modifications to an existing clerestory window

I have been looking at the current clerestory windows and thinking on what mods I would make in them after having lived with them for nearly 40 years.

1.  The upper outer window sill is flat.  This means is shades the top part of the glass during the peak sun part of the day.  Thus during the best part of the heat I am shading 1 1/2 to 3 inches of the top of the glass with the window sill.  Max good angle would be 51 degrees from the outside top edge of the glass to the bottom of the over hang eve.  Don't want to go nearly that far as I am shortening the thermal path around the glass by doing that much.  But chopping 30 to 45 degrees off that corner would remove most of the shade while minimally affecting the length of the thermal bridging path around the glass.  The ends of the sill should angle to for a similar reason.  Let more light in.  We are already paying for that glass in night time energy loss so don't we want to bring in as much as possible when we have the sun.  The glass itself is 28 inches high with about 27 inches of that usable glass.  If I get 1 1/2" more sun in for say the hour closest to noon that is a 5% gain vs the little bit of loss for the increased thermal bridging.  And at a 45 degree sun angle that is a 10% gain.



2.  The lower window ledge outside.  Looking at it that is 3 inches that if mirrored or at least pointed bright white would increase light in with little to no cost for the addition.  You can't see it from the ground so painting it white would have very little effect on the outside looks.  If it reflected 50% of the light in that would be like the window was 1 1/2" taller with no corresponding night time losses.

3.   inside lower window ledge also white or mirrored to carry the light as deep as possible inside.  Now the other glitch here is the current window ledge is flat.  Thus with a double pane window that has leaked its argon I now get frost at night that turns into water down the wall.(oops not in draining)  I want it angled with a routed v in the top to carry all the water to a central point and want to hide a water drain tube to each one going down in the wall out of site to a central water collection bucket.  Every fancy window the seals will eventually fail and we need to plan for that to minimize water damage till it can be replaced again.

4.  One window is over the stair well and I needed to plan for access cleaning and repairing it.  At 19 using the cabinets as a jungle gym to get to the top of the wall across the stairwell from it as a place for my upper body to fall out and catch me to work on the window was doable  At nearly 60 that is no longer the case.

So for those dealing with clerestory windows what else would be on your planning list.

That all looks totally rational to me!  :D

C. Letellier wrote:2.  The lower window ledge outside.  Looking at it that is 3 inches that if mirrored or at least pointed bright white would increase light in with little to no cost for the addition.  You can't see it from the ground so painting it white would have very little effect on the outside looks.  If it reflected 50% of the light in that would be like the window was 1 1/2" taller with no corresponding night time losses.

You could go whole hog, and add an exterior operable insulated shutter, hinged at the lower edge and aluminized on the interior surface.  The aluminized skin would reflect maximum visible light (as long as it didn't get dusty).  The shutter, when lowered, could be positioned a bit below horizontal.

I think Steve Baer of Zome Works (and probably a bunch of other) advocated for setups like this.  They work OK when snowfall amounts are low, or when the snow only comes in short (if heavy) bursts.  Where I live, most winters see between 200 and 300 inches (and a big year may be 350" or so), and we often get measurable accumulation (in other words, several inches) for weeks on end.  Even if we get a bit of a break - say a thaw of a couple of days, or a sunny day or two - then we'll usually be right back at it again for another protracted run of snowy weather.  Horizontally operable reflective shutters (i.e. with the hinges having vertical axes) might be able to "harvest" some of the daylight, but I think having the hinges at the bottom edge will be less fiddling over the course of the day to obtain decent gains.

On edit - here's a link to a slide show from Steve Baer and company which shows a similar setup (in this case to harvest solar thermal in water filled drums, rather than for daylighting):
http://www.zomeworks.com/wp-content/uploads/2012/04/Passive-Solar-Design-Slideshow.pdf
Slide 7-9 show such an arrangement.  There may be others in here as well, but I didn't dig further.

C. Letellier wrote:
3.   ... Thus with a double pane window that has leaked its argon I now get frost at night that turns into water down the wall.(oops not in draining)  I want it angled with a routed v in the top to carry all the water to a central point and want to hide a water drain tube to each one going down in the wall out of site to a central water collection bucket.  Every fancy window the seals will eventually fail and we need to plan for that to minimize water damage till it can be replaced again.

Here's a link to a video on mending failed argon filled Andersen thermal pane units

Back when there were a lot of these getting repaired (and replaced), Andersen provided a little drill jig block, which centered the drill between the panes.  I always ended up doing this on a cold, clear (i.e. dry) winter day, to minimize the amount of moisture let into the space between the panes when the vacuum was relieved.  But, the measure and calculate method of drill placement should work, and get your drill in about the right spot (unless one pane is much thicker, i.e. laminated, than the other pane).

Seal up the drilled hole with a goober of clear silicone and a sealing blind rivet.
Maybe something like this: https://www.mcmaster.com/products/blind-rivets/rivet-type~blind/fastener-head-type~domed/aluminum-domed-head-sealing-blind-rivets/

Dry atmospheric air isn't as good an insulator as argon, but it's a heck of a lot better than "all the argon leaked out"!  If you were a fuss-budget about it, you could drill two oles, purge with dry nitrogen, and cork up both of them.

If the argon leaked out of a window, it was replaced with outside air, not a vacuum. The issue would be that moist warm air got in, which would cause condensation in cold weather. Drilling two holes so cold dry air could replace the moist air would work, though it would likely take some cycles of cooling and warming to purge most of the water vapor. (A single hole might even work as well, if you are not going to pump fresh gas in.)  Then sealing the holes would keep the space dry. Injecting nitrogen would probably be good, forcing reactive oxygen and water vapor out. I don't know how pure nitrogen compares in insulating value.

The "window collapse" phenomenon would be a leak that allows high-pressure gas in hot weather to escape, and then the leak seals when there is no longer extra pressure inside. It is like a check valve. When the window is hot, the glass is being pushed apart and a tiny break in the seal can let gas out. At normal pressure, the glass is not being pushed apart and the seal works, and becomes stronger at low temperatures when the glass is being pushed together by outside air.

Glenn -

I may have misunderstood his problem, but if it's the one I'm acquainted with it goes something like this.

Andersen (and likely other manufacturers, but I worked on a bunch of Andersens) tried to fill thermal pane units with argon, rather than some other dry gas (dry nitrogen is cheap and ubiquitous), to achieve (very slightly) marginally better thermal performance - advertising and street cred more than actual performance, since some good drapes pulled at night would have done more for most people than the switch to argon.

Argon is noble, thus monatomic (does not combine chemically to form molecules).  It is small and sneaky and difficult to contain.  Not as sneaky as helium, but still pretty sneaky.

The existing thermal unit seal technology wasn't up to containing argon over the long haul (a matter of years).  The argon would weasel its way through.  Not all at once, but an atom here and an atom there, all day every day, for years on end.  The seals were up to the task of keeping other normal atmospheric constituents out (because that stuff is all "big" on the atomic scale, mostly molecular, and they were, after all, pretty good seals, just not quite up to containing argon in the long term).  To be sure, there is a very small amount of naturally occurring argon in the atmosphere as well, and no doubt very (very!) occasionally an atom of argon managed to find its way from the atmosphere through the seal and back into the thermal pane unit.  Given that the partial pressures of argon were very different between the inside of a newly manufactured thermal pane unit (high partial pressure  more or less pure argon, if I'm not mistaken) and the atmosphere (low partial pressure, since there is very little argon naturally occurring in the ambient air), most of the argon was leaving, not coming.  Basically, this is just a problem in statistical mechanics.  Keep rolling the dice, and more argon will leave than enters the thermal pane unit.

Eventually, the partial pressures would equalize between the interior and exterior of the thermal unit, or nearly so.  Which meant that there was a pretty substantial vacuum pulled between the panes.  Sometimes, the external pressure of the atmosphere, bearing on the many square inches of glass, simply pushed the two panes into contact by elastically deforming them.  Sometimes, one of the panes would crack, letting in a bunch of atmosphere and thus equalizing the pressure.  If the panes "kissed" in the middle, then the middle of the thermal unit essentially behaved as if it were a single pane window, at least locally at the point of contact between the two panes.  Which led to condensation, sill rot and other fun.

The "fix" for panes that had kissed was to drill a vent hole through the thermal unit seal, allowing some air to enter the space between the panes.  If done on a cold, dry day, then very little humidity would enter between the panes.  I did most of the repairs on clear days with below zero (F) temperatures.  Then, a blob of silicone sealant was goobered into the hole and a sealing pop rivet (like the ones I linked to) was set to effect a permanent seal.  If the unit had cracked, however, then it had to be replaced.

Andersen (and probably others, too) re-engineered their seals, solving the underlying problem.  Or, at least, solving it well enough to outlast the warranty period, which is good enough.

But, the OP may have a different problem, and I may have assumed too much.

Kevin

Thanks, Kevin! That makes sense... not a broken seal but chemistry/physics. I always wondered if argon made enough of a difference to be worthwhile. Obviously not in the early versions with the seal issues, maybe now, though I would have to see the relative costs. I went with heat mirror windows in the late '80s when they were new, and have had a number of them fail, some spectacularly (the mylar center "pane" shattering after decades of afternoon sun).

Kevin Olson wrote:

C. Letellier wrote:2.  The lower window ledge outside.  Looking at it that is 3 inches that if mirrored or at least pointed bright white would increase light in with little to no cost for the addition.  You can't see it from the ground so painting it white would have very little effect on the outside looks.  If it reflected 50% of the light in that would be like the window was 1 1/2" taller with no corresponding night time losses.

You could go whole hog, and add an exterior operable insulated shutter, hinged at the lower edge and aluminized on the interior surface.  The aluminized skin would reflect maximum visible light (as long as it didn't get dusty).  The shutter, when lowered, could be positioned a bit below horizontal.

C. Letellier wrote:
3.   ... Thus with a double pane window that has leaked its argon I now get frost at night that turns into water down the wall.(oops not in draining)  I want it angled with a routed v in the top to carry all the water to a central point and want to hide a water drain tube to each one going down in the wall out of site to a central water collection bucket.  Every fancy window the seals will eventually fail and we need to plan for that to minimize water damage till it can be replaced again.

Here's a link to a video on mending failed argon filled Andersen thermal pane units

Back when there were a lot of these getting repaired (and replaced), Andersen provided a little drill jig block, which centered the drill between the panes.  I always ended up doing this on a cold, clear (i.e. dry) winter day, to minimize the amount of moisture let into the space between the panes when the vacuum was relieved.  But, the measure and calculate method of drill placement should work, and get your drill in about the right spot (unless one pane is much thicker, i.e. laminated, than the other pane).

Seal up the drilled hole with a goober of clear silicone and a sealing blind rivet.
Maybe something like this: https://www.mcmaster.com/products/blind-rivets/rivet-type~blind/fastener-head-type~domed/aluminum-domed-head-sealing-blind-rivets/

Dry atmospheric air isn't as good an insulator as argon, but it's a heck of a lot better than "all the argon leaked out"!  If you were a fuss-budget about it, you could drill two oles, purge with dry nitrogen, and cork up both of them.

I have seriously looked at doing shutters but I am in Wyoming so extremely high winds at times meaning really rugged shutters would be needed.  The other catch has been the cost.  Figuring by the time I got rugged, tight sealing, insulate and hopefully fully automated that it would be at least $400 to $500 per window.  Have been seriously watching the vacuum insulated windows as replacements as an alternative.  R13 windows would do amazing things.  I would lose the infrared passive part because the windows would nearly totally block it out.  But once the visible light is absorbed inside it is mostly converted to infrared trapping it inside.  So I have been waiting watching prices and hoping things would improve price wise.  Since the current windows would have to be pulled entirely to vent them and get the moisture out the labor is the same either way.  And the cost of the shutters should eventually make a serious dent in the window cost for replacement.

Yeah, I spent a lot of the formative years of my childhood living on the west side of the Tetons, but we were over in Wyoming quite a bit, too.  Going to Pamida in Jackson was a big deal - they had Brach's pick-a-mix candies, by the pound!  My parents had friends over there, also in Montana and Nebraska, so we spent a lot of time, if not in Wyoming, then driving through.  It is windy, for sure, so the shutters might not be an appropriate choice.

And I concur - if you will need to pull the existing sashes to effect a repair, it pays to consider the upgrade.  The fogged ones could still be repaired, and repurposed - whether for cold frames or a greenhouse, or for someone doing a reno on a tight budget.

If the insulated shutters are a no-go, what you have proposed sounds perfectly reasonable to me.  Though I will take the liberty of suggesting a wild hair, at the end of this comment.

You are likely already well aware of the physical details, but for anyone coming upon this thread in the future, I'll include the following.

Regarding replacements filtering out the incoming IR, I suspect the difference (at those wavelengths - thermal IR, or roughly speaking 8 to 12 microns, maybe even somewhat longer than 12) between standard issue double pane thermal units, including the ones you currently have, and any new windows which you might install, no matter what technological fanciness may be included, is pretty much negligible.

Thermal cameras (whether mid-wave - 3-5 microns - or long wave - 8 microns and longer) require special materials - and coatings - for the lenses.  Ordinary optical glasses block too much of the radiant energy at those wavelengths to be useful as lenses - they are, for all intents and purposes, opaque to infrared.  The atmosphere itself absorbs fairly significantly between 5 and 8 microns, so manufacturers don't even bother with attempting to detect radiant energy in that bandwidth - "nothing to see here - move along, move along...".  

The shorter wavelengths (which will mostly pass through the glass, at least in the visible spectrum, as long as the incidence angle is not too far from the surface normal) are more energetic, and are what will get absorbed, then re-emitted at the longer thermal wavelengths by stuff inside the building.  And even a thin single pane of ordinary glass is pretty much opaque to thermal IR, so performance differences will depend on: differences in conduction through the panes (probably not significant if both old and new are glass); differences due to variations in convection in the gap between the panes (you've spec's the new replacements as vacuum, so should be quite a bit better than the existing, when new); and differences in radiation (emissivity and reflectivity) of either the inner or outer panes (and this could be significantly different, because modern coatings do offer improvements, especially in rejecting incident radiant energy at lower incidence angles, i.e. well off the surface normal, e.g. high summer).  If trying to annualize thermal gains, then rejecting summer incident radiation via coatings may not be the right choice, anyway; but if annualized solar isn't an objective, then the modern wonder coatings which alter the surface properties of the glass panes will be helpful.

The wild hair: the SolaRoof scheme (not Elon Musk's!) uses soap bubbles between panes as removable insulation.  This has been successfully used in greenhouses, but is a lot of plumbing and leakage potential, especially in a dwelling.  So, I don't know that I can recommend it as a solution in your case, and I don't (yet) have any experience, even in a greenhouse.  I think it is a pretty darn clever idea, but the complication and mess also seems a little daunting.  Told you it was a wild hair!