Magnetic Seal vs Compression Seal

What difference is a particular window attachment going to make to the comfort of your home? How effective is a magnetic seal or compression seal when used on a storm window? We’ll answer these questions in this blog and why Indow decided against magnetic window insulation.

Why We Said No to Magnetic Seal

When Indow first designed our window inserts, we considered putting magnets inside our compression tube, but we found that a magnetic window insulation created a lot of design flaws.

“It’s not very attractive, it’s cumbersome to install, and that metal frame remains in your window frame after you remove the insert and that’s ugly. So there were three things we didn’t like about the magnetic system.”

-Sam Pardue, Indow Founder

First, for a magnetic seal to form, magnets have to grab hold of something. That something is permanently attached to your window frame—generally a metal bracket fixed to the entire window frame needing many holes drilled into it. So it’s cumbersome to install.

Second, magnetic window insulation is not attractive either with the window insert installed or removed. If you take the window insert off, you still have a big metal bracket surrounding your window.

diagram of a magnetic window insulation system

Third, the acrylic used in most window inserts expands and contracts with the temperature. While the window insert and attached magnets move, the metal frame does not. So, whatever magnetic seal there was is broken and the whole panel can pop off.

Magnets attract in one direction, but compression tube creates spring force all the way around the window frame. It absorbs expansion and contraction in every direction and creates friction and resistance against air pressure.

So, we removed the magnet and created a window insert that relies on compression seal alone. The compression tube can do everything we need and the simplest solution is often the best solution.

woman installing Indow insert in window to create compression seal

Why Compression Seal is Better Than Magnetic Seal

The compression tube around our acrylic panels is the spring force that holds in insert in place. It absorbs all thermal expansion caused by temperature change. This ability to expand and contract creates a near airtight seal no matter the shape, size, or condition of your window. The compression tube is a seal against drafts and heat, and it keeps conditioned air inside.

close up of Indow window insert creating compression seal

A compression seal is stronger than a magnetic seal because it is better at dealing with out of square windows. If your home is older and has had time to settle, it most likely hasn’t settled perfectly straight – this causes out of square windows.

“The problem is that magnetic systems don’t always deal really easily with the fact that most window frames are really out of square. So sometimes you get a gap up in the corner, if it’s a really out of square window. With our system we’re going to make the insert the exact shape of the window opening, you’re going to get very tight seal all the way around—a nice even compression.”

– Sam Pardue, Indow Founder

Magnetic seals can get gaps because they were made for a perfectly square window frame. Compression seal adjusts for the out of square window so you continue to have a tight seal and even compression.

Our compression seal can accommodate expansion and contraction from heat and window frame inconsistencies without altering the window at all. Our compression seal is stronger than magnetic seal, fits any shape of window, and requires no hardware.

For more information read about our compression system.

Customer Reviews


4.49 Average 1477 Reviews logo

Matthew L

Indow inserts were easy to measure, order and install. They've provided great insulation for old single-pane and stained glass windows in an antique home. We can significantly feel how much better the home holds heat.

Posted 2 days ago

Ellis W

I ordered two Indow inserts for my home. They are doing a great job, entirely happy with them and the ordering process.

Posted 1 week ago

Elizabeth W

I can't say enough good things about this product and company. Our house is 101 years old and the sidelites next to our front door are single pane ancient wavy glass which means when it gets very cold (Chicago temps) we can have an inch of frost covering the INSIDE of our windows. I was desperately searching for a solution so our front vestibule was not so cold and a friend recommended Indow. The process could not have been simpler and the temperature difference it has made is off the charts.

Posted 2 weeks ago

Austin T

I have several historic single pane gridwork mullion windows. They're beautiful but have almost no thermal protection. Indows proved to be the perfect solution to preserve these windows while getting the thermal comfort we need. They were easy to install and work perfectly!

Posted 3 weeks ago

Kathryn M

Amazingly easy to install even the safety chain holders. I. Noticed an immediate sound level difference and the room atmosphere became more solid feeling and pleasant. They also gave an insulating feature to the window drafts are non existent! The house is 50ft off a State highway that is heavily traveled in warmer months I'm confident the indows will handle it. I'm very pleased!

Posted 1 month ago


We ordered the acoustic inserts to help with road noise, and we've been sleeping so much better with them!

Posted 1 month ago

Sienna K

We used the windows inserts in our skylight. They are great! They the horrible drafts and noise out and were cost efficient. My only comment would be to provide better measurement and installation instructions for skylights specifically. It took us a lot of guessing and research to measure and install because skylight directions were not provided and the windows install guide doesn't always apply to skylights. Other than that though great product and I would buy again!

Posted 1 month ago

ted t

Our home was built in the late 1800s and we have spent a lot of money over the last 20+years restoring it.We did not want to replace the windows with modern windows because of the cost and originality. But the single pane windows come with a price also. the main reason we purchased the Indow window inserts is because of the condensation on the inside of the windows.We would literally have a take a towel and wipe them down every morning in the winter. There would be a puddle on the sill,and wood and water dont get along to well. SO we looked into the best solution to our problem and found Indow. Was reluctant to spend that much money but am super glad we did!! They have been installed now for over two months and our condensation problem has been virtually eliminated.!!! AND our furnace does not run as much as it did before. Over all it was money well spent!! The process was a little scary at first but they have a simple formula. And our contact person,Reed was awesome. Answered any questions i had and was always available.

Posted 1 month ago


Used to block interior side of a garden window in the the kitchen. Without insert, cold air literally poured into the kitchen making a winter jacket almost mandatory when preparing meals or washing dishes

Posted 1 month ago

Rob S

Highly recommend! The team (Brian) took time to help me figure out the best solution. They were made and delivered faster than expected. It was very rewarding to install them because I could feel the cold air get squeezed out as they went flush against the single pane of glass. Solid quality and great fit.

Posted 1 month ago

Alexa L

My inserts fit beautifully into my 125 year old windows - many of which were 5 feet tall. Easy to unwrap and install. Great product and even better service! I liked the process of measuring the windows with a laser measuring tool which was easy to use and precise. The product came in good condition after shipping across country and was well marked. The customer support was excellent.

Posted 1 month ago

Sarah D

Received our Indow Windows and can tell they are blocking a lot of the noise we could hear. Right now the weather is mild, but hoping to notice a big difference when the summer heats up. Our house is in a historic district and we cannot change our windows. They are very drafty and thin glass. We only ordered two, but we are in the process of ordering for four more. Love that we don’t need to drill holes or anything and they just pop right in.

Posted 1 month ago

Allan F

Every thing arrived in perfect condition, thanks to the very secure packaging. Windows fit as expected, although quite tight. After installation we noticed that the cold drafts were gone and the room felt a lot warmer. We are very satisfied with the product and the result.

Posted 1 month ago

Adriana W

Great customer service! Super satisfied with our windows.

Posted 1 month ago

Thomas M

Indow service and product is good. Reduced outside noise considerably.

Posted 2 months ago