Building with a quality, high-performance material like aircrete can help you to ensure your self-build meets building regulations. Read on to find out exactly how, from Part L to Passivhaus.
Building Regulations
Part L of the Building Regulations covers the energy performance of buildings. It considers how the whole home performs, including the walls, floors and roof, together with insulation, windows, heating and ventilation.
An important part of this is reducing heat loss through the building fabric.
One way heat can escape is through thermal bridges. These are areas where heat can pass through the building more easily, typically at junctions between different parts of the structure. For example, where a wall meets a floor or roof, or around windows and doors. Thermal bridges can account for up to 30% of a building’s fabric heat loss, so careful design and construction of these junctions can make a real difference to the overall energy performance of a home.
Aircrete has relatively low thermal conductivity compared with denser masonry materials. This means it can help to reduce heat loss at junctions when used as part of an appropriately designed wall construction.
Aircrete can be used below and above ground level. H+H Foundation Blocks are designed to support solid or cavity walls, while Celcon Blocks, of all sizes and grades, are used above ground. Using aircrete below and above, can help maintain thermal performance between the foundations, floor and external walls.
The Future Homes Standard
The requirements for new homes are continuing to change.
The Future Homes Standard has now been introduced through changes to the Building Regulations in England. The new requirements come into force on 24 March 2027, subject to transitional arrangements for projects already underway.
The aim is for new homes to combine high levels of energy efficiency with low-carbon heating. The requirements continue to place importance on the performance of the building fabric, alongside heating, ventilation and other building services and introduces requirements for on-site renewable electricity generation for new homes.
Celcon Blocks can be incorporated into wall constructions designed to meet demanding energy-performance requirements. H+H provides technical information, construction details, U-value calculations and calculated Ψ-values to help designers and energy assessors select appropriate constructions.
If terms such as U-values and Ψ-values are unfamiliar, don’t worry. Put simply, U-values measure how effectively parts of your home, such as walls, retain heat, while Ψ-values help measure the additional heat lost at junctions between different parts of the building. In both cases, lower values generally indicate lower levels of heat loss.
Meeting the Building Regulations and having your home signed off by building control can seem daunting. Choosing construction materials with well-documented performance and making use of the technical expertise available can help make the process more straightforward.
How to comply with Part L of the Building Regulations
One of the best things you can do is involve an accredited energy assessor early in your project.
For new homes in England, SAP (the Standard Assessment Procedure) is currently used to assess the energy performance of a dwelling. SAP 10.3 is the current approved methodology. The Government is also developing the Home Energy Model (HEM), which is intended to provide an additional method of assessing compliance with the Future Homes Standard.
Your energy assessor will look at the design of your home and consider factors including insulation, walls, windows, heating, ventilation, renewable-energy systems and heat loss through junctions.
The assessment takes place at the design stage and again when the home is completed. This is important because the finished building needs to reflect the materials and construction details used in the original assessment.
If significant changes are made during construction, perhaps to the insulation, heating system or wall construction, these can affect the final energy assessment. Discussing changes with your designer and energy assessor before they are made can help avoid problems later.
The key is to involve your assessor early, follow the agreed specification and keep suitable records of the products and construction details used throughout the build.
H+H provides a range of free technical resources for people designing and building with Celcon Blocks. These include thousands of calculated Ψ-values covering different wall, floor and foundation junctions, together with construction details, U-value information and site guidance.
You don’t necessarily need to understand all of these calculations yourself. Your architect, designer or energy assessor can use the information to help design your home and demonstrate its energy performance.
Passivhaus self-build
You may also have heard of Passivhaus, sometimes called Passive House.
Passivhaus is an internationally recognised building-performance standard developed by the Passivhaus Institute in Germany. It is designed to create homes that need minimal energy to keep them comfortable. Rather than relying on one particular product or construction method, Passivhaus considers how the entire building works together.
This includes high levels of insulation, carefully designed junctions to reduce heat loss, very good airtightness, high-performance windows and an effective ventilation system. Together, these measures can significantly reduce the amount of energy needed to heat a home while maintaining a comfortable internal environment.
H+H Celcon Blocks can be incorporated into wall constructions designed to achieve the high levels of performance required for a Passivhaus project. Aircrete’s thermal properties can be particularly useful when designing junctions between different parts of the building, where controlling heat loss is important.
With an appropriate combination of Celcon Blocks, insulation and other components, high-performance aircrete cavity-wall constructions can achieve U-values of approximately 0.11 W/m²K, depending on the particular wall design and specification. As a guide, external walls in Passivhaus projects are commonly designed to achieve U-values in the region of 0.10–0.15 W/m²K. However, achieving Passivhaus stardard, whether you decide to seek certification or not, isn’t just about reaching a particular wall U-value. The performance of the whole home matters, including insulation, airtightness, windows, ventilation, orientation and the quality of construction.
If you are considering building to the Passivhaus standard, involve an experienced designer or Passivhaus consultant as early as possible. They can help ensure all of these elements work together from the beginning.
Getting the right advice
You don’t need to become a building expert to build an energy-efficient home. The important thing is to involve the right people early, choose products with clearly documented performance and make sure that what is designed is accurately carried through into construction.
H+H’s Technical Team can provide guidance on using Celcon Blocks and H+H aircrete products, together with technical information and construction details to support your architect, designer, energy assessor and builder throughout the project.