# Up to R-11 windows.



## Windy in Kansas (Jun 16, 2002)

Yesterday I learned of a company that produces windows of varying R value with the top of the line being R-11. Not sure if anyone could afford them or on the other hand could afford NOT to have them with the price of energy rising.

Seems pricing is only shown through the dealer network etc. so I don't have a clue what they cost.

Seems to be a great company and just made INC. magazine. The company is called Serious Materials if you'd like to have a look check it out at: http://www.seriousmaterials.com/

Until aerogel glass windows become available to the general public those might be the best alternative. 

And a link to the amazing aerogel glass at: http://p25ext.lanl.gov/~hubert/aerogel/ Good enough for NASA, good enough for me.


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## Harry Chickpea (Dec 19, 2008)

Interesting. The primary idea seems to be sticking two sheets of plastic between an inner and outer layer of glass, and keeping a space between everything. Using tinting and UV coatings on the plastic adds the bulk of the other innovative ideas. My first question is how expansion and contraction of the plastic is handled. I can see where it might sag and make contact over time, or even overheat from the greenhouse effect within the window itself.


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## klickitat (Dec 26, 2008)

hmmmm...... Your thread got me thinking. Has anyone tried doubling up windows? 

What I mean is setting your windows like normal, but then also putting another window on the inside of the wall. Not only would you have two winds insulating but also the dead air space in between the windows. 

This has got to be a minimum of R19 in a six inch wall. Not only that but, you can buy vinyl windows for a very reasonable price. Finishing would be a little different. If this is a new install then you could put the inside window behind the sheet rock. If this is a retro fit then you could trim it with standard molding. If you like a window sill then you could always build an add on and attach to the wall under the inside window.

I have been working on plans for a cabin that I want to build up in Alaska and I think I am now going to use this idea. Thanks for posting this thread. It gave me a good idea to use for myself.


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## ET1 SS (Oct 22, 2005)

We were told that windows do not have an 'R' value, they use the 'U' scale.

Currently a 'U' of 0.30 is considered the 'best', the lower the U value the better.

Our windows are Anderson: Triple-pane, Low-E, Argon-filled, hurricane rated, Energy Star with U=0.32

Our windows [which I put in 2 years ago] are 6 foot wide by 3 foot tall, and they cost me $120 each.


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## SolarGary (Sep 8, 2005)

ET1 SS said:


> We were told that windows do not have an 'R' value, they use the 'U' scale.
> 
> Currently a 'U' of 0.30 is considered the 'best', the lower the U value the better.
> 
> ...


The R value is just the U value divided into 1
That is

R = 1/U

So, an R11 window would have a U value of 1/11 = 0.09

U is thermal conductance (lower better)
R is thermal resistance (higher better)

Gary


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## vallyfarm (Oct 24, 2006)

I actually saw that two window idea. It was on an episode of House Hunters International on HGTV. They were looking at an older building in some former Soviet block country. They said many ney construction buildings still use this idea because it retains heat better. They were only using single pane windows that open from the side. Think "Hedi" in the way they open. Inside would swing in all the way to be against the wall, while the exterior glass swings outward. Mike


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## artificer (Feb 26, 2007)

klickitat said:


> hmmmm...... Your thread got me thinking. Has anyone tried doubling up windows?
> 
> What I mean is setting your windows like normal, but then also putting another window on the inside of the wall. Not only would you have two winds insulating but also the dead air space in between the windows.
> 
> ...


Using ET1 SS's tripple pane windows as an example, you have U=.3, or R=3.3
If you use two of these, you should be at R=6.6. Even if you give the airspace the same R value as one of the windows, you'll have R9.9 as a max. Its going to be less than that due to convective currents in the space between windows, as well as not being argon filled.


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## SolarGary (Sep 8, 2005)

Hi,
It seems to me that the two window units back to back with an airspace is not a bad way to go -- especially if the price is right. The premium, multi layer, heat mirror type windows that get these R9 type ratings are pricey.

One thing you have to watch out for is that some people rate the U value of the window in the center of the window, and others rate the U value of the whole window, including the heat transmitted through the frame. The stickers on windows sold in the US normally give the whole window rating.
Frames can result in a lot of the heat loss for the window, so (I think) its best to concentrate on the whole window rating. Often times when you see the really high ratings they are center of window ratings.

It seems to me that one advantage of using two separate glass units would be that you might be able to figure out how to do in such a way as to decrease heat loss through the frame. If a layer of rigid foam insulation could be sandwiched into the frame between the two glass units, I think it could be a significant improvement in overall window U value.

Another important thing is that for south facing windows in cold climates that can give passive solar heating, you want a high SHGC (Solar Heat Gain Coefficient). 

Good web site for windows stuff:
http://www.efficientwindows.org/index.cfm

Good program for window analysis including solar is RESFEN -- see third link down on this page:
http://www.builditsolar.com/References/windowanalysisrs.htm


Gary


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## TnAndy (Sep 15, 2005)

Only problem with trying to "sandwich" windows together is you either have to make they fairly 'leaky' OR they have to be sealed as tight as the glass units in a thermopane window.

If you'll notice older aluminum storm windows, they actually had vents at the bottom, not only to allow water that penetrated to flow out, but also to vent condensation....about all the old storm windows did was cut some loss due to cold directly hitting the outside glass of the main window....for the money, they weren't very effective.

If you try to seal a window TOO tight, you'll end up with condensation on the insides.....similar to what you see when a dual pane unit fails....they fog up, because the seal fails enough to allow moisture to penetrate, but not enough to escape well.

More effective, and cheaper, are 'window quilts'.....shades or coverings used at night that use a quilted fabric to completely close off a window in the inside.


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## Harry Chickpea (Dec 19, 2008)

"about all the old storm windows did was cut some loss due to cold directly hitting the outside glass of the main window....for the money, they weren't very effective."

Actually, the REAL old storm windows had wooden frames and felt weatherstripping, and were screwed to the exterior framing of the windows. They were quite effective, since they also protected the sash weight channel. My grandfather attached his using eyebolts. He had a spinner made of a hooked angle of rod, with a wooden handle that went over the part you had to twist. You could easily mount those windows in about a minute or two, and they would never come off in high winds.


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## ET1 SS (Oct 22, 2005)

Harry Chickpea said:


> "about all the old storm windows did was cut some loss due to cold directly hitting the outside glass of the main window....for the money, they weren't very effective."
> 
> Actually, the REAL old storm windows had wooden frames and felt weatherstripping, and were screwed to the exterior framing of the windows. They were quite effective, since they also protected the sash weight channel. My grandfather attached his using eyebolts. He had a spinner made of a hooked angle of rod, with a wooden handle that went over the part you had to twist. You could easily mount those windows in about a minute or two, and they would never come off in high winds.


I agree.

We have owned two homes which had the old style of storm windows.

They were hung from eyebolts, they never came loose in storms, they stopped drafts, overall they worked very good.

But they were 'old tech'.

One home we sold and still had those windows.

The second one, we bought into a sales pitch and had new vynal windows put in. The new windows worked, really their best point was that they were 'new'. I think that we would have been better off to have kept the old.


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## SolarGary (Sep 8, 2005)

TnAndy said:


> Only problem with trying to "sandwich" windows together is you either have to make they fairly 'leaky' OR they have to be sealed as tight as the glass units in a thermopane window.
> 
> If you'll notice older aluminum storm windows, they actually had vents at the bottom, not only to allow water that penetrated to flow out, but also to vent condensation....about all the old storm windows did was cut some loss due to cold directly hitting the outside glass of the main window....for the money, they weren't very effective.
> 
> ...


Hi Andy,

I think there is some climate dependence here. We use a combination of:

- Very good thermal shades on some windows -- these have tracks on the sides, internal reflective layers, ... They work fine.

- Single pane Acrylic panels on some windows --they are not sealed, and allow some exchange of air between the dual pane glass and the inside storm. They work fine also.

- For some windows where we want light but don't need a view, we use triple wall polycarbonate (as is used in greenhouses). These are not sealed, just screwed to the window frame. This also works fine.

We never really get condensation, and I think this is a function of our climate being dry. Humidity inside the house is always low.
On extreme cold mornings (like -20F) we sometimes get a little frost on some windows, but it disappears quickly.

The thermal shades are fine, but a lot of people just won't go through the the two times a day up in the morning and down at night, so its not an answer for them. 

It seems to me that with window frames like we have (Vinyl) it would be possible to seal a new dual pane to the inside of the frame quite well. I think that if you did this in dry weather, and put in some desicant packages, it would stay dry inside. I've cut open dual pane units, and they really arn't rocket science, its just a good sealer and around a metal spacer with desiccant in the spacer.

One interesting tool to see if you have a potential for condensation:
http://www.builditsolar.com/References/Calculators/Window/condensation.html

Gary


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