site built windows question

[NathanS]

I've about given up on sealed units, how much energy are we really saving if the glazing has to be replaced every 10-20 years because of seal failure. I'd agree that a vacuum is going to be better but maintaining that seal will be a deal breaker. Years ago I was building in the Black Hills, around a mile high, the argon filled windows had been made on the east coast close to sea level. We would watch the glass kind of balloon a little one day and call the local glass shop for a broken window the next 

100% in agreement with this.

I'll bet that the payback time for the $$$ high performance windows vs old single panes + storm windows w/ attention to sealing would take generations to pay back the energy savings difference.

And then, that doesn't account for the fact that the modern windows are unlikely to last as long as the storm window setup.

[JRR]

Perhaps we should forgo windows altogether.   Think more modernly.  Just hang high resolution digital displays on the interior walls.  On the exterior of our perfectly non-permeable structures, mount outward facing cameras aligned with the interior displays, and ...

[MountainDon]

Not a good idea I believe, for something like glass.

I have used vacuum bagging as a means of clamping a thin panel such as 0.030" thick aluminum to one side of a 2" thick XPS foam panel along with a 1/4" plywood panel on the other. Once the adhesive is applied the assembly is placed in a large plastic bag or wrapped with a plastic sheet. A hose and vacuum pump (sometimes a shop vac can be used) is used to evacuate the air. That is sometimes a challenge if a ready-made vacuum bag of the required size is not available. Anyhow, the atmospheric pressure clamping action of the panel assembly is superb at clamping the assembly and squeezing out all the excess adhesive.

Re: sealed units..... we have a window firm here that makes windows here in the same locale they sell. Their factory is a few hundred feet lower in elevation than our home. We installed their windows in 1985. They have all been replaced with a newer, improved version from the same maker, except for one window in the garage. That window still remains free of any internal indications of seal failure. The original windows were all still vapor free when replaced about 10 years ago. The only reason for replacement was to get the newer, much better-insulated frames and do away with the cold weather interior condensation. Not everyone is blessed with a top-rated window maker in their town though.

[NathanS]

Perhaps we should forgo windows altogether.   Think more modernly.  Just hang high resolution digital displays on the interior walls.  On the exterior of our perfectly non-permeable structures, mount outward facing cameras aligned with the interior displays, and ...

Hahaha

I remember a few years ago greenbuildingadvisor trying to advertise for someone attempting to sell "the most airtight" house in Alaska. I'm sure the measurements were astounding, but the house was hideous.

People don't take care of ugly things.

Sometimes "science" causes us "miss the forest for the trees."

[JRR]

Hahaha

People don't take care of ugly things.

Thanks for your kindness toward my effort at humor.  As for care of ugly things ... I'm well tended, so far.

Back on insulated windows, even if the space between glass panes is perfectly evacuated, there is still loss due to radiation.  Which may be significant as delta-temp increases.  No way to win!  Back to the trees and caves!

[1201]

Jrr,I personally would love to have vacuum glass. But I fear that, like a lot of other "high performance" building science, the cure is more costly then the problem.

[Don_P]

The glass in our windows is all shot, it's on the honeydew list. It was one of those bleeding edge of the tech products at the time. They suspended a mylar film layer between the two panes, effectively making a triple pane. The low E coating could be ordered to accept heat from outside or reflect it back inward depending on orientation and location. When new they were a very well insulated window and with the overhangs sized for the seasonal sun angles they did a good job solar tempering the house. The mylar contributed to seal failure so that one isn't done any more. I'm half tempted to make them this time, unsealed with a removable inner pane.

[JRR]

I'm half tempted to make them this time, unsealed with a removable inner pane.

Bingo!  My (real) thoughts exactly.  1/2" tempered in both planes.  With an 1" or more inner space.  Having the inner pane removable for occasional cleaning makes a whole bunch of sense to me.  On windows where visibility isn't an issue, one could always stuff in clear bubbled packaging material for improvements in U factor.

[Don_P]

I remember reading somewhere, sometime, long, long ago...  that at larger than about 3/4" between panes it sets up a convective loop. But yes, making them so they can be cleaned between the panes periodically. There was a prototype I saw somewhere that filled the space with insulation beads at night then sucked them up in the daytime, I don't think it was ever produced. Jefferson's Monticello has double sashes with about a foot in between them in the entry, heavy masonry walls. Another neat feature in that house was the air conditioning duct into his study. Out in the yard some distance from the house is a masonry inlet, then a subsurface small tunnel/duct that terminates in the wall in his study discharging the cooler groundish temp air inside as the breeze blew outside.

[MountainDon]

I'm half tempted to make them this time, unsealed with a removable inner pane.

The reverse of the windows in the house I grew up in.  That WW1 era house had exterior "storm windows" that were hung on the exterior every fall and removed every spring. That sure would have been easier for some of the windows considering it was a 2-1/2 story. 

[akwoodchuck]

Perhaps we should forgo windows altogether.   Think more modernly.  Just hang high resolution digital displays on the interior walls.  On the exterior of our perfectly non-permeable structures, mount outward facing cameras aligned with the interior displays, and ...

Once we have to move to the underground silos, that'll be one option...