Misunderstood Role of Insulation
Thermal insulation is designed to resist conductive heat flow through walls, roofs and floors. By improving the thermal resistance (R-value) and reducing the U-value of building assemblies, insulation helps limit heat transfer between indoor and outdoor environments.
However, insulation is not designed to stop airflow.
For HVAC systems, that distinction can be costly.
A building may be well insulated yet still consumes excessive energy if uncontrolled air leakage exists through cracks, joints, service penetrations, façade interfaces and construction gaps
What Drives Air Leakage?
The most common driving forces include:
- Wind Pressure
- Stack Effect
- HVAC Systems
Small Leaks, Big Consequences
A study by the Fraunhofer Institute for Building Physics found that uncontrolled air leakage can reduce the effectiveness of building insulation by a factor of up to 4.8. In other words, a building with uncontrolled air leakage requires 4.8x more energy to heat and cool the building
In practice, inadequate air control can lead to:
- Additional sensible loads from unwanted heat gain and heat loss
- Additional latent loads from moisture-laden outdoor air infiltration
- Increased cooling coil and heating coil loads
- Higher ventilation and air distribution energy consumption
- Increased HVAC plant operating costs and peak demand charges
- Reduced overall building energy performance and efficiency
While controlled ventilation is essential for maintaining healthy indoor environments, uncontrolled air leakage imposes a significant energy penalty on buildings. As unconditioned outdoor air infiltrates the building envelope, HVAC systems must expend additional energy to heat, cool, and dehumidify this air before indoor comfort conditions can be maintained. The result is increased sensible and latent loads, longer equipment operating hours, higher peak demand, and elevated energy consumption throughout the life of the building
~Khushi Thapa
khushi@swaconsultancy.com
