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(Semi) Eco House

Solar hot water - the story so far

23-Oct-10 06:46 Tags: None

We chose the Apricus 315L electric boost hot water system, which uses evacuated tubes.

We're fairly happy with the system so far, but not the way it was installed. We've been in the house since the beginning of winter, early June.

The system was installed in the only part of the roof where they are shaded in the early mornings (for at least 8 months of the year). We have a large expanse of north facing roof, and a small bit that juts up where the celestory windows are from a loft area. The tubes were installed directly to the west of this highest roof area. I don't know how much this effects their heating first thing, but it must be quite a bit in winter because it's at least a couple of hours of direct sun it blocks. If I can move them at some stage I will, but apparently they should be as close to the hot water tank as they can, so not sure if that will ever be possible.

I had misunderstood how the system was set up by default. I had read a lot on forums about having the boost that you could set to whatever time suited you - say between 3-6pm in the afternoon so that it would only come on if the day had not been sufficiently sunny. I had thought it was something you did in the control panel. Unfortunately it's not, it's something you have to get your electrician to set up at point of installation - put a timer switch in the electricity box. I didn't realise this til we were in the house for a few weeks and I got around to reading manuals of things.

So our electrician put the electric boost on Tariff 33, which in Qld is available for at least 18 hours a day. What this means in practice is that every time the Tariff 33 comes on, it checks the temperature of the tank, and if it's not at least 60 degrees, it boosts it. I don't know how often it boosts it during the day and night, specially in winter, it could boost several times a day for all I know, when it really only needs to boost once a day (for health and safety reasons).

I am thinking about getting our electrician to install the boost timer, it would cost over $200, so I'm just waiting for my next electricity bill to see if it's warranted.

Our first bill was for the three winter months since we moved in and our hot water component usage was the same or a bit more as my parent's who live next door, who have an electric system on Tariff 31 (super off peak) with about the same size tank. We probably use more water than them, having two small kids and they being frugal pensioners), but still, it made me a bit worried. I spoke to someone at Apricus to see if there was something wrong with our setup, but they seem to think that was a reasonable usage of power.

I don't know though, as our winters, though very cold at night (-3 or -4 most nights) are very sunny and ideal for water heating during the day.

I was thinking about manually turning the boost on when needed, but decided to leave it as is for this next three months and see how it goes for the next bill. If the usage of the boost is still high I'll probably get the electrician in to put it on a timer.

I'm also planning to build a little shelter around the tank to counter heat losses at night in cooler weather.

I'll update this post when I get the next bill.

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The perils of mixing "eco" with tradespeople

09-Jul-10 06:58 Tags: None

One of the biggest problems we've had with this project is convincing tradespeople that certain "eco" products are better than what they normally use.

Two examples.


Our builder had previously had a "bad experience" with an eco paint, and so brandished all eco paints with the same tar. We were planning to go with BioPaints for our internal wall paints after a friend having really good experiences with them. We had already decided that while Bauwerk lime based paints sounded fantastic, that they were just too different to convince our builder to use. Our builder still baulked at the idea, as Solver was his usual paint, and we ended up going with the low-VOC Solver Enviroguard paints.

Even then our builder didn't like their coverage and finish compared with their normal range. I, on the other hand, was quite happy with the finish (where the paint was decently applied), and the lack of smell was fantastic.

But using an eco product against a tradespersons advice allows them the upper hand. If the finish isn't great: well, of course it was the product not the application. We painted our doors ourselves, with a very good finish (if I do say so myself!). The next day the builder had placed all the doors upright touching each other (we had separated them all with polystyrene). When they took them to install, quite a few spots of paint pulled off almost all the doors. But was it because of him stacking them together still wet? No, apparently not, apparently it was the paint's fault - it "lacked guts".

Cork floor sealer

We ummed and ahhed about whether to use an eco sealer for the floors. It was going to cost an extra $1000 to do so (for an extra coat and the eco sealers themselves). The cork guy wouldn't guarantee the finish and said that it won't last (having never used the product before as a reference, mind you). But we decided that if we went to the trouble of having low VOC paints, we should go the whole hog and use low VOC floor finishes too.

So, we used the Bio Floor Varnish from Bio Paints. It looks ok to my untrained eye, except for the cork installer's sanding marks in the corners (but of course he could blame the product if he wanted to).


So, how can we use eco products when mainstream tradespeople can so easily blame them for everything that might go wrong?

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15-May-10 07:07 Tags: None

We chose fibreglass/glasswool insulation because of cost, and because I could not find any strong reasons to spend more on other products such as polyester or wool insulation. There were rumours that fibreglass insulation is a carcinogen, but this has been disproven.

In the roof we have R1.5 foil bonded with fibreglass batts and in the ceiling R3.5 fibreglass batts with a 50mm gap between them. This takes our roof/ceiling R value to R5.

In the walls we have R1 foil insulation plus R 2.5/3 fibreglass batts (a bit of each), with no air gap as there was not enough space. So R3.5 for the walls.

Find out more about insulation at the Your Home Technical Manual.


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08-May-10 06:59 Tags: None

There are a lot of windows in our house, including covering almost all the northern walls. We have large overhangs (600mm) from the roof on all sides to shade the windows in summer but let light in the northern windows in winter. All three southern windows are small and high. We do however, have three large eastern windows (one deep in the veranda) and one large western window that may cause heat issues in summer. We plan to plant decidous trees/vines to shade these eastern and western windows in summer, whilst allowing winter sun, but this will take some years to come into effect.

View from the north-east corner
View from the north east corner

The Your Home Technical Manual on Glazing says:

"Glazing has a major impact on the energy efficiency of the building envelope. Poorly designed windows, skylights and glazed surfaces can make your home too hot or too cold. If designed correctly, they’ll help maintain year-round comfort, reducing or eliminating the need for artificial heating and cooling.

Windows in a typical insulated home can account for more heat gain or loss than any other element in the building fabric. In summer heat gain through an unshaded window can be 100 times greater than through the same area of insulated wall. One square metre of ordinary glass can let in as much heat as would be produced by a single bar radiator. In winter, heat lost through a window can be ten times more than through the same area of insulated wall."

Unfortunately our budget did not allow us to get the best possible windows - we have single glazing, untinted glass on aluminium frames (the frames are white, which does help with reflecting heat a little). At some stage I would like to get tinting to reduce the UV wear on internal furnishings. We will have to rely on good blinds/curtains/external shades to help regulate our temperature. At this stage I am most worried about letting the cold in on winter nights. We haven't yet decided on window furnishings (it will depend on our budget at the end of the build) so if anyone has good suggestions, feel free to post them here in the comments field.

Our celestory windows should provide a very good temperature balance in our house. In winter they will allow the midday sun to hit our rammed earth wall and store the heat, releasing into the night. Although our ceilings at that point are around 4.5m high, we do have a ceiling fan on one half of that area which we will reverse to circulate warm air that has risen back around the room. In summer they will be shaded and can open to allow heat to move upwards using the stack effect principle.

Celestory windows Celestory windows

Sun hitting earth wall at 8.30am in May
Sun hitting earth wall at 8.30am in May

As a side note, all rooms in our house (excluding bathrooms and laundry) have light/windows on at least two sides - following Christopher Alexander's Pattern Language.

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Why not the "eco house blog"?

07-May-10 07:15 Tags: None

The reason this blog is called the "(Semi) Eco House" blog is that we're definitely not able to go eco/green in all aspects of the build.

Simply building a new house uses a whole lot of resources that would otherwise not have been used. Sure, we could have renovated a house or brought an old house onto the site or even bought a pre-fab house (there are some eco-friendly ones now too). But while those options were investigated, none suited our needs, and we do plan to be in this house for a long time. This is our "forever house".

We also can't afford to go green all the way. The budget for this build is around $250 000, which I think is pretty reasonable for a 4 bed, 2 bath house. I'll do a breakdown of costs in a later post.

Another reason for the "semi" part of the title is that it's really hard convincing builders and other tradespeople that eco friendly options are good. We sometimes manage to convince them, but other times they get their own way.

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