Passive Housing Technologies in New Builds

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Paul1977

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#251229 14-Jun-2019 11:16

I started a couple of threads about ducted heat pumps and solar power generation, and both threads very quickly turned to suggesting passive housing (or at least aspects of it).

I thought starting a thread specifically about passive housing technologies for new builds would be a good idea.

I only know what I've read over the past few days. In principal it sounds great, but can these things be done in a cost neutral fashion in NZ? There are a lot of comments along the lines of "if I built I'd do this...", but that's easy to say when you aren't the one paying for it. How many people have actually done it, and was it worth it from a financial perspective.

What technologies pay for themselves, and what ones don't?

Does the NZ building industry have appropriate expertise to implement these technologies properly?

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#2258336 14-Jun-2019 16:48

We have recently completed a 238sqm SIPS house in Christchurch.

Apart from the panel system some of the technology we used is as follows:

30cm Spray foam to the roof - I’m a firm believer in the notion of a warm roof and having no cold zones

Imported PVC Windows from China including windows with built in blinds

Energie’ thermodynamic hot water system (300 ltr system) from a Nelson Company

Nilan Combie Polar 302 Ventilation System – Imported from Denmark via UK

Viega ManaBloc water manifold – each tap in the house has its own water line allowing for more even distribution of water i.e. two showers going at once with little change in water temperature …only a small drop in pressure.

Our power bill for May was just over $160 and we are a family of 5, with me working from home and the mrs at home …the biggest chewer of power is our 90cm oven …cooking each day with that adds about a $1 a day

We do have a gas fire but its only been used for about 4 hours so far …mainly when the mother in-law stayed.

Right now, it’s 11 degrees outside with no sun all day and the house is 19 degree (according to my z-wave multisenor) with only the Combie Polar providing any heating …the coldest the house has been is 17 degrees when it was -3 outside.

I still have some issues to sort around tightening the airflow in the garage what will improve the house.

Cost wise:

Hot Water System was about 9,500

Ventilation System was about 15,00 including sourcing ducting from here in NZ

Water Manifold was about 280

Spray Foam was about 15,000

Overall was it worth it financially ...not sure or really care to be honest as the house we built is our forever house and not an investment.

If I look at it from comfort point of view very it worth every penny as my kids are just in t-shirts and shorts all the time at home.

All of what I did was driven by me but I got builders to understand what I wanted to achieve and spent a lot of time making sure I got what I wanted with many questions asked of them.

Paul1977

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#2258341 14-Jun-2019 17:03

dipper:

We have recently completed a 238sqm SIPS house in Christchurch.

Apart from the panel system some of the technology we used is as follows:

30cm Spray foam to the roof - I’m a firm believer in the notion of a warm roof and having no cold zones

Imported PVC Windows from China including windows with built in blinds

Energie’ thermodynamic hot water system (300 ltr system) from a Nelson Company

Nilan Combie Polar 302 Ventilation System – Imported from Denmark via UK

Viega ManaBloc water manifold – each tap in the house has its own water line allowing for more even distribution of water i.e. two showers going at once with little change in water temperature …only a small drop in pressure.

Our power bill for May was just over $160 and we are a family of 5, with me working from home and the mrs at home …the biggest chewer of power is our 90cm oven …cooking each day with that adds about a $1 a day

We do have a gas fire but its only been used for about 4 hours so far …mainly when the mother in-law stayed.

Right now, it’s 11 degrees outside with no sun all day and the house is 19 degree (according to my z-wave multisenor) with only the Combie Polar providing any heating …the coldest the house has been is 17 degrees when it was -3 outside.

I still have some issues to sort around tightening the airflow in the garage what will improve the house.

Cost wise:

Hot Water System was about 9,500

Ventilation System was about 15,00 including sourcing ducting from here in NZ

Water Manifold was about 280

Spray Foam was about 15,000

Overall was it worth it financially ...not sure or really care to be honest as the house we built is our forever house and not an investment.

If I look at it from comfort point of view very it worth every penny as my kids are just in t-shirts and shorts all the time at home.

All of what I did was driven by me but I got builders to understand what I wanted to achieve and spent a lot of time making sure I got what I wanted with many questions asked of them.

@dipper Can I ask what the final build cost was? You can PM me if you don't want to say on a public forum, or feel free to decline if you'd rather not say.

Jase2985

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#2258355 14-Jun-2019 17:42

you wont do it cost neutral. no way

but you can do it so some things pay for themselves.

Quotes below are quotes from a previous build

things like thicker frames, going from 90mm to 140mm only adds a small amount to the build cost but you can get thicker insulation into the walls, which again adds a small amount to the cost ($3sqm) but can increase your insulation from R2.8 to R4.1. R4.1 external walls R2.6 internal walls, R5.6 ceiling for 398sqm house $16k

An insulated slab is also something to look at as it will stop a bit of heat escaping through the floor. About $40K for a 232sqm slab

hot water heat pumps are about 1/2 the price to run than a standard electric hot water cylinder, but cost about 8k+ instillation and includes wifi control

aluminum double glazing with a thermal break or PVC double glazing will again increase the thermal efficency of the house. 39 windows of aluminum cladd timber $88K

depending on how hard out you go will depend on what sort of air tightness you go for. again its a cost you need to weigh up. would need a ventilation system. exterior weather tightness using a membrane product is about $5k + instillation

Mechanical heat exchange ventilation is a must, will take warm stale inside air, exchange the heat with fresh outside air (about 90% efficient on paper) $22k installed on a 320sqm house.

Most of those things will save you in running costs of the house, ie heating and cooling, but wont necessarily eliminate them. and they can pay for themselves over the life of the house.

Paul1977

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#2258401 14-Jun-2019 19:04

@jase2985 are those figures all additional? E.g. normal slab price plus an additional 40K?

Maybe a silly question, but why insulate internal walls?

Jase2985

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#2258482 14-Jun-2019 19:48

Paul1977: @jase2985 are those figures all additional? E.g. normal slab price plus an additional 40K?

Maybe a silly question, but why insulate internal walls?

yep complete slab

'25 mpa concrete 100mm slab, no colouring, single pour
Includes supply and installation of formwork, DPM, insulation, reinforcing, concrete pump and placing
PS1 Engineering of floor only
Plastering of slab final LM to be confirmed onsite. .
No allowance for any work in the subgrade or ground preparation
No allowance for any engineer or council inspections.'

insulating internal walls to stop heat transfer between rooms if you shut any off for what ever reason, and also for noise reduction.

bfginger

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#2258483 14-Jun-2019 19:49

Aluminium clad timber is a luxury fitout so it can cost far more than thermally broken aluminium. If you want European style joinery, that is available in thermally broken aluminium too.

Hot water heat pumps may pay their way better in high use situations. Their service life is finite and the locally made brand may provide better long term servicing than an import.

I'd be concerned about the long term servicing of an exotic imported ventilation system few in New Zealand are using or selling. Polymer membrane HRV systems don't have a strong reputation for longevity.

Shower heat recovery has a very good return ratio. See http://www.heatback.co.nz/ and https://www.showerex.com/

You install internal wall insulation to reduce noise. The wall between an internal garage and the rest of the house should be insulated like an external wall.

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mattwnz

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#2258486 14-Jun-2019 19:56

Jase2985:

insulating internal walls to stop heat transfer between rooms if you shut any off for what ever reason, and also for noise reduction.

IMO there can be pros and cons with insulating internal walls inbetween rooms, and you can end up with colder rooms than you would normally expect. This is an interesting article on this topic https://www.eboss.co.nz/detailed/keith-huntington/internal-walls-need-insulation-nz

raytaylor

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#2258532 14-Jun-2019 22:01

Check out the explanation of the roof profile on this house.

https://www.ngakereru.com/ecodesign

Scroll down to passive solar design.

I have been in a few of these style houses in winter. A couple in particular were built by one of our customers who rents them out on his semi rural farm.

You can walk in at 3pm on an overcast cloudy winter day when its 12 degrees outside, and without any heating running, you have to open the windows because its so hot like a sauna inside.

If i ever build a house, i think it would have to be of this design. I am a firm believer that every house should have a north facing roof for solar panels, but this design has the roof south facing, so solar panels would need to be mounted on a frame. But I think the passive heating benefits definitley outweigh the disadvantages when mounting the solar.

Also you might be interested in the eco house design known as an Earthship.

There was one built recently in coromandel and there are a few on youtube.

https://www.youtube.com/watch?v=fVcUJ6h4q5M

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mattwnz

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#2258578 15-Jun-2019 00:12

raytaylor:

Check out the explanation of the roof profile on this house.

https://www.ngakereru.com/ecodesign

Scroll down to passive solar design.

I have been in a few of these style houses in winter. A couple in particular were built by one of our customers who rents them out on his semi rural farm.

You can walk in at 3pm on an overcast cloudy winter day when its 12 degrees outside, and without any heating running, you have to open the windows because its so hot like a sauna inside.

If i ever build a house, i think it would have to be of this design. I am a firm believer that every house should have a north facing roof for solar panels, but this design has the roof south facing, so solar panels would need to be mounted on a frame. But I think the passive heating benefits definitley outweigh the disadvantages when mounting the solar.

Also you might be interested in the eco house design known as an Earthship.

There was one built recently in coromandel and there are a few on youtube.

https://www.youtube.com/watch?v=fVcUJ6h4q5M

One problem I have found with a passive solar building I did, is that allowing all that sun into a house fades the furniture and paintings etc. So often you will find that people end up putting in blinds and shades, which somewhat defeats the purpose. The problem with a shallower pitched south facing roof I have found, is that it is prone to a lot of lichen growing on it.

Jase2985

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#2258593 15-Jun-2019 08:00

@mattwnz you need to use better glass

Kickinbac

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#2258738 15-Jun-2019 14:01

The idea of not quite building to passive house standard appeals to me. A new home built only to NZ Building Code would achieve 3-4 Homestar on the scale. Aiming for say an 8 star homestar rating, possibly going zero energy, if you add PV. You would then get most of what a passive house would offer and would work well in NZ’s climate,depending on where you are in NZ.

Check out https://www.nzgbc.org.nz/Category?Action=View&Category_id=387

I like the philosophy of this Australian architecture firm http://lighthouseteam.com.au/ as they are looking at the building science. Some good articles in their journal.

Also look for podcasts by Undercover Architect that are good if you are planning a house. https://undercoverarchitect.com/

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Jase2985

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#2258753 15-Jun-2019 15:01

yea the thing with passive houses is you are aiming for less than .6 air changes per hour, anything less than about 3 is still pretty good, and doesnt require anywhere near the extra work or products to accomplish. and you still end up with a very good and efficient house.

mattwnz

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#2258777 15-Jun-2019 16:23

Jase2985:

@mattwnz you need to use better glass

Low E, double glazed, and also grey tinted. Not sure you can get get much better than that for larger north facing windows.

Jase2985

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#2258916 15-Jun-2019 21:39

given there are many houses with single glazing and no coatings etc that are north facing and dont have many issues something must be up. there should be about 20% uv coming in with tinted grey and a clear double glazed unit, which is under half the standard double glazed unit. low e coatings dont really reduce the UV coming in, only the heat going back out.

driller2000

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#2258919 15-Jun-2019 21:58

This is friends passive build project and there is a fair bit of content on their site: https://www.livinghouse.org.nz/

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