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Ice inside of windows....


setterguy

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I would start by Googling University of Minnesota Laboratories. When the Outside tempurature stays above 20 your indoor humidity can be in the 35% range but in severe cold(which is typically of short duration) the house can't handle moisture as well. If you have ice on your windows you probably have frost in your attic and even some in your walls. That can cause mold. There is nothing "Wrong" with the houuse; just lower your humidity levels in severe cold.

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There are alot of factors I think may not be addressed in the calculation. This is a new home, not old. That means it has to have a air exchanger in MN for code. But it doesnt say it has to be balanced or how the ducting should be done which can have a huge effect on the whole house. I had a house that had a blower door test of .07 CFM/FT2 @ 50 Pascals. In other words, very tight! I had triple pane windows which allow you to 'bump' up your humidity in the house without window condesation well into the 30-40% range and never had any moisture even with outside temps well below zero. Now I understand that he probably doesnt have triple pane windows, but you can't make a general statement about just the humidity being too high, its all relative to the construction process and the mechanical effciency etc...Besides were not taking about moisture, he's talking about ice actually forming. My guess is there is a few things, not just one thing, besides the windows themselves. That's why I was wondering about the windows.

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The house that initially started this discusson is under a year old. So that means it is required by code to have an air exchanger and to have it BALANCED. With new const. this almost always comes down to moisture/humidity levels inside the home, and this is a huge part of why they are required in all new res.const. Everyone produces humidity at different rates and with it this cold outside it needs to be at extremely low levels- 15-18%. WIth the combination of the humidifier and air exchanger this is not a difficult problem to control- most new homeowners just don't know how to correctly do it. Once they are informed it generally does not become a problem again. Wood floors will move with humidity levels- but will usually come back together when the correct levels are restored- 30-35%.....

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The code doesn't require an air exchanger as people understand it. The house has to replace it's indoor air every few hours. A Van-E type system certainly helps the moisture bounce in a new home but most people don't invest in them or triple pane windows.

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You are correct- the code does require air to be exchanged- but does not specify. As most builders prefer an active system- along with makeup air- they will install one of the types of air exchangers. Required?? ---No, But usefull???--- Extremely

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They were talking about this on am1500 this morning, the home and garden show.

The former building inspector they have hosting the show, he said this time of year your humidity should be run about 15% in your house.

A caller called up, has the same humidity as I, 35%.

My house is about 30ish years old, guess I need to get the air out of the house better.....

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Just wondering about the air exchangers - don't they sort of defeat the purpose of building a house tight to begin with? My house is about 20 years old and it's built tight enough so I need to watch the humidity inside the house, but nowadays with the foam insulation and triple insulated windows I can see where you could develop moisture problems quite easily. My question is (disregarding the code requirement for an air exhanger) - why spend all the extra money to make the house super tight when you have to just turn around and spend some more to circulate outside air through the house? Maybe I don't understand, but it doesn't make much sense to me. confused.gif

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I'll give you the short version. About 20 years ago the energy code changed and houses were built increasingly tighter. After about 10 years the effects of adding insulation, 2x6 walls, poly etc, started to develop different problems from increased moisture. The most obvious was moisture collecting on windows. The least obvious was moisture collecting inside the wall. As houses got even tighter the moisture now has smaller areas to collect where the holes in the building envelope allowed around elec. boxes, dryer vents, gas lines etc. The building being so tight has now become pressurized and actually draws moisture to these small holes causing rotting of materials and mold. Now the theory is to completly seal the inside of the home being careful to not allow moisture to reach inside of walls or attic spaces. As the house is sealed off there needs to be a way to discharge bad moisture rich air and bring in fresh air. The air exchanger is the most efficiant way to do this. Air echangers are balanced to allow the same amount of fresh air in the house. Along with expelling moisture the AE also has other benefits such as expelling cooking odors etc. The building code does not specically say that new homes need an AE only that the the house must have a system the echanges all the air in the house once every 3 hours. This can be accomplished be having an intake vent and some sort of exhaust system. The AE is a much more efficiant. Also this code is statewide and does not have anything to do with population of a city. All licensed builders must build to the minimum residential code whether the area they build in does inspections or not. If your home is not built by a licensed contractor then you are on your own to figure out if it is going to perform properly. Good Luck

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I built my own house, with some advice from a builder I knew and respected. Mine has 2x6 walls, and is sealed with poly on the inside and foam around the window openings, etc., but the builder's advice back then was to seal the inside of the walls and ceiling, and let the outside breathe. In other words, don't use foam, tyvek, poly, etc. on the outside of the walls. I do have a small (3") vent for fresh air in the basement, and also have two 6" flues going out - one for a small wood heater, and the other for my gas water heater and gas boiler. I generally don't use a humidifier, however, I have in the past but had to be careful not to run it too much or the windows in the house would start to fog up.

The reason I'm interested in this topic is because my sister & BIL built a new house 3 or 4 years ago - less square footage, at least as well insulated as mine, newer more efficient appliances, but their heat bill is higher. Their house is equipped with an air exchanger, so I blame it on that, but I do supplement with some wood and they don't.

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The 3" vent you have in the basement is probably for cumbustion air for your gas appliances as are the exhaust pipes.It is used to give the fire oxygen to burn. If your gas applinces are gravity vented and not power vented try this. Hold a lighter or a match next to the flue. Have somebody open and close the front door. When the door is open watch to see if the air is coming back down the flue. If this happens it could let Carbonmonoxide into your home . House wrap or "Tyvek" is mainly used to stop outside moisture, Rain etc. If it is installed correclty it keeps moisture that gets past your siding from soaking your wall. All siding will let moisture past. If you pull off a piece of siding after a blowing rain you will see what I mean.

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Quote:

The 3" vent you have in the basement is probably for cumbustion air for your gas appliances as are the exhaust pipes.It is used to give the fire oxygen to burn.


Yes, that's basically why I put it in - and to help the appliances vent better by providing a source of replacement air. I have a carbon monoxide detector installed downstairs and my vents work fine.

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There are many factors when you build a house as to why the cost of one vs. another retains heat more efficently. To blame one component such as the air exchanger is not looking at the entire picture. Some examples: Type of insulation in the walls and attic and how much. Energy efficent heals for trusses can vary alot. Rim Joist area how well its insulated and/or how. Basement insulation. Some use a 2x2 furring strip and cheap foam. Others use 2.5 inches on each side of the wall when using the ICF basements. How about foam under the concrete slabs in the house? Changing how you stud a house from the old standard 2x6 on 16" centers. I went to 24" centers; less wood, more insulation. Headers over windows and doors, attention to detail and sealing the overall house etc... The list is endless including how efficent of a model air exchanger was installed as well as the furnace or heat source. As you suggested as well, you supplement with wood too.

I was told by lots of contractors when I built my house that your going to build it too tight. Theres no such thing as long as you understand how to balance it. I had a great time proving the 'ney-sayers' wrong and got lots of help from my power company (MN Power-Dean Talbott) and the guys over at Conservation tech (Mike L. and Doug M.) to build the most energy effecient home that I could afford.

Did I mention that I built a ranch style home with a 9' basement. Each level was 1700 sq. feet. My worst heating bill never exceed $40/month with the thermostat set at 70 degrees. NO Supplemental heat, just the electric bill. Never had moisture problems of any kind either.

Jerk bait, I think your right on the money!

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Quote:

My worst heating bill never exceed $40/month with the thermostat set at 70 degrees. NO Supplemental heat, just the electric bill.


That's excellent, of course, but I suspect it's far from the norm.. It would be interesting to know what that same house would cost to heat with a conventional LP gas furnace.

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