Multistory Slab Edge Thermal Bridges

Questions, comments and suggestions about the Design Navigator R-value calculator

Multistory Slab Edge Thermal Bridges

Postby smcisaac » Thu Mar 02, 2017 2:52 pm

Confirming what I already believe to be true:

This NZS4214 calculation that the DN is following does not consider the effects of the uninsulated concrete slab at each floor in a multistory building does it? Steel frame wall with batt insulation between, batt insulation is interrupted at each floor by a concrete slab.

Is there any guidance for whether this slab edge thermal bridging should or shouldn't be included as it pertains to compliance with H1AS1 (NZS4218). In reality it should, but if there is a line somewhere in the standard that allows you to ignore this I'd love someone to point it out.
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Re: Multistory Slab Edge Thermal Bridges

Postby Albrecht Stoecklein » Thu Mar 02, 2017 4:30 pm

Hi smcisaac,

Yes, correct, the DesNav calculator basically assumes that around these slab perimeters there is the same insulation material as in the walls themselves.

If there isn't the thermal bridge created by the midfloor slab edges along the walls is ignored unless you specify these sections in DesNav as a separate wall type which is as high as the perimeter height.

There are a few of these types of details that are usually ignored, for exmaple the effects of additional framing timber around doors and windows.

I don't think there is a specific reference to the issue in the Standards or the Code.

I do believe that the heatlosses through these edges could be quite significant, but I guess it is technically not that easy (cheap) to insulate them. Insulating around the edges of slab on ground has similar challenges and we are only in the last few years seeing an awareness and some commercial products to address this. It can be done, but would require a different design approach and a willingness to pay for the additional costs by the developers.

Sunny regards

Albrecht Stoecklein
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Re: Multistory Slab Edge Thermal Bridges

Postby SullyOrlando » Thu Dec 06, 2018 9:59 pm

There are a few of these types of details that are usually ignored, for exmaple the e

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