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Air Tightness Testing
What is a blower door?
A blower door is a large calibrated fan that is temporarily mounted in a house door to measure the "Air Tightness" of the house and to assist in finding the location of the leaks. Modern blower doors have variable speed fans so that the pressure in the house can be adjusted, and they also have door mounting frames so that the fan can be sealed tightly into the door jamb. In order to measure the Air Tightness of the house, the blower door measures both the air flow through the fan and the pressure difference between the house inside and outside.
Fan fitted in Front Door                        Infiltec Blower Door

D M 4 Manometer
How can you use a blower door?
Air leaks can be simple and inexpensive to seal if you can just find them, and that is where the blower door comes in. First you use the blower door to measure the air leakage and see how the house rates on a scale of "leaky" to "tight". If it is already tight, then you can forget about air sealing and look at other ways to save energy. But if it is too leaky, then the blower door can tell you how bad it is and then it can help you to find the location of the leaks. After you seal the leaks, the blower door can tell you how well you have done.
What is Air Leakage?
In contrast to controlled ventilation, air leakage is the migration of uncontrolled air to and from a building, which does not have a design purpose such as providing fresh air. It is the flow of air through gaps and cracks in the fabric of the building (sometimes referred to as infiltration or draughts).

Typical Air Leakage Paths
Air Leakage
1.    Under floor ventilator grilles.
2.    Gaps in and around suspended timber floors.
3.    Leaky windows or doors.
4.  Pathways through floor/ceiling voids into cavity walls and then to the outside.
5.    Gaps around windows.
6.  Gaps at the ceiling-to-wall joint at the eaves.
7.    Open chimneys.
8.    Gaps around loft hatches.
9.    Service penetrations through   ceilings.
10.   Vents penetrating the ceiling/roof.
11.  Bathroom wall vent or extract fan.
12. Gaps around bathroom waste pipes.
13. Kitchen wall vent or extractor fan.
14. Gaps around kitchen waste pipes.
15. Gaps around floor-to-wall joints.
16. Gaps in and around electrical fittings in hollow walls.
Why should you care about air leakage in houses?
Everyone knows that air leakage can cause uncomfortable drafts in houses, but energy researchers have discovered that sealing air leaks is one of the simplest and least expensive way to save energy in homes. A typical house may lose about 1/3 of its heat through air leakage. A few hours of air sealing with inexpensive sealants can often reduce the air leakage by about 1/4 to 1/2, resulting in a saving of 10% to 20% of the total house heating bills. Each house has different amounts and types of air leakage, and the most efficient technique is to spend the most time sealing the leakiest houses. Therefore, you need a tool that can quickly identify the leaky houses and show you where the leaks are.
The revised building regulations (24th January 2008) introduce mandatory Air Tightness Testing for new dwellings. All new single dwellings will require an Air Tightness Test from 1st July 2008.
In the case of a development the following guidelines apply:
Number of pressure tests required per dwelling type
Number of units
Number of tests required                             
one test
two tests
5% of dwelling type
101+ (if target is reached)
101+ (if target is not reached)

The regulations apply to new houses and apartments where substantial work commences on or after  July 08.
Air Pressure Testing is an invaluable tool when auditing existing buildings for heat loss.
While the BER of a house tests the design, air pressure testing allows users examine workmanship.  
  Thermal Bridging aid Air infiltration 
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