Condensation on Curtain Wall

[moderne]

    Anyone have any experience with glass and steel curtain walls and cold weather condensation? 

[schugg]

heat on too high?

[aknowledgeableperson]

air circulation?

[nota]

Too much heat/humidity in the room, too little insulation in the walls/windows.

Turn down the heat a bit and run a fan. Keep the curtains open if you can.

[moderne]

        Does not seem to matter how high or low the heat is.  The humidity is down to 35%.  The window glass is R-17, but he aluminum framing is somewhat colder to the touch and the condensation forms around the bottoms of the frames.  There are no exterior walls to be insulated, but the interior walls do have insulation for soundproofing.  I am wondering if this is common with glass curtain walls in office bldgs also?

[jsoto3]

         Does not seem to matter how high or low the heat is.  The humidity is down to 35%.  The window glass is R-17, but he aluminum framing is somewhat colder to the touch and the condensation forms around the bottoms of the frames.  There are no exterior walls to be insulated, but the interior walls do have insulation for soundproofing.  I am wondering if this is common with glass curtain walls in office bldgs also?

It depends on the detailing of the frames.  They must be "thermally broken" (usually with a rubber gasket that splits the frame in two pieces interior-to-exterior) in order to prevent this problem, otherwise enough heat is lost through the frame such that it becomes cold enough on the inside to cause "sweating".

[moderne]

Windows here do have that rubber gasket separating glass from frames.

[Long]

Windows here do have that rubber gasket separating glass from frames.

I think the frame itself has to be separated into two pieces.  Otherwise, the frame, as one piece of metal, conducts the cold air from the outside all the way inside.  (That might not be the technically correct description from a scientific standpoint, but you get the idea).  In a properly detailed system, the two pieces of glass and two pieces of frame are separated by air space, with air being the "insulation." 

[Steve52]

        Does not seem to matter how high or low the heat is.  The humidity is down to 35%.  The window glass is R-17, but he aluminum framing is somewhat colder to the touch and the condensation forms around the bottoms of the frames.  There are no exterior walls to be insulated, but the interior walls do have insulation for soundproofing.  I am wondering if this is common with glass curtain walls in office bldgs also?

Aluminum frames are the culprit. Wood window frames insulate better. But they are not perfect unless they framing around the windows has been SUPER insulated and sealed.  Likely what is happening is the Aluminum frames are just very cold from the exterior temp extremes and transferring that cold throughout the entire frame. That's why the frames feel cold to touch on the inside during extreme temps.

Unless you have a serious problem like Ice Build Up you may have to live with a little condensation during sub freezing cold spells from time to time.  It's not uncommon.  One other thing might be  shrinkage of the sealants and or caulking on the exterior of the frame which is allowing a bit of cold air to seep through into the base of the window framing. If you want to see if you have any drafts coming in anywhere around those frames you can take a stick of incense and go around the frame and you will see the smoke react to any leakage.

If you do it's coming from the outside but caulking on the inside won't prevent cold air coming in and finding an alternative route into your sill. And it won't cure Aluminum frame freeze. We push our humidifier hard during the winter but it still produces about 35% Humidity when the heater is really working hard.  And still get a little condensation from time to time.

It is really HARD and expensive to air tight seal an older structure or building.

[jsoto3]

See attached "thermally broken curtain wall" diagram (produced for a KC project):



This represents the temperature gradient experienced in extreme winter conditions .  Note that the "Rubber Thermal Isolator" splits the window frame into two pieces to prevent direct thermal conduction from interior to exterior and vice-versa.  The "Glazing Gasket" separates the glass from the frame, more or less doing the same thing as the rubber thermal isolator.  Based on the engineering analysis for which this graphic was produced, any surface of the window assembly which is 44.7 degrees (the dew point) or less will experience condensation under the stated environmental conditions.

[moderne]

Its not a terrible problem, only happens on nights when it gets into the teens.  And it only happens in the bedroom.  Guess my breath is too juicy.