Window Condensation in Denver: What Foggy, Sweating, or Frosted Windows Are Telling You
Once the furnace kicks on for the season, I start getting calls about window condensation in Denver homes. Water beads on the glass in the morning, frost creeps up the bottom of the pane, or a window looks permanently foggy no matter how many times you wipe it. I'm David Kalec, owner of Remod Exteriors, and I want to help you figure out what that moisture actually means before anyone tries to sell you something.
Some condensation is normal and easy to fix. Some of it means a window has failed. The trick is knowing which side of the glass the water is on. This is the same walkthrough I give homeowners in Arvada, Westminster, Wheat Ridge, Lakewood, Golden and Aurora.
Why Window Condensation Happens in Colorado Winters
Condensation forms when warm air holding moisture touches a surface that is colder than the air. The air cools right at the glass, it cannot hold as much water, and the extra moisture lands on the window. Colorado makes this a little unusual. Our air is dry most of the year, so a lot of people are surprised to see wet windows at all. When it shows up, it usually comes from one of two things:
Extra moisture inside the house. Showers, cooking, a whole house humidifier, drying laundry indoors, a lot of houseplants or a full house over the holidays all add water to the air.
Very cold glass. On a frigid Front Range night, the inside surface of an older window can get cold enough to sweat or even frost, especially with single pane glass or metal frames.
Often it is a mix of both.
Three Kinds of Window Condensation and What Each One Means
1. Condensation on the Inside of the Glass
This is the most common one. You wake up and the inside of the window is wet, often heaviest along the bottom edge. On the coldest nights it can turn into frost.
What it usually means: there is more humidity in the room than that window can handle at that outdoor temperature. Bathrooms, kitchens and bedrooms with the door closed are the usual suspects.
A little of this on the coldest mornings is not a crisis. Heavy condensation every day is worth attention, because water sitting on the sill can stain drywall, peel paint, and lead to mold or rot. If only one or two windows sweat, look at those closely. A window with poor glass or a leaky frame runs colder than its neighbors and sweats first.
2. Condensation or Fog Between the Panes
This is the one that tells you something has failed. If the fog is trapped between the two panes, you cannot wipe it off from either side. Sometimes it comes and goes with the weather, and sometimes it leaves a cloudy film that never clears.
What it means: the seal around the insulated glass has broken. Dual pane windows are built as a sealed unit, and when that seal fails, outside air and moisture get into the space between the panes. Any gas fill that was in there escapes, and the window loses a good share of the insulating value it was built to give you.
There is no cleaning or caulking fix for a failed seal. If the frame is in good shape and the window is fairly new, replacing just the glass can make sense. If the frames are older and drafty, or several windows are failing at once, replacement is usually the better use of your money. I will tell you honestly which one I would do.
3. Condensation on the Outside of the Glass
On a cool, still morning you may see dew on the outside of the glass. It is usually the least concerning of the three.
What it usually means: your glass is doing its job. Good insulating glass keeps the heat inside the house, so the outer pane stays cool and collects dew the same way your lawn or car windshield does. It burns off as the sun hits it. No action needed.
Simple Ways to Cut Down Indoor Window Condensation
Before you replace anything, try these. They cost little or nothing.
Run your exhaust fans. Use the bathroom fan during and after showers and the range hood while you cook. Make sure they actually vent outside.
Turn the humidifier down on the coldest nights. A whole house humidifier makes a dry Denver winter more comfortable, but the setting that feels great in November can soak your windows in January. Turn it down when the temperature drops hard.
Let warm air reach the glass. Heavy curtains and closed blinds trap cold air against the window. Open them during the day, and keep furniture from blocking the heat vents under windows.
Keep air moving. A ceiling fan on low or leaving bedroom doors open helps even out temperature and moisture.
Wipe up and watch the sills. If water is pooling, dry it so it does not soak into wood or drywall while you sort out the cause.
If you do all of that and certain windows still sweat or frost every cold morning, the windows themselves are probably part of the problem.
Signs the Window Is the Problem, Not the Humidity
These are the things I look for when I visit a home about condensation:
Fog or film between the panes that you cannot wipe away
Frost forming on the frame itself, not just the glass
Drafts you can feel around the sash or along the edges
Soft, dark, or rotting wood on the sill or the bottom rail
Peeling paint, water stains or mold on the drywall below the window
Single pane glass or old metal frames that feel ice cold on a winter morning
If several of those sound familiar, our post on when to consider window replacement walks through the bigger picture.
How Replacement Windows Help With Winter Condensation in Denver
New windows will not remove humidity from your house. Your showers, cooking and humidifier still add moisture to the air. What a well built, well installed replacement window does is keep the inside pane much closer to room temperature, so it stays above the point where moisture condenses on most winter days.
Three things make the biggest difference:
Insulating glass. Modern dual pane glass with Low-E coatings and gas fill keeps the room side of the glass warmer. Our post on why Low-E and argon matter for Denver windows explains how that works.
Frames that do not carry the cold. Vinyl, fiberglass and wood frames stay warmer than old metal frames, so you see less sweating and frost along the edges.
The installation. A great window installed poorly will still leak air around the edges. Sealing and insulating the gap between the window and the opening is just as important as the window. You can read about how we handle that in our approach to window installation.
We install windows from manufacturers like Anlin and Marvin, and I help you pick the right product for your home and budget instead of pushing one line. You can see more on our window replacement page.
Can You Replace Windows in Winter in Denver?
Yes. Windows get replaced through the winter here, and winter is when you notice the problem windows most. Our guide to replacing windows heading into fall and winter covers timing, and our financing options can help spread out the cost.
Frequently Asked Questions
Is condensation on the inside of my windows bad?
A little on the coldest mornings is common and not a big deal. Heavy condensation every day can damage sills, drywall and paint, and lead to mold, so it is worth lowering indoor humidity and checking the window if it keeps happening.
Why are my windows foggy between the panes?
The seal on the insulated glass has failed and moisture has gotten between the panes. You cannot clean it out. The fix is new glass or a new window, depending on the condition of the frame.
Does condensation on the outside of my windows mean something is wrong?
Usually not. Dew on the outside glass on a cool morning often means your windows are insulating well, because the outer pane stays cold. It clears on its own as the day warms up.
Will new windows stop all condensation?
No window can stop condensation if the indoor air is very humid. Good replacement windows keep the inside glass warmer, so you will see far less of it in a normal Denver winter.
Do you replace windows in my area?
We replace windows across the Denver metro, including Arvada, Westminster, Wheat Ridge, Lakewood, Golden, Broomfield, Aurora and Denver. See our service area for more.
Get an Honest Look at Your Windows
If your windows are sweating, frosting or fogged between the panes, I will come look at them myself. I lead every estimate personally, and I will tell you whether it is a humidity issue you can fix for free or a window that needs to be replaced. No pressure, and we will always reach you the way you prefer, whether that is a call, a text or an email.
Call or text (720) 203-5014 or visit myremod.com to set up a visit.
Remod Exteriors
8557 Salvia Way, Arvada, CO 80007
(720) 203-5014
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