Dear All,
I am analyzing a rectangular building with each and west
facades structured glazed and forming longer sides of rectangle and i
shaded these facades with louvers (shading device)
I compared the annual heat gains of two case1 building with no shading case
2 building with shading(louvers) what i found was there is considerable
reduction in annual solar gains in building but the annual external
conduction gains in building have increased after shading i am unable to
understand this.
Any one who can share his ideas on this.
Warm Regards
Sambhav Tiwari
Hi All,
Thanks for the reply this analysis was done in ies ve and the
external conduction gains are increasing with shading while solar gains are
reducing
i am sending the snapsort of the building with shading in east and west
Regards
Sambhav
The VE doesn?t model thermal bridging, so that isn?t it. What climate is your building in? What percentage glazing are the east and west walls? Are you losing heat through the envelope or gaining it? It could have to do with the shades blocking more sun from heating up the outside of the envelope on those walls, which then changes the delta T and resulting conduction gain.
Cory Duggin, EI, LEED AP BD+C
Associate/Energy Engineer
TLC Engineering for Architecture
direct:
615-346-1939
Hi Sambhav,
Yeah - I'd agree with Cory - you probably have a higher glazing surface
temperature with the unshaded model and I wouldn't be surprised if that is
part of the conduction equation, meaning you are less likely to gain heat
through conduction if the glazing is in full sun.
cheers,
Andrew
Hi Sambhav,
You can send any question into support at iesve.com if you?re looking for help with understanding this. They?ll be able to take a detailed look at your model and help you set the model up correctly for what you?re trying to study.
Assuming you?ve modelled the shades as local shade and not a room, then you won?t see any impact of a ?thermal bridge?. However, if you modelled the shades (fins) as rooms, then you would see a ?thermal bridge? ? especially since the default construction that would be assigned the point where the two ?rooms? meet would be an interior partition made up of nothing but two pieces of gypsum board with an air gap between then.
This question has come up recently with regard to a project that has many non-thermally broken vertical fins in CZ6.
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Sambhav,
What do you mean when you say that the conduction gains have increased?
Do you mean that there's less conduction heat flow entering the
building, or more ? If it's the former, that makes a lot of sense,
since the shading is cutting off solar gain on the wall/window, thus
lowering its surface temperature (or more exactly, sol-air temperature)
and reducing heat flow into the building. If it's the latter, that
would be problematic, since I don't see how reducing solar gain would
increase conduction heat flow entering the building.
Joe
Joe Huang
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