Airtight Building - Airtight Houses - Air Leakage Testing
It is important that buildings achieve a high level of airtightness in order to maintain energy efficiency and provide comfort for occupants. The benefits of improved insulation and energy efficient systems will be lost, if warm air is allowed to leak out of a building and cold air can leak in
Design of Airtight Building
Warm air leaking out through gaps in a building’s external envelope is a major cause of heat loss and, consequently, wasted energy. Improving airtightness in buildings reduces the uncontrolled flow of air through gaps and cracks in the external fabric. With more stringent building regulations demanding higher energy efficiency, airtightness is an increasingly important issue.
The design of a building and the quality of its construction will have a major effect on the amount of air leakage. The issue of airtightness needs to be addressed at an early stage when the designer must identify the exact position of the airtight barrier in the thermal envelope.
Airtight Building - Air Barrier
The air barrier must form a continuous line around the building, passing through the external fabric and separating heated and unheated spaces. The position of the airtight barrier must be decided at the outset and the construction materials must be chosen with care and their detailing must be considered carefully.
Airtight Building - Heat Loss and Draughts
Heat loss occurs when the warm moist air inside a building is drawn out through holes, cracks and gaps in the envelope. This can lead to condensation occurring on cold surfaces which can damage the building fabric. The warm air leaving the building is replaced by cold air from the outside which is experienced on the inside as uncomfortable draughts.
Controlled Ventilation in Airtight Building
In the case of airtight houses the air movement through the external envelope will be so small that a system of controlled ventilation will be essential, for the comfort and safety of occupants. As the extracted air will also remove the heat, it is essential that a mechanical ventilation heat recovery system is installed.
Airtight Building - Ventilation with Heat Recovery
Ventilation with heat recovery is the process of exchanging the heat energy contained in air as it is
extracted from a dwelling and transferring it to the incoming replacement air. Mechanical ventilation with heat recovery can
take the form of either a central extract system or individual room fans (or a combination of both).
Airtight Building - Air Leakage Testing
Air leakage testing allows the permeability or air tightness performance of the building to be assessed. The technique is straightforward and can be carried out when the building envelope is complete.
Successful airtight construction and air leakage testing results from attention to detail at both the design and construction stages of the project.
In order to carry out the test, a fan is mounted in a temporary screen fitted into the frame of an external door opening. The fan is used to move air into or out of the building. The air leakage characteristics are determined by measuring the rates of air flow through the fan while a range of pressure differences between the inside and outside of the building are maintained.
Airtight Building - Building Regulations - Air Testing - Part L
In October 2010, the latest revision for air testing in Part L of the Building Regulations will come into force. As a result of this revision, the energy efficiency requirements for buildings have become tighter and the rules for the air testing of new dwellings has become more rigorous.
Occupants of Airtight Building
Having constructed an airtight building , it is important to make the occupants aware of the fact. The owner needs to know the location of the airtight barrier in order not to compromise its effectiveness when carrying out future alterations. The efficiency of the heating and ventilation provided to the building depends on the airtight barrier being well maintained.
Airtightness is an increasingly important part of a whole house approach to building. Airtight buildings will be more comfortable for occupants and also more energy efficient