Air tightness needs to be a priority throughout the construction process
– before, during and after.
The regulations require that every building is tested for air leakage. The frequency of testing is laid out in the Building Regulations Part L1A Domestic & Part L2A Commercial and the target is dependant on design and construction methodology.
The route to compliance with the regulation is to present Building Control a Certificate or report following a leakage test carried out by a registered tester, under the IATS scheme, which will conform to standards laid out in procedures in the technical document detailed in CIBSE Technical Memorandum 23 Chartered Institute of Building Service Engineers ATTM TSI. This then forms part of the building completion certificate or report.
Home energy use is responsible for 28 per cent of UK carbon dioxide emissions which contribute to climate change. By following the Energy Saving Trust’s best practice standards, new build and existing housing will reduce these emissions, saving energy, money and the environment. Air leakage from buildings, both new build and existing, is a major cause of energy loss and increasing emissions.
Improving airtightness in dwellings will reduce air leakage – the uncontrolled flow of air through gaps and makes sound commercial sense.
Air leakage is quantified as air permeability. This is the rate of leakage (m3/h/m2) in or out of the dwelling. It is measured at a reference pressure difference of 50 Pascals a between the inside and outside of the dwelling. In the UK the good and best practice standards for air permeability in dwellings are shown in Table 1. of the Building Regulations Part L1A.
Air Tightness Strategy
- Identify the line of the air barrier at an early stage of design.
- Refer to airtightness in all contracts which impact on the air barrier.
- Specify and select airtight components.
- Inform the site management team of the location and importance of the air barrier.
- Explain to site operatives the critical importance of airtightness.
- Check air barrier completeness before it becomes impossible to access.
- Schedule an airtightness test by L1 Testing Ltd.
- A pre – test visit to site by the testing body is recommended for larger sites.
- Ensure all airtightness works are complete.
- Contractor to have responsibility for sealing vents and open flues, closing trickle vents, external doors and windows in preparation for an airtightness test.
- Airtightness test carried out and results issued.
- Results submitted to Building Control/client by contractor.
Air Tightness – The Benefits
REMEMBER: BUILD TIGHT – VENTILATE RIGHT.
For Contractors, building “air-tight” – matters primarily because it is a key requirement of Approved Document Part L of the Building Regulations. However, there are numerous on-going benefits attributable to reduce air leakage in buildings.
- Presents a unique selling point for the developer! “We produce carbon efficient homes.”
- For the consumer, heating bills will be reduced considerably.
- Studies have proved that ‘draughty’ houses relate to illness and discomfort for the consumer.
- Reduction of noise transfer through the leakage paths are also of benefit to the home owner.
- Helps prevent decline of the building fabric due to interstitial condensation.
- 47% of the UK’s CO2 emissions are from homes, this will drop dramatically over the coming years.
Reducing Carbon Emissions
Part L is a vital part of the Government’s strategy towards achieving the UK’s carbon emissions reduction targets. Air leakage accounts for a large proportion of the energy wasted in buildings energy that by and large is generated at power stations most of which produce vast quantities of carbon gasses in the process – a major contributor to global warming.