Hi All

Wanted to get the opinion of an expert.

Attached is a photo of a customer's window.... as you can see there is a large cold spot above the window... Here's my opinion..am I right?

The large horizontal cold spot is thermal bridging from the double 2x6 or 8 top plate.

DO you agree?  The customer's pain was condensation on the windows.  WIndows were well installed with minimum leakage. The house was very tight, which I believe is the problem..not this.

Tags: ir, windows

Views: 567

Replies to This Discussion

Good start!   What is the direction of the wall?  Time of day?  Sun loading.  Delta T?  Is the Blower Door running or if it is after the Blower Door test, how long?



This wall is south, 11am, no to very little sun load ( Cleveland!!!), 35degree delta, blower door is running.

If you were 11 AM on a south wall, and there was no external shading (another building) then you had solar loading. 


I hate it when my images come out like this.  The focus point appears to be Finial on the Lamp.  That puts the wall out of focus.


I would agree the colder areas along the ceiling line are more to do with construction techniques and thermal bridging then they represent a problem you can deal with.  Is the wall insulated?  FG batts?  If so, it appears they may have pulled away, in the rounded corners, or perhaps are installed compressed, or out of contact with the drywall. This is harder because of the focus.


Let's see what the others have to say.

Hi Matthew,
Can you post the visible only image?  Can't tell if I'm looking at some sort of window treatment like curtains, or not.  Sure looks like a header to me.
Re: condensation on the windows - what kind of windows are they (single, double pane, storms)?  What was the temp outside and the humidity inside?
Where I live, when it gets cold (-30F), I'll see condensation on windows when the inside humidity gets above 30%.  I've seen people here using humidifiers to try to get the RH up to 50%.  The humidifier pumps it in and the cold windows take it out.  One guy had 1" of ice inside the home (aluminum frame single pane). 
Matthew.  Forgive me if you already know this.  Wood generally has an R factor of 1 per 1 inch of thickness.  So, the headers probably have an R value of something like 3 1/2 or 4.  And there is a lot of wood showing in your image resulting in thermal bridging.  Heat takes the path of least resistance going from hot to cold.  It leaves behind a 'lack of heat', which we call cold.  The window will be the path of least resistance leaving that area colder.  The next area of low resistance will be the framing/header areas in comparison to the fully insulated bays.  Condensation is a surface temperature related phenomena associated with dew point.  Air can hold a limited amount of moisture before it starts to condense.  100% RH at a certain temperature is dew point.  If the suface is at or below dew point condensation will occur.  Some families generate more moisture in the air (showers/cooking/etc) than other families.  And therefore they have more condensation. 
Matthew, any chance you can upload the .is2 file, or email it to me?
Sure will. I requested you as a friend so I can send. Would  not let me upload a is2 file.

Could you send me a copy of file with this pic as well?


Matthew, I never received the file... david at meiland dot com



Same image in the Ironbow palette....


My guess is that if you took off the drywall, you would find fiberglass batts jammed into the stud bays and not in contact with the drywall at the top. The double top plate is cold!


It's hard to tell from just the one pic - do you have a shot before the BD was run??

Since the BD was running, if it's the top floor or equivalent, I could make a case for no baffling and poor or no  alignment of the thermal envelope - in other words wind washing at the eaves all to heck and gone.

What does master J. Snell say?

Thanks for the "master" plug! I hope I can meet expectations. Jeezopeets! Anyway, it certainly appears to be a header. There may be an air space associated with it. Did you take other images before you depressurized with a blower door? That might help show you if it is just an uninsulated header or if there is also an air leakage pathway around it. There certainly seems to be air leakage along the top plate! What is the source of that? 


I'd suggest your saying "The house was very tight, which I believe is the problem" is actually not accurate. The house has humidity too high for the temperature conditions. Either reduce RH or increase window temperature to reduce condensation. I often see condensation in bedrooms (people like them cold) and sometimes there is no easy fix. It would not surprise me to hear there is staining or even mold on the wall along the cold top plate.


What is the RH? Anything between 30-50% is "normal," but if the bedroom is colder (it appears it is), RH will continue to increase there. I'd suggest you check for obvious sources of moisture—poorly vented dryer, bathroom vent fans, crawlspace with no ground cover, etc.—to see if moisture can be reduced at the source. If not, consider adding a continuous, low-velocity vent fan or heat exchanger.


One last thing, when you need to view your IR image, I'd suggest you not have picture-in-picture. Reformat it in the software so it is FULL IR and you'll often have an easier time seeing what is going on. Very easy to change it back and forth to other fusion modes. And, if I can be just a bit picky (:-)), work on sharpening focus/image freezing. So speaks The Master!



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