My parents are renovating a river house, and they're trying to find windows like the ones in their other house. We've been calling them quad-hung windows, but maybe there's another name for them. They're basically double hung windows with double the sashes. So there's two sashes on top, two on bottom, and all of the sashes are removable (except for maybe the upper exterior sash). Does anyone know where we can find something like this? They want the thermal insulation that two panes of glass provide, but want to avoid the condensation problems that insulated glass windows have when the hermetic seals break (they had lots of problems with fogging on one of their previous houses).