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Captron 04-07-11 07:57 PM

Hi Guys, what an excellent DIY thread:thumbup:. I wish you guys were working for me!

Just to be helpful, here are some guidelines we use that may take some of the mystery out of certain things discussed here.


The Doís:
1. Use 100mm to 150mm (4Ē to 6Ē) spacing in the slab with 10 and 15mm pipes respectively. Make sure the Pipeís bend radius is not exceeded by these numbers. 150mm (6Ē) thick is best for added thermal mass.

2. Make sure the pipes are at least 50mm (2Ē) deep in the concrete, preferably above the metal reinforcing screen

3. Make sure the pipes are suitable for direct burial in concrete and that it is designed for this type of heating purpose and that the pipe is oxygen proof.

4. Donít ponder the antifreeze issue, if you need it, and most of us do when using a solar offset, use it - the efficiency will not materially impact on the heat transfer in a real world. Make sure pumps and pipes are OK with this additive. Donít use Car antifreeze as the additives can be detrimental to long term usage.

5. Donít use XPE under a slab, use HDPS (High Density polystyrene). Always use it, we use 140mm (6Ē) but 90mm (~4Ē) would be the minimum we recommend. The house will not settle on this stuff. I have seen a concrete truck drive over this stuff with hardly as dent.

6. Donít use small diameter pipes over 100M (330í) in one go.

7. Lay the pies intelligently, donít try to heat places that donít need it such as under counters, under larders/pantries, but do include clothing closets.

8. Design the pipes to provide warmth to the bathroom(s) first, and in BR the warmer temps should be on the perimeter. Stay away from piping close to the outside wall by about 400mm (Just over a foot) to avoid heating the wall losses unless that spot is regularly walked upon.

9. Donít overheat the pipes, you are generally aiming for a 30c (85f) max floor temp in an energy efficient house. More if not. No warmer than 45c (120f) or you add to long term risks. At 30c you are about the same as a warm summer day and things like wooden floor coverings rarely have issues.

10. ALLWAYS insulated the edge of the slab!. You will lose easily 30% of your heat there in sub freezing temps and much more as the temps go down. We use ICF perimeter with added HDPS to achieve 100mm of insulation Ė minimum.

11. Hot water heat pump for back up is a good idea. We retail a 9kW unit to our clients, good down to -15c (5c) for about USD$ 2.8k You should be able to find similar deals in your areas. This will heat a 200SqM (2100SqFt) proper thermally efficient EE home down to about -10c (0f)

12. Insulated any through pipes (Toilet tacks etc) and stay away from these with your pipes.
13. Geothermal Heat Pumps: Lots of good and bad things about this, some of it is common sense:
a. Horizontal type: Stay well away from flower beds and trees as the ground around these pipes will freeze solid at the height of cooling.
b. Horizontal type: Stay way from paved driveways or you will turn them into Skid pads when there is no serious insolation.
c. Vertical: Keep transfer legs short and common sense insulated.
Hope this helps. Obviously much of this is averaged and some will be in colder places than other, so use some common sense.

John Guest company (UK) make a decent spreader plate to be stapled under existing wooden subflooring.

Stay Warm!


Ron Theaker CD
Digital Self-Heating Homes

ThomSjay 04-09-11 11:47 PM

Another great read for me!

I was thinking that with this style of floor(Warmboard) as in post #74 one could easily DIY by using a router to put in the grooves. Lay the sheets of sub-floor, router the grooves using guide boards, staple/glue on the copper or aluminum sheeting, and then put the desired surface on top.

AC_Hacker 04-13-11 07:20 PM


Originally Posted by ThomSjay (Post 12920)
...staple/glue on the copper or aluminum sheeting...

The Devil doesn't live in the details, The Devil lives in the sheet metal.

If anyone comes up with a good DIY method to put 0.025" aluminum down on a routed channel floor, I will personally buy that person a brand new Compact Florescent Light bulb.



pachai 04-13-11 08:11 PM

channels in Radiant tubing plates
I was discussing this problem with my friend.
(as far as engineering and design, I have just one :-)
He suggested this...

Fold the metal over a board, eg, a 2x4, so there is a
square channel. Special tools might be needed, but
maybe not.
Then take this upside-down U which is about 9" deep,
1.5" wide, and 12-24" long....
and raise the sides back up.
The folded edges become the shoulders of
your channel...and the valley forms by itself.
Nail it down to the sleepers.

The width of the wood is calculated...
1/2 circumference + 1 diameter...
Pi*D/2 + D = 1.5 D + D = 2.5D
5/8 * 2.5 = 10/8 + 5/16 = 25/16 = 1.5"

Note, other than seeing it done as a test,
I have not done this yet...
but I expect to soon.

Sadly, the only reason I am trying is...
Radiantec is back ordered and I need them soon.

I got flashing for $32/50' - bought 3.
I also got new tinsnips that are optimized for straight.

I used a couple of short 2x4 as "wheel chocks"
so the roll of material does not get away from me.
(Trust me, it's worth wearing gloves :-)

smith 04-17-11 12:06 PM

Great Thread i have not been able to read all of this side yet, took me 3 days to get through the manifesto. I was thinking about incorporating some baseboard heaters into my system(cheap fast easy look nice). I did a little more research and even at lower temps 110F the slant fin from home depot still give 160ish btu/hr per foot. Even if it was 100btu/hr still seems reasonable considering the price. 3' is 26$ or so. not sure but this might help with "cold" starts to bring the heat directly into the living space faster or even hooked up to a secondary heat source. Just something i found interesting i though i would pass on.

I will post some pics once i start with the in floor routing project, i did a few tests on spare piece of osb and it seemed to work fairly fast with a box cut bit.(I'm sure this has already been discussed)


smith 04-17-11 06:04 PM

I need to make a few more posts before i can do much ;) So while i was outside i was thinking but not sure how to test it, maybe someone else is better setup to do this. What about using heavy duty aluminum foil as a heat spreader, I'm not sure if it's thick enough to do much but it would be interesting to see the results of a test, or even multiple layers. It would be extremely easy to work with and the price is not that high either.

smith 04-17-11 09:18 PM

After reading the rest of the posts i feel it would be too thin. Anyways I like the idea of doing the press for forming my own spreaders, Look forward to seeing how things turn out with your press designs.

osolemio 04-18-11 03:07 AM


Originally Posted by Captron (Post 7387)

We did the development in NZ, and now have interest from all over since we received Patent Pending status.


I only saw this post now.

It seems to be quite similar to the project I am doing. The main difference between my project and Captrons is, that mine is (will be) open source, while Captrons is commercial and (apparently will be) patent protected.

In the USA and Canada, the principle of storing heat under the house for all year space heating is decades old. So I wonder what part of the system will be covered by patent?

In my philosophy, the main drive is that as many people as possible should be able to employ this principle of seasonal storage. If there are restrictions as to who are allowed to build and sell it, the use of it would be much less. The main purpose of solar heating is to beat the pants of fossil fuel use, and this is cause is not helped if restricted by patents.

Since the principle of storing heat in the ground is already well known, I doubt that any parts of that patent pending status will prevent others from doing similar projects. Like mine.

I did think of getting a patent somne years ago - if I could - only to ensure that others did not do so and thus restrict the success of the principle. But it would be way too expensive to get a patent - beyond my ability - with no return on that investment if made available to all.

Instead I asked the experts about how the principles could be protected AGAINST a future patent to limit its use. And I was informed that if the information is in the public domain and published, others cannot later patent an idea which already exists.

Captron might use some very special techniques they can patent, maybe their control system. But I seriously doubt they can patent pumping solar heated water under the house and use that a seasonal storage. They did not invent solar thermal heating, underfloor heating nor heat pumps.


In my system, which can be used in existing as well as new houses, I am using several different technologies in a combination, to add up to a design which will be up to 100% self sufficient. This is depending on the design, how well the house is insulated, how large the solar panels are, and so on.

Captron speaks of fear of getting his throat cut by revealing too many details of the way they have chosen to do it. I have the opposite fear - that their patent might be able to restrict how others can use this long used principle.

Here are some links to information about how this has been employed previously:

Greener Shelter

Capturing Heat While the Sun Shines

Although the above projects are using air as the heat transfer medium from roof to soil, the principle is the same if you use liquid rather than air.


These ideas above are liquid based as transport medium.

In my system, an existing house have had three 3.5 inch tubes inserted under the house, from a hole dug in the front. Inside the large tube is a smaller tube, about 1.25 inch, reaching to the end of the large tube. This allows water to be circulated all the way through, to deposit heat during the summer. Most of the heat extracted will dissipate to the top, naturally, while it is also possible to extract heat in the same manner. These tubes are inserted by a company that already specializes in placing tubing and cables under existing structures and other obstacles.

Building a new house, using this technique, there would be different layers - different depths - where heat is deposited. The tubes would be inserted into the ground by the same technique as described above - or it could be dug in but this is normally much more difficult. The several layers principle is to have more control over when the heat reaches the floor. During the summer, most of the heat will be deposited in the lowest layer, while during winter, any excess heat will be used at the topmost layer.

To conclude this - as much as I appreciate Captrons effort in this important area of seasonal solar heating, I fear that it will complicate things for the rest of us.

smith 04-18-11 07:43 PM

I may have missed it but can you point me to the links that talk about pex sizing? I did read through the information fairly fast and i prob missed it. I know 1/2 inch is standards but I'd like to see performance data for 3/8 and 5/16th sizes ( may not be practical just curious)

AC_Hacker 04-18-11 09:27 PM


Originally Posted by smith (Post 13097)
I may have missed it but can you point me to the links that talk about pex sizing? I did read through the information fairly fast and i prob missed it. I know 1/2 inch is standards but I'd like to see performance data for 3/8 and 5/16th sizes ( may not be practical just curious)

PEX spacing is extremely important when looking into this also

While you're investigating PEX diameters, you might also want to consider 5/8"... it's not so common but is available. It has almost 2x the volume per foot.

Might also consider bending diameters for various sizes of PEX.

There are some strategies for dealing with small spacing and bending diameters.

Keep in mind that most advice for sizing/spacing assumes that you will use a fossil fuel boiler.

It is so rare that you will find advice for low temperature heating, that you should post any resources you come across that address it.

PEX sizing...

Happy Hunting,


P.S.: Just came acros this link. Good discussion, good advice, but all the folks are using electric or fossil fuel boilers, so your spacing will need to be closer, if you are going low-temp heating.

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