Monday, June 1, 2009

Green comfort

We decided a while ago that a spa was not only a cool thing to have but would help with some health maintenance issues. Fortunately a spell of intense work provided the funds for it and after some back-verandah-meets-chainsaw action, we have a spa sunk into the back deck. How decadent. Now for the green accounting side of it:

  • New timber for deck mods - locally treated waxwood from plantation timber.
  • Spa itself - australian manufactured with exception of pump and electronics
  • Support pedestal - spare bricks and a paver lying around the house plus 1 bag of mortar
  • Water - 1500L from our rainwater tank
  • Heating - Currently electric system using 100% Greenpower from JackGreen.
The first heat-up took a whopping 77kWhrs of electricity, which is more than a week's worth of our normal power consumption, or in other terms, enough to run the fridge for 2-1/2 months. Holding it at 34degC overnight took 13kWhr and for the daytime 6kWhr (outside temp a rainy 8~16 degC).

As the fibreglass body only has a ~3mm coating of expanded foam coating as insulation, I stapled some sheets of plastic to the underside of the edge supporting timbers and pulled them all together. While I was doing this it was noticeable how warm the air was under the enclosed but not sealed deck. After the plastic was installed it was noticeable the temperature difference inside and outside the plastic, so it appears to be working. I also took the time to seal the corners where the curved spa sits in the square framed deck, as it was possible to feel the hot air rising from these small gaps. In time I'll put some thermometers around to measure exactly what's going on and how much effect it's having.

Ultimately I hope to majorly reduce the power consumption by connecting to a solar tube water heater which I picked up at 50% off while buying some tanks. This will get plumbed in as a recirculating closed loop system to provide heat to the spa, via a heat exchanger (as soon as I find or make one!)

So who says going green rules out some of the nicer things in life?

Oh, and I may tap some of the water off to spoil the dogs with hydronic floor heating for winter...

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