Air Tightness

A Passive House Principle…

In order to prevent unwanted movement from air (eg losing warm air/gaining cool air) a passive house is designed and built with air tightness in mind .

The term “air  tightness” is a description of the building envelope when it is tested for air leakage.

 To reach the passive house standard there must be no more than 0.6 air changes per hour at 50Pascals…in other words no more than 0.6 cubic metres of air change per hour for every square metre of floor area when the difference between air pressure inside and outside is 50 Pascals.

 To achieve this, there are techniques, products and materials used during the building process such as weather tight and airtight fabric, tape and passive house certified windows to name a few.

An air tightness test is performed in the form of a blower door test, enabling an accurate measurement of the air tightness

 During the blower door test, a fan is set up in a doorway of a main entrance to the building, windows and doors are closed and all fans and vents sealed. The fan is turned on and tested for over-pressurisation with 50 pascals of air being pumped into the house whilst the air flow rate is measured. Then this is reversed, with the air measured after the air is pumped out of the house at 50 pascals of pressure.

The average measurement of the two results are taken as the airtightness measurement of the building.

The benefits of achieving the passive house standard of air tightness include some of the following:

- reduced heat loss(winter)/ heat gain (summer),therefore reduced energy costs.

- greatly improved thermal comfort

- Reduced chance of mould and rot as moisture is less likely to find its way inside and become trapped in cavities

- combined with the necessary air ventilation system, a much healthier indoor environment.

The end result of a home built with Passive House principles will be a healthy, comfortable, energy efficient, long lasting home.

If you would like to learn more about Passive House Principles and how we use them in every single house we build, please click on this link to learn more about our membership

AIR TIGHTNESS

Using the correct tapes and other recommended materials is very important to ensure air tightness is achieved.

Blower Door Test

The first blower door test is recommended at pre-plaster stage in order to find any significant leaks while they can still be rectified.