Windows to the outside

[MariusP]

On my commercial build, I am planning some large windows ( 6’ wide x 9’ tall ) to view the nice trees outside of the sound rooms. This is a quiet area of town (it used to be residential). The attached diagram has the planned wall detail.
The outside of our building will be rock and stucco. We are copying other office buildings in the area – later we may want to sell this building to a doctor or dentist… Photo attached of similar building

As the wall detail diagram shows, there will be two isolated walls and hence two windows. For the outside window, I would like to use a prefab commercial window. Most commercial windows are double pane – and think I read that for best isolation, both windows should be a single pane of glass. But I REALLY would rather use a prefab window.
Reasons:
a. Simplicity
b. Lower cost (labor and materials)
c. a prefab window will have an established “R Rating” to satisfy city codes,
d. seems like it would look more “professional” for future buyers than a homemade window.

For the interior window, a prefab would be nice too… But we can build the interior window if necessary.

I am trying to achieve 45 – 50 dB isolation from the outside. I realize that the best commercially made exterior windows have an STC of 30 – 40. But since I have a double walls, the second window should increase the isolation. Right?

Please tell me what precautions and added measures I can take to utilize prefab windows. Perhaps we could use two different glass thicknesses for the two windows…

Thank you,
Marius Perron

[SoWhat]

Greetings Marius,

But since I have a double walls, the second window should increase the isolation. Right?

Remember that your isolation is only as good as the weakest element in the assembly. Thus, if you use a window that doesn't have the same mass as the wall it's in, the isolation suffers. To that end, big commercial windows with laminated glass (what you want/need) are available as I think they are used as exterior windows for buildings whose exteriors are "all windows" or "all glass". Now I have NO idea what they cost... Obviously, you'll need a more massive window for the interior too.

All the best,

Paul

[Paulus87]

On my commercial build, I am planning some large windows ( 6’ wide x 9’ tall ) to view the nice trees outside of the sound rooms. This is a quiet area of town (it used to be residential). The attached diagram has the planned wall detail.
The outside of our building will be rock and stucco. We are copying other office buildings in the area – later we may want to sell this building to a doctor or dentist… Photo attached of similar building

As the wall detail diagram shows, there will be two isolated walls and hence two windows. For the outside window, I would like to use a prefab commercial window. Most commercial windows are double pane – and think I read that for best isolation, both windows should be a single pane of glass. But I REALLY would rather use a prefab window.
Reasons:
a. Simplicity
b. Lower cost (labor and materials)
c. a prefab window will have an established “R Rating” to satisfy city codes,
d. seems like it would look more “professional” for future buyers than a homemade window.

For the interior window, a prefab would be nice too… But we can build the interior window if necessary.

I am trying to achieve 45 – 50 dB isolation from the outside. I realize that the best commercially made exterior windows have an STC of 30 – 40. But since I have a double walls, the second window should increase the isolation. Right?

Please tell me what precautions and added measures I can take to utilize prefab windows. Perhaps we could use two different glass thicknesses for the two windows…

Thank you,
Marius Perron

The problem with double pane (I'm assuming this is what we refer to as doubled glazed in the UK, two thin panes with an air gap filled with gas between them?) is that they resonate horribly. The second problem is the frames if made from uPVC they are hollow, and not very heavy. If solid aluminium frames then that is actually good. The third potential problem is most commercial installers will leave large gaps around the perimeter of the window frames that they fill with expanding foam = no good.

If you can get commercial units made with single pane toughened glass, non opening, aluminium frames and make sure the gaps around the window frames are not the weak spot then it'll be fine. You could live with the double glazed units on the exterior side if you don't mind them potentially resonating, you may find it is not a problem since your isolation goals are small.

Paul (a different one)