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Graham Temple focuses on the latest changes to the Building Regulations which cover energy performance, ventilation and overheating

In December 2021, the government released updates to Approved Documents Part L (energy efficiency) and Part F (ventilation) to further its net zero agenda. It also introduced a new Part O which deals with the issue of overheating in modern dwellings.

Also on the drawing board is another important future development in the form of the new Part Z of the building regulations, which will cover the embodied carbon in buildings.

The changes introduced in December 2021 will come into force from 15th June 2022.

So, what are the implications for the adoption of low-carbon technologies, and techniques to achieve this for both dwellings and non-dwellings?

There is a huge amount of detail and a lot to understand about the changes to the Building Regulations and I can only give a flavour of them here.

That is why we’ve just released a new CPD Guide on the latest updates to the Building Regulations which anyone can download from our document library.

We are also holding a CPD Webinar on the updates on Thursday 26th May at 2pm. You can register for the event here:

The overarching aim of the government in updating the Building Regulations is to drive the construction and property sectors to deliver lower-carbon energy efficient homes and other buildings that make greater use of green energy and decarbonised heating.

Parts L, F and O of the Building Regulations apply in England and Wales. Scotland and Northern Ireland have their own regulations dealing with building energy use and carbon emissions. Wales is also taking its own approach to delivering on some targets.

These changes will have a significant impact on building services.

Graham Temple Graham Temple Marketing Manager

Part L – Energy performance in dwellings

Part L 2021 Regulations are split into dwellings and non-dwellings, and each has different requirements for new-build and for existing buildings.

Under Part L, a new home or dwelling must achieve a ‘minimum standard of total energy performance’. This is tested by comparing the dwelling’s performance against that of a ‘notional’ dwelling of the same size and shape and is measured against three key metrics of primary energy rate, emission rate and fabric energy efficiency.

The government’s Standard Assessment Procedure was updated in early 2022 to accompany the new Part L and version SAP10.2 will be in force from summer 2022.The 2021 notional building sets higher standards for fabric efficiencies in terms of U-values for floors, walls, ceilings and windows. It also changes the requirement for airtightness from 5m3 /(h.m2 ) @50pa to 8m3 /(h.m2 ) @50pa – demonstrating a focus on indoor air quality over energy efficiency for new homes.

SAP 10.2 also includes the latest carbon factors for fuels such as gas and electricity. As the UK has increased its use of renewable generation, the allocated emissions of CO2 (equivalent) per kWh for electricity have been reduced from 0.398 to 0.233. The difference means that use of fossil fuels such as gas become less attractive option for new home designs, and alternatives such as electric heat pumps become more attractive.

The regulations state that: “Where a (dwelling) is erected it must be a nearly zero-energy building”. The definition of “nearly zero-energy” is given as a dwelling that meets the target emission rate and that an analysis has been made of the technical, environmental feasibility of using, “high-efficiency alternative systems which include decentralised energy supply systems based on energy from renewable sources”.

The Regulations also highlight the following as suitable high-efficiency systems:

  • Decentralised energy supply systems based on energy from renewable sources
  • Cogeneration
  • District or block heating or cooling, particularly where it is based entirely or partially on energy from renewable sources
  • Heat pumps

For existing dwellings Part L 2021 does not require them to be brought up to the new standards. However, where changes are made, they must meet the new Regulations for U-values for doors, walls, windows etc.

When a wet heating system is installed in a new home or fully replaced in an existing one, it must be designed to operate at 55°C. If this isn’t possible, it must operate at the lowest temperature possible, while meeting the heating needs of the dwelling.

Part L – Energy performance in non-dwellings

New buildings other than dwellings must be built to ‘near zero-energy’ and demonstrate compliance with Part L by meeting targets established with a notional building that is the same size and shape as the actual building.

The energy performance of the notional building establishes two main targets for the energy performance of the actual building. To comply with the Regulations, a building must meet both targets of primary energy rate and emission rate.

For existing non-dwellings a ‘consequential improvements’ rule is triggered in buildings with a floor area greater than 1000m2. This applies if the proposed extension is both greater than 100m2 and more than 25% of the total useful floor area of the building.

In addition, the installation of new fixed building services or an increase to the capacity of fixed building services will trigger the same rule. In these cases, consequential improvements must be carried out in the building to bring it up to Part L 2021 standards if these improvements are: “technically, functionally and economically feasible”.

The regulation states that the value of the works for consequential improvements must not be less than 10% of the value of the principal works. In the case of installing new or extending the capacity of fixed building services, the consequential improvements should include making energy efficiency improvements to the fixed building services to meet the requirements of Part L 2021. These improvements must be technically, functionally and economically feasible.

In addition to performance requirements for equipment, new non-dwellings over 1000m2 must provide the building owner with a forecast of ‘the actual energy use of the building’. This must be in kWh per year and broken down by fuel type.

Part F – Ventilation in dwellings

The new Part F of the Building Regulations reflects a growing understanding of the impact of indoor air quality on occupant health.

The updated regulations state that ventilation in new homes must minimise the entry of external pollutants. However, any means of ventilation applied in a dwelling must also:

  • Produce low levels of noise
  • Offer easy access for maintenance
  • Provide protection from cold draughts

There are now higher minimum whole-dwelling ventilation rates, depending on the number of bedrooms in the new dwelling.

For existing dwellings, any work carried out, such as replacing a window or door or carrying work to improve energy efficiency, means that the ventilation rate must be improved to Part F 2021 standards - or not be ‘less satisfactory’ than when the work was carried out.

This is an important point since many existing buildings rely on ‘infiltration’ rather than purposeful ventilation. Adding energy efficiency measures such as better insulation may well have a negative impact on ventilation in the home.

Part F 2021 therefore includes a list of ‘Energy efficiency measures’ that should be used as a checklist to identify types of work most likely to affect the ventilation in a dwelling.

Part F – Ventilation in non-dwellings

As with dwellings, the emphasis in the updated Part F is on creating high standards for indoor air quality to support occupant health in non-dwellings.

There are new standards on minimising the intake of external air pollutants if they exceed limits set out in Part F – or if the building is located close to sources of pollution. This might include buildings close to busy roads; near combustion plant such as heating systems or discharges from industrial processes.

Part F notes that ventilation intakes should always be away from direct impact of the sources of location, and that where buildings are next to busy roads “mechanical ventilation may be the most practical way of achieving this requirement”.

For existing non-dwellings, any work carried out must not result in any degradation of the ventilation standards in the building. 

However, when that building work in an existing building includes the ventilation system, then it must meet the relevant standards in the updated Part F 2021.

Part O – Overheating

The government has also set out to mitigate against the problem of overheating with the introduction of Part O (Overheating).

The focus on reducing the UK’s carbon footprint means that legislation is driving the development of airtight homes to save energy and reduce heating requirements. These dwellings are energy efficient and more comfortable in colder months, but more prone to suffer overheating in summer.

A balance is required, and the aim of Part O is therefore to protect the health and welfare of occupants in dwellings and other residential buildings by reducing the occurrence of high indoor temperatures.

The UK Health Security Agency states that in Summer 2020 there were over 2,500 deaths attributable to excess heat. It is also projected that the number of heat-related deaths in the UK will triple by 2050. The hottest summers on record in recent years will become our new ‘normal’.

The regulation applies in residential buildings, specifically:

  • * Dwellings - houses and flats
  • * Residential buildings where people sleep on the premises e.g., elderly or other care homes
  • * Student accommodation

In addition, any unit that contains living accommodation and workspace should be treated as a residential building, as long as the workspace can revert to residential use.

There are two key objectives under Part O:

Limit unwanted solar gains in summer

Provide an adequate means of removing excess heat from the indoor environment

Methods for removing excess heat allowed under Part O are:

  • Opening windows (a method which is improved by cross-ventilation)
  • Ventilation louvres in external walls
  • A mechanical ventilation system
  • A mechanical cooling system

Part O requires that passive means for overheating are prioritised and that mechanical methods are only used when all practical passive means have been used first, but mechanical means are not prohibited. In addition, a system for purge ventilation is required in each habitable room to comply with Part F.

Decarbonising heat

The 2021 updates to Parts L and F are interim steps on the way to 2025 when the new Standards will introduce further requirements for cutting carbon emissions and increasing energy efficiency in both dwellings and non-dwellings.

Government has also set out its intentions to reduce the UK’s reliance on natural gas for heating and hot water provision. The Heat and Buildings Strategy highlights the importance of technologies such as heat pumps and district heating to provide alternatives to the gas boiler for homes and other buildings.

There are also local requirements to consider, such as the London Plan which is also looking to reduce the capital’s reliance on fossil fuels by encouraging greater use of heat pumps in all buildings, as well as extending the development of heat networks.

The Plan also requires new large projects to provide energy use figures during the first five years of building operation – making a public commitment to reducing building energy use in London.

Embodied carbon

One important future development on the drawing board is a new Part Z of the Building Regulations, which will cover the embodied carbon in buildings.

Many leading engineering consultancies and construction clients support the development of this regulation to bring more focus on whole-life carbon assessments.

The proposed document has been authored by a joint panel including representatives of CIBSE, Institution of Structural Engineers, RIBA and RICS. Part Z proposes limiting embodied carbon emissions for all “major building projects”. 

The issue of whole-life carbon is not new but has come to the fore in recent years as many major construction clients focus on reducing the embodied carbon from their buildings to achieve corporate net zero carbon goals.

In conclusion

As previously stated, I can only give a brief snapshot of the changes here, but it is very clear that Building Regulations which focus on energy use, overheating, occupant health and decarbonisation will inevitably have a significant impact on the specification and operation of building services

One vital step on this road is that our domestic and commercial buildings must become more energy efficient and for example, adopt low-carbon technologies for space heating and hot water.

The UK’s increasingly ‘green’ electricity grid is what’s behind the adoption of heat pumps for heating and hot water provision in homes and other buildings. Not only do heat pumps enable the shift away from gas boilers, but they are also energy efficient.

At the same time, the importance of wellbeing in our homes and other buildings has grown in both the public and political arenas.

As a result, the government has also been looking into improving indoor air quality and tackling overheating, particularly in modern housing.

Many of the requirements of the new Regulations can be met with technology that is available today. However, their application and use require new ways of thinking about design and operation for consultants, building managers and the building occupants. 

Although there is a certain amount of new learning required, it could be regarded as an opportunity to adopt new and better ways of heating, cooling and managing our buildings.

It’s also worth highlighting that these changes are by no means the final word on Building Regulations. These interim changes are exactly that – a steppingstone towards 2025 when the Future Buildings Standard and Future Homes Standard are introduced.

You can register for our online webinar on 26th May, covering this topic in more detail here.

You can also download our free, CPD Guide to the updated Building Regulations 2021 here.

Graham Temple is Marketing Manager