Usually different building codes (BCA in Australia, as an example)
define windows as 'a device which transmits natural light directly from
the outside'. If you have an 'opaque' system this probably can not be
treated as a 'window'.
SHGC is '0' for any non-transparent/non-translucent systems including
'opaque windows'.
Strictly speaking, every construction (window or wall) has a non-zero SHGC. A portion of absorbed solar radiation will ultimately end up inside a space (via conduction through the surface and later radiation/convection into the space). A highly insulated wall will transmit a negligible amount of energy. The ASHRAE Handbook of Fundamentals (Fenestration chapter) provides a method for calculating the SHGC of window frames.
For your opaque windows, the transmittance may be zero, but the SHGC > 0. The magnitude will depend on the construction of the "window"; with higher U-values leading to a higher SHGC.
Why not use LBNL Window software to calculate it? I ran the following tests with opaque glass and clear glass. Here are the results:Plain opaque glass: SHGC = 0.31Opaque outside, air, Clear inside: SHGC = 0.16Clear outside, air, Opaque inside: SHGC = 0.5
Liam O'BrienAssistant ProfessorCarleton University
Date: Wed, 29 Feb 2012 19:11:02 -0500
From: energy.wwind at cox.net
To: bldg-sim at lists.onebuilding.org
Subject: Re: [Bldg-sim] "Opaque" windows
It depends which surface is black........ S1 (outside) clear
>>> normal reflected / transmitted fractions....etc.
Hi Robert,
If it's an opaque window, can't it be
described as a construction/wall material? Why still define it
as a window?
If you do decide to use WINDOW 6 to generate the SHGC, you can export an
Energy Plus input "snippet" in IDF format from the Window Library, Reports
button. Make the glazing system, then create a window using that glazing
system, and then you can generate the E+ IDF file for that window / glazing
system / frame system.
Hi Robert,
If it's an opaque window, can't it be described as a construction/wall material? Why still define it as a window?
Alex Krickx, LEED AP
Hi Robert
Usually different building codes (BCA in Australia, as an example)
define windows as 'a device which transmits natural light directly from
the outside'. If you have an 'opaque' system this probably can not be
treated as a 'window'.
SHGC is '0' for any non-transparent/non-translucent systems including
'opaque windows'.
Cheers
Sergey Zhukovskiy
It depends which surface is black........ S1 (outside) clear >>>
normal reflected / transmitted fractions....etc.
Strictly speaking, every construction (window or wall) has a non-zero SHGC. A portion of absorbed solar radiation will ultimately end up inside a space (via conduction through the surface and later radiation/convection into the space). A highly insulated wall will transmit a negligible amount of energy. The ASHRAE Handbook of Fundamentals (Fenestration chapter) provides a method for calculating the SHGC of window frames.
For your opaque windows, the transmittance may be zero, but the SHGC > 0. The magnitude will depend on the construction of the "window"; with higher U-values leading to a higher SHGC.
Why not use LBNL Window software to calculate it? I ran the following tests with opaque glass and clear glass. Here are the results:Plain opaque glass: SHGC = 0.31Opaque outside, air, Clear inside: SHGC = 0.16Clear outside, air, Opaque inside: SHGC = 0.5
Liam O'BrienAssistant ProfessorCarleton University
Date: Wed, 29 Feb 2012 19:11:02 -0500
From: energy.wwind at cox.net
To: bldg-sim at lists.onebuilding.org
Subject: Re: [Bldg-sim] "Opaque" windows
It depends which surface is black........ S1 (outside) clear
>>> normal reflected / transmitted fractions....etc.
Hi Robert,
If it's an opaque window, can't it be
described as a construction/wall material? Why still define it
as a window?
Alex Krickx, LEED AP
If you do decide to use WINDOW 6 to generate the SHGC, you can export an
Energy Plus input "snippet" in IDF format from the Window Library, Reports
button. Make the glazing system, then create a window using that glazing
system, and then you can generate the E+ IDF file for that window / glazing
system / frame system.
Robin Mitchell