Replies

1. 
   rez | Nov 30, 2004 09:45pm | #1

   Minimal at best?

    

2. 
   BossHog | Nov 30, 2004 10:14pm | #2

   I've wondered that too.

   Seems to me you could have a pretty good convection air currents running around inside that tube.

   There are two ways to be rich. Make more or desire less.
1. 
   jhausch | Nov 30, 2004 10:30pm | #3

   Quick! - someone patent a solar tube skylight with a solar controlled foamboard aperature.

3. 
   JohnSprung | Nov 30, 2004 11:29pm | #4

   I'd think you could improve them a lot by putting in a few horizontal plastic disks with spacers, maybe an inch or so apart.  Sort of like multiple horizontal storm windows.  Make the stack removable for occaisional cleaning.

    

   -- J.S.

    

1. 
   rez | Nov 30, 2004 11:34pm | #5

   Or removable magnifying lens for winter use of passive solar.

   be a sun 

4. 
   Sphere | Dec 01, 2004 12:33am | #6

   being technichally 'glazing'..i don't think there is an 'R' value.

   Maybe an 'e' value for emissivity, but not resistance to heat transfer.

    

   Spheramid Enterprises Architectural Woodworks

   Repairs, Remodeling, Restorations. 

    

    

1. 
   xMikeSmith | Dec 01, 2004 01:26am | #7

   john .. we've installed about  100 SunTunnel.. and aabout 3 Solartube..

    both of them have no insulation value..

   or as close to nil as you can get.

    the SunTunnel does have a double gasketed lens at the bottom which will reduce some of the convection losses..

   they will lose less heat than a conventional skylight..

   the column generally goes thru an uninsulated attic so the heat loss thru the room side lens is also losing to the column walls as well as the roof lens..

   if i were doing a heat loss calculation i would figure the nominal  area of the lens ( with Suntunnel that would be a 14" diameter or a 22" diameter ).. i would figure the delta -T at  70deg  ( 70 in - zero out ).. and the r-value at 1 which would also be your u-valueMike Smith   Rhode Island : Design / Build / Repair / Restore

1. 
   JohnT8 | Dec 01, 2004 08:04am | #8

   john .. we've installed about  100 SunTunnel.. and aabout 3 Solartube..

   So I take it that you prefer the SunTunnel?

   I've never installed one, but have seen them in use maybe half a dozen times.  Each time I was amazed at the amount of light they put out.  Basically 'free' light...assuming they're not drawing all the heat out of the house.

   I suppose if it was passing through an uninsulated attic (4 out of the 6 times I saw them), you could wrap insulation around the column.  I'm kinda surprised they haven't come up with a vacuum sealed top to them or some such to try and decrease the heat loss (a variation on Thermomax's solar heat collectors)... but vacuum sealed probably wouldn't last out the 10 year warrenty.

    

    jt8

1. 
   TJK1141 | Dec 06, 2004 11:06pm | #9

   If the top and bottom lenses of the tube are sealed to outside air, you essentially have a double-pane window three feet thick. Even if the air in the tube was at the outside temperature (at night?), the plastic lens at the bottom would be the only heat sink I can think of. Probably no worse than most window surrounds or vent fans.

1. 
   IMERC | Dec 06, 2004 11:09pm | #10

   condensation is always a problem...

   the tube seam is never always sealed...

   Life is not a journey to the grave with the intention of arriving safely in a pretty and well preserved body, but rather to skid in broadside, thoroughly used up, totally worn out, and loudly proclaiming

   WOW!!!   What a Ride!

2. 
   xMikeSmith | Dec 07, 2004 12:59am | #11

   you develop a convection current in spaces that big... so the transfer of heat  increases..

   SunTunnel offers a double glazed lens at the ceiling for cold climatesMike Smith   Rhode Island : Design / Build / Repair / Restore

3. 
   JohnT8 | Dec 08, 2004 12:29am | #12

   SunTunnel is your tube of choice in cold climates?

    jt8

4. 
   xMikeSmith | Dec 08, 2004 01:40am | #13

   SunTunnel is my tube of choice in any climate...

   Velux owns them nowMike Smith   Rhode Island : Design / Build / Repair / Restore