Air leakage refers to the unintended and uncontrolled flow of air into or out of a building through cracks, gaps, and openings in the building envelope. This phenomenon can significantly affect a building’s energy efficiency, indoor air quality, and overall comfort.
In the UK, air leakage is a critical consideration under the Building Regulations, particularly Part F (Ventilation) and Part L (Conservation of Fuel and Power). These regulations aim to ensure that buildings provide adequate ventilation while also maintaining energy efficiency.
Part F: Ventilation
- Requirement F1: This requirement mandates that adequate means of ventilation must be provided for people in the building. The intention is to protect the health of occupants by ensuring that indoor air quality is maintained.
- Air Leakage Measurement: Air leakage is typically quantified using the air permeability metric, measured in m³/(h·m²) at a pressure differential of 50 Pa. This measurement helps assess how well a building is sealed against air infiltration.
Part L: Conservation of Fuel and Power
- Energy Efficiency: Part L focuses on the energy performance of buildings, including the need to limit air leakage to reduce heating and cooling demands. The tighter the building envelope (lower air leakage), the less energy is required for heating and cooling.
- Target Values: The regulations set specific target air permeability values that must be met, which vary depending on the type of building. For example, new dwellings typically have a target air permeability of 10 m³/(h·m²) at 50 Pa, while more energy-efficient builds may aim for lower values.
Implications of Air Leakage
- Energy Costs: High levels of air leakage can lead to increased energy costs due to the need for additional heating or cooling to compensate for lost conditioned air. For instance, a poorly sealed home may require significantly more energy to maintain comfortable temperatures during winter months.
- Indoor Air Quality: While some air exchange is necessary for maintaining good indoor air quality, excessive air leakage can introduce outdoor pollutants, allergens, and moisture, leading to potential health issues for occupants.
- Building Performance: Air leakage can undermine the performance of insulation and ventilation systems, leading to issues such as condensation, mould growth, and structural damage over time.
Best Practices for Managing Air Leakage
- Blower Door Testing: Conducting blower door tests during and after construction can help identify air leakage points and ensure compliance with regulatory standards.
- Use of Airtightness Materials: Employing airtight membranes and high-quality sealants around joints, penetrations, and openings can effectively reduce air leakage.
- Ventilation Strategies: Integrating mechanical ventilation systems, such as MVHR (Mechanical Ventilation with Heat Recovery), allows for controlled air exchange while minimising energy loss due to air leakage.
Managing air leakage is essential for achieving compliance with UK building regulations, enhancing energy efficiency, and ensuring the health and comfort of occupants. By employing best practices in construction and retrofitting, stakeholders can significantly mitigate the impacts of air leakage, leading to more sustainable and liveable buildings.