular types of underfloor heating options currently being installed across the UK include:

•    Staple
•    Castellated plate
•    Low build panel

Read more: Underfloor heating systems: a complete guide



With continuous mechanical extract systems (MEV) and background ventilators with intermittent extractor fans, there will be higher related heating costs and the time required to heat cold air when using low-temperature heat sources such as underfloor heating will be an issue. Increased requirements for window vent sizes and noise pollution are also an issue for both of these methods.  Overall due to the challenges of natural ventilation combined with part F and part O building regulation requirements, mechanical ventilation will be the best option for new build apartments in the UK.

Continuous mechanical ventilation with heat recovery (MVHR) is an energy-efficient alternative with a range of advantages for future homes including continuous and controlled ventilation rates, suitability for use with heat pumps and underfloor heating, reduced risk of condensation, filtered air for improved health, no need for background ventilators (window vents) and the highest DER (Dwelling Emission Rate) performance of all the systems. 

Wavin Ventiza ventilation units are independently tested by BRE and conform to building regulation requirements. The range can be matched to property size for maximum efficiency and can be integrated with premium heat exchangers with extremely low power consumption and Sentio intelligent controls for optimal energy efficiency.

Read more:
MVHR systems explained
Can a well-ventilated house also be energy efficient?
How MVHR is at the frontline of damp prevention

Controls for integrated indoor climate solutions

Indoor climate is one system which needs a single smart control, providing space, time and temperature, hot water temperature, and automatic and user-controlled ventilation. This will allow users to minimise energy usage whilst achieving a comfortable indoor environment. Each room should be a zone to ensure the correct time and temperature profile within the apartment. Thermostats need to monitor temperature and humidity in rooms to ensure adequate temperature, and ventilation, and to prevent mould. The site-wide building management system should be able to interface with the control system in the apartment for alarms, and fault finding. Part F also requires control to enable the operation of ventilation without occupant intervention, but where manual control from the occupant is available.


The Wavin Sentio control unit can be linked to the Wavin Ventiza mechanical ventilation with heat recovery units (MVHR). This enables users to control underfloor heating, cooling, radiator, and ventilation systems from one controller, with one app.

Indoor Climate Solutions at Wavin

At Wavin, our purpose is to build healthy sustainable environments. Our tailored indoor climate solutions feature our market-leading systems and products including underfloor heating, heat interface units, MVHR and single controls (interfacing with all of these technologies). They provide the following benefits:

•    Improved energy efficiency
•    Low maintenance
•    More space and design freedom
•    Compatible with all floor types and coverings
•    Comfortable environments with even heat and less dust
•    Full zone control
•    Flexible solutions including installation and after-sales support
•    Design and system selection support
•    Wavin’s extensive experience in residential projects as a market leader in Europe