hose some water at it and see if it leaks.....

Is the first floor block more shaded than the second?

"Is the first floor block more shaded than the second? "

Yes.

Glass block is a poor insulator.

heat rises

"Glass block is a poor insulator."

when I pass the glass block window on the 1st fl, I can feel the wind. This is so uncomfortable and I am in chicago. Isn't there any improvement for this glass block for last 10 years?

207moak is maybe closest: unlike insulated windows or storefronts with an integrated thermal break, glass block will simply conduct heat or cold through.

while the problem shouldn't have been made worse if you replaced glass block with glass block, if you installed the glass block in the place of an insulated window, the difference in what you're feeling makes sense.

more or less caulk shouldn't, in itself, make the difference, unless there is an open cavity left somewhere.

finally, if the contractor rough framed the opening and then just trimmed in around the glass block, it's possible there is an air cavity left between the framing and the glass block at the perimeter of the glass. this should have been stuffed with insulation (or sprayed full of foam). if it wasn't, that could cause some draft.

the physics of it are pretty simple. two things:

1. you want as much material as possible - as dense as possible - between the inside and outside. siding on the outside and drywall on the inside, for example, means that there may only be 1 1/4" of material between you and the outdoors when there could be as much as 5 1/2" to 6" of material. the air in between doesn't do you any good unless its a vacuum-sealed assembly in an insulated window.

2. material that serves as a conductor rather than an insulator doesn't help with #1. metal exposed both outside and inside bridges rather than insulating - basically tries to deliver the same temperature at its outside and inside faces. same with glass. these can also cause larger issues because cold delivered from outside to inside can turn into condensation when it hits the heated interior. this kind of moisture is not your friend.

There's no thermal break.

And the jambs are uninsulated.The cavity around the window should be stuffed with insulation.

Is is a masonry building?

Where's there a valley in Chicago? It's FLAT!

Are you an Architect, CMRHM?

kill all glass block, most of it died in the eighties

Steven Ward:

It is always nice to see you posting your comments! Happy New Year!

Thanks for your explanation for including all the possibilities. I think there should have some air cavity in the joint around glass block and masonry wall. otherwise, there is no way the conduction of glass block can produce such strong chilly wind around that window area.

The contractor put a wood trim around the joint area. I doubt they might intend to cover sth. I am going to remove that trim to see what cause the problem.

make:

I am still taking ARE, so I am not.
Sorry to disappoint you if you think my q is too naive.
Also, may I ask you a question: do you own a house?

"I hired a contractor to replace a glass block window located on 1st and 2nd floor for me last year. These windows are facing the valley. So it might be colder than other places.

During this winter, every time I passed the glass block window in 1st fl, I felt so cold. 2nd floor is ok. I wonder if it is common or the work by contractor is not complete?

I believe the contractor did similar thing as following, but he didn't apply caulk to the joints between glass panel though.

http://www.rd.com/18517/article18517.html

any comments?"

Sorry. I meant "alley" instead of "valley". I apologize for my mistake.