This video shows our method of installing replacement windows in the new-construction style while increasing the insulation levels in the wall and taking care of a few other technical problems.
One benefit of the system is that you can pause for as long as you like between installing the window and insulating/re-siding the walls. This opportunity arises through the installation of a window buck which provides a finished window edge that extends far enough out to become the trim line for the future deepened wall assembly. During the period between installing the windows and residing, the trim will appear to extend out further than necessary since it is allowing for the addition of future layers of foam insulation, siding and a ventilation cavity known as the rain-screen cavity. Once these layers have been installed, the trim line will revert to a normal appearance.
The rain-screen cavity is a ventilation chamber that sits on the outside of the thermal boundary (foam) and in this instance is created by installing vertical 3/4″ strips as a siding backer. It drains against the weather-tight foam to the bottom of the assembly and allows the back of the siding to air-dry and maintain a temperature consistent with the front of the siding. These improvements benefit the owner by seriously extending the life of the paint and consequently extending the life of the siding. In traditional methods, this chamber did not exist, resulting in siding that remained permanently wet on the inside surface. This moisture would be driven through to the outside surface of the siding where it would gradually break the bond between the paint and the wood.
In order to complete the assembly, the foam needs to be carefully taped at all seams with a weather-barrier tape such as ‘Tyvek’ or ‘Dow’ brand. It is important to remember that the extruded polystyrene is the weather barrier in this assembly, that all flashing needs to be adhered to this layer with bitumenous membrane and taped at the top to avoid sagging.