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In a Fog? Understanding Replacement Windows and Condensation

One of the most common concerns about installing replacement windows, whether they’re vinyl replacement windows, fiberglass replacement windows, or wood replacement windows, has to do with humidity.  Homeowners who had normally had crystal clear windows, no matter what the weather was, are sometimes surprised by a fog or interior condensation that occurs after replacement windows are installed.

Why does this happen?  Is fog to be expected when one has replacement windows installed?  The answer is both yes — and not necessarily!

One of the advantages of having replacement windows installed is that they tighten the building envelope.  That’s a term that gets bandied around a lot, but you really have to understand what it means in order to see where the condensation issue comes from.  Generally, older or original construction windows leak.  They leak a lot, letting warm, moist interior air spill out, through leaks, cracks, and crevices you might not even see.  In fact, if you have single pane windows, that heat could be leaving your home right through the glass.  Removing these older, grossly inefficient windows and replacing them with highly efficient, attractive vinyl home replacement windows, for example, is one way to stop the air leakage.

It’s important to remember that along with the air that was leaking out of your home, moisture escaped.  Your home would reach a given level of humidity based upon how much air and moisture was lost, due to inefficient windows.  When those windows are replaced with home replacement windows, the warm air stays inside — and so does the moisture. The leaks that you weren’t even aware of let excess moisture out.  Now, that moisture can’t escape, so you get condensation and even fog on the inside of your windows.

This problem is easily remedied by ensuring your home has adequate fresh air exchange — something that’s absolutely integral to overall good health!  While this may have been a passive benefit of inefficient windows, many homeowners find they need to be slightly more proactive about ensuring adequate fresh air exchange once replacement windows are installed. This is especially pertinent in areas that are likely to have particularly moist air, such as a kitchen and bathroom.  Luckily, the solution is often as simple as flicking on the exhaust fan or vent.