air infiltration

Old windows make a major contribution to the authentic look of a façade, and maintaining those elements whenever possible is essential for the conservation of our architectural heritage. However, those are often leaky and are consequently responsible for high energy losses, acoustical and thermal discomfort, and incorrect sizing of the ventilation systems. Having a better knowledge of windows airtightness performance is crucial in assessing need for an intervention based on the balance between costs and impact.

Controlling air infiltration is crucial to ensure thermal comfort, optimal performance of ventilation systems, and the overall energy efficiency of buildings. The quantification of the overall airtightness of the building envelope, often conducted through pressurization tests, has been widely used. In addition, IR thermography is a valuable complementary tool for identifying and locating air leakage paths.  

Infiltration of unconditioned air through access openings and entrance doors with high recurrence can cause detrimental impacts to the energy performance, air quality and thermal comfort of buildings. Air curtains are of strategic importance to attenuate these negative impacts. In addition, air curtains are relevant in specialized HVAC applications for which the impediment of infiltration is also essential (e.g., reduction of smoke propagation in fire events, decrease of contamination hazard in clean rooms, preservation of refrigeration properties in cold rooms).

Air infiltration control is essential to guarantee thermal comfort, good performance of the ventilation systems, and more energy-efficient buildings. The evaluation of the global airtightness of the building envelope based on pressurization tests has been widely used combined with infrared thermography as a complementary tool to locate air leakage paths. This work proposes a new methodology whose main objective is the characterization of the air infiltration path using infrared thermography.

This report reviews the activities of the AIVC during its first twenty years of operation. It identifies key projects and addresses them in the context of research activities and associated issues of the time. Early issues included the need for energy conservation and reducing air infiltration loss. Much work concentrated on assessing the performance of numerical models and acquiring input and validation measurement data. Towards the end of the period attention focused towards energy efficient ventilation systems for good indoor air quality and comfort.

Across different territories there are various normative models for assessing energy demand of domestic dwellings, which use simplified approaches to account for the heat loss due to the air infiltration of a building.  For instance, the United Kingdom uses a dwelling energy model, known as the Standard Assessment Procedure (SAP), and this utilises a process where the measured air permeability value (q50), is simply divided by 20 to provide an infiltration rate (subsequent modification factors are then used for factors such as sheltering etc.).

Buildings represent approximately 40% of global energy demand and heat loss induced by uncontrolled air leakage through the building fabric can represent up to one third of the heating load in a building. This leakage of air at ambient pressure levels, is known as air infiltration and can be measured by tracer gas means, however, the method is disruptive and invasive. Air infiltration models are a non-disruptive way to calculate predictive values for air infiltration in buildings.

Indoor air quality is the chemical, physical and biological properties that indoor air must have to not cause any negative impact on occupants’ health and provide comfort: feel fresh, pleasant and stimulating.