...50% more insulation than required by the building code means we need little or no heating
Wall and Roof Construction
The construction of the walls and the roof will significantly influence the thermal performance of the building. This will affect the comfort of building occupants and the ability to achieve our goal of no heating. The more energy that escapes through the walls, the more energy must be introduced into the building to maintain the target temperature range. Most New Zealand homes will need a heating system to provide enough energy to keep the house warm. The insulation levels in the ZEH, will mean that target temperatures will be maintained primarily by the energy from the sun, but also from day to day living (heat from occupants, and electrical loads such as lighting, and cooking).
Wall Details
We are currently working through the wall construction options to identify a practical, highly insulated solution that provides an alternative to the standard 90mm framing that is used in most New Zealand homes. The insulation value of the wall (R value) is primarily a function of the R value of the insulation material and the percentage of framing in the wall. Standard 90mm framing with nogs has about 16% thermal bridging from the studs and nogs.
Some of the options we are considering are shown below. By cross battening on the inside or outside we can significantly reduce the thermal bridging. The extra thickness also allows more insulation to be fitted in the wall.
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External battening, 90mm stud, no nogs
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140mm studs, 90 nogs, external 35mm insulated sarking board
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Internal battening, 90mm stud, 90mm nogs
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140mm studs, 90 nogs
