Glass block window condensation - how to cure?

Old 01-02-02, 06:35 AM
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Question Glass block window condensation - how to cure?

I want to finish around the glass block windows in my basement but I have a condensation problem with one of them. The window has a small flip open pane (the block is 4 wide by 2 tall with the flip open pane on the top in the center) with an angle iron just above the glass block for support (I assume - as it is a weight bearing wall and the pane has a plasitc frame).
The problem is that liquid condenses (and freezes) on the angle iron. I have used Drylock concrete caulk to seal all the cracks aroung the windows. I have also removed the fliper window and taken apart the assembly to caulk the glass. I also put a thin foam weatherstrip around the opening to seal it against drafts when closed. The basement is dry and has normal humidity.

Is there something I can insulate the angle iron with so that I can drywall right up to it without worrying about the condensate soaking the drywall? What about installing small cedar or treated pieces on the iron and then putting a piece of 4 mil plastic over it?

Can anyone suggest a way for me to stop the condensation on the angle iron and/or a way to keep it from ruining drywall?

Old 01-05-02, 05:20 AM
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Wood is a natural insulator. I would cover the angle iron with wood trim on the inside and outside. You have to do both sides and that should solve the condensation problem. Just make sure all metal surfaces are covered by wood.
Old 10-23-09, 02:56 PM
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Angry Same here - condensation on glass blocks

Okay, so I hired this guy to do three small glass block jobs on my post-war bungalow here in Port Credit, Ontario.
No. 1: Rip out an antique single-pane window painted a hundred times and caulked a million times from 1952 and replace it with four glass blocks in the cold cellar. 10/10. No condensation. (Not a heated room right?)
No. 2: Take out the five original glass blocks at the side entrance where 3 were broken for the last 20 years any way and they used brick mortar way back in 1952 and replace with five new ones. So he did that. It looked great. But the bottom two blocks have condensation build-ups but mind you: the plaster inside this window must be wet from the old broken glass block windows that must have leaked moisture all these years. So let's not blame this glass block guy for this one but any advice is welcome!?
No. 3: Rip out the wood door from the milk box and replace with six glass blocks. This is proving to be a condensation nightmare. On chilly mornings, it's all fogged up. And this is Canada - it's not even Halowe'en yet! And yet this glass block contractor appeared thorough in his work. I even set up a leaf blower at full blast outside to hit this glass block window and lit a Bic lighter inside the glass block window and the flame was solid... meaning no air leaks. But crap, does this thing sweat when it gets chilly! Any ideas? Seal the mortar? Anything? Needless to mention the glass block company that knew everything about glass blocks before they had my money are now stumped by the problem and, you guessed it, "Never encountered this problem with a customer before..." and I never heard from them again.

Old 10-27-09, 12:53 PM
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The place to start, is why is there condensation?
Condensation forms when warm wet air, meets a cold surface.
The air temperature drops as it approaches the cold surface and the water vapour drops out as condensation.
The way to stop condensation is to warm the cold surface = no temperature drop= no condensation.
Stop creating water vapour in the home by venting it to the outside by having and using extractor fans in the kitchen and bathroom.
Or ignore it if it does no harm.
Or use a dehumidifier, that will warm the air and at the same time remove the water vapour.
However, if the water vapour is in the air outside (about two hundred times a year we have a situation where the ground is cold and warm wet air arrives to cause dew and or frost) there is little that you can do other than paint iron to prevent further rust and insulate to keep the surface warm.

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