Thermal bridges

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Dear all,

I am a student from Switzerland, studying building physics and I would like to ask you how LEED takes into account the thermal bridges.
Are there specific values for the linear thermal transmittance, like Passivhaus?

I would really appreciate if somebody can answer to my question.

I would like to thank you in advance,

Best regards,

Kyriaki Goulouti

Goulouti Kyriaki's picture
Joined: 2012-11-26
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LEED is no more specific than ASHRAE 90.1, which is not very specific on thermal bridges other than those occurring in the assembly (studs, cladding attachments, etc). It is not specific about thermal bridges such as slabs, shelf angles, parapets, etc.

Aside from LEED, standard linear transmittance values are available for common North American details, as per ASHRAE 1365-RP. Our company authored the report, which can be found here:

http://www.morrisonhershfield.com/ashrae1365research/Pages/Insights-Publications.aspx

Christian Cianfrone, M.A.Sc., P.Eng., LEED(r) AP BD+C

Christian Cianfrone's picture
Joined: 2012-11-26
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The 90.1 user's manual briefly touches on modeling uninsulated and minor
uninsulated assemblies; here are some snipets from the section that
describes modeling for PRM:

/All uninsulated assemblies shall be explicitly modeled. Examples
include projecting balconies, perimeter edges of intermediate floor
slabs, concrete floor beams over parking garages.//All//
//uninsulated assemblies shall be separately modeled using a separate
description of each of these assemblies within the energy simulation
model, or the area-weighted average U-factor based on separate
calculation of the U-factor for each of these assemblies. The latter
approach may only be used for assemblies with similar thermal mass/
...
/Provided that these assemblies are insulated, the method allows any
envelope assembly that covers less than 5% of the total area of a given
assembly type (e.g., exterior walls or roofs) to be added to an adjacent
assembly of the same type with the same orientation and the same thermal
properties. This is not intended, however to allow framing members in
walls to be ignored just because they have an area less than 5%./

There are some graphics that help illustrate the recommendations.

- David

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Joined: 2012-03-30
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