Alternative Technology Assn Forums

1. 

   mat-with-one-t
   Member

   Hi all. I have long been an avid subscriber to ATA and ReNew, and next year wil have the oppotunity to build a reno/extension for my bank to own for years to come. I thought I'd pick the brains' trust here on a bunch of items and get some ideas flowing. First, let me set the scene:
   - we've got an existing 1930 weatherboard which is on stumps with an uninsulated hardwood floor
   - we're adding a modern extension comprising of:
   basement
   three small bedrooms and a bathroom on a slab
   an offset-shape living area that will sit on posh-trusses over the basement, and that will have ample double-glazed windows to the north (and slightly to west ~20deg). These windows will have pelmets and heavy curtains inside, and outside pull down blinds to protect them from late summer sun
   total 40,000lt underground water storage
   evap cooling
   will add PV grid-connected system when affordable (should have roof space for maybe 4Kw
   separate gas boosted solar hot water
   - heating will be hydronic, on a modern condensing gas-driven boiler
   1. I have done some reading on pro's and con's of in-slab hydronic. We'll have slabs under the basement and the rooms above as described. I am currently thinking that panels only would be the go to best allow for overall moderation of heat. What do people think? Should it combine slab with panels, or panels only?
   2. It really doesn't sound worth it to connect up solar to the hydronic system. Given you want warmth in winter, when solar gain is poor, I'm feeling money is better spent on the highest efficiency condensing boiler available
   3. as the lounge will sit on posi-trusses over the basement, how do I create some thermal mass in such a floor to capture incoming sun in cooler months?
   4. can I make use of underground (~3meters to base of tanks) water storage for heating or cooling?

   Cheers all and keep those discussions flowing.

   Posted Thursday 19 Sep 2013 @ 3:51:53 am from IP #
2. 

   sun2steam
   Member

   My 20 cents:
   drop the gas booster for hot water, the electric booster is good enough, and use the savings (about $1000 ?) to install a larger PV system

   Posted Thursday 19 Sep 2013 @ 4:36:43 am from IP #
3. 

   Benny
   Member

   To get a floor with thermal mass over trusses (timber board floor ?) could you use phase change material in boards ?

   Posted Thursday 19 Sep 2013 @ 9:51:03 am from IP #
4. 

   mat-with-one-t
   Member

   Yeah I'm looking at these interesting phase change things. Bit pricey though...

   Posted Monday 30 Sep 2013 @ 4:39:48 am from IP #
5. 

   munter
   Member

   You will need an accomodating builder to complete a non-standard build. Finding one who is also competent, timely and fair priced will be a challenge. FWIW:
   I'd stick to either panels or slab heating. Trying to do both will double the controls, pumping and require two water sources for the two different temperatures. We are using in slab heating and haven't found it to be all that efficient yet but are only just begninning.
   Perhaps you can have a stone or brick internal wall to expand the amount of thermal mass in the building envelope?
   Water storage may help as a heat store but you will need to do heat balance calcs to make sure you don't boil or freeze it with a heat exchanger. I think I did a similar calc to see if we could use our water tanks as a low temperature heat supply in winter and came to the conclusion that they would likely freeze!

   Posted Tuesday 1 Oct 2013 @ 7:56:02 am from IP #
6. 

   Greg
   Member

   1. I don't quite follow why you would heat the basement. If that's the only place you have a slab id not bother unless it will be an occupied space.
   Not sure what munter means by additional controls. Normally you would have a programmer for on off time of day, day of week and thermostats. The hydronics have tempering valves to keep max temperature below 50 C. The radiators can take more heat. Your boiler will probably supply 70-80C.
   2. Agree, not worth it.
   3. Not sure what to suggest here. Have read of pcms but pricey. Blueboard with tiles would add a little. I guess you need to know how much mass you need first then see what you could use. Could do a suspended slab.
   4. If you were using them just as heat stores I cant see real value since your boiler will be able to supply the heat you need and solar would take all summer to heat any useful quantity. A cool store would work if you can keep it cold and pump it to a purpose made "fridge" otherwise again not much use. Different proposition if you were using a heat pump.
   Just my thoughts sounds like good fun so enjoy the journey.

   Posted Wednesday 2 Oct 2013 @ 9:23:00 pm from IP #
7. 

   mat-with-one-t
   Member

   Thanks for the replies. Yes - we plan to occupy the basement space as a music/rumpus/hang-out room, so heating will be installed. It sounds (from chats I've hhad) that it's best to just stick to panel hydronic heaters.
   As an aside, has anyone built a waterproof retaining wall/basement structure using pre-formed stuff like "AFS Rediwall" or similar? Our engineer has specified a standard core-filled double brick wall (which will also need tanking by a specialist waterproofing mob), whereas this seems pretty old and labour intensive to me....
   Cheers!

   Posted Tuesday 24 Jun 2014 @ 12:49:11 am from IP #
8. 

   darrynm
   Member

   On point 2 you're spot on about solar gain being poor in winter (vs what you need). We have 30 evacuated tubes connected to a 500L tank which runs our hydronic radiator central heating. In the cooler months the tubes provide just enough heat to take the chill from the house for 2-3 hours a day, but now in winter they barely generate enough heat to make a dent.... plus the heating requirement is so much higher.

   Solar for hydronic is an awesome idea but you need a heap of collectors to make it work.

   Rather than a gas boiler how about a heat pump? Then you can use the power generated by the solar PV system rather than feed to the grid.

   Posted Thursday 26 Jun 2014 @ 9:50:54 am from IP #

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