ICFconstruction
Veteran Member
Posts:1323
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| 17 Jun 2009 07:05 PM |
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How efficient are glass block windows? I may use glass block windows, on my own ICF house, put glass blocks flush with the outside and the inside of the wall, leaving 3-4" between them. What are opinions of that method? |
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| Brad Kvanbek - ICFconstruction.net |
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lambabbey
Basic Member
Posts:148
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| 17 Jun 2009 10:01 PM |
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I looked into glass blocks awhile back and was surprised to find that the most substantial ones from Corning were under an R-2. Obviously, going with two layers of glass block and a healthy air space between them is going to get you beyond an R-4, I just don't know how far. I would be more concerned about the amount of light you'd be allowing in through those four thick layers of glass. Those blocks are substantial.
Take a look at Corning's Vistabrik block, which is a solid 3"-thick block of glass that I believe you can still see through. Their R-values are even lower, however if light is what you're after, they may be a better solution. You'll find a PDF with the various Corning glass block products (including the Vistabrik) HERE.
John |
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| John A Gasbarre<br>Lamb Abbey Orchards<br>Union, ME 04862<br>[email protected]<br> |
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Alton
Veteran Member
Posts:2157
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| 18 Jun 2009 07:25 AM |
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Brad,
My only concern would be how would you ever be able to clean the inner surfaces of the glass block? |
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Residential Designer &
Construction Technology Consultant -- E-mail: Alton at Auburn dot Edu Use email format with @ and period .
334 826-3979 |
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ICFconstruction
Veteran Member
Posts:1323
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| 18 Jun 2009 07:34 AM |
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If it is sealed would I need to clean in-between the glass blocks? |
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| Brad Kvanbek - ICFconstruction.net |
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Alton
Veteran Member
Posts:2157
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| 18 Jun 2009 08:54 AM |
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Brad,
Since it is almost impossible to perfectly seal the air space between the two wythes of glass block, I would be concerned about moisture drying and leaving stains on the inside face. I may be wrong about the possibility of moisture getting inside but if it does then it would not be easy to remove. What if the inner wythe of glass block was removable? |
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Residential Designer &
Construction Technology Consultant -- E-mail: Alton at Auburn dot Edu Use email format with @ and period .
334 826-3979 |
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ICFconstruction
Veteran Member
Posts:1323
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| 18 Jun 2009 09:05 AM |
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"What if the inner wythe of glass block was removable?" That sounds difficult, maybe if the inner or outer was a storm window?
Isn't it Pella windows that has a system with an insulated window and a single pane that fits into the sash?
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| Brad Kvanbek - ICFconstruction.net |
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aardvarcus
Basic Member
Posts:226
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| 19 Jun 2009 07:37 PM |
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Speaking of Pella, don't they offer a window that has a removable wavy glass insert? That would give you the wavy glass look, a good insulated window, and a chance to change your mind and go to clear glass if you want. |
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Brock
Advanced Member
Posts:599
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| 23 Jun 2009 03:29 PM |
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I am not sure who made it, but we have "glass block" along our kitchen wall between the cupboards and countertop. It is great for extra light in there. It came in frosted, glass block, wavy, rain or clear and as aardvarcus said you can change out the glass if you really want to. We also have a storm for ours that has to be put on from the outside, but we really like it. |
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| Green Bay, WI. - 4 ton horizontal goethermal, 16k gallon indoor pool, 3kw solar PV setup, 2 ton air to air HP, 3400 sq ft |
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slenzen
Basic Member
Posts:434
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| 24 Jun 2009 09:25 PM |
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I saw some videos online of water filled glass block windows. Pretty interesting. Also what about acrylic or fiberglass glass block windows/panels such as Kalwall. |
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ICFconstruction
Veteran Member
Posts:1323
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| 24 Jun 2009 09:58 PM |
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Water filled? Not in MN. Does water insulate better than air, maybe magnify light?
The Kalwall look very nice but not cheap or readily available.
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| Brad Kvanbek - ICFconstruction.net |
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ICFconstruction
Veteran Member
Posts:1323
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| 30 Sep 2010 07:51 AM |
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I included openings in the 11" thick ICF wall for ten 48"x32" glass block windows. I plan on doing two windows per opening, one flush with the inside, one flush with the outside. There will be a 4" air space in-between.
I am thinking of putting shinny metal in the air space to help reflect light inside. I am thinking of the mirror like metal that they use inside the tube type sky lights. Anybody have any ideas? Where would I get it? |
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| Brad Kvanbek - ICFconstruction.net |
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arkie6
Veteran Member
Posts:1453
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| 01 Oct 2010 12:12 AM |
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You can get mirror like aluminum foil tape at most autoparts stores such as AutoZone. It comes in a roll ~2" wide. |
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ICFconstruction
Veteran Member
Posts:1323
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| 01 Oct 2010 06:52 AM |
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Whatever I put in there will forever be there, I am hoping for something heavier that I can mechanically fasten so it can't fall, or curl. |
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| Brad Kvanbek - ICFconstruction.net |
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arkie6
Veteran Member
Posts:1453
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| 01 Oct 2010 11:24 AM |
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Just an idea, but what about using actual cut-to-fit pieces of mirror glued with construction adhesive to the framing. |
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slenzen
Basic Member
Posts:434
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| 01 Oct 2010 11:34 AM |
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post some photos of your project, it sounds interesting |
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jerkylips
Basic Member
Posts:359
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| 01 Oct 2010 03:26 PM |
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just thinking out loud (well....on screen).. How much difference do you think there would be between something metallic/reflective vs. just painting that section a bright white before putting in the glass block? White reflects a lot of light as well.. |
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cmkavala
Veteran Member
Posts:4324
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| 01 Oct 2010 06:09 PM |
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get 4" mirror strips at a local glass shop, they probably throw a lot of the narrow stuff away |
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| Chris Kavala<br>[email protected]<br>1-877-321-SIPS<br /> |
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ICFconstruction
Veteran Member
Posts:1323
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| 02 Oct 2010 09:01 AM |
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Maybe mirrors would be the answer.
Steven, I will post some pictures, but things are going slow, I have to do customer jobs first. But you can always drive over, 5 miles west of Mound. |
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| Brad Kvanbek - ICFconstruction.net |
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greencleaning
New Member
Posts:50
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| 16 Dec 2010 07:13 AM |
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Even though glass block windows appear to be solid, residential glass blocks are hollow. When the two hollow glass block halves are fused together under heat, the air inside them contracts as it cools. This creates a partial vacuum to increase the insulation level. They become as airtight as an actual wall reducing air filtration and increasing energy efficiency.
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Here's to you, your health and the health of your family. <a href="http://www.cleaningcleaner.com">Eco friendly cleaning</a>
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ICFconstruction
Veteran Member
Posts:1323
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| 16 Dec 2010 07:43 AM |
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Has anyone heard of a "U" or "R" rating for glass block? |
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| Brad Kvanbek - ICFconstruction.net |
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Bigrig
New Member
Posts:92
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| 16 Dec 2010 04:22 PM |
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Per the Pittsburg Corning website:
"The insulation or R value of the Premiere Series (3 7/8 inch thick) glass block when installed with mortar is 1.96. The reciprocal U value is .51. The R value of our Thinline series (3 1/8 inch thick) glass block when installed with mortar is 1.75, the reciprocal U value is .57"
Not a heck of a lot! Two layers of block, with an airspace, would still be less than R-5. |
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ICFconstruction
Veteran Member
Posts:1323
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| 16 Dec 2010 07:25 PM |
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A little better than the average widow though. |
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| Brad Kvanbek - ICFconstruction.net |
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lambabbey
Basic Member
Posts:148
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| 16 Dec 2010 07:41 PM |
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Posted By ICFconstruction on 16 Dec 2010 07:25 PM
A little better than the average widow though.
I'd say a glass block wall made with a single layer of blocks would be on par with the typical CHEAP window, not "a little better than average window." An R-2 window is considered pretty shoddy these days. Mine are about an R-7.2 and I've seen them all the way up to R-9.6. Alternatively, the glass block wall with 2-layers of block and a space between would be quite an expense for the fixed thermal sinkhole you'd be creating. |
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| John A Gasbarre<br>Lamb Abbey Orchards<br>Union, ME 04862<br>[email protected]<br> |
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ICFconstruction
Veteran Member
Posts:1323
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| 16 Dec 2010 08:43 PM |
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The double glass block window won't be too expensive. But what do you mean "fixed thermal sinkhole"? |
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| Brad Kvanbek - ICFconstruction.net |
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lambabbey
Basic Member
Posts:148
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| 16 Dec 2010 09:14 PM |
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Posted By ICFconstruction on 16 Dec 2010 08:43 PM
The double glass block window won't be too expensive. But what do you mean "fixed thermal sinkhole"?
A glass block wall will likely be the point of greatest thermal loss in the whole structure. |
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| John A Gasbarre<br>Lamb Abbey Orchards<br>Union, ME 04862<br>[email protected]<br> |
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ICFconstruction
Veteran Member
Posts:1323
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| 16 Dec 2010 09:32 PM |
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That may be, but at 48" by 32" windows, I can live with it. |
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| Brad Kvanbek - ICFconstruction.net |
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lambabbey
Basic Member
Posts:148
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| 16 Dec 2010 10:09 PM |
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Posted By ICFconstruction on 16 Dec 2010 09:32 PM
That may be, but at 48" by 32" windows, I can live with it.
Just as long as you don't need to look out. . . |
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| John A Gasbarre<br>Lamb Abbey Orchards<br>Union, ME 04862<br>[email protected]<br> |
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ICFconstruction
Veteran Member
Posts:1323
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| 17 Dec 2010 07:14 AM |
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No I have other widows and doors for that, these will be high on 12' and 17' walls, for light. |
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| Brad Kvanbek - ICFconstruction.net |
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slenzen
Basic Member
Posts:434
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| 17 Dec 2010 09:19 AM |
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have you looked at acrylic block windows? they have fixed, casement, and awning if you need some ventilation. Hylite is the brand I am aware of. they claim a better performance than glass block, and equivalent to a double pane window.
http://www.hy-lite.com/homeowners/products/block_windows/
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slenzen
Basic Member
Posts:434
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| 17 Dec 2010 09:34 AM |
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or double/triple wall polycarbonate panels |
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Bigrig
New Member
Posts:92
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| 17 Dec 2010 12:49 PM |
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Assuming you really want the glass block for the outside portion of the window, I would place a fixed energy-efficient window on the inside. Something that can be removed if you need to get into the space between windows. I have yet to see glass block windows that would not let some moisture diffuse through the many mortar joints. In fact, if you look at the Pittsburg Corning website for installation betails they use "expansion strips" on some of the sides to allow expansion/contraction of the glass block. This will certainly prevent any assembly from being vaportight. |
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ICFconstruction
Veteran Member
Posts:1323
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| 17 Dec 2010 05:15 PM |
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I am concerned about moisture in-between the the two glass block windows. I was thinking when it is warmer in-between, the moisture would be forced out. Not sure how concrete would affect that.
I had thought about one window being a fixed pane, but I would not want a functional pane, and could not take out a nailer flange type. |
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| Brad Kvanbek - ICFconstruction.net |
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bsmith1051
New Member
Posts:17
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| 28 Apr 2011 07:45 PM |
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maybe throw a dehumidifier 'packet' in there before you close it? The kind they include in electronics shipments.
I've been thinking about doing something similar (dual rows of block-windows) but the still-relatively-poor insulation plus the condensation issue has dissuaded me. The newest acrylic or glass block-windows can be purchased with low-e coating and rate an R-3. I think the small 'window' size (hence, lots more framing material) hurts the performance of block-windows, in general.
P.S. Off-topic, but now I'm thinking about making a mini 'sunroom' instead, with regular high-performance windows separated by a foot or two. If I build it on the south-facing wall and include operable openings at top and bottom, then I might be able to use it as a combination trombe wall (winter) and solar-chimney (summer). |
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jonr
Senior Member
Posts:5341
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| 28 Apr 2011 11:25 PM |
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Just use a fixed window and stick on vinyl film if you really don't like the transparency.
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EnergyWiseBuilding
New Member
Posts:80
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| 29 Apr 2011 07:09 AM |
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I guess I don't understand why a double glass block window wouldn't be more energy efficient than a insulated plate glass window. Since glass is not a good insulator it must be up to the air in-between. A one inch insulated plate glass window would have 3/4" of air? And the double glass block window 5".
What am I missing? |
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jonr
Senior Member
Posts:5341
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| 29 Apr 2011 09:24 AM |
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It might be close except that many windows don't use air and that 5" causes more convection and performs worse than 3/4".
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bsmith1051
New Member
Posts:17
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| 29 Apr 2011 01:51 PM |
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The frame is an even worse insulator than the glass/air/glass combo and a block-window has lots of framing. |
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ICFconstruction
Veteran Member
Posts:1323
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| 12 May 2011 06:22 PM |
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should a put a weep rope to the outside? A small hole to the inside? |
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| Brad Kvanbek - ICFconstruction.net |
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dxjnorto
New Member
Posts:2
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| 15 Jan 2012 10:36 PM |
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I like glass block primarily for aesthetic reasons. I have always wanted a curved semicircular glass block shower that extends beyond the envelope of the home for natural light to wake up in the morning! The more I look into it, the more impractical it seems. I know there are all kinds of ways to bring "natural" type light into an indoor space, but I was looking for something unique, not a shower with a bunch of lights or a shower with a bunch of windows. While I was looking at the Vistabrik that lambabbey mentioned I found these — they are called Vistabrik solar wall tubes and Focus solar wall tubes. I'm new so the forum may not let me post the link, but FWIW here's the current link to that PDF — if the link goes dead it's under Resources/Product Literature. Would definitely not work for a curved wall at all, and I suppose a stacked wall made of them would be prohibitively expensive, but would work pretty good for what you guys are talking about, except they are not thick enough for most ICF structures. They come in singles and doubles, solid and hollow. For some reason the double hollows have a much better R-value than the single hollows. Maybe I could build a curved solid concrete thermal mass wall and put enough of these in there to give me the effect I am seeking. |
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dxjnorto
New Member
Posts:2
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| 15 Jan 2012 11:20 PM |
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Dayum. I guess that idea is out. I just found the Price List — would cost a thousand for a couple of them. It says they are made to order and they do come in different depths up to 16". Too bad. They look nice. On my budget I'll have to start collecting old pop bottles. If they can be found.  |
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ICFconstruction
Veteran Member
Posts:1323
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| 16 Jan 2012 08:14 PM |
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Can those prices be right?
For my windows, does anyone have an opinion, should a put a weep rope to the outside? A small hole to the inside? |
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| Brad Kvanbek - ICFconstruction.net |
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James Patrick
New Member
Posts:8
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| 11 Feb 2012 01:14 PM |
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Brad, good question. I don't know, but would depend on humidity. I don't see how it would hurt though.
I'm also thinking of doing double glass blocks to let light into the top gable ends of my great room/kitchen. Trapizoid & triangle windows are $$$
Rear of house will be built into a hill & I don't want anyone walking on the hill behind my property looking down into my house. I also want the greater strength there, blowing gravel etc.
Front of great room will allign with a drive through roofed portico, so the upper view would only be of the ceiling of portico with regular windows.
R value could be increased by installing 2 layers of clear UV resistant corrigated plastic in the air space between glass blocks, from big box store |
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ironlog
New Member
Posts:1
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| 07 Sep 2012 09:10 AM |
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Maybe you could use a thermopane, storm window for the outside 'layer' instead of another glass block window. Many window companies make what they call a 'dead lite' window for store fronts etc. The ones I had were from Wellington and were like vinyl storm windows but had thermopanes for the glazing. I used them as storm windows over leaded glass windows in a 100 yr old house. Worked great to keep the weather and sound at bay. They could be removed to clean inside the 'well'area. I sealed them in with caulk and needed to clean the insides only every 4-5 years. Worked great. |
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ICFconstruction
Veteran Member
Posts:1323
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| 07 Sep 2012 03:34 PM |
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I have put in three double glass block windows so far 32"x48". Hardly cheaper than regular windows, but they look good and since both sides are flush there is no where for dust, water or snow to sit. |
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| Brad Kvanbek - ICFconstruction.net |
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Roberth
New Member
Posts:97
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| 13 Sep 2012 01:51 AM |
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Posted By EnergyWiseBuilding on 29 Apr 2011 07:09 AM
I guess I don't understand why a double glass block window wouldn't be more energy efficient than a insulated plate glass window. Since glass is not a good insulator it must be up to the air in-between. A one inch insulated plate glass window would have 3/4" of air? And the double glass block window 5".
What am I missing?
There are several problems with blocks. The internal gap of the block is too large and promotes convection loops. There is also a lot of surface area (top, bottom, sides) that would contribute to thermal bridging. There will also convection loops in the air space between the 2 sets of blocks.
We know cold pulls in moisture so you would be pulling moisture in between the windows which would cause rot and or mold.
The mortar will be stressed by expansion/contraction, I wouldnt count on it staying air tight. Plus it would be vapor permeable with moisture being pulled to the cold center cavity.
All of the thermal bridging makes this window much different than a dual/triple pane window having the same area.
I also think there would be large reduction in light transmission with the second layer of blocks. If you are looking for natural light a smaller standard window would let in a similar amount of light. |
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ICFconstruction
Veteran Member
Posts:1323
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| 13 Sep 2012 11:18 AM |
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I will see this winter the temperature of the inside. The light appears the same. No condensation yet. |
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| Brad Kvanbek - ICFconstruction.net |
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ICFconstruction
Veteran Member
Posts:1323
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| 03 Dec 2012 08:32 PM |
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When My ICF walls were 70 degrees the double glass blocks were 68 and the Marvin Integrity window glass was 65. It would appear that in reality the double glass block windows are more efficient than thought. |
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| Brad Kvanbek - ICFconstruction.net |
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jonr
Senior Member
Posts:5341
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| 04 Dec 2012 09:43 AM |
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These look better than typical but a single block still can't outperform a good window. Surface temp is not an accurate test, I'd stick with manufacturer U values.
http://pittsburghcorning.com/products/energy-efficient-panels.aspx
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ICFconstruction
Veteran Member
Posts:1323
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| 04 Dec 2012 07:13 PM |
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Why wouldn't surface temp not be an accurate gauge of energy efficiency? |
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| Brad Kvanbek - ICFconstruction.net |
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jonr
Senior Member
Posts:5341
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| 04 Dec 2012 07:57 PM |
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You would have to at least make sure that 1) air flow via convection is exactly the same for all samples (both sides), 2) you don't disturb what you are testing - if you use an IR thermometer, the surfaces have to have the same emissivity and 3) how do you account for the frame? (ie, you have some averaging to do)
This is why ASTM has standards for testing.
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ICFconstruction
Veteran Member
Posts:1323
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| 04 Dec 2012 09:00 PM |
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I don't believe ASTM testing is all that. The two windows are at the same height near each other on adjoining walls, at night, so no sun. I have done it a few times and shoot the glass. It is apparent that the double glass block is more energy efficient than the Marvin Integrity low-e and all. |
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| Brad Kvanbek - ICFconstruction.net |
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jonr
Senior Member
Posts:5341
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| 04 Dec 2012 10:11 PM |
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Do you mean two layers of glass blocks or a single block (that has two glass layers)? The former (with 4 layers of glass) would do OK (according to ASTM measured U values).
When using an IR thermometer, stick some masking tape on the surfaces to get accurate comparisons. |
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ICFconstruction
Veteran Member
Posts:1323
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| 05 Dec 2012 07:44 AM |
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I put in two glass block windows in each opening of the ICF wall. One flush on the inside and one flush on the outside. We have done this before on commercial buildings and I wondered how energy efficient it was. The consensus here was that it was not as a decent low-e.
I am convinced it is better. |
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| Brad Kvanbek - ICFconstruction.net |
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jonr
Senior Member
Posts:5341
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| 05 Dec 2012 12:49 PM |
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The pittsburghcorning ones are around U .19 when doubled. That is better than most windows.
On the other hand, if you have test results that don't correspond with U values, I'm skeptical. |
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Lee Dodge
Advanced Member
Posts:714
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| 05 Dec 2012 01:14 PM |
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Posted By ICFconstruction on 03 Dec 2012 08:32 PM
When My ICF walls were 70 degrees the double glass blocks were 68 and the Marvin Integrity window glass was 65. It would appear that in reality the double glass block windows are more efficient than thought.
How were these temperatures measured? |
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Lee Dodge,
<a href="http://www.ResidentialEnergyLaboratory.com">Residential Energy Laboratory,</a>
in a net-zero source energy modified production house
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Dana1
Senior Member
Posts:6991
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| 05 Dec 2012 04:33 PM |
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Posted By jonr on 05 Dec 2012 12:49 PM
The pittsburghcorning ones are around U .19 when doubled. That is better than most windows.
On the other hand, if you have test results that don't correspond with U values, I'm skeptical.
The difference is that manufactured window U-factor values are the average for the whole assembly, not just center glass. To get to the true equivalency you'd have to factor in the losses through the mortar or silicone, etc. and the thermal bridging would still be pretty severe with some materials. But I agree that doubled-up, with even a 1/2" of air gap between them would deliver very decent performance. (It passed muster for basement windows on a recent deep energy retrofit I was involved with, but I didn't see what they assigned for a U-factor.) |
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