What is the notional dwelling and why is it important?

Whilst we await the release of the Future Homes Standard there has been lots of industry discussion regarding the level of uplift the notional dwelling will see over Part L 2021. In order to understand the requirements of the energy efficiency standards within Building Regulations this article examines the role of the notional dwelling.

Why is the notional dwelling important?

The specification applied to the notional dwelling is fundamental in determining the level of ambition set within the energy efficiency standards in Building Regulations. For Government, setting the notional dwelling specification appropriately is crucial. If it’s too ambitious, the cost of construction will increase substantially, but not ambitious enough and there could be criticism that Building Regulations are not demonstrating enough progress over previous iterations.

When the Future Homes Standard (FHS) is published, the national dwelling is expected to see a heat pump used as the heating system, replacing a gas boiler in the current Building Regulations. This is important because it will effectively make using fossil fuel heating (i.e. gas boilers) unviable if an outright ban is not imposed by Government. It is also expected that a number of Photovoltaic Panels will be included on the notional dwelling, but setting the capacity of the panels has been subject to some scrutiny by industry.

It is important to stress dwellings do not need to be built to the same exact specification as the notional dwelling; it is used to set the energy efficiency standards via SAP and HEM and then assessors and clients can choose to meet the standards however they want. When energy assessors are determining the best route to compliance, understanding the notional dwelling is vital. Being able to identify where the actual dwelling is performing against the different areas of the notional dwelling allows effective advice to be given to clients and a solution found without over/under specifying areas of the dwelling.

Is the notional dwelling approach appropriate?

Currently all regions of the UK use the notional dwelling approach to set their energy efficiency standards within Building Regulations. However there has been criticism in some areas of the notional dwelling approach from organisations such as LETI and RIBA. Some of the criticism relates to the notional dwelling using the same size and form of the actual dwelling. It is argued this effectively does not reward efficient building forms however the counter argument is that it does allow flexibility of design and form. Some areas of the industry would prefer absolute energy and carbon emissions targets that does not change with size and form of the dwelling, however no UK administration has currently adopted this approach.

Final thoughts

New Build Dwelling Manager Jason Hewins commented;

“Whilst we await the publication of the Future Homes Standard the industry is speculating what the notional dwelling will contain. Whilst we expect the heating system to be based on a heat pump, there is still some uncertainty on what fabric, ventilation and capacity of Photovoltaic Panels will also be incorporated. The industry is desperate to know the contents of the notional dwelling because it allows analysis of what improvements will be needed to the current specifications in order to comply with the Future Homes Standard and therefore what increase in build cost will be required. However, we do not expect this to be released before the Future Homes Standard is released in Autumn 2025.”