Introduction to Part L Building Regulations
Part L of the building regulations sets standards for the energy performance of new and current buildings in the UK, such as insulation sufficiency, and adequate airtightness. It focuses on current building regulations and future guidance of energy-efficiency requirements, ensuring buildings of tomorrow are constructed as sustainably and eco-friendly as possible.
Purpose: It's imperative to the future of the planet that the construction industry builds energy-efficient homes and extensions that help to reduce carbon emissions. Part L building regulations are key to promoting eco-friendly measures within buildings, such as limiting heat gain and loss, adding efficient lighting systems, harnessing solar power, and installing adequate heating and ventilation systems.
Who It Affects: Building regulations part L impacts anyone involved in the construction of new dwellings and existing buildings, such as designers, architects, builders, installers, developers, and construction companies.
Key Energy-Efficiency Standards in Part L
Energy-Efficiency Requirements: The specific environmental standards mandated by Part L building regulations differ for new builds and existing homes.
Part L requirements for new buildings include:
- Reduction of heat loss through adequate insulation ( a minimum level of insulation must be provided).
- Efficient heating and ventilation systems must be installed to minimise energy consumption.
- Windows, floors, and roofs must meet thermal performance standards to limit energy waste.
- Energy-efficient lighting should be installed.
- A minimum of 10% of the energy used in new builds to come from renewable sources.
Part L requirements for existing buildings
Renovation work on current buildings should include upgrades to the insulation, airtightness and heating system to improve the property's energy performance.
Replacement boilers must meet minimum energy-saving levels, while replacement windows and doors must comply with energy performance standards.
U Values
U-values are used to evaluate the energy performance of different parts of a building, such as walls, windows, doors, and roofs. The lower the U-value, the greater the energy efficiency.
Limiting Heat Gains and Losses
By introducing several heat loss measures, such as installing double glazing, insulating cavity walls and lofts, and adding carpets, curtains, and draught excludes, you will minimise your carbon footprint while also keeping energy bills low. Similarly, reducing solar heat gain through thermal insulation and window shades will eliminate the need for excessive cooling, lowering the property's carbon emissions and promoting environmental sustainability. Part L sets out guidance for the conservation of fuel and maintaining optimal indoor temperatures.
Ventilation Systems
An efficient ventilation system is important for maintaining good indoor air quality in the home and promoting well-being. By removing toxic pollutants and moisture in the air, good ventilation can eliminate health issues, like asthma, and ensure the stability of the building, by reducing mould and dampness. When it comes to eco-savings, mechanical ventilation with heat recovery (MVHR) operates in the region of 90% efficiency as it redistributes heat back into the home, which would otherwise be wasted through extract-only systems, ultimately reducing the demand on the home's heating system and the building's carbon emissions. Read our article on Building Regulations Part F for more details. (ADD LINK WHEN CREATED).
Part L Compliance: What Builders Need to Know
From planning through to completion, read our step-by-step guide to staying compliant with Part L:
Step 1 - Planning and design phase
Understand the regulations for new builds or existing homes being altered or extended and consult with qualified professionals experienced in energy-efficient building design. Be sure to choose construction materials with good thermal properties, like energy-efficient windows and doors, and consider using energy modelling software to assess if the building's energy performance meets the minimum values set out in Part L building regulations.
Step 2 - Construction phase
Ensure all work is carried out to a high standard and complies with plans for good insulation, airtightness, and the installation of energy-efficient systems. Keep detailed records of all materials used and inspections performed, as well as photographic evidence of energy-efficient construction methods. This information will play a crucial role in achieving Part L certification.
Step 3 - Completion
Ensure all energy-efficient systems, such as heating and lighting, are tested and comply with the regulations. Schedule a Standard Assessment Procedure (SAP) to show the building complies with Part L, and then submit all relevant documentation to the local building control body so they can issue an energy performance certificate.
Approved Documents
While building regulations are a legal requirement and therefore mandatory, Approved Documents, such as document Part L, are a guide on how to implement and enforce these compliance requirements into building work.
Building Control Body
The role of building control bodies is to survey construction sites and ensure building work meets regulations so they can issue approval.
SAP Calculations
Standard Assessment Procedure (SAP) is a way of calculating the energy performance of buildings. The higher the SAP rating the lower carbon emissions, and consequently, fuel costs. To gain approval from building control, a building must pass the SAP assessment to show the building is adequately energy efficient.
Air Leakage Testing
Air leakage testing is a method of determining if a building is sufficiently airtight and therefore compliant with building regulations. If it's not airtight, and it is leaking warm air through broken seals or wall cracks, this could result in poor indoor air quality and moisture problems, as well as impacting the building's energy performance.
Eco Solutions for Part L Compliance
Low Carbon Heating
Low carbon heating solutions, such as heat pumps and air source heat pumps, extract heat from the air, ground, or water and use electricity to move the heat around, rather than rely on fossil fuels, so are a more sustainable option.
Efficient Hot Water Systems
As gas boilers cannot be installed in new UK homes from 2025, developers are increasingly choosing to fit more sustainable hot water systems, such as electric water heaters, ground source or air source heat pumps, and solar water heaters. All these options utilise renewable energy sources and are a more cost-effective alternative to traditional water heating systems.
Thermal Bridging
Thermal bridging is a term for weak points in the building's envelope where some element of the structure, such as a joist, roof, or floor, allows heat to escape from inside to outside. To rectify thermal bridging the material causing the bridge should be either removed or replaced with a less conductive material, while thicker insulation can be added in more strategic locations to prevent the loss of heat.
Roof Windows and Insulation
Technological advancements in roof windows ensure they now feature well-insulated glazing and high-performance frames designed to reduce heat loss from the home. Roof windows also allow more natural light to flood into the interior, reducing the need for artificial light and lowering energy bills. Similarly, proper insulation in the walls, roofs and floors of homes also helps to reduce heat loss, enhancing energy efficiency and providing a comfortable environment.
Applying Part L to Different Types of Buildings
New Dwellings
Part L1A of the building regulations covers new builds, and specifically states all new homes must produce at least 31% less carbon emissions by 2025. It also recommends all newly built homes must maximise insulation, optimise airtightness, eliminate thermal bridging, as well as installing more energy-efficient heating systems, such as ground or air source heat pumps. There is also a focus on U-values, with an emphasis on using better-performance materials that prevent heat loss. Builders of new homes must also record all energy-efficient design details with photographic evidence to prove compliance and are then assessed under a new Standard Assessment Procedure (SAP) calculation called SAP10 to gain approval.
Existing Buildings
Part L1B of the building regulations covers renovations to current buildings and states that U-values need to be improved on replacement thermal elements, such as windows, doors and roofs, from 1.6W/m²K to 1.4W/m²K (watts per m² Kelvin). It also states that extensions have no more than 25% of floor area as glazing, or it must be demonstrated that the space complies with the U-value rate. Improvements are also required in lighting efficiency and flow temperatures for heating systems, reducing the flow temperature in a central heating system to 55°C, where it was previously over 75°C. Part L1B states that the renovations of existing properties will be looked at on a case-by-case basis as many older buildings may require more ventilation or insulation than modern buildings.
Commercial Projects
Part L standards also extend to newly built non-residential buildings and existing non-residential buildings, and still aim to improve the energy efficiency of the structure however, the main difference is the carbon emissions rate that must be reduced to 27%, unlike 31% in residential buildings.
Challenges and Common Pitfalls in Meeting Part L
Heat Loss and Gains
The main challenges of managing heat loss and gains in compliance efforts occur when there is not sufficient insulation fitted in walls, roofs, and floors, or when thermal bridging weak spots haven't been properly identified. Inadequate airtightness throughout the spaces is also tricky to manage and maintain.
Air Leakage Issues
The most common air leakage problems in properties occur through the frames of ill-fitted or old doors and windows, fissures in the building's envelope, fireplace flues, loft hatches, cracks in floorboards, and unsealed vents. The majority of these leakages can be resolved through adequate sealing, however, air leakage experts may be needed to treat specific areas to ensure longevity.
Misinterpreting U Values
The units used to express U-values are watts per m² Kelvin (W/m²K) and are known as k-values. U-values measure the thermal conductivity of materials, the higher the figure, the worse the thermal insulation quality. Problems occur when builders or developers select materials that may look the same as what has been specified, however, they differ in k-value and end up impacting the builds overall U-value. When this occurs, often more insulation is needed to recover the U-value, however, this can then impact the bottom line.
The Role of Part L in Driving Sustainable Construction
Impact on Energy Performance Certificates (EPCs)
To comply with Part L building regulations, all new or renovated buildings must have a valid EPC, which rates the energy efficiency of the building on a scale from A to G - A being the highest efficiency level.
Future Trends
Part L regulations aim to ensure all buildings are designed and constructed more energy-efficiently. This aligns with the UK's wider sustainability goal of achieving the Future Homes Standard that all new homes built from 2025 will produce 75-80% less carbon emissions and the even bigger goal of reducing carbon emissions to net Zero by 2050.
Technological Innovations
Emerging technologies, such as thermal imaging and advanced SAP tools can help builders meet Part L standards more easily. For example, thermal imaging can pinpoint where loss is occurring and identify areas that need improvements, while advanced SAP tools help to optimise the building's energy performance and cost-effectiveness.
Conclusion
It's vitally important that builders and construction companies not only comply with Part L for regulatory approval but also do their part in reducing greenhouse gases and saving the planet. By adhering to Part L standards and installing energy-efficient measures into buildings, owners will reap the benefits of many long-term cost savings.
Part L regulations are regularly updated due to advancements in technologies and construction materials, therefore builders, designers, and construction companies must stay on top of changes by subscribing to industry newsletters, networking with other industry professionals and regularly visiting the government website
