What is Air Permeability ?

Example Of Air Tightness Vapour Control LayerIt is the uncontrolled flow of air both into and out of  a building through cracks and gaps. Uncontrolled air flow accounts for a large proportion of energy wasted in dwellings.

Achieving improved air tightness is a key factor for a builder or contractor meeting the present buildings  regulations and improve the cost of running the building. It is expressed in terms of air leakage in  cubic meters per hour per square meter of the dwelling envelope area when the building subject to a differential pressure of 50 Pascal's

How to achieve Air Tightness and Why?

Air tightness simply means eradicating all drafts. Drafts can be so small e.g. under window boards, around windows and doors but an accumulation can have a drastic impact on the energy loss in the dwelling and lead to significant discomfort and high running costs.

The only way to achieve Air tightness is a consistent air-resistant layer all around the inside of the building. This includes the area where the wall/floor meet, around the door and window openings.

A layer of breathable membrane behind the plaster slab on the upper ceiling, regardless of the structure type, timber frame or masonry construction the air tightness layer must be continuous from floor to ceiling.

Why Choose Irish Energy Assessors To Apply The Tapes & Membranes

Example Of Air Tightness Vapour Control Layer RoofIrish Energy Assessors are certified contractors of the SIGA Air & Wind tightness System. This is comprised of a range of tapes and adhesives, and SIGA Majpell, a vapour control layer. This system has been certified by the The Irish Agrément Board.

The wind tightness tapes can be used with all suitable breathable roofing and facade membranes. The tapes and adhesives are free from residential toxins such as solvents (VOC), high boilers, formaldehyde, chlorine, plasticizers.

Get an Instant Estimate For The SIGA Air Tightness Application NOW!

Simply fill in the total squared meters of the building you wish to have the SIGA air & Wind Tightness applied to and you well get an instant estimate of the cost of having it installed.


To get a rough price of how much it would cost to apply the SIGA air tightness application to your house, enter the size of the house in square meters along with your name and email address and then click submit. You will then get an email with the estimate and further details in relation to getting the price fixed.

Air Tightness Terminology

  • Building envelope - external elements of the building, walls, windows, front and rear doors,  floors and ceilings
  • Air tightness  - defined as the resistance of the building  envelope to  inward  or  outward air leakage. Excessive air leakage results in increased energy consumption and a draught cold building.
  • Air leakage - defined as the amount of air gaps or cracks in the building envelope, driven by pressure differences between inside and outside. Areas of air leakage, cold bridges, i.e. around doors, windows and between floor levels
  • Air permeability - expressed as the amount of air leakage in cubic meters per hour per square  meter of the building envelope at a pressure differential of 50Pascals between inside and outside the building envelope, maximum permitted level  is 10  m2/m3hr@50Pascals, This is measured by the instillation of the blower-door fan into the main entrance of the dwelling.
  • Air changes  per hour-  measures the ventilation in the building. This can be controlled by mechanical ventilation heat recovery or opening windows and doors