Building airtightness can be defined as the resistance to inward or outward air leakage through unintentional leakage points or areas in the building envelope. This air leakage is driven by differential pressures across the building envelope due to the combined effects of stack, external wind and mechanical ventilation systems.
Airtightness is the fundamental building property that impacts infiltration and exfiltration. An airtight building has several positive impacts when combined with an appropriate ventilation system.
Lower heating bills due to less heat loss, with potentially smaller requirements for heating and cooling equipment capacities
Better performing ventilation system
Reduced chance of mold and condensation because moisture is less likely to enter and become trapped in cavities.
Fewer draughts and thus increased thermal comfort
Since most of our buildings are air conditioned, energy efficiency plays a key role. A less airtight building will increase the energy load on the HVAC systems, thus causing a higher cost.
An airtight building will help in eliminating moisture and mold, which is a common problem in the Middle East region. If a building leaks air, it starts to condensate, and whenever there is a condensation, mold and moisture will be created.
If a building is not airtight internally between the walls, the odour from the kitchen, toilet and risers will affect the internal air quality as well.
Airtightness is the control of air leakage, i.e., the elimination of unwanted draughts through the building envelope. This may be achieved by the correct and proper design and installation of an air barrier. Consequently condensation, mold, rot, damp and structural damage are also eliminated.
For an existing building, reducing the air leakage can be achieved by sealing off all the existing air leakage pathways such as Junctions between walls and other walls or floors, Junctions between window frames and walls, Electrical equipment, Access doors and other wall penetrations, etc.
To measure the leakage and to identify leakage areas in the building envelope several tests needto be conducted.
Air leakage through the building envelope can be measured by Airtightness Test. Building airtightness levels can be measured by using a fan, temporarily installed in the building envelope (a blower door) to pressurize the building. Air flow through the fan creates an internal, uniform, static pressure within the building. The aim of this type of measurement is to relate the pressure differential across the envelope to the air flow rate required to produce it. Generally, the higher the flow rate required to produce a given pressure difference, the less airtight the building. The fan pressurization technique is also described in many standard test methods, such as ASTM E779 - 10, ISO 9972:2015, ATTMA TSL1-4, etc.
Generally, the detection of the path or area of air infiltration or exfiltration can be achieved in two different methods.
Smoke test
Smoke Test for leak is very simple procedure consists of blowing large volumes of air into the building by a blower door equipment and simultaneously applying smoke through the building envelope using a smoke generator. The smoke follows the path of the intruding or extruding air to the building envelope, revealing the source of the problem within seconds.
Smoke Travels the path of least resistance, quickly identifying sources of inflow. Smoke can be induced through any clean-out opening in the system.
Smoke testing is an excellent technique for locating leaks and sources of odours in house causing condensation and mold.
Thermography
Thermal imaging is a simple, non-intrusive technique that is generally used to locate the weak points in the building envelope. This could be in one or more of the following forms: missing insulation, air leakage, thermal-bridging, presence of moisture etc.
Smoke test and Thermography are considered as a cost-effective solution and is being widely employed these days for energy savings, building audits, facilities management, envelope tightness etc.
Retrotec’s blower door equipment to blow air into or out of the building, along with a Manometer to detect the enclosure differential pressure and air flow.
A Retrotec’s 6000 series fan can produce an airflow up to 14000m3/hr.
A smoke generator to intrude the smoke into the building envelope.
The amount of smoke and type of smoke generator required are depends on how big the enclosure is to be tested.