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Community and Q&A

What do you think of this new build in New Zealand?

marcjb | Posted in Energy Efficiency and Durability on

Hi gang. I’ve been living in NZ for 18 months now and lately I’ve been working on a new house here. Previously I’ve been a builder in BC and I like to think that I produce warm cozy homes using the basic principles of building science like properly installed insulation and a detailed air barrier.

The building code here is different. While the structural part is excellent with close attention paid to seismic concerns, as it should (these are the shaky isles), I’m quite dismayed at no attention paid to air/vapour barrier. As in none. Also, the attic space is not vented. The building paper goes over top of the ridges and the soffit is made of 8mm hardie sheets, no vents. The exterior walls are 2×4 with three courses of blocking for rigidity, no sheathing. The wrb is stapled to the studs, seams and overlaps and edges are not taped, cavity battens (rain screen) over that, and then thick 15mm hardie board siding.

There will be multiple penetrations through the ceilings: recessed lights, sprinklers, ducts that will bring conditioned air from a heat pump. Drywall on the exterior walls will be penetrated by the usual powerpoints and switches etc.

While the roof is unvented it’s not air sealed either. My thought is that the stack effect will push warm humid air into the attic and the ceiling insulation will get humid and not perform to spec, and suck exterior air in from the usual places. The house is built on pilings. The subfloor is glued and screwed and I hope it’s a pretty good air barrier.

Anywho, I’m surprised that the concept of energy conservation hasn’t met the building code here. And we pay triple for electricity here compared to BC. Any thoughts, anyone?

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  1. user-6184358 | | #1

    Without plywood shear walls they would be quite deficient in the earthquake category. I don't know of any seismic testing on 2x4 walls with 3 rows of blocking that provides an allowable design load for the assembly. I don't think the Hardie board is rated for shear capacity.

  2. user-2310254 | | #2

    Friends who have visited New Zealand have told me it is a lot like the U.S. in the 1970s. Apparently, that is where the building codes are as well.

  3. marcjb | | #3

    Tim, I should have mentioned the huge amount of hardware that goes into the build, as well as the structural drywall they use on shear walls. This build is engineered for seismic resistance.

  4. GBA Editor
    Martin Holladay | | #4

    Your description of the typical house in New Zealand isn't that different from the typical California house in the 1960s or 1970s. Change takes time.

    One reason (I'm guessing) that New Zealanders don't worry too much about energy efficiency is that most New Zealanders live in areas with a very mild climate.

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