[pachai]

This thread is great - I have read much of it and it's giving me ideas. I'm in a funny situation - I am a DIYer, but with not too much time this year...and I am having an addition built, which will leave me with not a lot of money to do radiant and/or GSHP....

I discussed insulating the slab with my builder, and he reported
that he has another project where he is repairing a slab that collapsed on the styrofoam. So, right or wrong, I am going to let him pour a normal (up to code) slab. (I got to watch the masons today building the foundation walls :-). Note, I am talking about a basement, below the frost line.
When he leaves, I will put down a couple coats of InsulAdd on the floor.

When he asked me what type of heat for the addition, I said Geo. But geo around here is not affordable...and <whatever>. My boiler has a mod so it is now at a 1/12 duty cycle, and that is with current insulation levels. So I can very well afford to extend my boiler into the new space...and postpone the GSHP question till the summer.

But during this construction, I am thinking I can at least put in what a programmer would call "hooks" for future options.
For example, the builder agreed to give me a 6" conduit
to the back yard below the frost line. He said his tractor driver is willing to dig for me to lay ground loop, though I like the drilling idea, and tests looked good....or maybe a hybrid - a long discussion for a different thread.

But for now, framing should start next week.
Hooks that I am considering are....possibly, a pair of pipes to each room for ductless air handlers....(though I could just plan
on basement + attic for retrofit). Multiple pairs of insulated pipes to the attic for other things...like solar thermal.

...and most importantly, radiant pipes.

One possibility is for me to DIY (DIM?)...I saw a blog about this. The floors will be 3/4" tongue-groove. It occurred to me
that I could "notch" the floors for copper pipes. (Perpendicular to the joists). Though that may leave not much subfloor material, I need to learn how thin the radiant pipes can be. I may be able to have him use 1" plywood instead of 3/4" - since the architect originally wrote for 1/2" + 5/8".

(Reading Tube 02005 Refrigeration Copper Tubing 3/8" O.D. x 50' $46 - but maybe too thin.) but...Raiantec says...
Detailed research (DOE) has shown that 7/8" PEX tubing with 0.70" wall thickness and a circuit length of 200 feet is about ideal.

One thing that occorred to me is, what if I have grooves that are rectangular...can the tubing be forced (round peg, squarish hole). Or would that terribly diminish flow rate?

Flooring materials have not been chosen. The first floor addition would be kitchen and eating area; second floor would be Master BR and Master Bath. The old house is hardwood - first floor is HW on top of 2 subfloors of hardwood and planking.

Perhaps staple-up would make sense, even though it is "new" construction.

The main goal for radiant and GS is to eliminate boiler use in the "shoulder seasons" - it was almost 50 degrees in my town today.
I am thinking of all the options for how the water would be heated - solar thermal, etc.

If this sounds disjointed, it's mostly because there are many projects going on at once, and time is going to be tight - but with up to 8KW of solar, this house might end up pretty green.

Thanks
Seth