A key indicator of energy efficiency in a home is airtightness. The more airtight a home is, the less heat that can escape and therefore the warmer the house will be. A blower door test helps assess this.
Air tightness is required to reduce the amount of air leakage in a home and should not be confused with ventilation. To make a home airtight, local building company Evolution seals their buildings with an air tight moisture controllable membranes, Proclima's Intello and Solitex, that reduces unwanted air leakage and, with well fitted insulation, reduces power consumption and therefore CO2 emissions dramatically.
For example, a thick jersey in winter works really well until the wind picks up; add a breathable wind breaker and you have ultimate protection and warmth. The same principle applies to our homes. This principle works the opposite way also, so cooler in summer – warmer in winter!
The European and North America construction industry lead the way in air tightness and German homes are not ‘compliant’ to the building code unless they have an air tightness of less than 3 ach. This gives you an indication of what NZ homes should be achieving.
Most modern NZ homes have an air leakage rate of between 6 to 9 air changes per hour (ach) with most homes that are tested averaging nearer to 9 ach. This level of unwanted heat loss can be improved dramatically.
A blower door test is used to assess how airtight a home is. Homes are tested by an independent engineer who uses a computerized Blower Door Test. A fan is affixed to an exterior door and the house is alternatively pressurized and de-pressurized while readings are taken.
Evolution guarantees that the homes they build will receive a reading of 3 ach or better. Two homes completed in 2016 achieved impressive results of 1.47 ach and 1.98 ach. For those wanting to go further and achieve a Passive House standard, then the blower door test result must be under 0.6 ach.
Article provided by Evolution, a division of Rilean Construction.
NZHomes featured by Build me. that achieve high airtightness ratings: