Replies

1. 
   Guest_ | Nov 26, 1999 02:31am | #1

   *
   If you mean COST effective, a .75 double pane glass is it. Beyond that it is a case of diminishing returns.

1. 
   Guest_ | Nov 26, 1999 02:37am | #2

   *My understanding is that once you get over 3/4" space between the panes, you start to get the convection you mentioned, and begin to loose the effectiveness of having the space in the first place. I think the reason for wider spaces is to accomodate the flexing of larger panes. That is why as the unit gets larger, typically so does the spacer bar. I live in The Puget Sound region and have long questioned the added costs of "low e" and "argon". What have you found out about that stuff? - jb

2. 
   shurleey | Nov 26, 1999 03:59am | #3

   *
   I would say that cost is the ultimate measure of efficiency;
   after all we spend more on materials (glazing) to save money
   in long term, with added comfort a bonus. My information on
   low-e and argon in this climate suggests that low-e is worth
   the added cost ( especially since it is generaly needed to meet code required u values). Argon is not worth the cost window folks tell me and often leaks off after several years.

3. 
   Guest_ | Nov 26, 1999 04:08am | #4

   *
   Years ago I saw a system at an energy fair that would pneumatically fill the space between the panes with styrofoam bits when the window was not needed, such as at night. Practical only for fixed panes, of course, but wouldn't something like this be interesting? With a 2" space you could have an R-10 window, at least the 75% of the time you aren't around to look out it.

1. 
   Guest_ | Nov 26, 1999 06:07am | #5

   *I've only used the Low-E in four season sun rooms, skylights, and other areas with ALOT of windows where solar heating might be a problem. I can feel the difference on a warm sunny day.I've been told that the difference in price between argon and air isn't paid off in the usefull life of the window.I saw a vacuum filled window several years ago, had small glass beads every inch or so to keep the panes separate. If a true vacuum, the insulation would be better than the surrounding wall. Then again, if they can't keep moisture out of the glass panes now, how will they ever keep a vacuum in?

4. 
   shurleey | Nov 26, 1999 08:03am | #6

   *
   Years ago I had a roomate who salvaged sliding glass door
   panes and the big bean bag "chairs" filled with styrene
   beads for just such an insulation scheme as Andrew mentions.
   Trouble was static charges made it impossible to remove the beads from the glass by any practical means.Sure were a lot
   of beads all over the place.

5. 
   Guest_ | Nov 26, 1999 08:49am | #7

   *
   Surely our best minds can solve this one! It'd also make curtains unnecessary.

1. 
   Guest_ | Nov 26, 1999 12:04pm | #8

   *...so who's got curtains?

1. 
   Guest_ | Nov 26, 1999 07:29pm | #9

   *We wish you did.

1. 
   Guest_ | Nov 26, 1999 08:30pm | #10

   *The system you mentioned was "Beadwall". It was invented by Steve Baer of Zomeworks. Baer was a pioneer of passive solar energy. Zomeworks is still in buisness, but I don't think they market Beadwall any more.

1. 
   Guest_ | Nov 27, 1999 01:46am | #11

   *Geez, Mike, you are a deep well of knowlege.

2. 
   Guest_ | Nov 27, 1999 06:51am | #12

   *Mike. I kept thinking it was Bruce Anderson who invented the Beadwall. nnyway, the version I remember had an air pump/vacuum attached. The polystyrene beads were pumped into the space and the vacuum sucked the beads out.The designers of the Saskatchewan Conservation House had considered using this window system, but after careful and thorough analysis turned it down. I don't hear much about Steve these days. But then I don't read the solar journals. GerneL.

6. 
   Payson | Nov 30, 1999 06:23am | #13

   *
   shurleey,

   Almost all replacement window come with 7/8 units
   already which would leave approx. 5/8 insulating space.
   I live in the northeast(central Maine) and can tell you
   from experience, argon is not really worth the money, but
   low e is a must! On a different note the insulation value
   of your glazing also greatly depends on the thickness of
   your glass.
   Payson

7. 
   shurleey | Jan 04, 2000 11:46pm | #14

   *
   What's more effective (.5",.75",1.0")insulation
   gap between sealed panes assuming low-e modern
   glazing with modern high efficiency edge spacers.
   I understand that at some distance convective
   currents reduce thermal performance. By the way,
   my climate is in the northwest, damp and maritime,
   infrequently below freezing. Opinions? Theorys?