Ever since my living room double-pane window got foggy, I've noticed that I feel very uncomfortable/sick when it is a very sunny day (similar to the way I feel when I've been out for too long in the sun on a super hot summer day).

If I close my blackout curtains (which aren't the highest quality) I still feel pretty sick. They don't seem to be of much help.

If I move to another room (that faces the opposite direction of where the sun is shining) I feel better after a few minutes. For example, if this were my house, my movement would be from the Bed1 to the Lounge (in my house Bed1 is my living room and Lounge is my kitchen).

After the sun is set or is fairly low, or when it is on the other side of the house in the morning, the room is comfortable and I have no issues there.

Additionally, this problem used to only happen in the summer, but since my backyard neighbour cut a tree on his side (which used to partially block the sun coming in my window) it has been happening in the fall too. Even with the temperatures going down right now (fall), I am still feeling sick when the afternoon sun is at its strongest against the window.

The wall right in front of the window and the one parallel to it are mainly blank white walls (we haven't had the time or $ to decorate yet), which I think could be part of the problem.

The window is quite big, about 3 ft X 4 ft. And I would say 75% of it is now constantly (24/7 year-round) foggy or filled with water drops (we've asked the landlord to replace the window, but they are taking their sweet time).

I work from home, so I spend practically the whole day in this room. I don't feel uncomfortable immediately after the sun appears on the west side of the house (in the afternoon), but after a couple of hours (around 3 PM, when it is more or less at its strongest against the window) it starts happening.

From the answers in this related question and this one, it seems possible that the UV rays might be getting amplified by the water drops + the double panel + the white walls. Am I correct in making these assumptions? Or am I just going crazy?

Additionally, is there a way for me to objectively measure the UV index inside a room? (preferably using a free app on my phone, or some other free/cheap method)

Any help or ideas are appreciated!

  • $\begingroup$ No, it isn’t amplifying any UV. The glass keeps absorbing most of it. It isn’t insulating as well, which may impact your living quarters in other ways. $\endgroup$
    – Jon Custer
    Oct 11, 2019 at 0:09

2 Answers 2


The water droplets that make up the fog scatter the light that would otherwise have passed through the window without deflecting.

If they had passed through undeflected they likely would have hit the floor or some other not-particularly-reflective object and more than likely been absorbed.

Therefore, assuming you are in a position facing the window but out of direct sunlight, the window droplets cause more light to enter your eye: they scatter rays coming from the sun into your eye, which more than makes up for the bit of light that would have hit your pupil that gets scattered away.

Most of the extra light is not UV: as others have pointed out, most of that doesn’t make it through the glass. But the extra light you’re getting in the visible range could be what’s bothering you.


Jon Custer is right, but to put your mind at ease here is a quick and simple way to compare the UV exposure coming into the room through the window against that striking the outside of the window.

There is a thing called a UV Dosimetry Tag (google it) which is a paper sticker with a UV sensitive chemical on one side of it which starts out a pale yellow color and progressively changes to dark green as it accumulates UV exposure. The back side is sticky which allows you to peel it off the master sheet and attach it to any convenient surface. Each master sheet has dozens of individual stickers on it and costs less than $20.

If you place one of these out in the sun for, say, one hour on a piece of cardboard that you set in front of the window, it will begin turning green. You then take it indoors and store it away from light.

Then you place a sticker indoors facing the window for an hour at the same time of day, and let it turn green.

Then you compare how green these two tags are. The darker green one is the one that got more UV exposure.

By making a graduated set of greened tags which were exposed to 30 minutes, 60 minutes, 90 minutes, ... of time outdoors, you can then determine (for example) that sitting inside your room for one hour gives you the same UV dose as sitting outside in the sun for 10 minutes.

The tags are quite sensitive to fluorescent lights indoors, so be sure to store all the tags away from light.


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