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problem with the command alt solar gain heavywt and lighttwt

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Message 1 of 3
gibbov
756 Views, 2 Replies

problem with the command alt solar gain heavywt and lighttwt

Hi,

i am an architectural student and i tried to create a new model with Ecotect. I would like to create and set up a new one windows but i have  a problem with the settings of the element library. i don't understand the setting : alt solar gain heavywt and lighttwt. what's that mean? where can I find the value of my new window? What show?

I know and i have find the value of the solar heat gain coeff but i dont understand these two new values(alt solar gain heavywt and lighttwt).


i have tried to create my window and it is made of 2 layers of standar glass 1 ari space and other 2 layers of standar glass.

Thanks

 

by G.B. Venturino

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Message 2 of 3
Pennetier1
in reply to: gibbov

Hello gibbov

 

The settings Alt Solar Gains / Heavy and Light can indeed have an effect on the amount of solar heat gained within the thermal zone.

Unfortunately, if these Alt factors are not provided by the glazing manufacturer, they can be difficult to estimate.

 

Ecotect has some material data in its help files that lists some of the Alt factors.

Windows Properties.jpg

 

Unfortunately, these do not help much for other type of glazing.

There are formulae out there to derive these numbers but require to know the short wave shading coefficient (SWSC & LWSC) of the window. 

See page 19 of this document for the formulae.  Note that I do not think these Alt. factor matter if no internal shading is expected.

Also, use Ecotect as a tool to assess one design over another; everything else being the same, you should be able to identify an optimum solution regardless of your Alt. numbers.

One last thing to keep in mind: when doing thermal calculations, keep the Transparency of the glazing to 1.0, and use the manufacurer's SHGC.  If you use both, Ecotect will multiply one by the other.  For example, if the Vt is 0.5 and the SHGC is 0.3, Ecotect will reduce the amount of solar gain to (0.5*0.3) = 0.15 of the solar gain hitting the window.  Reversely, when performing daylighting analyses, use the correct Vt and set SHGC to 1.0.

 

I hope this helps a bit.

Let me know if you have more questions on this topic, otherwise please accept as a solution so that others can benefit from this information.

Cheers,

Olivier A. PENNETIER

SYMPHYSIS

www.symphysis.net

Message 3 of 3
gibbov
in reply to: Pennetier1

thank you very much. you are so kind and you are answered a my problem.
by G.B.V

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