As part of the conservation team, Morrison Hershfield provided design advice for the replacement of the copper roof with a new insulated air tight assembly while respecting the proportion of the original design.  We also assisted with the reinstatement of the steel frame window system in keeping the original windows that had previously been replaced with aluminum framed units.  To minimize air leakage and condensation issues we used a dual framed window assembly that allowed the use of steel frame windows matching the original profiles without compromising performance. During this assignment, great care was taken to minimize the effects of construction on building occupants, including the Prime Minister.  Methods included customized dust enclosures and appropriate scheduling to minimize noise levels.

The project involved:

• Restoration of existing historic windows, including removals (where necessary), replacement of key sealants and institution of functioning air/vapor barrier connections
• Replacement of historic copper roofing, bringing the system up to modern water penetration resistance standards and providing an insulated air barrier to improve occupant comfort in the attic level office