If anyone here has ever used one of these or had one, you know how awesome they are. Really clean look with no dusting required. Unfortunately, the blinds between the glass windows are usually not the greatest performers, just looking at their numbers at least.

Anyone here know of any windows with this "blinds between the glass" feature that actually have good performance ratings? Or do you steer clear of them if you're interested in energy efficiency?

strategery;

I think their test data is usually based on "non" blind insulated glass, I have installed them on several projects and never had any issues with them. I am only guessing that the blind would only improve efficiency

Posted By strategery on 22 May 2012 03:47 AM
If anyone here has ever used one of these or had one, you know how awesome they are. Really clean look with no dusting required. Unfortunately, the blinds between the glass windows are usually not the greatest performers, just looking at their numbers at least.

Anyone here know of any windows with this "blinds between the glass" feature that actually have good performance ratings? Or do you steer clear of them if you're interested in energy efficiency?

It is a nice feature but that third pane of glass where the blinds sit is not really the same as a sealed pane of glass with argon or similar gas. A true triple pane window will have better U-Value ratings than a triple pane with blinds.

If you like the blind feature, they are decent, but if you want true top of the line triple pane windows, don't get the blind feature.

Posted By Lbear on 25 May 2012 03:38 AM

Posted By strategery on 22 May 2012 03:47 AM
If anyone here has ever used one of these or had one, you know how awesome they are. Really clean look with no dusting required. Unfortunately, the blinds between the glass windows are usually not the greatest performers, just looking at their numbers at least.

Anyone here know of any windows with this "blinds between the glass" feature that actually have good performance ratings? Or do you steer clear of them if you're interested in energy efficiency?

It is a nice feature but that third pane of glass where the blinds sit is not really the same as a sealed pane of glass with argon or similar gas. A true triple pane window will have better U-Value ratings than a triple pane with blinds.

If you like the blind feature, they are decent, but if you want true top of the line triple pane windows, don't get the blind feature.

They still perform better than double pane windows though, right? That third pane although not a sealed igu, still improves the performance over a double pane. I have one and it has a u-factor of .26.

Posted By strategery on 25 May 2012 08:55 AM

Posted By Lbear on 25 May 2012 03:38 AM

It is a nice feature but that third pane of glass where the blinds sit is not really the same as a sealed pane of glass with argon or similar gas. A true triple pane window will have better U-Value ratings than a triple pane with blinds.

If you like the blind feature, they are decent, but if you want true top of the line triple pane windows, don't get the blind feature.

They still perform better than double pane windows though, right? That third pane although not a sealed igu, still improves the performance over a double pane. I have one and it has a u-factor of .26.

Depends. There are double pane windows with U-Values lower than 0.26

In theory the third pane does add some air space but as mentioned, it is not a sealed space so that third pane energy value is very minimal at best.

True sealed triple pane windows have U-Values in the < 0.20 range.

The true purpose of the blinds in the window is the benefit of not having to deal with exterior blinds. Any added energy benefits are very minimal at best.

If you get the windows, get them for the blinds, not for their triple pane. The triple pane windows I am looking to get have 0.16 U-Values. As they are true sealed panes of glass.

Good point. The one I got is a south-facing casement window. If I were replacing a north-facing window, I think I'd go with a triple pane without this feature.

depending on the climate, the difference between a a .26 and <.2 is dollars a year. Even in my climate zone 6, triple pane has a 35 year payback. I certainly would not stress over a few u point value differences. however in most cases, the blinds in the glass actually cost a great deal more then triple pane options. Pella and Eagle are about the only 2 that I know of who offer a good blind system. Both use a 3rd pane of glass to protect the blinds. However factor in the cost of a high quality blind to add to it, and figure if the added benefit of being protected behind glass is worth it. I went down that route due to cleaning, but also pets. I have 2 small dogs, one of which loves to look out the window and blinds doesnt top him! What I landed on was a triple pane glass unit with external blinds. This is higher performing at a lower cost then blinds in the glass. Despite the payback time not making much sense, the difference between dual and triple in the whole sceme of things is only about 1k add, so the added comfort benefits are worth it.

I find the negative arguments being made on this thread mostly conjecture with no supporting calculations or thought.  Just looking at the idea of putting blinds between the glass panes from a theoretical standpoint, it looks like an excellent idea.  I have never seen test results for such a configuration, but consider the following:

1.  A typical spacing for the two glass panes where the blinds are placed is 1.12" for a triple-pane window, which is much greater than the optimum for minimum heat transfer of about 1/2" (0.5") to 5/8" (0.625").  However, if the space is divided in half by blinds that are closed at night, then two spaces about 0.5" thick are created, so now there would be an imperfectly sealed set of 3 air spaces for a triple pane window, so now more like a quadruple-paned window with close to optimum air spacing.  (The optimum spacing of around 1/2" results from experimental testing, but is explained by the fact that direct conduction of heat through the air decreases with increasing spacing until the thickness is great enough for convective heat transfer, air motion due to the temperature differences between the glass panes, begins to dominate.)  Therefore, in a predominately heating environment, the blinds could be open or raised during the day, letting in lots of solar gain, while being closed at night, creating something like four panes of glass due to the three air spaces of the optimum width.  (The insulation value of glass or aluminum blinds are both insignificant relative to the insulating value of the air spaces.) 

2.  For a triple-pane window, the low-e coating is often put on surface 5 counting from the outside to the inside.  Therefore, the outer surface of the inner-most glass pane has the low-e coating.  But as it radiates IR energy outward, the radiation immediately hits the aluminum blinds, and we might assume that the long-wavelength IR reflectivity of these blinds might be on the order of 0.8 (80%) or better.  So most of the IR energy radiated from surface 5 is reflected back toward that surface and into the room, saving heat energy.  Further, the reflectivity of 0.8 or higher corresponds to an emissivity of 0.2 or lower, so the window would have a second low-e surface that would further reduce the radiative heat losses. 

In those times when solar heating of the house needs to be reduced, having reflective blinds closed between the glass would be more efficient that having blinds inside those three glass panes.  The closed blinds would reflect almost all the solar energy, and the absorbed solar energy would radiate with low efficiency into the room.  Further a convective loop inside the room across the hot blinds would be avoided. 

The idea of blinds between the glass looks like an EXCELLENT idea from an energy management standpoint, both at times when the house is being heating or cooled.