I'm looking at a new build made from masonry with beam and block flooring throughout. The plan would be to insulate in the cavity but I can't seem to work out how to avoid thermal bridges between the floor and the walls/supports on the ground floor.

It seems that the beams are typically supported on the internal skin of the walls, and pillars inside the floorplan where needed to support internal walls. The internal walls and inner skin of the outside walls then effectively sit on the beam and block floor. (Hope I have this right.)

Insulating the walls can be done in the cavity, and I can just about see how to make this continuous into the roof, however, the ground floor seems more difficult.

I can't see that it is possible to put insulation between the beams and the supporting walls (have the whole house weight to support) nor between the beams and the internal skin/internal walls (unless these are lightweight and non-loadbearing).

If my understanding is right, it seems that there will always be thermal bridges between internal walls and the floor, and then from the floor to the supporting walls.

How can the floor structure be built to remove/minimise these thermal bridges? (Please, no comments about using SIPS or timber frame instead of masonry.)

Thanks very much,
Mark.

Hi Mark, have a look at this http://www.tonyshouse.info/plandetail.pdf

Not beam and block, but the same principle is the same, at least at the perimeter

I see Tony beat me to it!

Edit, re-reading I think I misunderstood the question - will think on it

Posted By: tony
I too worry about this detail but consider that the soil/fill under the house is an insulator, however if you have to ventilate beneath the suspended floor you introduce an in house cooling mechanism -- they all do it but why should we?

I notice from your plans that you basically have no insulation on the ground slab - you're just relying on the soil/fill underneath. I'm surprised that this is good enough, although you are 2.6m below ground level, so the temperature gradient won't be so high.

We're looking at a partial basement, so not all of the ground floor is above a basement.

Posted By: tony
Ground bearing slab insulate way down if necessary fill with low density polystyrene under floor and do an in-situ concrete poured floor.

Yes, I can see that this might work, but I'd still be concerned about the ability of this "sandwich" to support the internal skin and load bearing walls. (If I understand what you are saying correctly.)

OK, this sounds like it might work. Let me check I have it right.

Pour a concrete raft foundation.
On top of this, build an insulated tray that extends beyond the inner skin of the wall.
Pour another re-inforced concrete raft on top of the tray.
The outer skin is built on the first raft, the inner skin and internal walls are built direct on the inner raft.
The cavity insulation can be pushed down to meet the sides on the insulation tray.

This should give a complete insulating wrapper around the floor, but it seems like a lot of concrete.

What sort of insulation would be recommended for this?

Thanks,
Mark.

some good info/diagrams here , but you need to be a member to download pdf

http://www.aecb.net/silverstandardpdf.php

http://www.aecb.net/join.php