Kathy,

We just recently began doing Sunlight Studies using our 3D and Virtual Reality Technology! We are able to make a VR model of the room(s) you'd like to observe, and show you the sunlight throughout the day. I have linked our website, where you can find more information that may be helpful to you! We work remotely all over the world, so don't worry about location! Give us a call if you have any questions!

Morgan Prock

715-210-5195

www.simonsondesignstudios.com

I never really thought about this before. Interesting question, so I googled and this is what I found:

For Natural Light

"A given room must have a window or glass door that is sized to equal at least ten percent of the floor area of the room. So, if a room is 10 feet wide x 12 feet long, then the room area would be 120 square feet and the minimum size of the window in that room would have to be12 square feet. A three foot by four foot window would provide 12 square feet of natural light to the room – again, the required minimum. Pretty simple really. For every 10 feet of floor area you need one foot of natural light area."

So, your bedroom is 144 sq ft. Your minimum size would be 14.4 sq feet. If the French door is 5’x8’= 40 sq ft, according to this article, you have lots of light and ventilation from that door. It also meet code egress.

Hope my math is correct. Have someone check it. LOL!

That is just a regurgitation of section R303 of the IRC.

https://codes.iccsafe.org/public/document/code/553/9807076

It does not take into account whether the window is tinted or Low-E, or if the occupant is 10 or 80 years old. I consider it a bare minimum with today's energy codes requiring Low-E glass that does not let in as much light. Of course, the code also says that you do not need natural light from a window if you have artificial light of 6 footcandles which is not that bright.

Fred S…what regurgitation?

It is a direct quote…don’t get upset, just give the OP YOUR expert opinion on whether French door will give enough natural light in the room. A simple yes or no might work.

A footcandle? You want Kat to work with that info? Times six?

Regurgitation - Your direct quote (not you) is just spewing out half digested information from another source - that does not take into account most of the criteria necessary to give even an educated guess. That is the bare minimum in the NEC and IRC, which I would not consider "enough" without supplemental artificial illumination for most tasks. 6 footcandles is also the bare minimum according to the same code. (Don't shoot the messenger) The code's goal is to swap out one thing for something that is roughly equal. I guess a person has to use their imagination to guess what 6 of those are. The math to convert that to bulb lumens in a light fixture is very complex, and has to include things like height of ceiling, the color of the walls, ceilings, floors, furniture, etc. If the room were bright white with no light loss, it would be roughly equal to one 864 lumen bulb, which is one of the old time 60 watt incandescent bulbs. It might be two bulbs in a darker room...or 30 times that (181.5Lumens/ft²) @ 5.5 feet away in a black hole ;).

My guess would be that a 40 sq ft window under trees would give about the same amount of light as a 14.4 - 18 sq ft window without trees.... depending on the time of day. There is not enough information to answer the relative nature of the question (low-e, 80yrs old, room color, tasks expected to be performed without additional light, etc)

Is the light equivalence of between 1 and 2 60watt or 860lumen bulbs "enough"? For what? In my professional opinion, it would probably not be enough for a woman to pick out and put on clothes, but it would be enough for me to get them off.