Good advice from a man who should know a thing or two about windows. Mr. Glaze.
A distinct color difference. But what would you say is the temp difference, and what would you calculate that to be in energy loss? I am not sure what the numbers would be.
This is one of several inconsistencies in the InterNACHI SOP…
The inspector is not required to…determine the integrity of multiple-pane window glazing or thermal window seals.; BUT,…The inspector shall report as in need of correction…any window that was obviously fogged or displayed other evidence of broken seals.
The purpose of a window is to provide natural light, ventilation and a means of egress. IMO, it has only become “significantly deficient” when it fails in one or more of these areas.
I would estimate less than a dollar per month for this one door.
Q = U x A x ΔT Where: Q – is the heat loss in BTUs per hour. U – is the heat transfer coefficient for double pane glass with air in between the panes. A – is the area of the double glazing in square feet. ΔT is the difference in temperature between the inside and outside of the window. The heat loss from the window can be calculated using the following formula: Q = 0.65 x A x ΔT
Q = 0.65 * 3sqft * 35°F = 68.6 BTU/hr
24 hours and 30 days = 1 month
Q = 49,000 BTU/Month
1 millon BTU costs about $13.38 right now (Nation average today)
49k BTU = $0.66
Of course the temperature changes throughout the day. Other factors play a role as well like wind, changes in the temperature in the room throughout the day, shade vs sunlight, and more. This is just a rough estimate.
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Love it Bert! So me of course not really understanding all of your calculations, is this the total amount of estimated heat loss for the window, or is this just the additional heat loss due to the failed seal?
total for the bad window. But that’s assuming constant weather and stuff. That’s a pretty cold morning for TN.
The “good” window in this example is losing about 1/2 as much energy (BTU/hr) in these pictures.
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So one could say in your generalized sample, the failed seal is causing 50 cents of energy loss per month, understanding that this probably amplifies based on actual temperature, winds, energy prices, and probably a few other things.
And an actual window, as opposed to a door, would probably be 1/3 of that, or 15 cents per month.
Although this isn’t much for a single home, having the most efficient windows possible is good for helping with worldwide energy usage.
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Yes, that’s a big “window” and also a completely failed seal with just air inside (no more argon)
Many times, a filed seal doesn’t show up with this much temperature difference. Extreme weather helps highlight the heat loss. On a nice spring day you might not even have a noticeable difference in temperature between a good window and a failed one side by side.
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Only Ryan did so far (which i kind of agree with most of the time, but my state specifically requires reporting “obvious fogging” as deficient), the article says nothing about cosmetics. The decision that was made is regarding latent vs patent. The buyers are quoted as having acknowledged the “film” on the window before putting in the offer. Thus, it was a patent observation and the onus falls on the buyer.
I’ve put a disclaimer in my report after having a client come back at me for some very light fogging that showed up 5 months after the inspection:
A Note on Insulated Windows: The inspector’s observations and reports regarding discoloration or fogging between window panes are limited to the conditions apparent at the time of inspection in the environmental conditions at the time of inspection. Observations made and this inspection report are not a comprehensive assessment of potential defects potentially apparent during all environmental conditions and times. Consult an expert glazier for the potential identification of defects that may have been imperceptible at the time of inspection.
I understood ya. What I tell my clients is :
If you ask a physicist, “Is there energy loss due to the failed seals?!” They would say “YES THERE IS!”
But how long will it take for you to get a return on your repair investment in the form of utility bill savings? I can’t tell you. Maybe very long. In my opinion, the bigger implication is the cosmetic one. A dirty window really kills the vibe in the room and you won’t be able to clean it.
But yea, in the context of windows, a severe enough cosmetic problem becomes a deficiency, I suppose.
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Agreed. And I hope everyone is putting them in their reports. I always have. My comments are not to be taken as an opinion that this is not a defect, as it certainly is. My comment (opinion) about this defect though is that it is mostly a cosmetic one.
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I was hitting up open houses once, shaking hands with Realtors, and one guy asked me
"you’re not going to call out every window as failed seal, are you?! I had an inspector say it was failed once, and it was just dirty!!!"
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I actually have a limitation I turn on when the windows are very dirty. It says I may not be able to determine if the windows have failed seals, lol.
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im usually able to rub on the outside of the window and see if it cleans off, but thats a great idea either way
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Those calculations are right in line with everyone else’s. “Probably not much”.
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Research has shown a tiny difference in energy transfer between fogged windows and clear windows.
Great photo there. Actual temp measurement of each pane would be interesting. As you explained, the actual energy loss isn’t much and averaged over a year might only be a couple of bucks. But there is also another consideration, that a milky fogged window will also reflect radiant energy more than a clear window, and on hot sunny days, may be more energy efficient!
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