Hello,

When performing energy modeling to determine compliance with the Canadian
Energy Code (MNECB), penetrations through the building envelope must be
taken into account when calculating wall R-values if their area exceeds 2%
of envelope area. I'm working on a LEED project and trying to calculate the
wall R-value of a Hotel taking into account heat losses from the balconies
which are extensions of the floor slab (balcony penetrations exceed 2% of
envelope area).

I realize this is a rather complex heat transfer problem but hope there may
be an easy approximation. My first thought was to treat them like a
parallel path heat transfer problem: 1/Req = %slab/Rslab + %wall/Rwall but
I'm thinking that may not be fair (perhaps this would be used if you had
concrete studs in the wall). My other thought is to treat the slab
penetrations as a separate wall type (uninsulated concrete wall) - this
would have a reduced affect on the overall wall R-value.

Does anyone have thoughts on this?

Thanks,

Aaron Smith, P.Eng