Tony From West Oz
Member
We are replacing the tiles on our floors and would like to install hydronic heating. This would mean cutting trenches in the floor, installing the pipes, mudding the pipes in place and then re-tiling over it. We would like to use an existing (wet back) wood fire to heat the water with a pump to circulate the water.
Has anyone done this?
What were the issues and how far apart did you install the hydronic pipes?
All comments will be appreciated.
Tony
karmacoma
Member
Better check your soil type, as you may end up cutting through the slab mesh in places. Quite possibly many places. Reactive clay will then do the rest and crack it for you. Designed-from-scratch hydronic slabs are (should be) 120mm thick, not 100mm. A retrofit would normally screed the slab up higher, with the pipes buried in the screed.
If you're up for such major work, why not think instead about doing what's required to get winter sun onto the existing slab (tiled or polished, not carpeted) through double glazed windows? You know, punch holes for floor to 2100 windows along your sunny north walls, and even move internal walls around if you have to, to get your living area onto that side. And of course, at the least insulate everywhere and plug drafts.
Hydronic heating costs money each year in gas bills. Compromising your slab for the sake of what the sun could provide free may not be the best cost-benefit outcome. If you really think the house design or site is so stuffed that you can't get sun into it for one reason or another and so you have to use an active system, would reverse-cycle aircon used now and then be enough? Or check out Marty's one-room solar hydronic thread. And there's other ideas too.
Ian
Tony From West Oz
Member
Thanks for your responses.
Some further information:
Our home was built in the mid '80s by an environmental scientist. It has rammed earth walls and solar north orientation. A 8M wide glass wall has good winter insolation, onto terracotta tiles which absorb the heat to some extent. At night and when cloudy, the house loses heat rapidly through the rammed earth (good thermal mass, moderately good thermal conductivity) walls. All windows are single glazed and would need to be replaced to get the space to install double glazed panes.
We have removed about 20 large down lights (which acted as small chimneys, sucking heat out of our home) and replaced them with adapter plates and small down light fittings and LED lamps.
We have insulation in the ceilings and all windows have drapes with sealed tops to prevent the 'chimney effect' where no pelmets are fitted.
All doors have draft seals.
Using smoke (incense sticks) to identify air leaks has not revealed any. I have searched Perth for someone with a thermal imaging system so that I can identify any other thermal leaks, to no avail.
We plan to use a solid fuel heater (which we currently use to boost our solar HWS during winter) in conjunction with a water pump, to provide heat for the hydronic system. This heater can be set to run at a low heat for many hours, which should work well for the hydronic heating system.
The trigger for this project is that my wife would like to replace the terracotta tiles with ceramic ones.
Tony From West Oz
Member
Ian,
I searched for "Or check out Marty's one-room solar hydronic thread." but could not locate it. Do you have a link to that thread?
Thanks,
Tony
karmacoma
Member
Sorry, yes I was being too brief.
Marty's thread is "Fitting hydronics after you have built your home"
http://www.ata.org.au/forums/topic/15596
and is a work in progress, but very promising.
Sounds like your house is superb, except for the fact that the rammed earth walls aren't insulated on the exterior. What are the chances of doing something about that? Not high, I suppose.
Ian
Tony From West Oz
Member
We did consider insulation on the outside walls - for about 1 second!
Part of our love of this home is the earthy look of the rammed earth. Even insulative paints (very poor insulation also) change the look markedly. That wasn't going to happen either.
I will check out Marty's thread.
thanks,
Tony
Tony From West Oz
Member
OK,
Marty was going to put a timber floor and run the hydronic piping under that. Not a bad idea. That would still raise the floor level in most of the house by about 25mm, but better than 50mm with a screed over piping. He will not have the thermal mass of the concrete slab floor working for him though.
I will look at the slab plans for our home (If I can find any) to see how deep the reinforcing mesh is likely to be.
Thanks again,
Tony
karmacoma
Member
No, he moved on to another idea - using wall radiators powered by an evacuated tube solar collector, via a storage tank. There's also that other current post with the guy who wants to power radiators with a wood heater, that's another variant. Wall radiators are used heaps in Europe but are inconvenient - they take up valuable wall space. There are skirting board types around though. And it beats messing with the slab - but if you do go the slab route, how about $300 to get a structural engineer to look at the plans first.
You'd expect in theory that the mesh is midway in the slab - that's probably how it would have been drawn on the plans, but whether that's what the builders actually did is a guess. They probably would have used bar chairs, so you could suppose from that what the likely height prior to the pour was (unless they did something unexpected), but then during the pour the concretors would have walked all over it, possibly springing some parts up and pushing other parts down. Your risk is mostly dependent on soil type - how much the ground moves seasonally. Clay would be the most suspect.
Just as well even the deep-earth types have moved away from mud brick and rammed earth buildings onto haybales and other insulated designs. My sister lives in a 1980s mud brick house in Victoria. Recycled bridge beams, cathedral ceilings, all that. Yeah, looks nice, but way too cold in winter, just can't get the place warm. Give me wall insulation any day.
Benny
Member
Tony - I have a FLIR thermal camera. I'm in Maylands.
Did you read all Marty's thread ? He has some wall radiators for sale that could be driven by your wet-back. Installing radiators would be a lot easier than floor hydronics.
Given that you have the stove in there for heating, why do you need to connect it to a hydronic system ? Is it just to redistribute the heat ? Unless you plan to run the stove harder you won't be getting any more heat in the house. Have you considered using in-ceiling air distribution to move the heat around? ie a vent over the heater + fan + ducting and exit vents in other areas.
Tony From West Oz
Member
Karcooma,
I will seek advice from a structural engineer.
Benny,
Would you care to either:
1. Come over to my home and check for air leaks, or
2. Allow me to borrow your FLIR camera (FLIR = Forward Looking Infra Red?). I am happy to provide a reasonable deposit as security for its safe return.
To get meaningful results, I would need to obtain an extraction fan, put it in a window and seal any gaps, turn it on to lower the inside pressure so that the cold air is drawn in. This should show any significant air leaks into the building.
Is this how we should do this test?
Regards,
Tony
Tony From West Oz
Member
Benny,
you asked[quote] Installing radiators would be a lot easier than floor hydronics.
Given that you have the stove in there for heating, why do you need to connect it to a hydronic system ? Is it just to redistribute the heat ? Unless you plan to run the stove harder you won't be getting any more heat in the house. Have you considered using in-ceiling air distribution to move the heat around? ie a vent over the heater + fan + ducting and exit vents in other areas. [/quote]
Hydronic heating will enable us to smooth out the peaks and dips in temperature, using the thermal mass of the floor. It will also spread the heat from the room the heater is in, to all parts of the house in 3 or 4 zones so we can control where the heat goes.
If we have air leaks, simply redistributing the air via in-line fans and ducting (I have these in case we cannot go Hydronic) will not achieve the smoothing of the peaks and dips in temperature.
I plan to fuel the heater with used cooking oil (I am Chair of WA Renewable Fuels association Inc. warfa.asn.au) so it can operate for longer periods of time without constant stoking. By using hydronic heating, we can operate the heater without overheating our hot water system.
axess
Member
Hi TFWO,
I live in a 13 year old rammed earth house on a concrete slab in Melbourne. I too love our rammed earth walls and wouldn't change their appearance for quids. I also love hydronic heating even though we didn't include it in our build. All our windows are double-glazed, we have very high insulation levels and the northerly aspect is highlighted in the design.
We rely on a single gas Rinnai space heater with supplementary electric panel heaters when required (very rarely used). We have just installed a 2.5Kw split system into the southern part of the house to provide additional heating and cooling if required. We haven't used it yet. Maybe next summer as we are getting on now and need to sleep.
What about wall heaters with exterior feed lines chased into the outside walls and covered with an insulated decorative strip? Our walls were rammed in 1200mm panel modules and the tie rod conduits (to hold the forms apart) are still in place albeit filled on each side. They could serve as pipe entry/exit points and the piping system could be designed to keep the runs as short as possible. Anything is better than damaging the slab floor.
Good luck with your solution.
Hi Tony
I am working on piping solar heated air in hollow skirtings along a brickwall in my home. I am going to use PVC swimming pool pipe and drilling holes along the length and face these against the wall. So far i have used flexable ducting as used in Air Con and aiming the air at the brick wall. The air rising over the surface seems to heat the bricks and allows the wall to radiate this heat as the room cools down.
I actually manufacture Solrheting air systems and this is an experiment in trying to store some heat after the sun has gone down.
I cant give you my product name or web site as last time I tried to help someone I got banned for spamming. I am happy to receive an email if you are interested in information.
The systems are made in Armidale NSW where we are used to cold weather.
Its just another idea for you to consider.
Tony From West Oz
Member
Con,
That is another way of doing it. My greatest need for heat is when the sun is blocked by clouds, especially after a clear night (=COLD).
That is why I want to use the wet back wood fire as my heat source.
I have discussed this project with a hydronic system installer and they always use a 40mm screed over the piping, laid on top of the slab.
When asked why they do it that way, they stated that it allows more even heat transfer to the floor surface.
If I have a 12mm wide trench cut 30mm deep and lay floor tiles over the grouted in piping, the finished floor would be approx 40mm above the bottom of the trench, which should have similar thermal properties as the 40mm screed over the slab.
So the plan at present is that we cut 30mm deep trenches at 200mm centers and have multiple circuits in parallel for each of the zones.
I am still on the look out for a structural engineer to discuss impact, of cutting 30mm deep trenches, on the strength of the slab.
Thanks
Tony
axess
Member
Hi TFWO,
Your description of the proposed "grooving" of your slab with 12mm wide slots, 30mm deep at 200mm centres would possibly encourage stress relief of the suspended slab either upwards or downwards, similar to "scarfing" a piece of timber to deflect it. I would be very interested in what a structural engineer would say about such an idea. Please keep us posted.
Tony From West Oz
Member
The slab is not "suspended", it is "slab on ground".
The smallest pipe generally available is 16mm, which will mean the slab will need to have 20mm "grooves".
Tony
Tony From West Oz
Member
We have decided against in-slab heating. We have purchased 3 hydronic radiators to heat the extremities of our home from the wood fired wet back heater. We will run a pair of main line distribution pipes under the brick paving along the back of out home and tee off them to feed the radiators.
I have been experimenting with an oil fired burner, which I plan to install in the heating stove. This will allow the heating stove to operate without constant feeding with firewood. I am looking at getting an oil tank like what was used with the Vulcan oil heaters in the '70s and '80s, to supply the burner with used cooking oil.
Here is a link to a video of testing the burner in a pot belly stove.
Someone put a tremendous amount of work into this. It's amazing to watch.
[url] http://www.youtube.com/embed/foqGirKxbvk [/url]
