Airtightness

Airtightness

What is air leakage and airtightness ?

Air ‘leakage’ is defined as the escape of air through the gaps and cracks in the building fabric: to the walls, floors and roof. 

In a majority of building air leakage is “pot luck” and airtightness is achieved by making a “reasonable” effort at design and installation stage. With passive house it is about meticulous detailing , a scientific approach and careful and precise installation and monitoring on site at all stages of the build. 

Current building regulations for airtightness 
Current regulations state that air leakage must not be greater than  10m³/h/m²@50pa — or 10m3/hr but in practice to meet the overall energy efficiency of the building (SAP calculations  ) most new buildings try and achieve between 5-7 m3/hr/m2@50Pa What this means is that no more than 5-7 cubic metres of air can escape per hour for every square metre of the envelope surface area, with an internal air pressure of 50 Pascals.

Testing for Airtightness


Testing to ensure that you have achieved the correct standard is critical. To achieve a passive house standard testing is often carried out 2 or 3 times throughout the building process.


For further information on testing please see link attached  -  link -  https://www.albaatt.co.uk

Passive House Standards

Passivhaus standard requires a figure equivalent to <0.6 air changes/hour @n50

How to achieve an air tight building

Airtightness is achieved by installing an air tightness membrane wrapped inside your home around the timber frame of the building and behind the plasterboard.
This membrane (Intello in the photos) is taped to the walls and ceiling and around each penetration. 
Careful attention must be paid to ensure that all the tapes are correctly installed.
Challening areas are corners, penetrations, windows and doors.
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