Air-tight construction for passive houses in New Zealand, and Christchurch in particular, is a very important
Air-tight construction enables the house user to effectively achieve some of the most important goals of passive house construction. It means that air-flow into and out of the house is not left to the chance vagaries of wind and temperature.
In a cold climate, an airtight house can be a warm house.
Passive houses have air-tight construction combined with specified ventilation systems which deliver filtered warmed air (or in summer, cooled air) to all parts of the house, in exchange for extraction of stale too-moist air.
The air-tight construction technique prevents the most common causes of inadequate heat conservation; draughty gaps such as cracks under doors and poorly fitting windows letting cold air enter from outside, and in particular, gross gaps in roofing around ridge lines the zone between the lower end of roof cover and the guttering, between roof elements such as individual clay tiles or between individual sheets of roofing iron, and through porous walls.
Many builders accept these gaps as being matter-of-course, and may take no great measures in the construction of a "normal" house to plug them.
Cat doors, ceiling downlights, and fireplace chimneys also make houses needlessly draughty.
We have all experienced the situation when the weather changes rapidly as a cold front comes through. Suddenly, a chill sweeps through the house. This is due primarily to air leaks enabling gale-force air to penetrate into the living space. Such cooling ( or the reverse, when a NW wind blasts its furnace breath into the house) becomes a thing of the past in a passive house with its air-tight construction and electrically controlled ventilation.
Especially during cold winter conditions, especially in the Central North Island of New Zealand, and in much of the South Island, especially in Christchurch, Dunedin, Invercargill, and Central Otago, and in the higher altitudes, it is very important to control and restrict the escape of warmed air out of the house. Such warmth has cost a lot to achieve, and it is imperative to retain it and not let it get lost through holes in the building shell.
Passive house building techniques and component requirements, along with pressure testing after construction is done, achieve good sealing and control of gas movement in and out of the house.
HOWEVER, the latest building regulations give effect to the knowledge that modern houses are now more air-tight than houses built pre-1970, for example, and that if the occupants do not have the commonsense or the ability to ventilate their house, air moisture-content and harmful gasses can increase to damaging concentrations. It is now required that ventilation devices to be provided in the house construction so that a specified percentage of the house air volume can be exchanged with outside air per hour..
THERE ARE PROBLEMS inherent with these regulations; these include:
You can follow the blog of the first build at
New Zealand's first Passive house blog-spot
Another NZ passive-house is documented on-line, on facebook. If you are a facebook user, you should have no problems viewing these pages.
A New Zealand Passive house set of informative pages
A New Zealand Passive house - the base page
Congratulations to Brooke the Architect (MOAA Architects) for what looks like a thorough job, and likewise the builder for following instructions so well. Lots of construction detail in here.
Links to pages about the seven precepts of Passive House design.
Very efficient Insulation
No thermal bridges
Passive solar gain