The process of retrofitting old aluminum windows allows a typical homeowner the ability to install energy efficient vinyl windows without having to perform major construction, such as cutting stucco or siding, pulling out the old frame, then installing a water barrier to the new window fins, repairing the exterior material, and finally, patching any interior drywall damage. The retrofit frame was developed in California, where stucco is common. The retrofit fin fits neatly over the aluminum frame and rests on the stucco. This page is for homeowners and contractors who live in areas of the Country where the California retrofit frames are not available. I am going to explain how to create your own retrofit frames, using a replacement frame and vinyl flat trim. Please keep in mind that the concept of retrofitting only applies if you are replacing ALUMINUM WINDOWS with VINYL WINDOWS.
The retrofit fin is also known as a flush fin in some areas of the country. This is a picture of the retrofit frame when viewed from the back. The reason it is known as a flush fin frame is because the retrofit fin is flush with the outside face of the window. This is not to be confused with a new construction window frame, where the nailing fin is set back about an inch from the face of the window. The nailing fin will not work as a retrofit fin when doing a replacement. The only time you want to use a window with a nailing fin is if you are building a new home from scratch, or you are going to completely tear out the old window down to the studs.
The picture to the left is called a replacement frame. You can see how the replacement frame is just a box with no fins at all. These frames are made to replace an old wood window. The frame fits into the wood pocket, so no fins are required. In areas of the country where the retrofit frame is not available, you can get the replacement frame. I will explain how to use a replacement frame in combination with my vinyl flat trim to create a retrofit style window that will allow you to replace old metal windows without having to do all the labor involved in tearing out the old window frame and then patching the interior and exterior after installing the new window.
At places such as Home Depot or Lowes, you will find new construction windows on the shelf, but those sizes will not work when you leave the old frame attached. It alters the opening size so stock sizes will not work. You want to custom order a replacement frame window. In some areas of the country, if you order a replacement frame, they will simply sell you a new construction frame with the nail fins removed. This may or may not work depending on how thick your old window frame is. When you retrofit, the new frame has to be thicker than the old frame so the window extends further into the room than the old one. A new construction frame is 2 5/8" in depth. If your windows are single pane aluminum windows, you can use the new construction frame without the fins because your old frame is only about 1 1/2" in depth. However, if you are replacing dual pane aluminum windows, the new construction frame will not be deep enough. You will need to specify that you want a replacement frame with a depth of 3 1/4".
When you measure for the new window, you want to take the smallest width and height dimension and deduct 1/4". You remove the fixed and sliding panels of the old window, leaving only the portion of the frame on the perimeter that is attached to the studs. When you install the new window, make sure it sticks out slightly further than the existing metal frame, about 1/16-1/8". Attach the new frame by installing screws through the side and top jambs into the studs.You will now have the old frame around the outer edge and the new window sitting inside the old frame. If you purchased a 3 1/4" replacement frame, it will protrude into the room much further than the old frame.
This picture shows a corner sample of a replacement frame along with a piece of my vinyl flat trim. The trim comes with 3/4" wide double stick tape on the back with a paper backing. After you have installed your replacement frame, you would cut the flat trim to size, then peel the paper off, and stick the tape onto the face of the vinyl frame, while butting the edge of the trim against your brick or siding. My flat trim uses an acrylic modified adhesive on the back, which forms a permanent bond with PVC, the stuff that vinyl windows are made of. The bond between the tape and the vinyl actually gets stronger as time goes by. In contrast, most trim on the market uses Styrene Isoprene Styrene (S.I.S), which is a rubber based adhesive, and has ZERO adhesion to PVC. Manufacturers of this type of adhesive use something called a tackifier, which is very sticky to the touch, and will hold the trim in place UNTIL THE TACKIFIER EVAPORATES! Tackifier is a temporary holding agent, so when it evaporates, the only thing holding your trim in place is the caulk or silicone you used to finish the job. Please don't ruin a quality job by using a cheap trim product.
When you screwed the vinyl window in place, your new frame should stick out past the old frame just enough that you can apply a thick bead of silicone directly onto the old metal frame, and when you peel off the paper and stick the trim to the new vinyl frame, the back of the vinyl trim will seal to the face of the metal with the bead of silicone. The edge of the trim should butt against whatever material your exterior is made of, whether it's brick, siding, or wood trim. Ideally, you want the tape on the trim to completely attach to the vinyl frame, and since the tape is 3/4" wide, you want a trim width that will reach the brick or wood. The widest trim that I sell is 2 1/2", so if you have a gap from the edge of the new window to the brick of 1 3/4", the trim will fit perfectly. If the gap is more than 2", I do not recommend this type of installation. If the gap is less than 1 3/4", the trim has deep grooves on the back every 1/4", so you can reduce the width of the trim to fit. After you have trimmed all four sides, you caulk where the edge of the trim mates with the brick or wood. Now you go inside and, before installing the trim, stuff some attic insulation in the space. It does two things. First, it reduces the ability of air to infiltrate the opening. It also insulates the metal so it doesn't get condensation during times of extreme changes in temperature.
The final step is to install the flat trim like you did outside. Your gap to the wall will most likely be less than the outside gap, and in most cases 1 3/4" trim will work. Most of the time, a job like this will require a combination of 1 3/4" and 2 1/2" trim. You should purchase the exterior grade trim for doing the outside. The interior grade trim will do the job outside, but the exterior trim has more UV inhibitors to prevent the color from fading over time. You can order the flat trim HERE. If you need a color other than white, call for a quote.
I also sell screw hole plugs to hide any installation screws. When installing a replacement frame, you screw the frame in place through the sides and top. Since vinyl windows have two walls of vinyl separated by a hollow chamber, you can pre drill a 3/8" hole through the first wall of vinyl, drive the installation screw into the large hole and through the second wall of vinyl, then pop in a hole plug, and the screws are completely hidden. The plugs are subtle, and blend in so well with the frame, you can hardly tell they are there. You can watch a short video demonstration on youtube.