Fogging windows (glass, dryer, price, warm)

[sacredgrooves]

No matter how much you spend on a window, it wont be a good insulator Like I mentioned before, the energy loss of a "fogged" window is infitesimal. It is more of an aesthetic issue than anything. Remember, people that sell/repair windows have a vested interest in upselling.

[MikeJaquish]

Mike is saying, and I quote him directly, that it is important to have an inert gas fill between the panes for a couple of reasons:

1. The clean gas will not have all the chemicals and water that "air" will have and will not bring those contaminants into the sealed area.

2. The gas, being chemically inert, will not itself interact with the Low E coating, or the aluminum or neoprene spacers that hold the glass apart. Components of "air" might interact, particularly oxygen and nitrogen.

I don't believe the insulation value of the gas is significant to the overall performance of the heating/cooling envelope of the home. but I would NOT want a sealed double or triple window filled with "air."

[sandycat]

Hi Vicki,

I (the hubby) started with the original post. Thankx to everybody's comments I can make a better decision now. I want to chip in one more point for everybody. Besides cosmetic and insulator considerations which have a different importance depending on somebody's viewpoint. Here is the kicker everybody as a seller has to face:

Once a fogging window is showing up on the complaint list after inspection during a sale this item becomes an open record even if the the contract falls through and a new potential buyer starts to negotiate. With other words this item will be the 800 pound gorilla during the sale of the house. It's good to know what the options are to keep a good negotiation environment. You might think it's cosmetic as a seller but once it's in the records it's more than that.

The hubby ......

[K'ledgeBldr]

Originally Posted by sandycat

Once a fogging window is showing up on the complaint list after inspection during a sale this item becomes an open record even if the the contract falls through and a new potential buyer starts to negotiate. With other words this item will be the 800 pound gorilla during the sale of the house. It's good to know what the options are to keep a good negotiation environment. You might think it's cosmetic as a seller but once it's in the records it's more than that.

The hubby ......

The inspection (private inspector you hire) is for you, and you only. It does carry to the next potential buyer. So, unless its noted on a disclosure form it not an issue to the seller (maybe unethical?). As some other posters stated, ask the seller to replace the faulty sashes.
With that said, they may be able to replaced at no cost (still under warranty),as someone stated earlier- find out who the builder was- if they are still in town they can inform you who supplied them the windows. If you run into a deadend, heres some suggestions-
What kind of windows are they- Wood, Aluminium, vinyl? Single hung (one sash moves)or double hung (both sashes move)?
If they are wood- more than likely you would have to replace the whole sash. Some wood sashes are screwed together, so you could disassemble and replace just the glazing.
Aluminium windows are just a matter of replacing the glazing- A plastic snap frame on the interior holds the glazing in place. Remove the frame pieces, cut the seal on the outside with a putty knife and push the glazing to the interior side.
Vinyl- replace the whole sash. The glazing is installed into the frame during the manufacturing process, and is welded together.
All-in-all, if the house is only 5years old it should be under warranty. And if the seller really wants to sell he should step up to the plate. If he wants to play hardball- let it reflect in your offer.

[BigJon3475]

These windows fog on the inside or outside? This is happening in the winter only?


Just because windows fog or moisture forms on them does not mean they are always bad. If the house does not have enough infiltration humidity builds up in the winter and leaves the windows below the dew point inside. Do you have a hygrometer or thermometer that shows relative humidity.

@ 70ºF with a 40% RH the dew point is 44.6ºF.....That means any thing colder than that in the house will start to condense water on it. I'm sure if it's 40ºF or lower outside your windows are at or close to the same temp. Most windows don't have much more of a insulation rating more than R-2

If the temp goes up to 75ºF with 45% relative humidity. The dew point is 52.25ºF


Winter air is much dryer than summer air. Unless it rains, 30-40% inside relative humidity readings are average depending on where you live.

That's why I ask is it condensation on the inside or outside?

[OmegaBaby]

Originally Posted by BigJon3475

These windows fog on the inside or outside? This is happening in the winter only?


Just because windows fog or moisture forms on them does not mean they are always bad. If the house does not have enough infiltration humidity builds up in the winter and leaves the windows below the dew point inside. Do you have a hygrometer or thermometer that shows relative humidity.

@ 70ºF with a 40% RH the dew point is 44.6ºF.....That means any thing colder than that in the house will start to condense water on it. I'm sure if it's 40ºF or lower outside your windows are at or close to the same temp. Most windows don't have much more of a insulation rating more than R-2

If the temp goes up to 75ºF with 45% relative humidity. The dew point is 52.25ºF


Winter air is much dryer than summer air. Unless it rains, 30-40% inside relative humidity readings are average depending on where you live.

That's why I ask is it condensation on the inside or outside?

You bring up an important point. Condensation on the inside or outside of a window is normal.

However, what is being discussed here is condensation that forms between the panes of glass. This is never normal, since the air between the panes of glass should have no moisture in it to begin with (since it's sealed at the factory).

This distinction is often confusing for homeowners. However, in this case, this issue was brought to attention by a home inspector, who you can reasonably assume knows the distinction.

[BigJon3475]

I see your point. I guess I didn't read the thread close enough.

[BigJon3475]

The U value is the reciprocal of the R value one in the same. The U-value is used for thermal calculations.

You also forgot a NFRC rating. (Fenestration) *same material different pile*

The cold feeling next to the window most of the time isn't infiltration it the heat being equalized from the colder window.....The heat is being sucked out of the home. Infiltration mostly happens by a stack effect (warm air leaving your home from rising and being replaced by air through leaks or cracks in the structure)

25% Air exchange rate/hour is recommended for IAQ.


By the way have the sellers fix it or have them knock some money off the price of the home to compensate that repair....that'smy .02



As far as something like this pertaining to your power bill......Get curtains/window treatments (as thick as you can deal with)....extra insulation in the winter.....blocks out radiant heat in the summer.

[Oberon476]

A really really interesting discussion!

This is my first post here and by way of introduction, I work in the glass and window industry in the areas of quality, product development, and certifications. I do not work for a window company and I don't sell anything to anyone. I am a primarily a researcher in these areas. Although I work primarily in a laboratory setting, I travel a great deal and visit real-live houses as well as various test sites and other labs...so here goes.

There is some very good information in some of these posts and some incorrect information as well. I am going to attempt to clarify a few things that were written in some of the posts...this thing is likely to get very long I am afraid.

Going back to the initial question -

First, fog build up inside an IG (insulating glass) unit may not affect the overall (original) performance of that unit, unless the unit had been originally gas-filled in which case the loss of the gas infill (replaced by "ordinary" air) will lower the overall efficiency of the unit. But, it may be unsightly and may be worth changing if the homeowner feels the need to do so.

One thing to keep in mind is that window warranties are not always transferable. So if the unit was inder warranty to the seller then what might have been a free or inexpensive fix for the seller becomes much more expensive for the buyer once the sale is closed. So it would certainly be in the buyers interest to get the seller to do the "dirty work" before the sale of the home.

As an aside, if you are buying windows for a new construction or for remodeling or replacement, don't even consider windows with an IG warranty less than 20 years. Some folks mentioned 5 or 10 year glass warranties - and they are certainly out there - but the better products have 20 year warranties - or better in some cases. Also, buy from a company that will be around at the end of 20 years. There are about 1000 window companies in North America and while some of them are very very good, some of them are very very bad as well.

And I would not necessarily suggest good or bad by the window "material" either. There are some very good wood windows and some very good vinyl windows as well - not to mention fiberglass - which is the newest kid-on-the-block. There are also some bad wood window companies and some very bad vinyl window sellers out there - those are the ones that give replacement window folks a bad name in some places.

As to changing out the IG, depends on who built the thing really. Most IG units can be replaced without having to change the entire sash - and I know of NO reason to change an entire window because an IG is bad - anyone who states that they have to replace an entire window because an IG has interior fogging is (a) ignorant, or (b) trying to rip you off. Again, most windows (but not all) will allow you to change the glass without having to change the entire window sash. Your best bet is to contact the manufacturer or if you don't know who it is (common with builder grade windows, unfortunately), then a glass shop might be able to help.

Despite claims to the contrary noted in a couple of previous posts, argon and krypton fill actually DO improve the thermal performance of the IG / window. The improvement is actually linear with a 100% argon fill improving thermal performance of the IGU 16% over an air fill and with a 50% argon and 50% air (or more commonly pure nitrogen) fill offering an 8% overall improvement. 25% argon improves performance 4%...See the pattern?

A clear glass dual pane window has similar energy performance to a single pane window with a storm window. In fact, the dual pane was developed to match the performance of a single pane with storm in a single construction - without needing the storm. As was also previously mentioned, a clear glass dual pane window has a R-value of about a 2. Ain't much really.

Someone has already mentioned that the best way to measure window performance is using U-value rather than R-value. This is 100% true.

It was also mentioned previously that R-value and U-value are inverse or reciprocal and thus different ways of saying the same thing - which is half true and half not-as-true. R and U are in fact reciprocal, but they are not really different ways of saying the same thing since R-value measures thermal resistance while U-value measures thermal transmittance. This discussion can get complex, so I am leaving it here. But if anyone wishes to continue in this area I could certainly do so...

Windows are rated for their U-value - or U-factor as more correctly stated, while R-value, when applied to a window, generally (but not always) is a center-of-glass measurement and is not a good indicator of overall unit performance. U-factor is an indicator of the overall window performance.

The only advantage of using R-value over U-value in a discussion of thermal performance is the “intuitiveness” of R-value over U-value for comparison...going "up" as an improvement just "feels better" than going down. I have used that in discussions when people have asked why to use one over the other. In other words, an R-value of 2 is a U-value of .5…simple enough, but as R-value increases to show improved performance, U-value decreases to indicate improved performance. So, if we improve an R-value to 10 (for example) then our U-value has improved to .1. Certainly not as clear to most folks to compare a “2 to 10” improvement to a “.5 to .1” improvement – thus many folks prefer R-value even if it is not the best method for comparison.

And can windows be good insulators? Well, the windows I put in my daughters new house have a U-factor of .21 (operators) and .16 (fixed). To use R-value since it is easier to understand (if not entirely correct), U-.21 is an R-4.75 and U-.16 is an R-6.25. There are windows on the market that achieve a U-.1 or an R-10, but they can be pricey.

I am stopping now because this thing is already too long, but again, great thread

[BigJon3475]

Thanks for the info Oberon476....