casement window
a window in which the operating vents move out (casement outswing) or in (casement inswing) from the master frame. Each vent is hinged on the vertical axis to permit easy operation.
back to top

caulk stop
an accessory added to the exterior leg of a window frame or exterior panning leg to create a parallel-sided caulking joint.
back to top

cfm
cubic feet per minute - a unit of measure used in air infiltration testing, e.g., "maximum .10 cfm per square foot of window area."
back to top

CMR
Centerline of Meeting Rail - a reference line used to locate integral mullions and/or to size oriel (unequal) sash, e.g., "the height of the lower sash shall be 22" from the frame sill to CMR."
back to top

condensation
when the air inside an enclosure is warmer than the air outside the enclosure, the moisture vapor in the interior air will condense, creating small water droplets at the intersection of dissimilar materials (aluminum and gaskets).
back to top

continuous air spacer
an air spacer within an insulating glass unit (IGU) that does not use corner keys to hold the spacer together, thereby eliminating the corner joint, the largest cause of seal failure.
back to top

crack length
total outside perimeter of window sash or vent.
back to top

CRF
Condensation Resistance Factor - an indication of a window's ability to resist condensation (the higher the better).
back to top

curved eave lean-to
the rounded bent corner transition between the roof and front wall.
back to top

custodial lock
window hardware only operable with a tool or key.
back to top