Green Building Forum - compacfoam.

compacfoam.

djh — Thu, 19 Oct 2017 20:43:47 +0100

Posted By: Doubting_ThomasI'd be interested to know people's opinions on the threaded bar - this is presumably necessary to tie it into the slab in case the insulation below deforms.

It needs to be stainless threaded rod, as stated in the Isoquick drawing, because of the thermal conductivity. I was going to say it stops the insulation moving sideways, but actually it won't unless it is glued into the compacfoam, since the compacfoam will just have to be pushed onto the end of it. But assuming it is glued, then it stops sideways movement, which also stops twisting. The load is transferred through the compacfoam onto the rebate in the slab that it is sitting on; there shouldn't be much load on the Isoquick insulation. An engineer should specify the diameter of the rod, perhaps the one who specified the slab? Or whoever prepared that drawing? I would guess something like 12 mm would be fine, but I'm not on the line if it falls apart!

compacfoam.

Doubting_Thomas — Fri, 20 Oct 2017 13:54:27 +0100

Thanks everyone for the replies. Particularly with my questionable maths!

Posted By: djhThe load is transferred through the compacfoam onto the rebate in the slab that it is sitting on; there shouldn't be much load on the Isoquick insulation.

djh,

I'm actually trying to sit the door onto the insulation layer as I was concerned about the potential cold bridge if it sat straight onto the concrete.

My detail below, it's a little unclear (as the section is cut through typical wall, not opening - plus it was drawn at A1), but you can see from the adjacent plan that the door line sits around 240mm out and the slab only extends to 175 beyond the same line. I'm intending to follow the Isoquick detail and recess the compacfoam into the Isoquick but still tie laterally into the concrete. Thanks for explaining why this is needed.

compacfoam.

Doubting_Thomas — Fri, 20 Oct 2017 13:56:38 +0100

*edited to add two separate drawings so they appear larger*

compacfoam.

djh — Sat, 21 Oct 2017 11:38:21 +0100

Posted By: Doubting_ThomasI'm actually trying to sit the door onto the insulation layer as I was concerned about the potential cold bridge if it sat straight onto the concrete.

In that case, you need to repeat the stress and strain calculation for the Isoquick insulation, and worry about stress concentrations at material junctions.

compacfoam.

goodevans — Sat, 21 Oct 2017 18:16:18 +0100

Here's an alternative low tech variant for your cill detail - don't be fooled by the thermal performance of stainless steel - yes it's 3 times better than regular steel - but its still more than 100 times worse than wood.

One 8mm diameter SS bolt lets as much heat through as much as 350mm length of 13mm ply. All the wood is on the warm and dry side of the build so it should not be a problem.

compacfoam.

TimSmall — Sun, 29 Oct 2017 20:20:58 +0000

Posted By: djh
It should be the width of the door times its thickness, 2.6 x 0.2 I presume = 0.52 mÂ². So the stress is 3413/0.52 = 6563 N/mÂ² or 0.0066 N/mmÂ², which is way less than the max working stress of 1.01 N/mmÂ².

It's perhaps a bit different with the lift+slide leaf. This typically sits on two bogies - one at each end of the door - increasing the stress at each end of the door. When slid fully open, nearly all the weight is going to be on one half of the door (since the opener is sitting "in front of", instead of "next to" the fixed glazing).

Perhaps that explains the apparent over-spec - concentrated stresses at the bottom of the threshold could reasonably be 20x the uniformly distributed load I think.

I decided to put nominal 600 kPa insulation under the slider portion of my lift+slide door (i.e. the inner 100mm), with the outer 100mm (fixed pane) requiring much less 150 kPa (e.g. standard PIR) being OK by my reckoning.

compacfoam.

TimSmall — Sun, 29 Oct 2017 20:21:45 +0000

This was useful for XPS long term creep etc. http://web.ornl.gov/sci/buildings/conf-archive/2004%20B9%20papers/046_Merkel.pdf

compacfoam.

djh — Sun, 29 Oct 2017 21:33:27 +0000

Posted By: TimSmallIt's perhaps a bit different with the lift+slide leaf. This typically sits on two bogies - one at each end of the door - increasing the stress at each end of the door. When slid fully open, nearly all the weight is going to be on one half of the door (since the opener is sitting "in front of", instead of "next to" the fixed glazing).

I take your point that the weight isn't evenly spread, particularly when the door is fully open, but I think the runners spread the weight fairly well.

Perhaps that explains the apparent over-spec - concentrated stresses at the bottom of the threshold could reasonably be 20x the uniformly distributed load I think

I'd be surprised if it was as much as 20x but the over-spec is getting on for 200x

compacfoam.

goodevans — Sun, 29 Oct 2017 23:52:54 +0000

btw if you are going for compactfoam - those bolts can be much smaller than 12mm - the only job these bolts are doing is to stop the foam toppling over the rc rebate. But put great big fat washers on them - tighten the nuts until you see deformation of the foam under the washer - and no more.