Oct 12, 2014: Lessons learned so far

Cintia and I have been living in the Greeeny Flat for over five months now. Our testing and monitoring will continue for at least one full year so we have a long way to go and lots more to learn. Nevertheless there are a few lessons that we have learned already and will probably do differently in our next project.

One major thing is that we will probably choose not to install a solar hot water system in the next one. We have an Apricus evacuated tube solar hot water system on the Greeny Flat which does a decent job of heating our water. However it cost over $6000, does not provide any sort of user interface for monitoring or controlling the system, and we have had all sorts of trouble getting any response from Apricus when we have had issues or questions.

Meanwhile our 3kW PV system (which cost less than $5000) is producing way more power than we are using. So for large parts of the day we are exporting our excess power and getting paid $0.08c/kWh for it. We would be better off to have an electric heat-pump hot water system or even just an electric tank water heater with a standard element. This would allow us to use our excess power during the day to heat water for use at night, reduce the amount of power that we are putting into the grid, and save a significant amount on the initial cost of the system. Heat pumps are much more efficient than a standard tank water heater but they are also more expensive, make a significant amount of noise, and are much more complicated with motors and moving parts that could wear out over time.

But regardless of whether we used a heat pump or regular tank water heater, I’m pretty sure we won’t be forking out for another evacuated tube solar hot water system… and certainly not one from Apricus.

Another thing we would do differently is to insulate the edge of the concrete slab. The reason we didn’t do this on the Greeny Flat is because we needed to expose the edge of the slab for termite protection. However we have since learned of a termite barrier that would allow us to insulate the slab edge. This would significantly reduce the amount of heat loss in the winter and make the Greeny Flat even more energy efficient. Also, while we love the dark colour of our polished concrete floor, we are finding that it shows every speck of dirt so we may well choose to use a lighter colour for our next floor.

In other news, I have been asked to submit an article about the Greeny Flat for the next issue of ReNew magazine. I have just completed a rough draft which is far too long. I would appreciate any feedback about the draft and/or suggestions on what to leave out of the final article.

Click here to read the draft ReNew article.

6 comments to Oct 12, 2014: Lessons learned so far

  • Noel

    In the second paragraph, you say that you would not choose to install a solar power system in the next house. Is that a typo? It seemed like you were referring to not installing a solar hot water system?

  • Mary Bowe

    Interested in your comments, re termite barrier which allows insulating to the slab edge. Care to share the product name? Thanks, found your article in Renew 130 very interesting. M. Bowe, Environmental Designer.

    • admin

      Mary, thanks for your kind words about the ReNew article. I will be writing another one for the winter edition about Glenn and Lee Robinson’s house in Bundanoon. That is where I have seen the termite barrier over slab edge insulation. Unfortunately I don’t know the name of it off the top of my head but I will endeavour to find out and get back to you. Regards, Andy.

    • admin

      Mary, the termite barrier that can allow insulation on the slab edge is called “Trithor” and is a combined mechanical and chemical deterrent. Here’s a link to their website. http://www.trithor.com.au/

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