This page is for those who already know how a traditional window goes together and are familiar with contemporary materials. The description begins assuming both sash are uninstalled and either no sash or jamb remediation is required, or it is complete.
We are going to remove some material from the sash so we can apply fin-seal to the stiles and a bulb seal at the meeting rails (items A, B and C). This weather-stripping will not be seen. We then line the jamb and sill with precision fit, maintenance free materials that are practically invisible once installed (items D and E). Weather-stripping is applied to the sill and head (items G and F). The sash are then reinstalled using one of a few different balance systems (H is recommended), two of which are also maintenance free.
Trim the Sash
If the sash already fits the jamb, properly saw off the minimum amounts from the sash side edges (5/16 each) and the top and bottom rails (1/4" each). If the sash are too loose or too tight, these dims can be adjusted to get proper fit. The bottom rail should match the sill bevel.
Route the Sash
Dado the meeting rails to accommodate the bulb seal (A above)
Use adhesive caulk and staples to attache the Fin Pile Carrier and fin-pile (B and C above to each edge of the sash (4 sides). Staple the Meeting Rail Bulb Seal in the Meeting Rail dados (the seal is adhesive backed already). If the original balances will be used, place staples out of the way of the rope/chain plow.
Prep for Balances
Depending on the balance method chosen, either mortise the jamb or the sash for the constant force balance (H above), or route the Fin Pile Carrier to accommodate the rope or chain that will be used.
Apply Sill Treatment
Lay in beads of caulk around the sill and jamb joint, and embed the flashing (not show) into the bed. Repeat and apply more caulk where necessary (i.e. prime sill, sub sill joint) prior to applying the Sill Wrap (D above).
Install Jamb Liner
Miter the bottom sections of the Jamb Liners (E above) to match the sill bevel. Cut the mitered units so their top lands at where the meeting rail will be (to hide joints). Measure and cut the top two Jamb Liners to fit above their respective bottoms. Caulk and screw or staple three of the four Jamb Liners into position, leaving one of the bottoms free to remove to install the upper sash. When applying the Jamb Liners, ensure they are firmly placed against the blind stops. Depending on balancing, method cut Jamb Liner to accommodate balance devices. This is not necessary if using a sash mounted Constant Force Balance (H above).
Cut the Bulb Seal Retainer and its bulb seals (F and G above) to fit snugly between the jambs just in front of the stool. Caulk and screw or staple it in place using moisture resistant fasteners. The process is repeated for the head for the top sash between the parting stop and blind stop.
Install the Sash
Attach one side of the balance system to the appropriate side of the upper sash. Place that edge of that sash into position (between the blind stop and the new parting stop) in the jamb. Attach the other side's balance system to the other edge of the sash. Using a piece of trim coil as a guide (to keep the balance attachment from catching on the jamb), slide the other side into position against the blind stop. Raise the upper sash into position and apply the missing lower Jamb liner. Repeat the process for the lower sash.
Apply Interior Stop
Apply the interior stop by bumping it up to the new jamb liner. This will ensure the proper jamb width for proper sealing and operation.