In the last decade or two, home builders have gone towards glass French doors as opposed to regular doors, and dual French doors as opposed to sliding glass doors. This makes pet door installation more of a hassle, but it can still be done and this blog will tell you what to look for and how to do it. All of these installation instructions will also apply to windows and sliding glass doors as well.
Door vs Window Glass
By law in the USA, door glass must be tempered. I don't know how long that law has been in place, but I can say that the house I grew up in, built in 1975 had tempered glass in it and I think the law has been in place longer than that. Tempering is a heat treatment that is done to the glass; it makes it a lot stronger, and if it should break it comes apart in a million tiny pieces as opposed to big dangerous shards that could really injure a person. Unfortunately, tempered glass cannot be cut. When installing a pet door in a French door with tempered glass, you have to start with a new piece of glass, cut it, then temper it, and then install the pet door and fit it all into the door.
Window glass is usually not tempered. Tempered glass will usually (always???) have a little stamp or etching in the corner that will have the name of the glass shop that manufactured it, and say "tempered glass" and sometimes a date of manufacture. If you see this stamp, which is sometimes referred to as a "bug" it should be a fairly reliable indicator of whether or not you can cut the glass.
Single Pane vs Dual Pane
As homes have become more energy efficient dual pane glass has become the standard. Most homes built in the 1990s or later will have dual pane glass, and many older homes are retrofitted with dual pane. If you are not sure whether you have single or double pane, the easiest way to tell is to open a door and try to touch your fingers together through the glass. If it feels like they're far apart, double pane. Most single pane is only 3/16" thick so they won't feel oddly far apart if you do the test on a single pane window. On a double pane window you can usually see the aluminum spacer between the two panes of glass.
Installing a pet door in a single pane window is pretty simple. The Hale In Glass door for single panel is the one to use. If the glass is in a window and not tempered, you can remove the glass from the window frame and cut the corner to fit the pet door. The door has a slot in the top corner which slides over the glass and a tab that sticks out in the other corner which plugs into the window frame. As discussed in the installation instructions, all inside cuts should be radiused to remove stress risers. If the original glass is tempered, you will have to work with a local glass company. The new glass will have to be cut and then tempered and then the pet door can be installed.
French Doors With Multiple Panes
Many French doors have a grid work with smaller windows. These doors can be tricky. Older French doors typically have wood framing or "mullions" separating each individual pane of glass. If you have a door that has separate panes of glass in each little window, installing a pet door is really straightforward. You can remove one piece of glass and install a custom size Hale pet door.
Info on custom Hale pet doors here.
In newer doors it is fairly common to use one large dual pane glass window and then lay a grid over the top to make it look like separate windows. Sometimes the grid is put in between the panes so that it doesn't get dusty. If your French door has one big sheet of dual pane glass, then the custom door isn't an option and you'll have to do one of the typical in glass installations as described below.
Double Pane Glass Installation Options
For dual pane glass, you have a few options. The easiest is the
Pet Door Guys replacement window, which is a window glass replacement that has the dog door already installed. To order we need the dimensions of the glass, and in order to get them you have to disassemble the door or window and take the glass out, then measure it and reinstall. Fill out the order form, we have the replacement built to fit. It takes about 3 weeks to ship out, then when it arrives, you just pull the frame back apart, take the original glass out and install the new Pet Door Guys glass unit (the original glass can be saved and stored in a garage or closet and swapped back in at a later date). We always ask glass shops what they charge for measuring and installing, and $250 seems like a pretty usual price for the entire procedure. It is possible to do this job yourself, I had a customer tell me that she looked up replacing sliding door glass on youtube and was able to figure out the whole thing herself. While I haven't done it myself, $250 for two trips out tells me that it probably isn't very difficult. The downside to the Pet Door Guys option is that the new window unit will have a T frame in the bottom, so you will have one larger window on top, with the T frame below and one window on one side, with the pet door in the other side.
EDIT--Now I have done this install myself. Filmed the whole process top to bottom. You can watch here:
The Hale In Glass doggy door for dual pane glass is a nicer looking end product, but it is more complicated to install and more expensive by the time it gets done. In this Hale In Glass Dog Door case, you're going to have to find a local glass shop willing to do the work. This job is not the easiest and often glass shops won't want to do it. When they do it can be pretty expensive. We typically hear prices between $900 and $1200 for a sliding door install, but have heard quotes as high as $2500. Those prices are for the glass, not including the pet door itself. The glass company will start with two raw pieces of glass, cut the notch for the pet door, then temper the glass if it's for a door, then seal the two pieces together, then install the pet door onto the glass and finally swap the pet door into the door or window frame. Where the pet door and the window frame meet up, we end up with two female parts; there is a slot in the window frame where the glass plugs in, and there is a slot on the two sides of the pet door frame as well. Hale sends "compensation strips" which bridge this gap with the pet doors.
The actual pet door used in this application is the same door that would be used for a wood door installation, and it is made to fit a 1 3/4" door thickness. Glass won't be as thick as a door, and there are two ways to deal with this situation. Hale will include a "buildout" which is an aluminum frame that goes between the glass and the dog door. For example, if your glass is 1" thick, and the doggie door is made to fit 1 3/4" thickness, they would send a 3/4" thick aluminum frame with the pet door. The buildout frame can be installed on either side of the glass, but it will push one side of the dog door frame out 3/4" away from the glass. The other way to deal with this is to cut the pet door frame down to fit the thickness of the glass. Hale can cut the doggy door frame down to a minimum of 3/4". They do not charge for this service, but it does make it a final sale, so no returns. The advantage to using the buildout is that you get more space between the flaps, so should have better insulation. The advantage to cutting the pet door down is that it looks nicer.
Electronic Cat Doors for Glass InstallationSureFlap In Glass cat door electronic
The SureFlap company makes a very good electronic cat door that works with implanted microchips. If your cat already has a chip implanted, it should operate the door just fine. We sell a glass adapter for the SureFlap door which is a big round plastic disk. This adapter allows you to cut a large, round hole in the glass to install the pet door. SureFlap's installation instructions describe cutting holes in the glass and sealing the space between the glass in a double pane glass window installation (shown on p12-13), but I have my doubts about this. If you've ever seen a dual pane window that has lost its seal and then started to sweat and get condensation in between the panes, you will know why. Seems to me that it would be really difficult to get the window sealed well enough to prevent this from happening. On a single pane glass, the adapter is a great idea. We would suggest that for double pane installations you contact a glass shop and have the two panes cut and sealed by the glass shop, which probably means that they would do this on a new window and then swap the glass out.