Do you have wood or vinyl windows? I wouldn't wait the hour or two for it to evaporate on its own - wipe it off and get ahead of any problems. Your closed shades may be making it worse but you could have that problem even if they were open - we do. Cooking, bathing, laundry even breathing all produce moisture and with our new tight houses it has no where to go. We keep ceiling fans running, it helps but we still have condensation on cold mornings.

They are the Andersen 100 series, which are made of fibrex, a combination of fiberglass and wood.

I'm in Minneapolis. It gets cold here. I have Marvin, wood, low E windows.

You have to watch the outside temp and the relative humidity inside your home. If it's too humid and it's cold enough outside, you will have condensation - on the lower 1" of the window.

When it's really cold, we don't pull our cellular blinds all the way down - leave about 1" of glass exposed - so air can circulate.

I have the same problem, with my older wood windows. Only when I pull the shades all the way down. In colder weather, I do what geoffrey does. Just leave them about an inch or two up at the bottom. It does prevent this from happening. Before I changed them all out to window shades, I had the crummy mini blinds, which I hated. However, because, they are not air tight, the condensation was not a problem with them.

You set humidity control based on outdoor temps, not indoor temps. What's the outdoor temp when condensation occurs?

I also do what geoffrey_b said. I have a cellular shade that I leave an inch or two opened at night.

Hi Mike,

I have the exact same Anderson 100 windows as you do. It got down to 11 degrees last night and I keep our thermostat set at 68 degrees. We haven't had any problems with condensation.

However, I live in Southern Utah which has very low humidity and I have wood blinds that are not airtight.

I think it might be your shades that are causing the problem and/or the humidity level in your house.

Michael, its sounds like you are already aware of the causes of the condensation, kudos to you. Will this be a long term issue? Do you mean condensation present as the problem, or any damage that it can do?

If condensation being present, then yes. This issue will not go away without some changes. Either reduce the RH in the home as it relates to the exterior temps (the colder it is, the dryer it needs to be in the home), OR open those blinds a little bit at night and see how that helps... or both

If your question is on the long term effects of the moisture produced by condensation, I'd say potentially yes as well. I've seen organic growth (mold, mildew, etc) on the back side of window treatments, and any moisture that runs onto a porous surface such as adjacent woodwork could be damaged as well. There is some though that a constant presence of moisture present around that lower glass seal can reduce its life expectancy as well. I've not seen solid colored fibrex damaged by moisture, only the wood laminate available in the Renewal line... If you are unable to get rid of the condensation or at least reduce it to only the most extreme conditions (temps around or below zero, etc), you will want to wipe that off daily at minimum.

So this morning I made it a point to look for the condensation, and there was none, even after the honeycomb shade was closed all the way for the entire night. Outdoor temps overnight was around 40. A few days ago when I noticed the condensation issue, the temps were in the upper 20's overnight.

It will be a PITB to wipe the condensation off of the glass every morning, because the screens are on the inside of the window. I'd have to remove the screen first. I guess I could remove the screen for the winter, it would probably let in more light/solar gain that way. Since I have alot of hardwood floors and some custom wood work, I really don't want to drop the indoor humidity much lower than what it is now, about 35%

Funny how I might actually end up running my dehumidifier in the winter time. I had the option of getting both the dehumidifier and a humidifier in the build, and the builder told me if I pick just one, to go with the humidifier. Glad I picked the dehumidifier instead...

-newer, tighter home retains more moisture

-it’s fall, there’s excess moisture in the home this time of year

- good call on the dehumidifier. Your builder was a moron for recommending a humidifier. It’s not 1986, newer homes in cold climates have plenty of moistures generated by their inhabitants in most cases, in fact more than enough where some sort of added air exchange is needed

- 35% should be fine most of the winter, but in the super cold times you may want to run Exhaust fans and adjust the dehumidifier a little more aggressively to compensate. Getting rh below 30% during those times should alleviate much of the condensation and shouldnt be too uncomfortable for those periods of days, or maybe a week or two.

- as the others said, raise those blinds a little bit. A few inches should still afford you privacy but make a big difference on the condensation

We remove our screens for the winter just for that reason - don't want that water sitting on the windows so when it's cold enough outside, it;s a morning ritual to wipe them down.

But I feel that if I raise those honeycomb shades abit(don't fully close them), I'll be giving up the extra insulation benefit they were providing. Its amazing how cold the sill and glass behind them will get after they are closed overnight.

Don’t think your shades are doing much for insulation.

I too was skeptical of the claims made by the shade salesman, but they do make a difference. These completely seal on the top and the bottom, and have about an 1/8" gap on the sides. They create a dead pocket of air, which seems to work.

If you have hardwood floors be careful you don't have too low of humidity. I have to use a humidifier in the winter. I certainly get moisture all winter but need to leave the shades up slightly and need to wipe the sill off occasionally. I even get ice on the northside windows when its sub zero out.

As I said earlier, I keep my cellular shades open an inch or two. I live in a climate where winter night temps are frequently below zero. The window I am talking about is very large, and even with good quality window, such a large one will feel cold when the temps are below zero all night. The cellular shade makes an enormous difference in shielding from that cold, and keeping it just 1-2" open prevents condensation on the window.

Your post makes it appear you've rejected the suggestion out of hand to keep the shade open an inch or two. Despite that people have posted that this works. Not sure what else to tell you, since you are declining such an easy solution.

Michael, having the blinds 95% closed will still mitigate a lot of radiant heat loss. Having them as close to sealed is better of course for that purpose, but much like the RH, you are trying to find a balance where you can mitigate as much of one issue as possible without creating others. Try that (slightly raised blinds) for a few nights and see how it feels in the room, as well if it helps the condensation. It should help the latter without causing much change to the former, and without creating any additional measurable expenditure on energy.

@Miranda33 - If I were lowering the blinds by hand it would be easy to leave the 1" or 2" gap at the bottom. But these shades are motorized and automated, so its all done by a computer. I think I can change the programming, but it was a pain the butt just to get it working as smoothly as it is now, not looking forward to messing with it again.

I don't want to hijack this thread, but I am wondering how much the window frame material affects condensation. I get tons of condensation (puddles of water on the interior window sills) from my aluminum windows when I never got condensation from the builder grade vinyl windows in my other house a couple miles from my new one. I am hoping this situation will improve once I change the windows to vinyl (please let me know if that is not the case). The OP mentions that he has Anderson fibrex windows -- is that material a factor too? Or does window frame material not matter?

Michael,

To correct your error above, Anderson 100 includes absolutely NO fiberglass. Their trademark Fibrex is misleading. Fibrex is composed of recycled wood (40%) and pvc (60%) to create a composite they market as stronger than vinyl (marginally). It is by no means comparable to fiberglass.

I noticed on my windows I had a thin layer of ice not only on the glass but also on the bottom corners on the frame on the lower sash. The temperature outside was -22 F with the wind chill -50 F I had the shades down to prevent the cold air from coming in. When I raised the shades the ice on the frames and glass did go away. Is this normal under these weather conditions or would there be a draft coming from the windows?

I’d say yes, but -22 is pushing the extremes.