Committing to a target of net-zero carbon emissions before the middle of this century is challenging enough. Existing stock must be upgraded, and this will be time-consuming and costly. In addition to this, construction companies will need to ensure that new-builds are also up to scratch.
In the vanguard of legislation falling out of the ambitious zero-carbon target setting, will result in the publication of revised Parts L for new dwellings and F of the Building Regulations for new dwellings in England and Wales. When they come into force, these regulations will set out the requirements for the energy performance and ventilation of the property.
These documents have been designed as a natural step towards more stringent standards due to come into force in 2025. This raises the importance of a phased approach for the construction industry since they will have not only to ensure current regulations are adhered to, but also ensure they can up their game to comply with 2025 standards.
Here, we’ll consider the most critical sections in Parts L, and F consultations in England and Wales, in what ways they are limited, and in particular actions construction practitioners need to take to prepare for 2025 standards.
Targets
Control of Building Regulations is devolved within the UK. Recent consultations in England and Wales concerned themselves with parts L and F of the Building Regulations for domestic properties. The documents deal with different requirements. Each document contains recommendations on how to become compliant. So far, consultation has taken place solely on requirements concerning new domestic properties. Non-domestic and refurbishment standards will follow close on their heels.
The Part L requirements have been constructed around a core performance measurement, which must be achieved for every property. In the past, this target related to a carbon emissions target. Most recent consultations produced two alternatives for further reducing the emissions target. For England, 20% or 31% (preferred) reduction over the current requirements. For Wales, the targets exceeded that of England— 37% (preferred) or 56%.
This requires some explanation. The calculations indicate reductions in carbon emissions. However, these were constructed around a new metric–primary energy. The carbon emissions metric has not been discarded; it has been retained as a back-up metric.
This change proved necessary because they do not directly measure energy efficiency. While efforts continue to decarbonise fuel, and in the end, to power dwellings with zero-carbon electricity, low emissions figures reveal little of importance about the energy efficiency of property in regular use. The primary energy measurement has been designed to generate a more precise figure for total energy use, factoring in the energy required for fuel preparation and a property’s ultimate energy demands.
Primary Energy Calculations
Each fuel type is calculated to have a primary energy factor (PEF), starting with the amount of energy employed during upstream production.
Factors include:
- Planting and cultivation of biofuel sources
- Extraction
- Processing and transformation
- Transportation
- Transmission
All PEF factors are worked out in advance and are contained in the Standard Assessment Procedure (SAP) specification. Energy demands are then worked out for specific uses. Examples include:
- Space heating
- Water heating
- Lighting
The energy required in each case is then multiplied by the PEF matching its fuel type. The addition of these figures provides the total primary energy demand for the property.
Here’s an example of how to calculate primary energy demand for heating:
(property energy demand/efficiency of heating technology) x PEF
Let’s start with a property heated by totally efficient electric powered panel heaters rated at 10,000kWh. We know that the fuel factor for electricity is 1.501, allowing us to derive primary energy demand as follows:
(10,000kWh / 1) x 1.501 = 15,010kWh
Primary energy calculations consider all renewable energy generated on-site to be subtracted from overall energy demand. For example, if we included a PV array producing 1,500kWh for exclusive use in the above-mentioned property, the calculation becomes:
([10,000kWh – 1,500kWh] / 1) x 1.501 = 12,759kWh
Dropping of the Fabric Energy Efficiency Standard
It is generally agreed that the move from carbon emissions as the primary indicator of how energy-efficient a property is, to Primary Energy Calculations, offers a more accurate snapshot. There have been critical voices, however, about the way in which is to be implemented in the draft in force in England.
The current situation is that the English Approved Document for new dwellings (ADL1A) uses the Fabric Energy Efficiency Standard (FEES). This sets minimum energy performance targets for the fabric elements of buildings. To simply the system when primary energy targets were introduced in the 2020 version of Part L, some argued for the removal of FEES. This meant that to exercise control over a building’s fabric performance would require the use of the worst-case backstop U-values. This is what currently happens in Wales because the FEES was never introduced in that country. However, the backstop U-values proposed for England are less onerous than their existing Welsh counterparts (as shown in Table 1 below).
