Passive Housing Technologies in New Builds

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bfginger

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#2258946 16-Jun-2019 01:01

Laminated glass can reduce fading as the plastic blocks 99% of UV.

Grey tint reduces the amount of light coming through glazing and can make a room feel like being in a cave in winter (although that may be want some people want). It also reduces the amount of heat coming through which is seldom what you want in a passive house during winter. There are special low e glasses that can reduce heat input more effectively than tinting and without dramatic reductions in visible light and clarity

But a passive house can instead use external shutters to more effectively block heat input in summer without committing to the same in winter

The recent trend of tinting everything reflects the bad practices and ignorance of the New Zealand building industry. Designers like to place huge windows on every wall which leads to extreme overheating in summer. So they use green or grey tint. They aren't aware the same can be done better with special low e glass but either way most of those houses are going to be cold in winter.

Paul1977

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#2259319 17-Jun-2019 09:49

I'm getting our plans priced up now based on standard NZ house specs. We'll then see what the price difference is to improve insulation, air tightness, upgrade to low e glass, and add fresh air ventilation with heat recovery.

I anticipate this will have to add a significant amount to the build cost, but lets assume it "only" adds $50,000.

Over 20 years at 4% this would add just over $300 a month to the mortgage payments. Even over 30 years it would still add almost $240 a month to the mortgage. I can't see that it could possibly save me that much power per month, so how could it ever pay for itself?

What am I missing?

bfginger

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#2261172 19-Jun-2019 23:53

The average New Zealand builder would be at a loss over blower test grade air tightness. Take care with low e glass as they are unlikely to quote for anything good unless you specifically ask for it.

Building materials are severely overpriced in New Zealand so a house could be built to passivehouse standard overseas much cheaper than to build to code in New Zealand.

The additional cost of better building is exaggerated in New Zealand because it is so rare to go above code. If better standards were mandatory the prices to meet those standards would go down.

The passivehouse standard has its origins in central Europe where there are colder temperatures, diesel smog and very little winter sun. Strict air tightness is an ideal but isn't as important in most of New Zealand. New houses are much more air tight than older ones so long as there aren't faults with the windows or doors.

From a cost point of view we could build $50,000 cheaper if the New Zealand bulding code was weaker than it is. But that would make for a terrible house. And a code house is often a terrible house relative to a better designed house that costs more. Often new builds have granite benchtops, overpriced stainless steel German appliances, huge doors or a chandelier and an expensive car in the front. Being able to afford to meet passivehouse standards isn;t the issue for many clients but very few are interested in building beyond code.

Most of the benefits of a passivehouse can be achieved without the expense of full certification. In warmer climates insulating under the slab makes little difference relative to insulating the edge of the slab. A local HRV system like Cleanaire is cheaper than an imported Swiss unit. A bump from R2.2 to R2.6 wall insulation costs little. Good low-e glass increases build cost by little more than 1% over plain. Bad windows aren't much cheaper than good ones. Many of the problems people encounter with new builds involve bad design not budget factors, like using black bricks or inappropriate windows.

Back to the subject of tinting, I know of a $1m build where the architect has used green tint everywhere when they could have just specified a low e glass that does the same thing but better and doesn't look green. Grey tint is more appropriate for privacy applications than climate control as it separates the indoors and outdoors. The eyes adjust to grey tint's reduced sunlight but you should be sure dulling the day is what you want as it'd be polarising.

jonathan18

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#2261297 20-Jun-2019 09:51

OP - assume you've had a good read through that PDF booklet (and/or listened to the interview) I linked to in your other thread on heat pumps?

Guide available at https://sustainableengineering.co.nz/ph4nzwarmhealthyhomes/

I'm sure the author would be happy to chew the fat on this stuff if you contacted him; given he probably knows more about passive house design than most in NZ he may well be a good source for further information.

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