Heating a 7 star house

philbert83 · Mar 05, 2017 4:38 pm

We are about to start on a 2 story house (Rawson Windermere) in the ACT which the builder says will be pretty close to 7 stars with upgraded insulation/double glazing/good northern aspect with big windows onto dark tile floor/etc.

I had wanted to have in-slab heating for part of the downstairs living area (about 60m2) however I am now wondering whether it is worth even bothering if the house has that many stars. Plus the builder throws in a huge reverse cycle air con (20kw) anyway.

Options are:
1. RCAC + Electric in-slab - not too expensive to install, can cost a bomb to run, had hoped to run off solar but that seems impractical the more I research. Could run during the day a little when the solar panels are at peak production although no doubt it would use a bit of network power too.
2. RCAC + Hydronic in-slab - expensive to install. I thought you could run it off Apricus evacuated tubes and probably avoid all boosting, but I'm yet to find anyone who has done that who says it has worked a treat. It seems you would need so many tubes it is impractical, so would end up costing a bit in gas.
3. Just stick to the RCAC on its own, invest in slippers and a few rugs. It's already included in the build cost, but could be expensive to run if you got really carried away during peaks from 7-9am and 5-8pm, perhaps try to run from 6-7am and 4-5pm on timer, + during day with some solar.

Any thoughts or experience welcomed.

bashworth · Mar 05, 2017 5:15 pm

I would be going for the RC heating as its about 3 times as efficient as electric in slab.

On sunny days you will get sun warming the slab, and running the RC will stop it loosing heat too fast.

Bels · Mar 05, 2017 9:41 pm

With a 7 star house you'd be going backwards going with electric in slab heating. Reverse cycle heating is only as expensive as how you wish to run it. If you use it with a sensible setpoint in winter (20-21 degrees for example) it's not going to be any where as expensive to run as if you get the setpoint at something more unrealistic (eg. 24-25 degrees).

If your reverse cycle heating is going to be zoned, you could realistically shut off the upstairs zones during the day if you were going to be running it while the solar outputting so therefore you're not going to be heating space upstairs unnecessarily. Heat rises anyways so it's likely upstairs will get some sort of heating regardless.

If your air con controls had remote access functionality, you could adjust your setpoint up depending on your solar output to use more of it and heat your space up a bit more.