Asked on Jun 20, 2012

What is this mysterious blue powder that keeps collecting on the inside of our window and sill?

Erica F
by Erica F
Our home was built in 1989 and all of the windows are original. We purchased the house in 2010 and it had the original builder grade trim on all the windows and sills. This window was a little cruddy on the inside when we bought the house, but we chalked it up to the fact that the house sat vacant for several months after foreclosure. But we had the trim replaced and it is a custom made casement. We're stumped as to the source and the identity of this mysterious blue powder. We've simply been vacuuming it up and wiping the window to remove it periodically.
We have noticed this blue fluff on the latch and above.
You can see whatever this stuff is, how it collects in drifts on the inside. We have not seen this stuff on the outside of the windows.
The window, sill and apron before we made any changes [aside from the painting]. :)
Exterior of the house, window in question...
This is the side of the window that shows the largest concentration of the "blue stuff" mostly in the corner [not seen in this shot], but is even visible to the edge of the sill.
Another view of the left corner.
View on the left side of the window of the piece that is broken [prevents the window from staying up without being propped - newer version of a sash weight?]. You can see it is out of its track or case and leaning out toward the right
Another view of this same piece that is broken.
  26 answers
  • Walter Reeves Walter Reeves on Jun 20, 2012
    Very strange! Does the powder dissolve in water or not? Are there any holes from which it could be dropping?
  • Erica F Erica F on Jun 20, 2012
    Hi Walter, no we haven't noticed any water leaks or anything like that....and we have wondered if it is some kind of insulation. The wierd thing is - we didn't see anything that looked like that substance when we removed the old window frame trim. Before we did anything to it - the window opening was sheetrocked and only had a sill plate and apron trim underneath it. My dad built the new interior sill and frame as one piece that slid into the window opening and it butts all the way up to the glass. So there are no openings in the trim. We may just end up having to caulk around the window where the trim and window unit meet. But again we don't know the source of this substance. The only thing near the window on the outside is a large rhodedendron and haven't seen anything like this powder on the outside of the house or the foliage of that plant.
  • KMS Woodworks KMS Woodworks on Jun 20, 2012
    When I first saw this I thought that is might be sawdust from some type of burrowing insect larvae. The only building material I can think of that is blue is the blue rigid foam insulation. ( this is the Dow product, the Owens Corning stuff is pink) I have known of some termite type activity that will burrow through other materials to get to the "food". I you scoop up some of this, take it out side and place it on a concrete surface and lite a match to it, if it "melts" and has a plastic kind of smell then it most likely is residue of the blue foam insulation...if that is the case then you have some type of bug eating through your house...time to call in a exterminator.
  • Erica F Erica F on Jun 20, 2012
    Thanks - we will try that when we get home this evening.
  • I was thinking the same as KMS. It could be the insulation on the outside of the house, but then how is it getting inside? Check to see if you have any ants or carpenter bees flying around. These critters will bore into the foam causing this sawdust type of result. This also can be from foam in the walls being destroyed by insects as well. Lastly. During the construction phase of the house, lots of cutting, drilling and banging goes on. This foam type product that you see may be the result of those actions when the house was constructed. As the house ages gaps begin to form around windows and doors due to settlement and poor construction practices. If that is the case, what your seeing is these particles falling out from within the wall area. Check the quality of the sealants around the window frame and trims. Did you drill any holes to hang blinds? Does it appear to be coming out of the corners of the top of the window frame? Sometimes there are small openings in that area where stuff like this can fall out. FYI the windows were constructed in 1988. February for that matter. :)
  • Erica F Erica F on Jun 20, 2012
    Thanks KMS Woodworks & Woodbridge Environmental - we will be taking a closer look at this when we return home this evening. My husband also wondered if the substance could be coming from within the actual window. There is a channel on either side of the window and I'm not sure how to describe it other than there is a piece that helps prop the window up when it is open where a spring or some other integral part has broken on the left side and that piece is visible. I could take a photo of it this evening and add tomorrow for review. @Woodbridge - since you brought up the manufacture date for the windows - could you tell me a bit more about them? All I know is that they are double paned glass with a decorative piece sandwiched in between them to simulate the appearance of a traditional multi-paned window.
  • Bernice H Bernice H on Jun 20, 2012
    Erica, i also am curious...sounds intriguing! Let us know about the match test!
  • Marg C Marg C on Jun 21, 2012
    this is quite the mystery and I'd also love to know what's making that happen. It does resemble tiny bits of insulation and that was my first thought. And I wonder if you have pests that are bringing it in but then again it does look like it's coming from the corner.....
  • Marge most windows have openings in the corners to allow for the balance strings to operate. This observance of the foam is right on. I too saw the piles more near the corners as well. Thinking it was coming from these tiny holes at the top of the window. I doubt its coming from outside however. Unless there is no screen and the window has been left open.
  • Therese C Therese C on Jun 21, 2012
    Marge I too, have had this problem. The first thing that was ask of me is this; are the windows newly installed or more than 2 years old? answer: more like 75 years old. So we found out that there was indeed an insect population burrowing around. The exterminator drilled many fascinating holes in my walls and the piling stopped. If it had been new windows it would have been assumed to be very new insect activity (not so many fascinating holes) or improperly installed windows allowing gaps. Good luck...dagnabit I missed doing the match thingy!
  • Therese C Therese C on Jun 21, 2012
    Oh and the stuff coming out of mine was a horrible murky yellow-ish color and felt like strange sand.
  • Erica F Erica F on Jun 21, 2012
    Ok folks....I am going to add some more photos. The residue did not dissolve in water and it did melt when exposed to flame....however, it did not give off a burned plastic smell - according to my husband. I took some more photos from both inside and outside of the house. I apologize, but the inside ones are not as good [due to poor lighting] as they were previously. Of course at the thought of possibly dealing with some sort of infestation - I did a little research online. The exterior of the house does not show any evidence of mud tubes where termites might be present. Although I realize this is not the only indicator for those specific pests and there are also other undesirables that may be to blame instead. Our house is on a slab foundation with cinder block wall for the first level of the house. The way the house is built, the first floor is considered a basement since the back portion of the house is below grade. It is built into the side of a hill, with the front entry being grade level. There is a faux stone facade over the block on the first level and wood siding on the second level. My husband also wanted to add that when he removed the old sill plate and apron, he also removed portions of the sheetrock around the opening because it was a little uneven [the new sill/casement was built as a single unit and slid into the opening] and and took it back to the studs and didn't see any of what we're seeing now or any damage to the studs. That's why he was wondering if possibly the "blue stuff" is coming out of the piece on the left side of the window that is broken. Hopefully, the pictures will illustrate the piece that I'm trying to describe. While there is residue on the inside of the window, it is concentrated on the left side. Also like to note - it is rare that we have opened the windows. We live in an area that seems to have higher than usuall pollen counts during the more temperature friendly months and I have allergies and asthma, so we generally do not leave windows open for comfort.
    • Creig Steven Flatley Creig Steven Flatley on Apr 14, 2018

      Funny I too have had a blue powder or dust on a side window and the front door window ... Also on the wood were my exhaust for my gas stove goes tbru the cupboards in the kitchen .. And I just bought a molecule air purifier and the outside the silver capsule seems to have that same blue dust on it ? but the air purifier is in the a cornor of the room ???

  • Termites would not be the insect that would cause this. It would be ants. So that is what you would be looking for. Being on a slab of sorts, you need to check carefully along the outside foundation for access areas in which they may be coming and going. The window you have is metal? or so it appears from the first photo that you provided. My guess is that its insulation either from a foam from window sealant, or within the wall cavity. I doubt your seeing any foam partials from any insulation under the sheathing outside of the home. Will wait for additional photos to be taken.
  • The more I look at this the more I think its insects in the wall cavity. I am very familiar with these low end windows you have in the house. The metal sash balances were incorrectly designed and the window manufacture was sued on a class action basis because of the failure of many of their windows such as this. My thinking is that when they were installed the contractor used blue window and door foam that comes out of a can. Something is eating at it and the openings where the sash connects is where its coming out of. It could be coming from a loose trim board inside, but i think based on the stuff on the top of the lower sash its coming in from the upper corners of the windows. Is there any holes or openings in that area of the window?
  • KMS Woodworks KMS Woodworks on Jun 22, 2012
    I pretty sure we have ID'd the stuff as residue from some foam is the critter that is eating it ( or more precisely burrowing through it) ...I'm also thinking some type of ant.
  • Marg C Marg C on Jun 23, 2012
    I was thinking carpenter ants. That was my feeling from the start. Any updates on finding out?
  • My Opinion is that the house has blue foam polystyrene insulation board under the siding and carpenter ants are burrowing through it to make their home
  • Bernice H Bernice H on Jul 08, 2012
    Has there been any follow up on this mystery? I am still curious to know what has happened here.
  • Erica F Erica F on Aug 20, 2012
    Sorry folks...long time, no response. Haven't checked back lately and partly from my own embarrassment. The mystery critters causing the problem WERE indeed ants. They were very tiny ants...little pieces of ant body parts started appearing in the blue fluff in the windowsill along with dead and dying ants after spraying around the area and the source trail we found on the front porch column. Mystery solved! Thanks to all who offered their comments & suggestions. :)
  • Bernice H Bernice H on Aug 20, 2012
    Eureka!!! I love it when a mystery is solved!!!! Thanks for replying back, we like to know the results of our friends situations.
    • Irene Irene on Oct 06, 2013
      @Bernice H Hi Bernice, Gosh this is an old one 2012. This is the first time i've seen this one. Very interesting about the ants. I see that Erica lives in Va. each state seems to have different buggy problems. I hope things are going well for you. Wa. makes me think of all the wonderful apples. Fourty some years ago a man came to the door selling boxes of apples from Wa. They were so delicious. My kids couldn't get enough of them and I ate my share too.
  • KMS Woodworks KMS Woodworks on Aug 21, 2012
    glad to hear the mystery was solved...teamwork wins again.
  • Marg C Marg C on Aug 21, 2012
    yes! thanks for letting us know! so not carpenter ants but those small ants? strange, right?
  • Even small ants can be the carpenter ant variety
  • Marg C Marg C on Aug 22, 2012
    wow, learn something new every day.
  • Judy Ellison Judy Ellison on Apr 05, 2014
    That was a good one.
  • Katherine Katherine on Nov 23, 2017

    You might want to get a second opinion if anything but the color of residue is bothering you. This was behind my fridge and is presumed to be termites and my family's clothes have been drastically "eaten". To where you can see the bug/bugs moving when still bite holes as well as other fabrics. If anyone has answers on this please help. Glad you're problem was solved.