Comments on: Accidental Dehumidification – A Preventable Mess

By: Jeremy

Jeremy — Tue, 19 Jan 2016 22:32:48 +0000

In reply to Hunter. Thank you, Hunter.
Thank you, Hunter. Along those lines I've found that yes, condensation on windows with screens still in place is significant while adjacent windows with no screens have little to no condensation. Similarly, the worst offenders are windows with honeycomb or fiberglass light-blocking shades, even if they're not directly above a baseboard heater. Removing most screens and keeping shades at least partially raised has made a very big difference!

By: Hunter

Hunter — Tue, 19 Jan 2016 21:17:24 +0000

In reply to Jeremy Marin. Jeremy, it sounds like
Jeremy, it sounds like something is making the bottom of the window cooler than the top. Could there be a poor design in the weatherstripping at the bottom of the windows allowing air leakage to cool that edge? Or it could have something to do with the cavity for the crank mechanism creating a lower R value for the lower rail. I think we too often think only about the temperature gradient across assemblies and forget that surface temperatures can be effected too. I use to live in a 1920's house with single pane windows. I would only get condensation on the windows with storm screens (condensation on the storm window) but not on ones with just a single pane of glass. My theory is that the indoor air was warming the inside face of the glass to just above the dew point. On the other windows the storm glass was staying below it and the air leaking into the separation was condensing. It's possible that your windows overall on the surface are above but close to the dew point but something is dipping the bottom section to just below it.

By: Charles Leahy

Charles Leahy — Tue, 19 Jan 2016 18:50:12 +0000

To prevent this from
To prevent this from happening in the walls, a basic and passive solution is to simply eliminate air cavities within the walls - we do this by entirely encapsulating (injecting) closed cell urethane insulation into all wall cavities. When you eliminate air pockets caused by traditional building methods, and virtually eliminate thermal bridging from the outside, you eliminate the opportunities for failure with the building envelope for any number of systemic issues.

By: Wynn White

Wynn White — Tue, 19 Jan 2016 16:30:22 +0000

Allison–great article! Like
Allison–great article! Like you, we’ve seen condensation on the inside of windows in winter. We’ve also seen it on the outside of those windows in summer–a sure indicator of thermal bridges in the window. And you’re spot on, getting wood wet leads to rot and mold.

Other options for the windows is to replace them (with a better window) or heat them (heating windows does not reduce energy consumption!). Oh, as you point out, if the condensation is occurring within the wall, replacing or heating windows will not help!

By: Jeremy Marin

Jeremy Marin — Thu, 03 Dec 2015 05:41:31 +0000

I’d love to get thoughts
I’d love to get thoughts/suggestions: Humidity (as per hygrometers around the home) is appropriate relative to the outdoor temp, using Minnesota recommendations as a guide.

Windows are double-pane casement style, probably from 1990s. Most mornings there is condensation only on the lowest 1″-2″ of glass, but it stays there all day unless I wipe it off. This is causing mold problems. The exceptions are windows with no shades or obstructions, which means no screens or shades.

Relatively tight home – 1400 cfm for 1400 sq ft home, just outside Boston. Baseboard heat, no ERV.

Run exhaust fans periodically? Other suggestions?

Thank you in advance.

By: Shawn LeMons

Shawn LeMons — Fri, 20 Nov 2015 20:23:15 +0000

In reply to Dennis Brachfeld. Thanks Allison. Although
Thanks Allison. Although simple and straightforward, I'm always able to glean useful tidbits. Dennis, sounds like your relative humor hit the pun point this morning. Cheers!

By: Dennis Brachfeld

Dennis Brachfeld — Fri, 20 Nov 2015 19:24:20 +0000

It is relative,where and how
It is relative,where and how you live. Climatic information and changes can make a difference. By having a portable humidistat in your home, will not condense your indoor air quality and information, but expand it! Where and how you live is significant, a lot of U.S. experts talk too much and create humidity. talking, cooking and showering. Which reminds me in the dry climate of Denver CO, that it is time to stop my dry sense of humor and hit the shower and get ready to get to work, thanks for sharing and caring about thermal dynamics, so we don't have to sweat it!

By: Colin Genge

Colin Genge — Fri, 20 Nov 2015 18:24:58 +0000

We've all seen condensation
We've all seen condensation on a glass of water and ice. Now install one of those foam beer cooler jackets and no condensation. Then how about a porous insulator around the glass where you can see the condensation at the glass to insulation boundary. I hope that using every day examples like this might get the point across?