Calc. U-value wall of composite wall with its own frame

[Anonymous]

Hi guys,

I'm struggling in out office with calculating the U-Value of the wall that has a framing, like here:



How to calculate it or actually how to approach it? I did the composite wall but for BIM model it is enough that we are putting the columns (and beams) in the insulation layer. The problem is that Energy Model Review tool doesn't count it at all 😕 (like the whole wall was done only from this composite wall that doesn't have any structure).

Please help,

Cheers,

Zbieraj

[Anonymous]

Hi, look at standard ISO 13788:2012 and related info. And it is important, what must be the result? Proper U-value used in calculation or proper U-value calculated by ArchiCAD? Technically you can take an average л-value for non-homogeneous layer. In case of timber stud wall (the most common wall type used in Skandinavia) the average persentage (building overall) of timber studs in wall layer is ~12%.
The calculation algorithm is:
R = Rsi + R(int finish) + R(non-homo)+ R(ext finish) + Rse
R(non-homo) is what you need to find. As an example we will take Construction timber л=0.13 W/mK, mineral wool л=0.04 W/mK
So the average л of non-homogeneous layer is 0,13*12%/100% + 0,04*88%/100% = 0,051 W/mK
If the layer thickness is 0,2 m the R(non-homo) will be 0,2/0,051=3.92 m2K/W

[gpowless]

This link: http://www.nrcan.gc.ca/energy/efficiency/housing/new-homes/energy-star/14176#a4 Natural Resources Canada

has a table that will provide various effective RSI-values (and R-values) for different assemblies depending on various insulation values and a number of different structural member spacings. Then the R.Eff can be added to the R-values of components that make up the assembly. ie.

[Anonymous]

I know how to calculate it manually and stuff 😉. I asked how to deal with in in ArchiCAD...

[Anonymous]

You can add thermal bridge value to each zone, which will compensate heat loss through the frames. Yes, the value is different for each room.
Or you can change the U-value manually for every wall in the model.