Any idea what this is and what caused it?

[Mike Krueger]

There is a hard clear film/coating on three of the seven windows on the East side of the home. ? The film is not between the panes of glass it’s on the basement side (interior side). ? These window are in a finished off basement. ? There is a mirror in this room with the same film on it (the bottom 1/3 of the mirror). ? There are white deposits at the base of the window that appears to be efflorescence (mineral deposit). ? Does anyone have an educated guess as to what could have caused this? ? This house has been empty for about 5 months.

[Michael A Clark]

Hi Mike. Could it be an installed film for privacy? Doesn't explain the bottom part of the mirror, but in this business I have developed an understanding.."I'm almost always amazed but never surprised at what people will do".. The efflorescence is probably caused from moisture on the glass in the empty house, especially if the utilities were off.

[Michael A Clark]

sorry Mike-I didn't see the pics before. The mirror seems to have deteriorating silica, it's just going bad. I can't tell from the window picture, maybe the film I described in my first post. The good news is from an inspection standpoint they are not defects but cosmetic.

[Mike Krueger]

Thanks Mike.

The house is only 6 years old. 

Sorry I didn't add the pics until after I posted the question.  For some reason it wouldn't take the post with the pics.

[Jeffrey R. Jonas]

Am I wrong, or is the "film" at the same height at the windows and the mirror? Where are you and this home located at? Vacant for the last 5 months... I suspect it is related to moisture not being controlled while vacant... condensation or elevated humidity, mixed with stratification (think frost pocket) of stale air (no circulation).

Just a WAG, but interesting.

(Don't forget... enter your location in your profile).

[Mike Krueger]

Thank you Jeff.  I live in Wisconsin.

No it's not at the same heighth. 

It's strange 7 windows in a row in the same room and only three have this.  The mirror is in that room too. 

[Jeffrey R. Jonas]

Anything seem to make it a pattern, such as someone spraying some bug killer, or mildecide. or etc...?

[Paul Baker]

Mike - There are after market films that can be installed on windows that some municipalities will accept to meet a "tempered glass" requirement. Look at the locations of the windows this is installed on, are they close to the floor, near a stairway etc. It may have been installed on the bathroom mirror for the same reason, just in case someone slipped and stuck out their hand to break their fall.

[Mike Krueger]

Due to the efflorescence I am thinking it had to do with moisture.  They buyer was there and was able to wash the residue off.  It has me puzzled.  I didn’t find any other evidence of elevated moisture, odor (other than what was in the pile of garbage bags) a small amount of surface mold in the bathroom around the ceiling fan but that was it. 

These windows and mirror are located in a family room with a wet bar no need for safety glass.

This one will remain a mystery. 

Thanks all for your ideas.