Infiltration rate is a crucial parameter in building science that quantifies the rate at which outdoor air enters a building through cracks, gaps, and openings in its envelope. Understanding the factors that influence infiltration, its effects on indoor air quality and energy efficiency, and strategies to control and reduce infiltration is essential for creating comfortable, energy-efficient, and healthy indoor environments in residential and commercial buildings.
Key aspects and details about infiltration rate include:
1. Definition and Importance:
- Air Leakage: Infiltration rate measures the flow of outdoor air into a building due to leaks and openings.
- Indoor Air Quality: Controlling infiltration is vital for maintaining indoor air quality and comfort.
- Energy Efficiency: Uncontrolled infiltration can lead to energy waste and discomfort.
2. Factors Affecting Infiltration Rate:
- Building Envelope: The quality of the building’s envelope, including walls, roofs, windows, and doors, influences infiltration.
- Weather Conditions: Wind, temperature differences, and outdoor air pressure affect infiltration.
- Building Design: Architectural features and structural details can create opportunities for infiltration.
- Ventilation Systems: Mechanical ventilation systems, if not balanced, can contribute to infiltration.
- Building Age: Older buildings may have more leakage points due to wear and tear.
3. Impact on Indoor Air Quality:
- Contaminant Entry: Uncontrolled infiltration can introduce outdoor pollutants, allergens, and moisture into indoor spaces.
- Comfort: Infiltration can lead to drafts, temperature fluctuations, and discomfort.
4. Impact on Energy Efficiency:
- Heating and Cooling Costs: Excessive infiltration can result in increased energy consumption for heating and cooling.
- Load on HVAC Systems: HVAC systems work harder to maintain desired temperatures in the presence of infiltration.
5. Strategies to Manage and Reduce Infiltration:
- Air Sealing: Identify and seal gaps, cracks, and openings in the building envelope.
- Weatherstripping: Install weatherstripping around doors and windows to prevent air leaks.
- Insulation: Adequate insulation reduces heat transfer and can minimise infiltration.
- Balanced Ventilation: Implement mechanical ventilation systems with heat recovery to control indoor air quality and reduce infiltration.
- Thermal Barriers: Design features like vestibules and thermal breaks can reduce infiltration.
- Regular Maintenance: Periodic inspections and maintenance can help identify and address infiltration points.
6. Building Codes and Standards:
- Energy Codes: Building codes often include requirements related to air tightness and infiltration rates.
- Energy Performance Certificates: Infiltration is a factor in energy performance assessments.
7. Indoor Air Quality Considerations:
- Air Filtration: The use of air filtration systems can help mitigate pollutants introduced through infiltration.
Controlling and managing the infiltration rate is essential for creating energy-efficient and comfortable indoor environments. By addressing air leakage through air sealing, insulation, and balanced ventilation, building owners and occupants can enhance energy efficiency and indoor air quality while reducing heating and cooling costs.