New house build in Western Australia
 

Hello everyone!
What a thread this is: 57 pages, 580 posts....

I have been reading all day, followed countless links and learned a lot, thank you all!!!

My interest is in a new home I will be building in 4~5 months, hopefully the last home I have to build:

• The ground floor is 196mq - garage= 150mq and the first floor is 122mq.
• The floors will be solid concrete on sand and limestone ground.
• Walls and roofs will be properly insulated,
• Flat metal roofs.
• Here it never freezes, but we need to heat the house 3~4 months a year
• 8~9 months we open the windows and let the sea breeze in the afternoon and the land breeze at night, but some days it goes over 40c (100F), so cooling ability will help.

I am exploring the ideas of:

1. Geothermal floor heating using a heat pump with solar as well.
2. Perhaps cooling with cool air exchange??
3. I am thinking to place the slinkies below the house in trenches, before I build the concrete floor slab, is that a good idea?

Any help to get on the right track deeply appreciated!

Keep smiling
Stefano

Hi all,
Just wandering if I can use black poly irrigation pipes for in-the-slab floor heating for the above house?

I have just copied this to the "The Homemade Heat Pump Manifesto" thread as I think it is more appropriate.
See you there.

SPIV no you should not use that kind of pipe for that application. I forget what kind of pex you need to use but only pex should be used

Only use O2 barrier PEX if u have any iron or steel in contact with the heating water, it will keep rusting by pulling Oxygen in through any non-O2 barrier type of tubing, best type is pex-al-pex with an aluminum layer in the middle, next down in price is PEX-A still good, lowest in price & quality is PEX-B

If I may join in...

PEX is High Density PolyEthylene (which is heat weldable) that has been subjected to a process that causes some of the molecule chains to cross-link. The 'PE' is Polyethylene and the 'X' indicates cross-link. Cross-Linking makes is no longer weldable (I tried and failed). It also makes it much stronger. It was designed in Europe specifically for hydronic floors. It is cheap and it is the industry standard. Why risk any other kind of pipe when PEX is so strong and affordable??

Everything BBP said about Oxygen barrier is correct.

With the addition that if you design your system carefully to use no iron (bronze or stainless pumps for instance), you don't need to worry about oxygen barrier.

I don't agree with BBP regarding the hierarchy of quality of PEX, as he does. I think each type has its own advantages.

PEX-AL-PEX is definitely the best O2 barrier. It does have a larger bending radius however, and is more likely to kink if the bend is very tight. If you are after high-performance floors, you will want close spacing which usually require smaller radius bends. Beware PEX-AL-PEX.

PEX-B is good as an O2 barrier. It has a coating on the outside which is designed to prevent O2 from entering the system. The outside coating is a bit 'sticky'. In concrete, this is not a problem. But if you are going under floor or above floor, or in-wall, the sticky surface can 'grab' and 'let go' when hydronic temperatures change. Which will be noisy (ask me how I know this). PEX-A has a normal bending radius.

PEX-A is not coated on the outside, and it is rather slippery by comparison to PEX-B. This might make it cheaper, but that doesn't make it lower quality. If your system has no iron components, it works just fine. PEX-B has the smallest bending radius.

-AC

NOTE: edit per BBC

A/C sorry but u have the properties of PEX-A & PEX-B reversed.
I used both types recently on my Sons house.
PEX-B has the O2 barrier on the outside, which can be peeled off somewhat.
It is also more difficult to pull through holes in the wood framing.
I much prefer the more expensive PEX-A
I used Mr. Pex brand

Sons house, 8,888' altitude in Crested Butte Colorado, zone 6.
I used over 10,000' of 1/2" & over 1,000' of 3/4" between boiler room & 6x manifold sets.
Sorry to say, only concrete slab was in garage, 4" of XPS under. I think this is the cheapest & best way to heat.
Rest of house, demanded by Son, the pex has to transfer heat to air & then to finished surfaces. Less efficient & must use much hotter water, because of this I used a modern cast iron high temperature boiler, Burnham ESC6
The 1/2" pex (4" OC) is suspended about 1-2" below subfloors with R30 Rock wool a couple inches below pex.
I Installed a couple thousand feet of 1/2" pex in interior walls wherever possible.
House has WAY too many large windows.

heat loss program was performed by the architects office (RESCheck)
They came up with 110,000 BTU / hour at design temp of -20*F
So I chose the boiler slightly larger at 113,000 at this high altitude.
I expect the boiler to run non stop at design temp

Buffalobillpatrick

I don't want to cause you grief but I had done staple up on a bedroom and an ensuite bathroom over a garage. The garage was heated but only to about 10 Deg C. It was a 1/2 poly-b tube on a 6" centre to centre with R28 fibreglass insulation beneath. The house is extremely well insulated.

The room was uncomfortably cold here in our Canadian climate. The water circulated was 80 Deg. C. and offered up no appreciatable heat.

The rooms have been changed to above subfloor Uponor system.

The balance of the system is in slab and now with 40 Deg C. (Geo and solar heated) water which is absolute nirvana.

Just a word of caution. Again I don't wish any ill will.

If your going forward and the work is complete I pray to the in-floor heating gods your result will be markedly better!!

Randen