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2 posts
Posted Today, 10:07 AM
From my reading of it, the Immersun unit is to be used as an addition to a grid-tied inverter fed from a PV array. The Immersun unit simply connects excess energy, at 240V AC, and that would otherwise be fed back to the grid, to a hot water cylinder element. I don't think that addresses BobI's initial post.

11 posts
Posted Yesterday, 9:49 PM
For what it's worth, I'm in the process of putting together a smallish, simple hot water PV setup, as per my original inquiry on this strand: this is a deliberately low budget effort, to see what can be done.
Since it will not be big enough to meet our estimated HW needs, it will be supplemented by grid (on a timeswitch, midnight to 6am, already fitted to optimise our wetback use.)

Once I have this going, I aim to set up 24/7 data logging (via old PLC and SCADA system). This should give me some hard data on PV output for our particular area. And once I have a reasonable slice of that, i'll publish what I have, for better or for worse, for the benefit of whoever may be interested.

We are classed as a high wind area, and right now I'm considering how best to mount the PV (3 panels) atop one of our water tanks. By best, I mean sufficiently strong and rigid, while also cost-effective. The tanks are Devan, polyethylene, 25000L, with 4 big lifting lugs on top.

As always, comments and suggestions are welcomed.


11 posts
Posted Yesterday, 6:30 PM
Hi Mike,

that's pretty well exactly what is required. It does presuppose a workable design (or the ability to come up with that), the tools and ability to put together the hardware, then the tools and ability to program it to perform as described.
Questions: can you point the rest of us to any proven sources for these things.
I realise that a simple search throws up quite a selection of circuits (for instance), but most people would need some confidence they were working to a proven design before embarking on construction. In my view....



1 posts
Posted Yesterday, 10:07 AM
Hello all, this is my first post here so I apologise if I get things wrong. I have searched and not found anything that answers my specific question.

I am looking at building a house in the central north island. I already have solar + wetback in my existing house, which is in the Auckland region. The solar system there is mains pressure and the wetback connects via a heat exchanger. The solar has a manual electric boost, which is off the vast majority of the time. I find that the wetback only contributes heat when the water temp is pretty low -- in the early 20°s or cooler. Even then, the water doesn't even get to showerable temperatures from running the fire for say 4 hours in the evening.

Part of the reason for this, I know, is the distance the wetback-heated water has to go to get to the heat exchanger.

In my new house I would like things to run better than this. I would also like to have mains pressure water in the house.

I have an idea which may be totally off-the-wall or, even if practical, would not be accepted by building inspectors. I'm not a tradesperson of any description, much less a plumber. I'd like to know what you people think.

What I would like to do is have a low-pressure cylinder in the roof space right above the fireplace, thus reducing the distance the water has to go. The solar would be connected to a second cylinder, a mains-pressure one, sited above the solar collectors on the outside of the roof. The 'wetback cylinder' would be connected to the 'solar cylinder' BUT ONLY WHEN I CHOOSE. The idea is in the mornings when the fire is cold I would manually open a valve, and let the thermosiphon effect do its magic.

Comments please? :-) Is this totally off-the-wall? What would the average NZ building inspector be likely to think of it?

A further question: if this wouldn't get past a building inspector during the initial build process, is this something that could be retrofitted (obviously without requiring further consents and inspections) once I have the final sign-off?

Many thanks!

1 posts
Posted 21 Aug 14 3:34 PM
you should look at the 'immersun'. It will heat your hot water, only when it sees your system exporting to the grid. All other times, your hot water is off. There are timer settings that allow you to set the hot water heating times when the sun isn't out and you need hot water.
It is sold in the UK and OZ. From what I have read they are going to be producing and/or selling he unit here soon.

111 posts
Posted 20 Aug 14 10:30 PM
Hi the number relates to the kilowatt hours per year usage. ie if it says 365 kwh per year then it will use 1 kilowatt per day.
I have an off grid holiday home , I have found the Samsung inverter fridge freezer to have an excellent star rating . Also price was very good compared to other energy efficient fridges. I have checked my fridge freezer with a watt meter and the actual rating is a little better than what they state.

2 posts
Posted 20 Aug 14 9:55 PM
Hi has anyone installed a euro style multipoint lock on their entrance door. I am having difficulty locating suppliers in NZ.
Cheers milo

220 posts
Posted 20 Aug 14 5:16 PM
Ecoply is just a brand of plywood with different specifications for different purposes. There is also an Ecoply tape for seams though it seemed hideously expensive when I enquired about it.

I think the acceptale solution ply option for a simple house specified only 7mm as sufficient. I used 7mm(perhaps 7.5) on some of my house and it felt just a bit too light to me and so I switched to 9mm which has a more solid feel about it and easier to match for shimming.

3 posts
Posted 20 Aug 14 4:54 PM
One of the builders I've contacted has suggested he'd use Ecoply instead of plain old structural ply.

Any thoughts on the difference? Should I use 7mm, 9mm, or something thicker?

Are there diminishing returns once you get above a certain thickness?

9 posts
Posted 19 Aug 14 3:51 PM
In my case the cylinder is open vented. I like to keep things as low tech as possible. I'm a bit dubious of the Techluck device and the Liberty box is expensive. I think with a closed cylinder using an inverter or micro-inverters are the way to go. Without these devices the I can see an open vent cylinder and battery bank a good option as you have a stable voltage and can match the element to it.

120 posts
Posted 19 Aug 14 12:42 PM
If your HWC is not open vented, then to meet NZ regs a thermostat that cuts off the heating element directly must be fitted, there can be no other relays; thus the power feed to the element must be AC or alternating switched DC, to prevent excessive arcing of the thermostat contacts and so burning out, were they to operate from pure DC.

I have yet to locate thermostats with suitable DC rated contacts, I don't think they exist.

The DC switching device can be very simple, 4 * IgFets in a H bridge configuration driven by a 50hz wave form, these would alternate the DC polarity to the element and the thermostat, effectively quenching any arcs formed upon the contacts opening. Approx cost for parts would be $80 - 100 for a DIY electronics person. This switch could be driven by a small cpu measuring the current into the element and thus vary the width of the switching wave form for mppt operation when driven from a solar panel source; parts for this bit would be $150 approx.


15 posts
Posted 19 Aug 14 8:55 AM
Hi all.
HELP PLEASE..... we are completely off the Grid with Hydro and Solar. We have been in our new home for 2 yrs and are now getting our "real" kitchen built. The thing is, we are unsure of how the stars verse the kph readings work on new appliances,especially fridges and freezers.
1)which should we use as the best guide.
2) any advice on most efficient brands.
Cheers and I look forward to your advice.

9 posts
Posted 19 Aug 14 6:49 AM
Hi, I am planning to do this too. They sell the Techluck unit in Australia but it's low wattage. I plan to feed a 24volt element from the battery bank via this unit. Diversion load Controller
An MTTP controller will supplies the batteries. I have 2kw of panels. Most people on the forums (US) generally think PV hot water is a silly idea so to get advice I say the house load is about 0.6kwh otherwise they just go on about how inefficient it is.

70 posts
Posted 17 Aug 14 10:24 PM
it would be a lot simpler to remove the internal linings and fit insulation , unless your cladding is already had its day. you could staple breathable building wrap in each hole before you install the batts. your 1950 house will likely be uninsulated so this will make a world of difference . it just depends how far you want to go and how much you want to spend.

2 posts
Posted 17 Aug 14 1:13 PM
I have been looking at polyurethane pray foam and have found a supplier in Auckland. I know they use spray foam a lot in the US. Dose anyone have any experience with it?

220 posts
Posted 17 Aug 14 12:24 PM
Adding ply means you have a few things to work around. Window frames will likely need to be shimmed in order for the window trim boards to be at the right level. I'd suggest choosing a ply thickness that matches a suitably available shim eg 9 or 10mm. With a two storey house, if you only do one storey, that will also create a transition point where you may need some type of flashing.

I would start with a "friendly" visit to the council to see what their attitude is to such a solution, the problem is that native timber is no longer an acceptable solution for framing even though the type of wall you propose is and I have heard of councils turning down requests for wall insulation on that type of basis.

Perhaps there is someone in Wellington that specializes in retrofits that might be able to assist.

Regarding use for bracing I suspect your house is reasonably well braced but, if you do use ply, it might be a worthwhile thing to get techical input just to get it to modern compliance. The acceptable solution for a simple house gives specification for ply bracing and nailing type and pattern etc but it would likely be different for two storey and different stud heights.

3 posts
Posted 16 Aug 14 6:50 PM
Thanks for the advice.

I'm not really wanting to spend a lot, however I do like doing a good job and if there's little point insulating from the inside and really to do a proper job I should re-clad and add ply then I'll re-clad.

I've just checked and downstairs has no building paper (and a noticeable draft coming out the hole in the wall for the power socket) and upstairs has paper and little draft.

Sounds like a re-clad.

- Can anyone recommend a decent builder in Wellington to do this?

- What should I expect in terms of disruption during the process? Attached to the weatherboard on the side the re-clad would occur on is our incoming power from the pole and Infinity hot water unit.

- Would I be best employing a project manager to run the job for me, or is it small and simple enough to just employ the services of a good builder?

220 posts
Posted 16 Aug 14 6:39 PM
Just to add that if your wall has building paper already, insulating from inside or an external infill method would likely be allowed. I guess it depends on the state of weatherboards, how much time and money you want to put in to it etc.

220 posts
Posted 16 Aug 14 5:04 PM
Firstly, when insulating walls you need to check with your council re building consent. They can be concerned that native timber may become vulnerable to rot if the air space is removed and as the wall will be colder and could have more condensation with insulation. In most NZ situations this shouldn't be a problem but councils can be risk adverse after leaky homes.

Ply has a few advantages. If detailed correctly it can help with air-tightness, is probably quite a good screen for water infiltration especially in combination with a rain-screen gap and you could also use it to provide earthquake bracing that many older homes don't have.

I think your approach is sound as long as your council are happy with it.

9 posts
Posted 16 Aug 14 2:50 PM
Thanks for update and info link Allen, good stuff

3 posts
Posted 15 Aug 14 10:39 PM
Hey guys and gals,

We're looking to insulate our 1950's house in Wellington, prior to next winter.

I've checked out the wall and it looks like we have our existing cladding (bevel back weatherboard) then building paper, then framing.

I was going to look to get a quote to insulate from the inside, thinking for the section we want to do might be roughly $5k.

After doing a bit of research (mostly on this site) it looks like a better approach would be to re-clad and insulate in the process, using R4 insulation, then 12mm ply, then building paper (or Tyrek) then new cladding.

What are the pros and cons of each approach? Do I really need to re-clad or is building paper sufficient to create a space of dead air, enabling the insulation to do it's thing to it's full potential?

220 posts
Posted 15 Aug 14 7:02 PM
Likely you are going to have to work with the authorities re the upper gap which would probably be the 50mm (from memory) of the standard solution. I believe that's to allow any water ingress, and possibly condensation, to disperse.

As far as condensation is concerned your roof works just like the principle for double/secondary glazing, it is the internal air leakage which will cause any condensation, not external, so the internal surface should be sealed as well as possible. Your poly won't affect things but they will be wary that things above it are permeable.

2 posts
Posted 15 Aug 14 3:01 PM
I have looked through the other posts here similar but not found something that will work for my situation. The house was built in 77 with exposed beams. on top of the beams are 50mm x 50mm batons. The silver backed GIB is nailed to one side of the baton and the Decromastic tile are on the other side. Given the tile recess there is only a 20mm gap. There is no paper or netting that I can see. My thoughts for what they are worth was to remove the tiles and check wiring. Then pack out existing baton and find a high density closed cell insulation like they use in europe. Then re roof. I have seen differing opinions on air gaps. Some saying to avoid them with closed cell. But I'll need to work with Auckland city council.

23 posts
Posted 15 Aug 14 7:47 AM
Hi guys, just an update: My fridge completed its third year after insulation and runs flawlessly without complaints or hazzles!

Greetings Allen

1 posts
Posted 15 Aug 14 6:56 AM
Does anyone know of any non toxic adhesive avaliable in NZ.

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