b'BEFOREF-ChannelInstallation Proper installation of replacement windows requires Cappingthat if the old opening (with or without the old frame)be sealed in such a way that any of the degradationor irregularities in the old frame are covered and thenew installation is adequately integrated with the F-Channel Legswater management system of the wall.In order to accomplish this, it is also important thatwhatever is done to the old opening melds with thenew window to prevent water, moisture and air infil-tration while allowing the opening to breathe, toavoid the trapping of condensation in the old cavity. CappingWhen removing the old window, whether it is the old sash of a double hung, or the removal of a fin-mounted sliding window, or even an embedded steelcasement window. often the opening needs somemodification to cover where the old window partswere, and/or to adequately prepare the opening forF-Channel Installation can be very effective where thea properly installed new window. old opening is degraded.A perfect alternative installation method involves an extruded piece called an F-Channel. Thisextruded piece has two legs which fit precisely overthe frame of the new vinyl window, and the width ofthe F-Channel extends past the second leg to coverthe full 3-1/2 opening, as shown in the diagrams.For sash replacement, the two sash and partingTrimmedstops are removed. The exterior blind stop is cut off Blindstopas in an outside-in installation (described elsewherein this book). The F-Channel is affixed to the oldopening on the sides and top and the new windowCaulk,is snapped-in the channels from the outside. Seal andWhile the fit should be fine, if there is extra play,Insulate asthe window can be centered and anchored to theNecessaryF-Channels using pop rivets.If the FChannel is made with a Nailing Fin, it can be slipped up under old siding, and with the F Fin can beChannel turned upside down, and one leg trimmed used to leveloff, the fin can be modified to create a level sill Channel forwhile providing a functional sill pan for drainage. use as Sill Panwith one legPerhaps the best part of this method of installationtrimmedis that the capping can be placed over the extendedportion of the F-Channel as shown.This protects the installation fromwater penetration without excessivecaulking, allowing the opening tobreathe. This is important as warmmoist air on the interior migratestowards the outside during colderWindow Fitters Guide to Window Installation882020 AWDI, LLC Do not reproduce without permission'