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Any factor which affect to heat gain from window?

asked 2021-08-17 07:45:31 -0500

katsuya.obara gravatar image

updated 2021-08-17 11:53:08 -0500

I was doing shoe box study with rectangle plan for 4 floors.
I set same window to wall ratio(40%) and same window setting without any shading and surrounding building which affect to window heat gain.
However when I check the result, higher floor get more heat gain compared to lower floor.
I wonder are there any factor which affect to heat gain from window other than following parameter. Could anyone help?

  • Window Area
  • Window Specification (Solar Heat Gain Coefficient)
  • Shading

Result (Higher floor got more heat gain from window)
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Window Input Information
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answered 2021-08-17 14:49:11 -0500

saeranv gravatar image

updated 2021-08-17 18:11:29 -0500

Yeah, there's two I can think of. The outdoor air temperature used for surface conduction and convection calculations is modified to account for the air temperature gradient with respect to height (-0.0065 K/m)[1]. Similarily the local wind speed is modified to account for increase in wind speed with height[2].

Both of these then impact surface convection[3], either directly (outdoor air temperature) or indirectly (wind speed used in derivation of heat transfer coefficient). So your interior and exterior surface temperatures will vary, and impact your surface conduction/convection rates, and the long-wave radiation absorbed by the interior surfaces and masses. Both your opaque and window surfaces are impacted, but of course the higher U-value of the window means it'll have a much higher magnitude of heat transfer then opaque surfaces, and thus illustrate a higher energy variance along its height.

EDIT One thing I can't figure out is why exactly it results in heat gain at higher levels. What climate are you in? My guess is if you're in a cooling-dominated climate, then the higher convective heat transfer alone could drive the heat gain. I'm not certain, and would be curious if anyone else has better insight.

  1. Local Outdoor Air Temperature Calculation.
  2. Local Wind Speed Calculation.
  3. Outdoor/Exterior Convection.
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Asked: 2021-08-17 07:45:31 -0500

Seen: 37 times

Last updated: Aug 17