glass blocks windows


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Old 08-26-08, 03:23 PM
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glass blocks windows

Hi, I want to install two columns of glass blocks (7' by 14") in between three studs in the bathroom so we have some natural light. I want to go vertically so I don't have to cut the studs and then to re-do the loading distribution of the exterior wall ( I assume is load bearing). Any thoughts for/ against? Also, the house has aluminum siding and I am not sure how to finish the exterior of the window (frame, insulation). I would appreciate any advice.
 
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Old 08-26-08, 04:56 PM
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Welcome to the forums. A challenging project for your first post, I see!

The most popular glass block system is made by Pittsburgh Corning, so you might Google for more information on them. In short, they have 4 main sizes of block. 6x6 and 8x8 are the most common, but they also have 4x8 and 6x8.

For your application, here's one technique you could use. It might take a little more skill than your average DIY'er could accomplish: make yourself a jamb out of a PVC material like Azek, making it just the right size for the block you intend to use. You'd basically be making your own window. For instance, if you went with the 6x8 block (which would likely be not a stock item, special order), you'd make a window jamb that would be slightly larger- 12 1/2 x 80 1/2- might be a good size for what you want to do. You'd shim the jambs (outside jamb measurement would be 14x82) into place, attaching them to the studs, insulating their perimeter with insulation such as DAP latex foam. I'd recommend Azek PVC for the exterior trim as well- a traditional sloped sill on the bottom and either brickmould or 5/4 trim on the exterior side. The interior could be trimmed in your choice, since the jamb would be only as wide as the glass block itself is... 3 1/4" or so. You'd then grout the block into place using glass block mortar.

You'd need to find out from your local code inspector if it is okay to use glass block so close to the floor, because usually window glass must be tempered if it is within a certain distance (usually <18") from the floor. So I don't think a 7' tall window is realistic.

Keep in mind that glass is a terrible insulator, and bathrooms have high humidity. Put those together in winter months and you'll have some sweaty (or icy) glass and a cold bathroom.

As far as the siding is concerned, it's probably not a DIY job. You would either have to be very good at cutting a finished opening in your siding, slipping in j-channels behind the siding... or take all the siding down in that area of the house and reinstall it once the windows are installed and trimmed.
 
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Old 08-26-08, 08:20 PM
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Originally Posted by XSleeper
Welcome to the forums. A challenging project for your first post, I see!

The most popular glass block system is made by Pittsburgh Corning, so you might Google for more information on them. In short, they have 4 main sizes of block. 6x6 and 8x8 are the most common, but they also have 4x8 and 6x8.

For your application, here's one technique you could use. It might take a little more skill than your average DIY'er could accomplish: make yourself a jamb out of a PVC material like Azek, making it just the right size for the block you intend to use. You'd basically be making your own window. For instance, if you went with the 6x8 block (which would likely be not a stock item, special order), you'd make a window jamb that would be slightly larger- 12 1/2 x 80 1/2- might be a good size for what you want to do. You'd shim the jambs (outside jamb measurement would be 14x82) into place, attaching them to the studs, insulating their perimeter with insulation such as DAP latex foam. I'd recommend Azek PVC for the exterior trim as well- a traditional sloped sill on the bottom and either brickmould or 5/4 trim on the exterior side. The interior could be trimmed in your choice, since the jamb would be only as wide as the glass block itself is... 3 1/4" or so. You'd then grout the block into place using glass block mortar.

You'd need to find out from your local code inspector if it is okay to use glass block so close to the floor, because usually window glass must be tempered if it is within a certain distance (usually <18") from the floor. So I don't think a 7' tall window is realistic.

Keep in mind that glass is a terrible insulator, and bathrooms have high humidity. Put those together in winter months and you'll have some sweaty (or icy) glass and a cold bathroom.

As far as the siding is concerned, it's probably not a DIY job. You would either have to be very good at cutting a finished opening in your siding, slipping in j-channels behind the siding... or take all the siding down in that area of the house and reinstall it once the windows are installed and trimmed.
Hi, thank you so much for the specific info and the advice. Re: the last part, I was thinking that the windows won't open, they are narrow and we also intend to install warming floor system under tiles. Do you think this may help the stuation? Also, the vent would be exactly underneath the windows and we have a ceiling vent.
 
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Old 08-27-08, 05:25 AM
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It depends how cold your winters are, but no- I don't think that will help much. It has to do with heat loss through the glass block, and nothing to do with the window opening or not. Fill a "glass" up with ice water and feel how cold it is to the touch compared to a styrofoam cup filled with ice water. The "glass" also sweats, while the styrofoam cup doesn't. That's a comparison between what your glass blocks will do inside a humid bathroom in the winter, and what your current wall filled with insulation is like.

It's a cool idea, but the bathroom may just be a bad place for it because of the extra humidity and heat. I'm not trying to squash your idea, just warning you about the possible problems that may result.
 
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Old 08-27-08, 06:16 AM
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I understand what you're saying. Is just I don't see how a glass block window in a bathroom will be any different from a regular window. Also, I was thinking the sealed air within the block will act as a "cushion" and I've seen/read in many places about people installing this window in the bathroom. I am glad though that you are honest in your opinion. I still hope that this idea will work.
 
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Old 08-27-08, 06:41 AM
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The block will be better than a standard window due to the thickness of the glass and the overall thickness of the block and airspace itself. It won't be as good as an insulated wall, nor will it be as good as a hi-eff double pane window since it has no LoE coating or thermal break between the panes of glass.

The windows most people put in are pre-built as windows and are much smaller than what you desire. Normally pretty high up on the wall in a std tub/shower or maybe a couple of sq ft in a large walk-in.

If you really want this, I'd suggest looking at pre-made windows from Pittsburg-Corning or one of the acylic block makers. Then you can treat it as a regular window for install.
Building it yourself could cause issues with water penetration and mortar degradation on the exterior. Do you really want to have to re-point the mortar in your windows down the road?
 
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Old 08-27-08, 01:10 PM
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Hi,
Thank you for the answer. I am not expecting the glass blocks to perform better or worse than regular windows. My only concern is that if I go with a premade window, I will have to work also on the structure of the wall and I think is too much trouble for me. I am a handy person and somehow in the field but I know where to stop. If I wouldn't have to re-distribute the loading, etc, then it will be easier. Any ideas?
 
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Old 08-27-08, 02:02 PM
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I'm not sure, as I don't have access to the info anymore, but you used to be able to order the block windows in whatever configuration you wanted. Ex: 2 wide x 6 high, 3 high x 6 wide, etc, etc.

It was a completely sealed unit (no sill or anything) so you could install it in any position you liked, much like some skylights. Nailing flanges all around so it's relatively easy to weatherproof and trim out on the exterior and interior. You could even get them with extension jambs pre-installed.

Of course you would be limited to the multiples of standard block sizes (plus frame), so you might have to frame down a bit between the studs, but you'd prob need to do that anyway.

Heres a link to P-C. Take a look at their sizing. Looks like they have some up to 80" tall or so, though not quite as wide as you said earlier. Easier to close down than to build out.

http://www.pittsburghcorning.com/hom.../lightwise.asp

If you want to do it, I just think it would be better than trying to build your own and expect it to be weatherproof.
 

Last edited by Gunguy45; 08-27-08 at 02:10 PM. Reason: new info
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Old 08-28-08, 10:38 AM
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I am more worried about having to do any modifications to the wall itself. It is a load bearing wall, right (as any other exterior wall). I thought that, giving the fact that I'm laready down to studs, I'kll just build the frame, put the blocks in, insulate, trim and done.
 
 

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