Question-and-Answer Resource for the Building Energy Modeling Community
Get s tarted with the Help page
Ask Your Question
2

Any factor which affect to heat gain from window?

asked 2021-08-17 07:45:31 -0600

katsuya.obara gravatar image

updated 2021-08-17 11:53:08 -0600

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)
image description

Window Input Information
image description

edit retag flag offensive close merge delete

1 Answer

Sort by ยป oldest newest most voted
2

answered 2021-08-17 14:49:11 -0600

saeranv gravatar image

updated 2021-08-17 18:11:29 -0600

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. https://bigladdersoftware.com/epx/doc...
  2. Local Wind Speed Calculation. https://bigladdersoftware.com/epx/doc...
  3. Outdoor/Exterior Convection. https://bigladdersoftware.com/epx/doc...
edit flag offensive delete link more

Your Answer

Please start posting anonymously - your entry will be published after you log in or create a new account.

Add Answer

 

Question Tools

2 followers

Stats

Asked: 2021-08-17 07:45:31 -0600

Seen: 45 times

Last updated: Aug 17