Air Pressure Testing 101: What Is It? And How It Works
Air pressure testing, or air tightness testing, measures the amount of air leakage through uncontrolled ventilation in a building. A fan pressurises or depressurises the building to approximately 50 pascals, and the result is the air permeability of the building.
When building new dwellings, it is necessary to perform air pressure testing to comply with Approved Document L: Volume 1 of the current Building Regulations. This applies to various types of buildings, such as houses, maisonettes, bungalows, and blocks of flats. Air leakage, uncontrolled air flow through gaps and cracks in a building fabric, is also known as infiltration or draughts.
To comply with Approved Document L, a dwelling must pass an air pressure test of 8m3/h/m2 or less at a pressure differential of 50 pascals. There are several advantages to having an airtight property, including:
- Lower Heating Costs
- Lower Carbon Emissions
- Occupants can enjoy improved comfort.
- Heating and Ventilation systems now require less power.
According to research, up to 40% of heat loss can be attributed to poor air tightness in buildings. For air pressure testing services, it is recommended that organisations be registered as part of an approved scheme, such as the Air Tightness Testing & Measurement Association (ATTMA).
H2 What Is The Process?
To test the air pressure in houses, a fan pressurisation or depressurisation technique is used. In the UK, the Air Permeability of a dwelling is measured at a pressure differential of 50 pascals between the inside and outside.
A calibrated fan is used within the building envelope to test for air tightness. The fan is placed temporarily to provide the required flow for the test. Usually, the main door of the property is the best location for fan installation.
Our technician will prep the house first to run the air pressure test. They’ll seal intended ventilation points temporarily, like cooker hoods, extract fans, and trickle vents. This list provides our quotes to inform clients of the process before the test.
To ensure accurate building envelope calculations, the property will undergo measurements. During the test, all heating and ventilation systems must be switched off, and all internal doors must be open.
Before and after the air pressure test, various environmental readings are recorded. These include temperature, barometric pressure, and wind speed. The purpose of these readings is to confirm that the conditions are suitable for the air pressure test to be conducted.
The technician will measure 7-10 pressure differences during the test. One of these readings must be at 50 pascals. The air pressure test lasts around 20 minutes, and results are immediately available. Contractors usually set aside 2 hours to complete the test.
H2 The Finer Details
New dwellings must undergo an air pressure test under Approved Document L: Volume 1 of the Building Regulations. In the past, air pressure testing was only required on three units or 50% of a dwelling type. However, Part L1A of the Building Regulations has changed this requirement.
For a dwelling to be categorized as the same “type” as another, it must possess specific characteristics.
- The types of homes listed include detached houses, end-terraced houses, mid-terraced houses, semi-detached houses, ground-floor flats, top-floor flats, and bungalows.
- Include the same number of storeys
- Both designs have the same air permeability and air pressure test target.
- Spaces like garages and unheated stairwells should be located close to each other.
- Have the same regulation construction details
- Have an envelope area that does not differ by more than 10%
- Have a similar number of penetrations, such as windows & doors
Dwellings that weren’t tested had an increased result of +2 m3/h/m2. This made the system complex, so testing every dwelling was suggested to close the performance gap. To comply with Approved Document L 2021, it is now necessary to complete an air pressure test for every new dwelling.
