For independent double wall construction, I use double independent frames. You will want to 'seal' the opening between the walls and windows with a rubber sheet 360 degrees around the frame. You can also use garden plastic for this. This seals the window interior space from the wall space and prevents moisture vapor between the glass. Do not couple the walls. The devil is in the details and this is not all of them.
Neoprene is great! but not for sealing a wall cavity.. too expensive. By garden plastic, I mean the 6 mil black plastic that gardeners use to cover ground to prevent any growth. Clear or black - it doesn't matter. They have it at Home Depot.. basically any plastic that can make a permanent seal will work.
oh and I was wondering should i put some dessicant packets inside the insulation between the 2 rooms just in case the window would moist up? I'm in Hong Kong and humid here is such a big issue.
the only plastic tape i can get here is max 3" which is not wide enough to cover my frame. If I use garden plastic how should i stick on it? and would garden plastic be too soft and thin?
Any plastic or rubber roll that will seal the gap is fine. Use a butyl caulk around the frames, attach the plastic/rubber with staples & put your trim boards on top.. build your window.
Desiccant packs are required. - Place them under the fabric covered rock woll between the two window frames.
thanks man!! i understand now! : ) u r very helpful! well here in hong kong i can only buy rubbers that are 3 inch wide. so ill prob have to tape a lot the other way around to make them fit. is that ok too?
Keep looking. I'm sure you will be able to find larger sheets or rolls. If you tape it together, the tape will come off over time and allow moisture into the window cavity.
Just what ever you use, make sure that it is permanent.