As part of my renovation about 100sqm will be entirely rebuilt. I have hydronic heating and so it makes sense to me to use the already installed system and connect it to the in-slab heating, or re-use radiators. The system already copes well for the surface we have, so it wouldn't be an issue as we will have a similar surface in the end. My architect had been thinking in-slab electric, as it requires little work and is cheap to install. I wonder what recommendations you may have as to what should be the cheapest way to do this in-slab heating as well as to what would be most efficient to run? I am assuming the material for the coil is some sort of plastic? Finally what depth should the coil be placed? Thanks
in slab heating
(19 posts) (11 voices)-
ghostgum
MemberYou need to talk to a hydronic heating company.
My understanding is that slab heating uses water at a different temperature to panel radiators, so I don't know if you can mix the two.
You want the heating near the top of the slab. One method is to poor the slab, then to place the coils in formers on the surface, and then to put a screed over the top.
If putting water pipes through the slab (or in a screed on top), you use the same plastic pipe that is used to connect the panel radiators. Our pipes are Rehau Rautitan.My father's workplace had in-slab electric heating, built in the 1960s. By 1980 enough wires had broken that it was no longer working, and they had fan heaters in each office.
Electric resistive heating is an expensive way to heat. Cheaper would be to use natural gas, or heat pump air heater (reverse air-conditioner), or heat pump hot water.
My first thought would be to take the some of the panel radiator return water and feed it through the slab, but that may mess up zoning.
The cheapest would be to add another 2-3 panel radiators to your current hydronic system, but that wouldn't make it warm under foot.
Let the sun heat up the slab instead.
Posted Monday 13 Dec 2010 @ 10:19:19 am from IP # -
marie
MemberThanks for that I have talked to the suppliers of my boiler, and they say that I will need a pump mixing station, as well as the manifold and coils. I am going to call a few plumbers to get an idea of how much that would cost. Our renovation is designed to make full use of passive solar heating but I am told in winter you still need some heating...Recommendations and comments still very welcome.
Posted Monday 13 Dec 2010 @ 11:03:09 pm from IP # -
Have you considered using radiator heating instead of slab heating?
It is cheaper and I regard it as less wasteful. Is there really a need to heat the whole house in winter? For instance kitchen and bedrooms need hardly any heating in moderate Australian climate zones.Posted Monday 13 Dec 2010 @ 11:44:00 pm from IP # -
marie
MemberThanks, Yes I have and I could re-use those I will have from the demolished part of the house. At this stage it is part of a ongoing discussion with my architect, who being in Sydney is not familiar with hydronic heating. In europe of course radiators are re-painted with each renovation, but here people often say that it will not work and look out of date with the rest of the house etc etc...
Posted Tuesday 14 Dec 2010 @ 1:38:20 am from IP # -
Peterws
MemberIn-slab is a lovely heat however its expensive and inefficient, we use a rate of $50/m2 for say 150m2 $7500 including a small boiler 30kw which could heat up to 300m2
as suggested above a more efficient and cheaper solution would be radiators, the heat is not as evenly spread but if efficiency is a factor your way ahead.
Posted Tuesday 14 Dec 2010 @ 1:50:02 am from IP # -
Solgen
MemberAs others have noted, electric slab heating is probably the best heating solution for comfort as there is no sound and no air movement and virtually no stratification just an overall pleasant warmth in the living space.
However, there are a number of disadvantages as well.
- Difficult to find anyone in Australia who is skilled in the installation and if they mess up the installation it is virtually impossible to repair.
- Uses a lot of electricity but because it is at off peak rates, the costs are not extravagant but probably more expensive than a heatpump(air conditioner).
- It is a good system in cold climates but in moderate climates or during the autumn or spring can be problem if warm weather occurs as you simply cannot turn off the heating as it is stored in the slab and can days or weeks to cool down.
- The slab must be insulated as well which once again is unfamiliar territory to most builders.
Hope this helps.Posted Tuesday 14 Dec 2010 @ 2:24:36 am from IP # -
dave lawrence
Membervery good point made by solgen, regarding insulating the slab . that is critical if you are going to the trouble of inslab heating. I tend to favour the reuse of the wall mounted radiators and SLAB insulation . Actually i don't advocate slabs but that is another story. My preference (as documented on many other posts in this forum )is for incorporating thermal mass into internal walls and then you could mount your radiators on those walls .
Posted Tuesday 14 Dec 2010 @ 5:42:56 am from IP # -
marie
MemberI would think that hydronic in-slab is the way to go if I am gonna have in-slab heating. I am assuming that it should be fairly efficient in particular if I am going to get the perimeter of the slab insulated. Has anyone got a specific idea as to whether it can be? Isn't the ground supposed to be at 22 in which case we wouldn't loose so much heat going down? thanks
Posted Thursday 16 Dec 2010 @ 7:46:17 am from IP # -
dave lawrence
Memberthere was a massive discussion on the pros and cons of inslab heating earlier this year with much useful information posted by folk with way more quantitative data than I know about , dymonite from memory.
the main point of it was ...harder than you think and less efficient than you would hope. a lot of it comes down to the (cost of the ) source of the heat for the hydronic heatingPosted Thursday 16 Dec 2010 @ 8:30:11 pm from IP # -
tintac
MemberMarie, I've just had a slab poured with pipe for hyrdronic heating installed (can't do it afterwards!).
A great source of info was
1. http://www.concrete.net.au/ where I found the paper "Briefing 07 - Concrete Floor Heating" and
2. the installers I approached for quotes.We did not insulate the slab edge as we needed it exposed as a termite barrier so it will be interesting to see what happens when it's eventually commissioned.
We will also add radiators to the existing rooms eventually (a long term plan).
Good luck with yours
Posted Thursday 16 Dec 2010 @ 9:42:17 pm from IP # -
TAZ
MemberHi Marie,
I have hydronic heating in my house in Hobart it consists of panel heaters in each room and works extremely well. We chose not to use the in floor set up due to the fact that it takes a long time to heat up where as the panel heaters are hot within 5 minutes of turning on, which you would know seeing that you aready have the same system.We can have sun for half the day but then can change to cloud over cast cold weather for the rest of the day meaning that we may only need heating for the latter part of the day. We generally run the heaters between 5pm-10pm and 5am to 8am this is enough to heat the living areas and only costs us $700 a year for heating in a 24 square meter house(includes hot water ) Why don't you try to ensure that the concrete floor (ours is polished to show the different coloured rocks)is exposed to the sun which means it will act as a heat bank this is what we have done and it results in a warm to touch floor, use double glazing as well. By doing this you will save the expence of in floor heating plus the expence of running this sytem which would off set the price of the double glazing. Don't get me wrong at times the floor can be cool to walk on but is very rare, you also need to ensure that the slab is insulated around the edges and underneath for the first meter around the perimeter. Get the book warm house cool house as this will tell you all these things and more. Hope I have helped in some way regards SimonPosted Thursday 16 Dec 2010 @ 11:27:06 pm from IP # -
marie
MemberThanks everyone you certainly have given me plenty to consider!
Simon great to hear about your personal experience of the concrete floor, initially I have been warned it is gonna feel cold under feet. Our rebuilt part of the house will face north so we are going to make great use of the sun to heat bank, we will also have double glazing. Cheers
Posted Friday 17 Dec 2010 @ 1:11:25 am from IP # -
termite
MemberYes, I suspect that in-slab heating is best when there is someone to use it all day. The delay in heat up/cool down probably is a disadvantage and an inefficiency if you only need it for an hour or so in the morning and then not till around 6pm.
Posted Friday 17 Dec 2010 @ 1:31:40 am from IP # -
tintac
MemberDave, I'm not entirely sure that we'll need to actually commission the in slab heating as the new space will have good solar exposure, but it seemed prudent to install it in the slab, which will not be covered. Later, when we install the radiators in the coldest part of the house we will use a gas boiler.
It would be good to be able to combine it with solar preheating but those costs are astronomical for us.
Marie, your project sounds a lot like ours. Good luck with it.Posted Tuesday 21 Dec 2010 @ 11:04:40 am from IP # -
I am all for the potential of floor hydronic heating but I do recall an experience near Switzerland where the house was nice and warm but so was the water from cold water taps. Since the place was a little overheated getting a drink from the ensuit in the middle of the night (or the bottle on the table) both resulted in a luke warm drink was a little unpleasant.
Lesson - Keep heating away from your plumbing.
Posted Wednesday 22 Dec 2010 @ 3:13:13 am from IP #
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