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Topics in this forum relate to sustainable real estate and sustainable property development.
20 May 15 5:01 AM
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This forum is for discussions on World Environment Day. What are you, or your organisation, doing for World Environment Day? Do you know of any activities happening around the country for World Environment Day? 81 Posts

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7 posts
Posted Today, 1:22 PM
Thanks so much for your ideas. I want a house to grow old in too and hadn't considered falls with the concrete floor so that raises a good point. My research on concrete floors indicated you had to approach it very carefully to make it work – only using it where it gets direct sun and shading it in the summer but if it is an a lot more expensive I don't see the benefit either if I can achieve similar results without it.
Many thanks again!

46 posts
Posted Today, 12:21 PM
Blower test. Very definitely!

46 posts
Posted Today, 12:18 PM
Thermal mass. Very, very interesting topic. It's part of the 'black magic' part of thermal design, with very little understanding of how it really works. This is why the more-is-better mantra is encountered very often. I did a lot of digging around to find solid, science based data. There is very little.

The passive heating folks will not be happy with what I'm saying, but the science very clearly says that a well designed Passivhaus (or similar) needs very little thermal mass to maintain comfortable indoor conditions in summer and winter. Thermal mass does have disadvantages, but these rarely get air time.

Thermal mass evens out temperature swings and drives the house toward it's average internal temperature. This does not matter much with a Passivhaus type house, as there is little normal temperature variation and the case for special consideration of thermal mass becomes complicated and marginal.

Because thermal mass increases the thermal inertia of the house, it also means that the house responds slower to desired temperature changes (like our changes either side of sleeping temperatures).

The most often mention of thermal mass is in relation to daytime solar heating and then releasing the heat over a period. This is true, but it can be unwanted energy (eg like on sunny winter days).

Often mentioned is the ability to cool the thermal mass at night to keep the house cool during the day - sure, but you need to introduce lots of air significantly below the temperature of the thermal mass to cool it down. The big plus with thermal mass is when it's possible to selectively shade it so the thermal gain is controllable.

About 70% of the effect of thermal mass comes from the first 50mm of depth, and it drops off to almost nothing by 100mm. So huge, thick thermal mass bodies are an exercise in expensive wishful thinking.

My bottom line? Thermal mass - don't care (gotta love science)! With a Passivhaus type design and a decent HRV, I don't believe it is worth spending a cent more to gain more thermal mass than the structure and contents provide.

Heavy duty science -

More science -

Even more science (from P20) -

46 posts
Posted Today, 11:14 AM
It seems that airtightness is sorted. I say this because 1) TW acknowledges that that we did not get this perfect here, and the what I've heard about how it's now dealt with is exactly what I would do if doing this again. Make your expectations very clear and I reckon you will get good results. I'm not certain what they're doing about thermal bridges. The technology is not prone to them, but they can occur.

We're have bridging where the doors and windows are attached. We used complicated folded steel sections with gaps and spacers to get some thermal isolation. None of us (me, TM or EuroWindows) were entirely happy with the design, but the build was being delayed so we went with what we had. We have achieved modest thermal isolation, but there definitely is some bridging. If I were doing it again, I would have EuroWindows make up some sort of a flanged PVC frame that would push flat against the inner skin.

btw - I was very happy with EuroWindows' joinery. They went out of their way to revise the design multiple times to bring it within my budget. We used a combination of fixed panes and tilt & turn doors, avoiding the expense of extra window elements. Tilt & turn gear is a joy to use - definitely something I would use again. Low emissivity glass was around $1500 extra for our whole build - great bang for buck.

No concrete. There were two main big reasons for going with panel floors; barring catastrophes, we expect this to be the last house we live in and I badly wanted a floor that is forgiving with falls. I also wanted to avoid the thermal losses associated with a concrete slab. Sure - you can insulate under a slab, but I found that while there are ways of reducing edge losses, there are no really good ways.

7 posts
Posted Today, 8:53 AM
Thanks so much for that data and info! Hope I can just ask a couple of other questions?
I was just wondering what recommendations, if you have any, you had to help ensure Thermawise make my home airtight and limit the thermal bridging or do you think they have that down packed now? Would it be worth getting a blower test?

Also with your flooring did you put concrete on top of the panels to create thermal mass or is it just the panels by themselves? I haven't done my calculations yet to work out whether it is economical long term to put in a thermal mass floor or just have a well insulated floor. It comes down to what can I afford really.

Sounds like you have pretty much created the sort of house I am after so thank you so much for sharing.

46 posts
Posted Today, 12:33 AM
Ecobob shrunk the heck out of that image. Trying again with a different orientation.

46 posts
Posted Today, 12:29 AM
That sounds an awful lot like the approach I took, apart from not (yet) having a decent HRV. I have updated my spreadsheet of electricity use, and I'm embarrassed to see how far I was out with my first comments (I responded during a break at the office - without the data at hand). This shows just a little over three years of data. Average annual use is 5786kWh/year.

The blue bar shows what use would look like if I swapped in a decent HRV (with about 50W average electricity consumption). Average annual use would drop to 4134kWh/year.

I also took a look at the power meter I've had plugged into the heat pump since 1 July last year. It's showing 1508kWh, with 6 weeks to go for a full year of data, and will be well below the figure I mentioned earlier. Factor in better thermal recovery efficiency from a decent HRV and eliminate the thermal bridges and air leaks we have, and I can't see that we would easily go below 4000kWh/year.

The energy used things other than heating and cooling is somewhat elastic. It all depends on what sort of gear is used and isn't comparable across households.

I noticed that the zero energy house does not use an HRV, and that indoor temperatures are well below 20° for extended periods - I would find that quite uncomfortable. Their lighting figures seem incredibly low at around 300Wh/day. I did a quick calculation and we currently have around 100W of lighting (all energy efficient stuff) running from a little before sunset until late (about 5 to 6 hours a day). That's around 700Wh/day. These folk must be extremely frugal.

You also asked about glazing and daylighting. Levels are very good, but it's largely because the house is a 7.5 x 21 rectangle with the long sides facing N and S and has lots of open plan space. It would not work with a more conventional square(ish) house with lots of walled passages.

PS: one of the huge advantages of the panels is how far they can span without intermediate support. We have a clear span of 7.5m and a 3.5m cantilever toward the north. That cantilever is wonderful - it gives us around 70m² of covered outdoor space and it did not cost much more. Too far back to recall the details unfortunately.

When I decided to do the garage/workshop I got prices for a lined and insulated building (I work in their at night) and from Thermawise. There was very little difference in cost and I'm very happy with it. One of the things that convinced me was how the roof is just 150mm panel. No trusses or other supporting structures. So I have a good amount of vertical space, but a low roof line.

Re: HRVs - there is lots of good information available on Ecobob about local and imported HRVs. Some of the local models are very decent.

Hope that helps a bit. Best of luck with the adventure.

7 posts
Posted Yesterday, 4:15 PM
I totally agree with that sentiment. For me I don't care about meeting the passive house standard but want a house that is warm and healthy all year round without having to spend lots of money on heating and cooling it. I don't want to spend too much money on a house either as having a huge mortgage would be stressful for me. Also the passive houses I have looked at building are out of my budget range. I don't see those particular houses I looked at to be economical as the cost savings I would get in running those houses would be way out-weighed by the price tag which was $200,000 more than the same-sized conventionally built house. Thermawise appear to build cheaper or at around the same price as standard houses but it seems they are way more energy efficient and healthier.
So I think they are probably the best company I have come across in my budget range. So if I can upgrade the thickness of their SIP panels to what my budget can allow, get them to make it as airtight as possible, buy the best quality windows I can afford and buy an HRV system (German one if I can afford it) I hope I would achieve my goal. It is such a big decision on who I go with and what I build and your input has been invaluable. I feel quite confident Thermawise could create what I want after reading your comments.

1 posts
Posted Yesterday, 12:16 PM
Hey helyar

I'm looking into this at the moment as well. May I ask who offered to charr it and how were they going to go about it? Was it going to be done on site or pre-charred?

I really wish it was more standard-procedure around the world, it's so much better than staining. Thanks

46 posts
Posted Yesterday, 9:41 AM
Cool - thanks. Someone asked (perhaps in this thread) how the cost of doing a Passivhaus compared with the value of the saving (and the comfort). I remember thinking that this went to the heart of a discussion that often gets bogged down in technical (or sometimes idealogical) debate without address that all important question.

7 posts
Posted Yesterday, 8:37 AM
I don't use wood very often (a few times a year) so it is really just electricity for everything. However, in winter I shut a lot of the house up and we only live in part of it (so only heat that area) and it probably only gets to about 18-20 degrees with the heatpump working as hard as it can.

46 posts
Posted Yesterday, 1:19 AM
No problem. It's useful to compare notes so it's possible to get a sense of costs, advantages and disadvantages. I'm going to take a bit of a closer look at the zero energy house before responding. Also - to help do a useful comparison, I need to know if your cottage uses any energy source apart from electricity? Gas, wood, etc.

7 posts
Posted 28 May 15 7:55 PM
Thank you so much for all your great advice! If I understand your figures correctly then the average house total energy consumption of a typical home in Auckland (being around 7000–8000 kWh/year is well below the PH standard. I currently live in a 1860s cottage that is drafty and has no sun at all for 3 months of winter and takes a lot of energy to heat in the cold Wairarapa winters (and I run a 30,000 litre swimming pool pump in summer which uses a lot of energy) and we typically use less than 7000 kWh/year in energy consumption (there is only two of us though). We can use over 1000Kwh in the middle of winter though on the coldest month. Looking at the Zero Energy house in Auckland ( they use about 2400 kWh/year which is a figure I would lvoe to achieve as I am going to build in Auckland. They used standard timber and insulation batts but double the amount of batts in the walls by doubling the thickness of the walls. Even your house is really well insulated your energy consumption is almost twice mine by the looks of it. What was your energy consumption in your previous house (presuming it was a standard NZ build)?
Do you think just having glazing on the north of your house generate enough heat for your house?
Is it quite dark in the house as a result?
Again thank you so much for your help! I am sure this thread will be useful for many other like-minded people.

46 posts
Posted 28 May 15 4:41 PM
PS: Passivhaus target criteria are:
* total heating & cooling <15 kWh/m²/year
* total energy <120 kWh/m²/year

Our place now
* total heating & cooling 13 kWh/m²/year
* total energy 42 kWh/m²/year

You can achieve PH performance figures use readily available materials and on a tight budget.

46 posts
Posted 28 May 15 3:08 PM
I’m reasonably happy with the thermal efficiency we’ve achieved. The minor flaws niggle (they are being resolved over time) and I know that although the glazing/joinery is good by our standards, it falls far short of what is achievable with off-the-shelf gear available in parts of Europe. Give some thought to thicker panels – I don’t recall the details, but the cost difference between 100 and 250 mm panels was a relatively low number. We also pioneered Thermawise using panels for the floor – I was uncertain at the time, but it works exceptionally well.

The heating cooling cost is going to be a long answer. We’re on a day/night rate, so without lots of usage by hour data, I don’t have the information to accurately calculate costs. The best I can do is give you energy use numbers over the 2½ years we’ve been living in the house and do some rough calculations.

We allow temperatures to swing a fair bit to minimise running heating/cooling. Our key temperatures are:
* Sleeping target 19-20 (typically 19 in winter and 20 in summer).
* Non-sleeping target 22-24 (typically 22 in winter and 24 in summer).

Our total energy use is around 7000kWh/year. Eyeballing the monthly numbers suggests that our base load (i.e. the months we do not heat or cool) is around 400kWh/month (4800kWh/year). So energy for heating and cooling = 7000 - 4800 = 2200kWh/year.

Our peak heating was 625kWh and 650 kWh respectively in July/August last year, but it seems that we usually run closer to about 550kWh during heating months. Cooling months seem to run at around 450kWh. By removing the base load, it seems that we’re using around 50kWh/month when cooling and 150 to 250kWh/month when heating.

Two things to keep in mind – we use one small heat pump for heating and cooling, which works just fine, but it is about 10 years old and consumes about 750W to produce about 2kW heating and about 3kW cooling. Newer heat pumps will need about 30% less energy than ours (about 500W), and the HRV we’re using is delivering about 30% thermal efficiency at best, and probably closer to 25%. Compare this with 60% to 85% thermal efficiency with a decent HRV. A new heat pump and a decent HRV could easily halve our heating/cooling energy use.

Also relevant is that the house has almost no S, W or E facing glazing. The N facing glazing is very heavily shaded in summer, but allows sunshine to penetrate almost the full width of the house from May to August. This is one area where a Passivhaus practitioner is invaluable - they have the tools to calculate the solar heat gain/loss and advise on placement/sizing of glazing and have certainty of the results. I've achieved reasonable results, but it was hugely difficult to work out and there was always a very real risk that I had missed something.

Heating and cooling only come into play when the HRV is unable to cope in either recovery or bypass mode. We don’t need to heat for sleeping unless the overnight temperature is below 10 for an extended period (3 or more hours) – the house manages fine on HRV and internal heat sources. Bypass works fantastic in winter when indoor temperatures exceed the maximum (it happens on sunny days) and outdoor temperatures are lower than indoor. Bypass in summer runs into basic physics; it can't do much when outdoor air temperatures are higher than indoor, so cooling is needed when it becomes really warm.

I highly recommend an HRV (the technology, not the brand). Even if it’s basic, it keeps the air in the house fresh and clean smelling with minimal dust, it helps hugely with thermal efficiency and thermal management, and a decent unit does not cost a lot to run. Ours is a bad example; it churns through over a quarter of our annual energy use (about 1700kWh), but a decent HRV will run at about 50W (about 450kWh/year) or less. My wife is an only-window-air-is-fresh-air type, but I pointed out to her after a year of living in the house that she had not once opened a window. It’s that good.

77 posts
Posted 28 May 15 1:50 PM
We have today been advised by Meridian that in addition to their much reduced feed in tariff they will also be increasing their supply charge (for imported electricity) as at the 1st July by roughly 1c/kWh.

I have been in conversation with TrustPower in the past months and have crunched the number comparing Trustpower with Meridian. This latest price change has tipped the balance and in our case Trustpower will be equal if not slightly cheaper than Meridian during Meridian's "Summer" (1 Oct - 30 Apr) rate period, and only 30-50c/day dearer in Winter. TP's rates are slightly higher but their Prompt Payment Discount offsets this.

Your situation may be different but well worth checking out, particularly if you are in the Tauranga region (which we aren't) as this would make you elegible for TrustPower's TECT rebate.

77 posts
Posted 28 May 15 1:36 PM
I also have a sensitivity to formaldehyde so have well tuned 'radar' when in contact to products that contain this toxic substance.

In the past I have not only had reaction to building products (i.e. office furniture) and (sisall) carpet, but also clothing. I have a a puffer jacket and a fleece jacket, both of which cause me respiratory distress if worn for long periods of time, particularly if I get too warm in them. Both garments have been washed numerous times but although the 'off gassing' has lessened it still stubbornly continues at low levels.

Our business specialises in organic 'nil-toxicity' garments and fabrics and from our feedback from numerous customers that have chemical sensitivity or other environmentally induced health issues the amount of people who have serious reactions to chemically laced textiles is not insignificant and seems to be increasing.

Note that formaldehyde is commonly used in cheap clothing and fabrics as a fabric dressing and in dyeing. That skin reaction (dermatitus) that you get after wearing clothing items, and particular skin contacting garments such as underwear, socks or hats, is probably due to formaldehyde.

7 posts
Posted 28 May 15 11:34 AM
Thanks so much for that Leonard! Very helpful.
I was hoping for something similar to the passive house standard but that may be out of my budget as that requires at least an R-value rating of 10 for insulation.

I guess the big question is how much heating do you need in your current house to keep it 20 degrees in winter and how much cooling do you need to use to keep it below 25 degrees in summer?

You are using 250mm panels aren't you? Are they sufficient do you think? Are you happy with the energy efficiency of your house?

46 posts
Posted 28 May 15 11:13 AM
Hi Michael. Yep - I used Thermawise. There were some difficulties with thermal bridges and air tightness caused by their (and my) lack of experience. But although we did not quite achieve the results I wanted, I think it would be fair to say that I was their first client who fixates about these things (which is appropriate for this type of house). They clearly understood what I wanted to achieve and went to a lot of effort to achieve it.

But that's not the end of this story. I've kept in contact and I can see that they have learned from the experience of building for me and subsequent thermally fixated customers, and have developed ways of avoiding these flaws. Technical issues aside, I found them to be fair, easy to work with, and always accommodating.

If I was to build another house, it would take me half a second to decide to use them again.

7 posts
Posted 27 May 15 9:34 PM
Hi Leonard. I am looking at making a energy efficient home similar to the passive house standard if the budget allows. I have come across Thermawise and they seem to be onto it when it comes to making airtight well insulated homes. Did you use them in the end and if so what was your experience with their service?
Warm regards,

3 posts
Posted 27 May 15 6:28 PM
Tumeke tearai,
The Arizona site is a good one, plenty to digest here

1 posts
Posted 25 May 15 8:11 PM
hello Lyttlescotty. I have had my pyroclassic 4 days so far :)and love it. I'm not getting an overnight burn though and I think its because of he length of the wood. Today i emailed 6 well known wood merchants here in Christchurch asking if they do the longer length wood as I required it for a pyroclassic fire. One told me that there 10 inch wood will burn overnight, one completely ignored the question.....where do you get your wood from ? any advice appreciated

121 posts
Posted 24 May 15 11:22 AM
hi .this site is a great place for info

In Auckland there is Able solar , or independent power , or aa solar .
This is a blog from a recent solar install

3 posts
Posted 23 May 15 9:38 PM
Hi tearai,
glad to hear from someone so soon. I'm wanting to talk to peeps that have solar power, preferably off-grid, that may wish to share their knowledge and experience with this system.
Perhaps suggest where I can purchase items like PV's, Inverter Chargers and MPPT Charge Controllers and provide feedback on these products.
I've conducted a lot of research on the subject, there's so much info to absorb it makes my head spin. So if theres anyone out there who can assist me I'd love to hear from youz.
Cheers sunseeker

121 posts
Posted 23 May 15 8:51 PM
hi . What is it you are looking to know about .
there are a lot of competent company's in nz to talk to . American site wind sun has a good forum .

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