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how design builder calculates daylight?

asked 2018-06-14 07:31:55 -0500

andreea's avatar

updated 2018-06-14 09:25:59 -0500

I have to do a BREEAM daylighting report and i do not understant how daylighting is calculatet in design builder. The result of the program calculation is an average of natural light hours throughout the year, or does the report show the result of a day at a certain time that can be set to 'visualize'?image description

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answered 2018-07-20 01:46:07 -0500

Justyna's avatar

For BREEAM you take into account daylight factor. "A pass requires that both the following conditions are met: a) At least 80% of net lettable floor area in occupied spaces is adequately daylit, having an average daylight factor of at least 2.0% at the working plane height of 0.7m under a uniform CIE overcast design sky; b) A uniformity ratio of at least 0.3 or a minimum point daylight factor of 0.8% (spaces with glazed roofs, such as atria, must achieve a uniformity ratio of at least 0.0 or a minimum point daylight factor of at least 1.4%)."

Dalight factor not depends of a day. DF is a is the ratio of the light level inside a structure to the light level outside the structure (definition from Wikipedia ;) ) look here: Daylight factor take into account outdoor illuminance with overcast sky. So not the day is important, but the model of sky. :) I hope it's helpul for you.

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your explanation is really helpful! thank you very much!

andreea's avatar andreea  ( 2018-07-27 01:38:19 -0500 )edit

answered 2018-06-16 01:59:47 -0500

Dave's avatar

Firstly to clarify that the DesignBuilder daylighting tab switches to use the Radiance engine and uses the model data you've already input (perhaps for energy/thermal/comfort simulations using EnergyPlus) which includes shading, glazing and surface reflectance properties etc. necessary for daylighting calculations. Within the daylighting tab in the current version you have two options, one is the "traditional" daylight illuminance distribution method that reports static outputs at specified conditions for illuminance and daylight factors. The other is annual climate-based daylight calculations using the Daysim engine. Your question seems to relate to the "traditional" daylight illuminance distribution method. The Help file provides some information and also refers to the (free) online DesignBuilder daylighting tutorial so you should review that as your starting point.

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answered 2018-06-15 00:43:48 -0500

banicu's avatar

You are looking in the wrong place. For a daylingting calculation go the Daylighting tab (bottom right corner of your picture) and a window will pop-up with several types of calculations, including the BREEAM one.

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Thanks for the reply! I know the daylighting button is computing the breeam report, but my question was what time of day or day of the year is taking this report into account or if it calculates an average of all sunny days in the year. I do not understant its mathot of calculation and i read in the manual but i didnt find anything.

andreea's avatar andreea  ( 2018-06-15 01:54:07 -0500 )edit

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Asked: 2018-06-14 07:31:55 -0500

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Last updated: Jun 16 '18