I just saw my Upanor layout for my 2 storey ICF home. Both floors are to be concrete. The upper is to be a 4" slab with Hambro joists with the slab and joist left exposed. The Upanor plan showed a section in which was noted that insulation under the lines be 5x that above the lines. I can't see how I can achieve that ratio without insulating and then finishing the ceiling below the suspended slab. Does anyone have a solution to this. How about a prediction of the effectiveness of the upstairs heat with no underslab insulation?

You simply can't isolate the zones sufficiently using concrete as insulation.

To predict how out of balance it'll be without the insulation is impossible without an extremely good model of the heat loss of both zones.

Let's see - you could do 1/2" tubes at 1/4" below the surface of the slab, that gives you an average depth of 1/2" and an average of 3.5" below - so technically it meets the spec. Or just paint the underside with low emissivity paint and run ceiling fans upstairs to greatly increase heat transfer from the slab.

No, I'm not serious about any of this.

A quick test I did with a warm plate (equal temps both sides) and small sealed cavities above and below indicates that about 70% of the heat goes upwards. 78% with a low emissivity coating on the underside.

If you can design for 30% of your heat going downstairs, then you may not have an issue (other than that warm ceiling, warm floor isn't ideal for downstairs comfort).

The suggestion from Uponor is pour one slab over the joists. Then 1" EPS and heating tubes, then cover that in a second pour. Back to structural now to see if that requires more overall concrete and therefore a different Hambro size.

The plan right from the outset was hot water heat in an exposed suspended slab. My next question is should anyone have spotted this problem before I noticed it on the mechanical drawing the day the footings started? Architect, heating contractor, heating designer/supplier project manager?

yes, yes, and yes?

Possibly some type of stucco/foam/concrete sandwich would be cheaper.

Daniel, I can't offer you any help with your heating design questions, but I'd love to hear more about your houseplans with Hambro floor systems.
What kind of spans are you using them for?  When is construction expected to start, and what part of the country are you in?

Thanks,
Jay

The first floor is all stacked and poured and braces off. The Hambro arrives Monday A.M. from Calgary (I am in Victoria). The house is 23'x55'. Originally Hambro sketched the joists as running the long way, but the architect had them turned to cross ways. With a wall and a big beam down the center the Hambro will only need to span 11 feet. At the roof the Hambro will span the entire width.