So we are building in SIPs with the outer wall being stone and architect has designed in a 50mm gap. I'm quite interested in the Teplo-L wall ties which have an amazingly low U value, but seem to only be designed for bigger gaps. Since the stone wall end is plain, and the drip ring is moveable, I'm sure they could be cropped if over long, but so far the only price I can find for them online is a loony £1.75 each.

I am wondering if they are worth the price for the effect (i.e if a normal timber frame-masonry steel wall tie, (like Staifix STF-6) nailed onto our SIPs panels will *really* conduct that much heat out anyway since we will have 142mm SIPs then 100mm Kingspan on the inner wall. In one respect it seems to be such a tiny bit of cold bridging that it's not worth the bother, but then also, if you add up the hundreds used across the whole house, it may actually add up to a worthwhile number. Anyone used these or have any thoughts on the value of using them ?

Hi Glen, you don't need thermally efficient wall ties outside a SIPs wall because the cavity and the external face of the timber frame wall is the same temperature as the stone.
SIPs construction has too many cold bridges at the wall/floor, wall/roof junctions, where each panel meets and around the windows.

''How will you keep the 50mm gap clear with stone, it is hard enough with brick?''

Really hard if the stone is not clean-cut on the back face. I have just done significant remedial works to a timber-framed structure where the wall-builders did not ensure a clear cavity.

For the gap, I'm using recycled backed off stone so it's actually pretty smooth on the back face, and uniform enough in depth (but also random enough to look natural and fit in with the solid stone built properties in the area) to do this. It was a nice find... from a demolished girls school!

Point taken re no point in using lo u value ties in this context. Some money saved. Thanks guys.