Daylight analysis - inter-reflection

Luana,

You need to consider both in regards to daylight simulations. There are alot of items that you should consider when performing daylight simulation to ensure the results are as close as possible to the actual performance.

1.Include adjacent structures, especially ones that will shade a facade or produce reflections. These surfaces should have at least a reflectance. Include the ground and even dense vegetation.

2.Interior surfaces, at minimum, floors, walls, and ceilings should be either have the actual reflectance or a default of 30, 60-70, and 80.

3.Permanently mounted partitions should be inlcuded in your model. Furniture is not required for LEED, but we sometimes include when we know what has been specified. My biggest issue with furniture, especially desks and cubicles is to ensure the specified colors maintain a good contrast ratio.

Todd,
Is it correct that in case of an adjacent wall with openings in it, we can not use the prescriptive method. Or could we calculate the % of wall openings and apply that % to window surface?

Emmanuel,
Are you talking about an adjacent exterior wall with openings in it next to the window? Or, are you talking about an adjacent space inside a building, which does not have an exterior wall.

Case 1, I would need to see more. How far away is the wall, height, etc. etc. With the prescriptive method, its about access to the sky vault.

Case 2. The prescriptive method cannot be used for spaces with shared daylighting scenarios. This is only for spaces that are separated by another layer of glass. The prescriptive calculation cannot determine compliant percentage through multiple layers of glass. Now if the space adjacent to the perimeter space is separated by a wall with just openings with no glass, and it falls within daylight zone, then some of that space's square footage could be considered in the calculations. Again, without really seeing more of the situation, i could not reliable say it could or how much could actually be considered.

I hope i answered what you were looking for.

30% reflectance is generally hard to achieve with flooring that doesn't show dirt. Traditionally, 20% has been used as a default reflectance for floors, but I've heard that in actuality, most flooring is in the 10-20% range. 70% for walls is achievable, but for me, I'd rather use a more conservative number of 50% and be surprised in a good way when the actual numbers are known.

I can't think of a situation using the prescriptive method where any adjacent wall, interior or exterior could be used. You'll have to describe your situation more accurately.

Todd,
It is an outside wall but it is next to the window. So really, only the openings of the wall let light through and we were thinking to take the openings in the wall as transparent area.

Is it like a brise soleil scenario or is this wall part of another building? If the wall is not part of this building, then it can be ignored with the prescriptive method.

How are you determining the depth of your daylight zone? Are you using the 63 degree angles from the top edge of the opening in the exterior wall?

If the wall is right up against the window and part of the building, and these are larger openings, then their "might" be an argument to using the prescriptive method. But, without really seeing what you got, i can;t say for sure.

If your not wanting to use simulations, might be best to take measurements at the end of construction instead of trying to deal with this type of scenario and have it denied in the review.

From what you are saying, it looks like the prescriptive method is going to be a challenge. The wall is part of the building. We have a large window area on the ground floor (floor to ceiling window) and there is a wall at more or less half a meter from that window. But the wall is sort of like a chess board with the white squares open and the black squares closed. We wanted to use the surface of the openings, but since it is a thick wall and if we use the 63 degree angle from the top outside edge, that would reduce the opening substantially. But I get your point and I guess in the end we will simulate ...

Correct. This is not a situation that can be submitted via the prescriptive option.