Low energy buildings
The planned introduction of the Future Homes and Future Buildings standards in 2025, is a key element of the government’s zero-carbon agenda, in which, low energy building design is a core requirement. The aim is to deliver new buildings that are zero-carbon ready; in other words, able to become zero-carbon with no future retrofitting as the electricity grid continues to decarbonise. The first steps have already been taken with recent updates to Part L of the Building Regulations, which came into force in 2022.
Part L continues to be underpinned by the government’s “fabric first” policy, the rationale being that fabric performance is built-in, maintenance-free and lasts the lifetime of the building. In this regard, concrete and masonry construction performs particularly well, with inherent durability and thermal mass.
This is also relevant to the newly introduced Part O of the Building Regulations, which addresses overheating in new dwellings, and prioritises the use of passive measures. This includes the use of thermal mass, which is accounted for when overheating risk is assessed using dynamic thermal modeling; one of two options for demonstrating compliance with the regulations.
The Concrete Centre has a variety of guidance that can inform the design of low energy buildings and help address the risk of overheating:
Specifically for the design of housing there is also:
Fabric energy efficiency
Over the years, concrete and masonry construction systems have responded well to the uplift in thermal performance required by updates to building regulations. This continues today, with the 2021 edition of Part L and the anticipated 2025 Future Homes/Buildings Standards, which are likely to require a U-value of around 0.15 for the external walls of dwellings; a significant improvement over past requirements. The simplicity and adaptability of concrete and masonry systems ensures they will continue to keep pace with ever increasing demands on thermal performance.
Below are links to useful further guidance on each area.
Insulation
Thermal Performance Part L1A includes a large selection of performance data for walls and floors for a variety of concrete and masonry construction solutions and different types of insulation. Each one is illustrated with their construction dimensions and corresponding insulation (U-values) and thermal mass value (k-value.)
Reducing thermal bridges
A comprehensive range of high-performance masonry construction details are available to download with pre-calculated PSI-values for use with SAP to meet thermal bridging performance criteria using different block types and insulation options. These details provide an effective means of minimising a dwelling’s overall heat loss from thermal bridging.
The MPA Masonry website provides further explanation and all necessary links.
A range of products are available from specialist suppliers to reduce thermal bridging using concrete and masonry construction. These include low conductivity ties for cavity walls, and insulated precast sandwich panels, plus high performance lintels and insulation for cavity walls, as well as thermally insulated balcony connectors.
Airtightess
Concrete and masonry construction offers high levels of airtightness and can provide the basis for a resilient, long lasting air barrier. Cast insitu and large format precast panels are inherently simple to detail providing a robust structure with few joints, helping minimise air leakage. For masonry construction, the plasterboard lining is typically used to provide the air barrier, with highest levels of performance achieved when a parge coat is first applied to the blockwork. Alternatively, the plasterboard can be replaced by a wet plaster finish, which provides a durable air barrier that can be easily repaired if damaged.
More details on airtightness.Thermal mass
Useful levels of thermal mass are provided by concrete and masonry construction and can be used to enhance year-round thermal performance of buildings. More specifically, it can be used towards helping achieve our zero carbon goals. Specific areas where it can play a role include:
- Helping to avoid the need for air conditioning and reducing the cooling load in buildings where it is installed.
- Reducing the risk of overheating in passively cooled buildings.
- Enabling the use of passive solar design for enhanced thermal performance during the heating season.
- Enabling hybrid heating/cooling systems to operate efficiently e.g. where low temperature heating/cooling pipes are embed in concrete floors.
- Actively storing and releasing heat so a building’s energy demand responds sympathetically to the peaks and troughs of the renewable energy feeding the grid.
Further guidance on the use of thermal mass.