What is an airtight membrane?

By providing a windtight seal, external airtightness membranes work to regulate humidity within the building, maintaining a pleasant environment and reducing the risk of condensation. Our range of breathable airtight and windtight membranes includes products to suit any project – from new build to retrofit.

What is ASTM e779?

Standard Test Method for Determining Air Leakage Rate by Fan Pressurization. 1.1 This test method measures air-leakage rates through a building envelope under controlled pressurization and de-pressurization.

Where does air tightness membrane go?

The airtightness / vapour control layer is still toward the inside face of the insulation. In their typical timber frame construction, the insulation layers are commonly outside the framing line, so when you employ an airtightness layer it too is outside the framing line, but still on the inside of the insulation line.

How do you calculate air tightness?

The airtightness of a building is often expressed in terms of the leakage airflow rate through the building’s envelope at a given reference pressure (usually 50 pascal) divided by the: Heated building volume V. At 50·Pa, it is called the air change rate at 50 Pa and usually noted n50(units: h−1).

Is air tight membrane a vapour barrier?

A moisture-variable vapour barrier for use in the air-tight layer. The functional membrane changes its diffusion resistance depending on the current humidity. During the winter months room atmosphere is generally dryer. The sd-value of the vapour barrier increases.

Can I use breathable membrane as a vapour barrier?

A breather membrane is positioned on the outer side of the insulation, allowing vapour to escape from inside while repelling any water that tries to enter. A vapour control layer, positioned on the inner side of the insulation, reduces vapour transfer in a building.

What is an envelope leakage test?

An envelope leakage test is performed with a blower door. The blower door consists of a powerful, calibrated fan, installed in an exterior doorway which creates a pressure difference between the inside and outside of the building, thereby forcing air through the breaches and penetrations of the building envelope.

What is a building leakage test?

A building enclosure airtightness test, or an air leakage test, is conducted using orifice blower door fans that induce a series of positive and negative pressures on the building envelope.

What is a good air tightness test result?

What’s a good air tightness test result? Current building regulations say that new dwellings should achieve an air leakage of around 10m3/hm3 or less. This is the air leakage per hour, per square metre of envelope/fabric area.

What is a good air tightness score?

What is a good result for an air permeability test?

However, as a general rule new dwellings should achieve an Air Permeability of 5 m3h-1m-2 or less. A test between 3 – 5 m3h-1m-2 would usually be acceptable by building control and your SAP assessor. A reading of less than 3 m3h-1m-2 might mean the building is too airtight.

Where do you place a breather membrane?