Endura Flap Thermo Sash 3e Pet Doors for Sash Windows
- Insulating sash window insert: Endura Flap Thermo Sash 3e Pet Door fits windows 22"-43" wide and 1" thick track
- Easy, semi-permanent installation: Spring-loaded design suitable for renters and vacation homes
- Flexible polyolefin polymer flap: Remains functional in temperatures down to -40°F with superior sealing
- Locking cover included: Enhances insulation and security, while providing pet access control
-
Extra Large Flap 22" - 25" Width Panel is made with plexiglass
Product Details
Sizing & Fit
Installation Guide
FAQs
ReviewsProduct Details
The Endura Flap Thermo Sash 3e Pet Door for Sash Windows combines elegance, functionality, and energy efficiency to provide your pets with the freedom to come and go as they please.
This insulating sash window insert is designed to fit snugly into the track of most windows, with sizes available for windows ranging from 22" to 43" in width and at least a 1" thick track. The spring-loaded design ensures a secure fit without the need for permanent installation, making it an excellent choice for renters and vacation homes.
The Thermo Sash 3e is crafted with a heavy extruded aluminum frame, available in white, dark bronze, and brushed aluminum to blend seamlessly with your existing window. The flexible polyolefin polymer flap remains functional in temperatures as low as -40°F, ensuring your pets can access it during extreme weather conditions. Magnets lining the edges of the flap provide superior sealing to keep out drafts and harsh weather.
For added security and insulation, a locking cover and weather stripping are included with the Thermo Sash 3e. It also comes with a lifetime warranty and a 90-day return policy, giving you peace of mind in your investment.
Choose the Endura Flap Thermo Sash 3e Pet Door for Sash Windows and experience the perfect balance of convenience, energy efficiency, and style for your home and your pets.
Please note that the Extra Large Flap 22" - 25" Width Panel is made with plexiglass, is custom-made-to-order, and is non-returnable.
Features:
- Heavy-duty aluminum frame: Available in white, dark bronze, and brushed aluminum to blend with your window
- Weather-resistant flap design: Magnets lining the edges ensure a secure seal during extreme weather
- Accommodates various pets: Taller and slimmer design allows both dogs and cats to use the door
- Enhanced insulation: Weather stripping and locking cover included for added insulation and energy efficiency
- Peace of mind: Comes with a lifetime warranty and 90-day return policy for a worry-free purchase
Size Chart
- Small6"w x 11"h
- Medium 8"w x 15"h
- Large 10"w x 19"h
- Extra Large 12"w x 23"h
Flap Dimensions:
6"w x 11”h
The entry way your dog goes through.
Height To Raise Window
18 1/2"
How high you must raise your window in order to fit the panel into the track.Flap Dimensions:
8"w x 15"h
The entry way your dog goes through.
Height To Raise Window
22 1/2"
How high you must raise your window in order to fit the panel into the track.Flap Dimensions:
10"w x 19"h
The entry way your dog goes through. Height To Raise Window
26 1/2"
How high you must raise your window in order to fit the panel into the track.Flap Dimensions:
12"w x 23"h
The entry way your dog goes through. Height To Raise Window
30 1/2”
How high you must raise your window in order to fit the panel into the track.| Flap Size | Flap Dimension | Height To Raise Window | Recommended Pet Height |
|---|---|---|---|
| Small | 6" w x 11" h | 18 1/2" | 9" - 15" |
| Medium | 8" w x 15" h | 22 1/2" | 9" - 21" |
| Large | 10" w x 19" h | 26 1/2" | 9" - 27" |
| Extra Large | 12" w x 23" h | 30 1/2" | 9" - 34" |
For your adjustment range, you need to measure the length of your sash window track from the furthest left to right. The adjustment range of your pet door should ideally have your track length in the middle. The following adjustment ranges are available:
- 22"-25"
- 25"-28"
- 28"-31"
- 31"-34"
- 34"-37"
- 37"-40"
- 40"-43"
Custom orders are subject to special restrictions.
Installation Instructions
Difficulty
Easy
Steps
04
Time Required
0.5 hours
Sections
01
Flags
01
Parts
- Sash Window Pet Door
- Foam Weather Strip
- Center Post Weather Seal Draft Stopper
- Screwdriver
Tools
- Flathead Screwdriver
Please read instructions & notes thoroughly before installation.
Step 1 Release Spring Mechanism
- Loosen the width adjustment locks at the end of the pet door insert with the screwdriver. This allows the spring mechanism to move freely from side to side.
Step 2 Check Panel Fit
- Insert the sash into the window track. Push against the spring mechanism and swing the opposite end into the opposite window track. Gently release. Tighten the width adjustment locks.
Step 3 Apply Weatherstripping
- Remove panel from window track.
- Apply the foam weather-stripping by peeling back the paper and exposing the adhesive. Unroll it along the edge of the sash, pressing to ensure it adheres. Install on both the top and the bottom. Trim to fit with scissors.
Step 4 Mount Seal Draft Stopper
- Mount the Center Post Weather Seal Draft Stopper. This strip prevents air from leaking between the window frame when raised to accommodate the sash. Trim to fit with scissors.
- Put the panel back into the window track. Tighten width adjustment locks.
Switch the Side of the Flap
You can switch which side of the sash panel the pet door flap is on to best fit your home.
Step 1
- Remove the screws on the top and bottom closest to the edge of the pet door. Then slightly loosen the screws closest to the glass. Next, slide off the side piece, then the flap assembly.
Step 2
- Rotate the flap assembly (essentially flipping it upside down) then slide it back in. Make sure the locking cover is on the same side as the width adjustment locks.
Step 3
- Replace the end spacer and screws.
LOCKING YOUR WINDOW
For a permanent lock, install a wood screw in the track immediately above the window on both sides. You will no longer be able to raise the window. For a temporary lock, place a removable wooden dowel or Charley bar in either track above the window, shown in Detail 1.
HEIGHT OF YOUR WINDOW
Make sure you place steps or ramps leading to your pet’s door at a height that works! When they go through the flap, the top of the flap should be at least 1" (2,5 cm) higher than the top of their back. Watch your pet and adjust as needed to keep them comfortable.
Videos
FAQ
What things should I measure/consider when choosing a cat flap door for my sash window?Four things:
|
How do I determine the size of pet door my pet will need?The door should be wide enough that it does not touch your pet's sides as they go through, and the top of the pet door should clear your pet's back by at least one inch. Take a look at our guide on how to measure your pet for more information. For a large cat door or dog door, make sure that the window you are installing in will accommodate the flap height you choose. |
What makes the Thermo Sash 3e better than the other manufacturer's sash window pet doors?The Thermo Sash includes the patented Endura Flap Pet Door which has a dual-layered flap employing magnets around the edges for superior sealability and insulation. Both of these are housed in a sturdy aluminum frame. It is made in the USA and backed by a lifetime warranty. |
How wide does the window track have to be to accommodate the Thermo Sash 3e?Your window track must be at least 1 inch wide for thermo sash 3e pet door installation. |
Which Thermo Sashes are considered custom and are not returnable?All Extra Large pet door sashes and any pet door size in a sash width with a 22"-25" adjustment range. |
Can I move the flap on the Thermo Sash from the left side to the right?Yes you can switch the side the pet door is on. You start by removing the screws on the top and bottom, then sliding the flap assembly out. Once it is removed you simply flip it upside down and slide it right back in. Next you put the screws back in, tighten them all down and you're finished. You'll want to make sure the thumb screws and locking cover are on the same side. |
Can you make a Thermo Sash smaller than 22" wide?You can make it 3/4" smaller by trimming the right side (spring loaded piece). |
What tools are needed to install a Thermo Sash?You will need a flathead screwdriver to install the thermo sash. |
How high do I have to raise my window to install the Thermo Sash?It varies based on the pet door size: Small is 19", Medium is 23", Large is 27" and Extra Large is 31" high. |
I ordered a 22"-25" adjustment range and mis-measured. My window is 25.5" wide. Is there anything I can do?We make a width adjustment which extends the width by 3/4". You can order Patio panel height extensions for additional height. You could also cut, paint and use a small piece of wood to extend the width. |
Can I adjust the height of the Thermo Sash?The Thermo Sash does not have an adjustable height. The height of the unit is determined by the height of the pet door. |
Which window cat door insert will keep out the desert heat?The most energy efficient one is the Thermo Sash 3e Pet Doors for Sash Windows. |
What energy saving dog door window insert do you have?The Thermo Sash 3e pet door is the most energy efficient pet door window insert on the market. |
I see the Thermo Sash 3e Pet Door for Sash Windows, what side sliding window cat door do you offer?There is a vertical version of the Thermo Sash called the Thermo Panel. I is available in the same four flap sizes. It has three standard height ranges. If your window is shorter, a custom panel can be made. |
Do you make Doggie Doors for Windows?Yes! The Thermo Sash is designed for windows that lift up and down. The Thermo Panel is designed for windows that slide left to right. Both are available in Custom sizes. |
Can I install a dog door in window if the window is not at ground level.Yes. We've seen many creative ways to help our dog access the window. Pet parents usually install steps or a ramp on both sides of the window to the doggy access the window. This may require training, but can be successful. |
Warranty
Endura Flap products have a lifetime warranty against defects in materials and workmanship under standard regular use. Damage caused by not using the product as intended, improper installation, and chewing is not covered under this warranty.
Customer Reviews
Size Chart
- Small6"w x 11"h
- Medium 8"w x 15"h
- Large 10"w x 19"h
- Extra Large 12"w x 23"h
Flap Dimensions:
6"w x 11”h
The entry way your dog goes through. Height To Raise Window
18 1/2"
How high you must raise your window in order to fit the panel into the track.Flap Dimensions:
8"w x 15"h
The entry way your dog goes through. Height To Raise Window
22 1/2"
How high you must raise your window in order to fit the panel into the track.Flap Dimensions:
10"w x 19"h
The entry way your dog goes through. Height To Raise Window
26 1/2"
How high you must raise your window in order to fit the panel into the track.Flap Dimensions:
12"w x 23"h
The entry way your dog goes through. Height To Raise Window
30 1/2”
How high you must raise your window in order to fit the panel into the track.| Flap Size | Flap Dimension | Height To Raise Window | Recommended Pet Height |
|---|---|---|---|
| Small | 6" w x 11" h | 18 1/2" | 9" - 15" |
| Medium | 8" w x 15" h | 22 1/2" | 9" - 21" |
| Large | 10" w x 19" h | 26 1/2" | 9" - 27" |
| Extra Large | 12" w x 23" h | 30 1/2" | 9" - 34" |
For your adjustment range, you need to measure the length of your sash window track from the furthest left to right. The adjustment range of your pet door should ideally have your track length in the middle. The following adjustment ranges are available:
- 22"-25"
- 25"-28"
- 28"-31"
- 31"-34"
- 34"-37"
- 37"-40"
- 40"-43"
Custom orders are subject to special restrictions.
Difficulty
Easy
Steps
04
Time Required
0.5 hours
Sections
01
Flags
01
Parts
- Sash Window Pet Door
- Foam Weather Strip
- Center Post Weather Seal Draft Stopper
- Screwdriver
Tools
- Flathead Screwdriver
Please read instructions & notes thoroughly before installation.
Step 1 Release Spring Mechanism
- Loosen the width adjustment locks at the end of the pet door insert with the screwdriver. This allows the spring mechanism to move freely from side to side.
Step 2 Check Panel Fit
- Insert the sash into the window track. Push against the spring mechanism and swing the opposite end into the opposite window track. Gently release. Tighten the width adjustment locks.
Step 3 Apply Weatherstripping
- Remove panel from window track.
- Apply the foam weather-stripping by peeling back the paper and exposing the adhesive. Unroll it along the edge of the sash, pressing to ensure it adheres. Install on both the top and the bottom. Trim to fit with scissors.
Step 4 Mount Seal Draft Stopper
- Mount the Center Post Weather Seal Draft Stopper. This strip prevents air from leaking between the window frame when raised to accommodate the sash. Trim to fit with scissors.
- Put the panel back into the window track. Tighten width adjustment locks.
Switch the Side of the Flap
You can switch which side of the sash panel the pet door flap is on to best fit your home.
Step 1
- Remove the screws on the top and bottom closest to the edge of the pet door. Then slightly loosen the screws closest to the glass. Next, slide off the side piece, then the flap assembly.
Step 2
- Rotate the flap assembly (essentially flipping it upside down) then slide it back in. Make sure the locking cover is on the same side as the width adjustment locks.
Step 3
- Replace the end spacer and screws.
LOCKING YOUR WINDOW
For a permanent lock, install a wood screw in the track immediately above the window on both sides. You will no longer be able to raise the window. For a temporary lock, place a removable wooden dowel or Charley bar in either track above the window, shown in Detail 1.
HEIGHT OF YOUR WINDOW
Make sure you place steps or ramps leading to your pet’s door at a height that works! When they go through the flap, the top of the flap should be at least 1" (2,5 cm) higher than the top of their back. Watch your pet and adjust as needed to keep them comfortable.
Videos
FAQ
What things should I measure/consider when choosing a cat flap door for my sash window?Four things:
|
How do I determine the size of pet door my pet will need?The door should be wide enough that it does not touch your pet's sides as they go through, and the top of the pet door should clear your pet's back by at least one inch. Take a look at our guide on how to measure your pet for more information. For a large cat door or dog door, make sure that the window you are installing in will accommodate the flap height you choose. |
What makes the Thermo Sash 3e better than the other manufacturer's sash window pet doors?The Thermo Sash includes the patented Endura Flap Pet Door which has a dual-layered flap employing magnets around the edges for superior sealability and insulation. Both of these are housed in a sturdy aluminum frame. It is made in the USA and backed by a lifetime warranty. |
How wide does the window track have to be to accommodate the Thermo Sash 3e?Your window track must be at least 1 inch wide for thermo sash 3e pet door installation. |
Which Thermo Sashes are considered custom and are not returnable?All Extra Large pet door sashes and any pet door size in a sash width with a 22"-25" adjustment range. |
Can I move the flap on the Thermo Sash from the left side to the right?Yes you can switch the side the pet door is on. You start by removing the screws on the top and bottom, then sliding the flap assembly out. Once it is removed you simply flip it upside down and slide it right back in. Next you put the screws back in, tighten them all down and you're finished. You'll want to make sure the thumb screws and locking cover are on the same side. |
Can you make a Thermo Sash smaller than 22" wide?You can make it 3/4" smaller by trimming the right side (spring loaded piece). |
What tools are needed to install a Thermo Sash?You will need a flathead screwdriver to install the thermo sash. |
How high do I have to raise my window to install the Thermo Sash?It varies based on the pet door size: Small is 19", Medium is 23", Large is 27" and Extra Large is 31" high. |
I ordered a 22"-25" adjustment range and mis-measured. My window is 25.5" wide. Is there anything I can do?We make a width adjustment which extends the width by 3/4". You can order Patio panel height extensions for additional height. You could also cut, paint and use a small piece of wood to extend the width. |
Can I adjust the height of the Thermo Sash?The Thermo Sash does not have an adjustable height. The height of the unit is determined by the height of the pet door. |
Which window cat door insert will keep out the desert heat?The most energy efficient one is the Thermo Sash 3e Pet Doors for Sash Windows. |
What energy saving dog door window insert do you have?The Thermo Sash 3e pet door is the most energy efficient pet door window insert on the market. |
I see the Thermo Sash 3e Pet Door for Sash Windows, what side sliding window cat door do you offer?There is a vertical version of the Thermo Sash called the Thermo Panel. I is available in the same four flap sizes. It has three standard height ranges. If your window is shorter, a custom panel can be made. |
Do you make Doggie Doors for Windows?Yes! The Thermo Sash is designed for windows that lift up and down. The Thermo Panel is designed for windows that slide left to right. Both are available in Custom sizes. |
Can I install a dog door in window if the window is not at ground level.Yes. We've seen many creative ways to help our dog access the window. Pet parents usually install steps or a ramp on both sides of the window to the doggy access the window. This may require training, but can be successful. |
Warranty
Endura Flap products have a lifetime warranty against defects in materials and workmanship under standard regular use. Damage caused by not using the product as intended, improper installation, and chewing is not covered under this warranty.
