I'm going to throw a lot of statistics at you to address your issues regarding ice buildup on your windows. Keep in mind that these stats are based on a worst-case scenario of 0 outside and 70° inside, which is applicable in your area but doesn't apply to southern, warmer climates.

You mentioned that the window supplier said you have Low E glass. I hope for your sake that you do have it. If not, your windows will be much more prone to condensation and ice. You also mentioned that the higher humidity areas (i.e. bathroom & kitchen) are more prone to the problem, which makes sense because the higher the humidity, the greater chance of the buildup of ice or condensation.

Now for some stats. If vinyl windows, or any window for that matter, is double glazed clear insulating glass, the center-of-glass roomside temperature would be about 44-45°F. (Incidentally, single pane windows with a storm window would be about the same) Adding a Low E coating to the glass bumps it up to about 52°F, and Low E insulating glass with Argon gas raises the glass temperature to 57-58°F. Not bad for 0° outside.

However, the edge-of-glass temperatures are much lower than center-of-glass. The type of spacer that separates the panes of glass greatly affects the edge temperature, and much could be said about the merits of different types of spacers. Naturally, condensation, and even ice, would normally occur at the edge first, since that's the cold "weak spot." Clear IG with an aluminum box spacer has an edge temp of only about 29°F. Low E glass with an aluminum spacer only raises it to about 32°. Then there are "warm edge" spacers, which are warmer and provide more condensation resistance. Stainless steel spacers are about 37° edge temp on a Low E/argon unit, and presumably (don't have exact stats on this) Superspacer and TPS would be at the top at 39-40°. Again, warm edge spacers typically range from 35-40°, but still tend to max out usually in the upper 30°s.

Now for the fun part. If you cover a Low E/Argon gas unit with some type of roomside window treatment (blind, shade, shutter, etc.) the center-of-glass temperature drops from about 57° to only 36°. That's an amazing 21° drop. I don't have any exact stats on what that does to the edge temperature, but I would imagine it must drop 5-15° as well. The reason it drops is because the air in the room is no longer freely circulating against the glass. Even a couch or desk in front of a window will significantly reduce the glass temperature if the furniture is partially blocking part of the window.

Enough stats. Condensation, and worse yet, ice, can NOT occur unless two conditions are present at the same time: high humidity and cold temperatures. The cold temperatures on your windows could be due in part to concealed damage, missing or defective weatherstrip, poorly-fitting windows, faulty installation, or just because of cold winter weather. If you have cold weather but low humidity, condensation can not occur. Both have to be there. If you're experiencing ice buildup on your windows, you have too much humidity given the current outside temperature with the existing glass system that is in the home (assuming that the windows are properly installed and not defective in some way). There are TWO basic solutions: raise the glass temperature or lower the humidity. That's it in a nutshell - those two things. More about those in a bit. First, I'd buy a digital hygrometer from Home Depot, Radioshack, a hardware store, etc. to measure the amount of humidity in the house (about $10-$29). You need to know that. Then I'd contact the vinyl window dealer to see if there is anyone that can come to the home to troubleshoot any obvious problems (good luck with that). They can hopefully also provide you with a brochure on condensation that has recommended humidity levels for various outdoor temperatures. Most window manufacturers have one. You can even look online for window manufacturer's recommended humidity levels. And as you mentioned there is a guide shown on your humidistat. Most of them will state that when it's 0 degrees outside your humidity level inside should be in the 20-25% range. Incidentally, with better spacers between the glass, one is able to have a higher humidity level before condensation would occur.

RAISE THE GLASS TEMPERATURE - There are many things that can be done to raise the glass temperature. For old existing windows, the best solution is often to replace them with modern, energy-efficient windows. Obviously that's not your solution - you have a home with relatively new windows. (If you do replace the other original windows that have not yet been replaced, it would be advisable to get warm-edge spacers and gas filling in the unit to hopefully avoid condensation). Another way to increase the glass temp is to upgrade to Low E glass, but let's hope you already have that. But there still ARE many ways to improve your situation. One that doesn't cost anything is to keep your window shades open during bitter cold spells. Although you will avoid the huge temperature drop previously mentioned, privacy is compromised, and it may help but not completely solve your problem because yours is so severe. Other ways to raise the glass temperature include taking out roomside casement screens during the winter, using free standing fans or ceiling fans to better circulate air against the glass, and adding another layer of glass or plastic (I hate to see that though - it shouldn't be necessary).

LOWER THE HUMIDITY - I haven't seen any previous posts on reducing humidity, but if they exist could someone please post a link to that topic? One of the best solutions for a new home is to have an air-to-air heat exchange ventilator installed to the furnace. It's required by code I believe in some areas. It brings in the dry fresh air from the outside and exhausts the stale humid air - giving you healthy air to breathe and lowering the humidity to the desired level. New homes are built so much more airtight than older homes, so they often need mechanical help to get air exchanges. Older homes exchanged air by being drafty. Dehumidifiers will help too, but are not as effective, since they usually can't get the humidity low enough. Great for basements though. Other ways include running exhaust fans when showering (and leave them on for a while), or simply stop bathing ;-)

In summary, unless there is a defect with the windows (there probably isn't) or with installation, condensation can and will occur under the proper conditions. Even ice can form if the humidity is high enough, the temperature is low enough, and other factors are in place such as restricted airflow to the glass. You need a humidity-measuring device to see if your humidity is too high. You might want to contact the dealer. And ultimately somebody has to address raising the glass temperature or lowering the humidity. Let us know what happens, please!

Thanks - I will have to do some detective work regarding the window supplier/manufacturer, fortunately for me, this cold spell is making everyone hark back to the 'old days' - Kamloops winters aren't always this cold (and it's still autumn!) - I arrived here last December, and I don't think we ever got down this cold - currently it's -19.9 C (-4 F) and I'm at the lower limit of what my wireless electronic thermometer will read....hygrometer (I have one) read off the scale this morning, which means it was below 30%

I will turn the humidifier down or off, Kamloops is renowned for being dry, our total annual rainfall is only around a foot, we'd be a real desert if it wasn't for the Thompson rivers that run through (and people here still use water like it's going out of style, for someone who's been living in Australia, in the middle of a drought, it's quite an adjustment)

OK so not covering the windows - that makes sense although it's counter-intuitive, since to save energy, we want to cover them....but I just checked in a room with old windows, and a holland blind, pulled down, and the ice is the worst there - I used to live in Ontario and I don't ever remember anything like that - we had storm windows and it was well before these modern sealed windows, and I certainly don't remember icing like that.

So that makes one decision for me, when we get more window coverings, we'll get venetians, at least they allow air circulation. I will put some of that plastic film over the old windows if I can get the ice melted, I suppose if I get an electric heater and slowly warm them up....wouldn't want to crack the glass just now! One room had a mattress covering the register, which obviously doesn't help - I'll make sure all registers are clear. I suppose this is why registers are next to windows?

Life in a cold climate - everybody thinks I was crazy to leave Australia (+6C is about as cold as it ever gets where I lived, most of the time) and maybe they're right, lol.

Like I said, I wonder about the low-E rating since there's no labels on the windows (except one of the old ones, which says it's high efficiency!) and I have noticed that, apart from icing on the glass, there is ice around some of the seams on some of them....which would suggest a leak to me. From what you've said, low-e glass sounds like a retrofit-able item, if a window ever got broken, could I replace the glass (assuming vinyl windows can have their glass replaced) with low-e glass?

Would there be any harm in running silicone into those joints where the ice is forming? For the most part, they wouldn't interfere with the opening of the windows....of course, that might have to wait til spring or summer, since I imagine it's too cold and with the ice, I couldn't do it now.

There is one odd thing, with the vinyl windows - they're slide open sorts, and the icing is pretty much exclusively on the 'outer' part, the 'inner' part which slides, tends not to ice as much. Does recessing them in that little bit make such a difference?

Thanks again tru blu, I've learned a lot in the past few days. The cold front has moved on and it's now a (relatively) 'balmy' -9 C - the ice has all but disappeared except in several seams or grooves. I wonder if I could seal them somehow, they don't affect the sliding of the window, but I wonder if they're part of the draining system...at some point I should find the weep holes on the outside ones and see that they're clear. I guess even some tape would seal those grooves better (speaking of bad installation, I noticed on the bedroom window, that's the good low-e one, I finally did confirm it had low-e glass) some gaps opening up between the window and the woodwork. If it's not too cold, I'll seal it with a paintable, flexible sealant.

I did make sure the heat registers were not blocked and moved the bathroom towels for a bit to make sure the air could blow towards the windows, and found a light in the kitchen over the sink put out enough to ensure the window warmed up -all are de-icing now - I never realised the significance of heat registers under the windows til now - they help keep them clear (and counteract the cold air off the glass.

Apparently we're not the only ones whose windows iced up...but I didn't like it happening. As one who likes to keep the humidity at 'normal' the idea of dehumidifying in winter's anathema, but if I have to, I will. I adjusted the humidistat accordingly (wouldn't it be nice to have one with an outdoor sensor so it was self-adjusting?) but like the idea of the whole-house air exchanger/cleaner. We have a puppy who's turned out to be a real shedder so anything that filters/vacuums the air sounds like a good idea to me, and fresh air is nice (since the furnace fan is set to run 100% of the time - I suppose that may or may not have helped with the de-icing, the non-heated air might have made it worse?) - we should have had a better supply of fresh air with the fan running as there's a duct that draws fresh into the house and puts it into the cold air return, so I guess there's more flow with the fan running.

I'll be a little more vigilant about moisture, and might put plastic over the old windows. We have a 'feature' window that's original and not so efficient, I had been thinking about a layer of lexan inside to improve its insulation qualities...has anyone ever tried this?

pjb999,

In the good old days, houses were a long way from being air tight. They breathed....usually thru the windows and doors. The windows and doors were simply not very good at keeping inside and outside weather inside and outside, respectively.

Heat travels to cold. Moisture travels to dryness. Ultimately, both heat and moisture want to negotiate with cold and dry until everybody is equal. Basically, heat and cold and wet and dry want to reach equilibrium or balance with their respective opposite.

Nature does not like things that are not in balance, and so, since the air inside of a home in winter is both warmer and wetter than is the air outside of the home, nature does not like this situation and tries very hard to fix it.

In the old days this was very simple - the house wasnt tight (especially around the windows) and all that heat and moist air simply went thru the windows and attempted to equalize the cold, dry air outside. Since this wasnt even remotely physically possible, it became a continuous cyclewarm up the air inside the home and out it goes trying very hard to get the outside warm.

The people living in the house had other ideas about that situation, however, and they pumped prodigious amounts of heat into that house in an attempt to stay warm. This worked, within reason, but the homes were then very dry. People generally attributed this to the warm air from the furnace "drying" out the air in the house when it was actually because moisture from inside the house was migrating to outside the house along with the warm air - natures attempt to equalize the inside and outside temperatures and moisture levels as well.

As air inside warms up it does feel dryer than it did when it was coolerthe relative humidity goes down as the temperature goes up. The warmth isnt actually drying the air, it is simply changing our perception of it.

When the air became very dry, it was not very comfortable, so people began to add moisture to their air in an attempt to raise the relative humidity to more comfortable levels. As long as the house remained relatively loose, this "new" warm and moist air migrated to the outside and was replaced inside.

But, newer houses are tighter. Newer windows are tighter. We have caused a rift between what Mother Nature intended and what we allow her to do. We are trying very hard to keep the heat inside our homes and avoiding it going outside. This has the added "benefit" of also keeping moisture inside as well.often more than we would like to keep inside.

Houses today are often too wet, rather than too dry. In the winter furnace humidifiers are often "overkill" for the requirements of todays homes. Obviously, I would never suggest that a home will ever need additional humidification, but in todays world it is also not correct to say that all homes will need humidification either. It is very dependent on both the construction of the home and the lifestyle of the people living in it. And obviously, there are many, many houses that are still leaking air and moisture to the outside in the winter