Best Acrylic Storm Windows (2026)

An interior acrylic storm window is a clear panel that sits in or over the inside of an existing window frame and traps a layer of still air against the glass. That air gap is what does the work. It roughly doubles the resistance to conductive heat loss of a single-pane window, stops the drafts that leak around old sashes, and, because acrylic is a poorer conductor of sound than glass, takes a noticeable bite out of street noise.

The appeal is that you keep your original windows. That matters in a historic home where replacement is either forbidden or heartbreaking, in a rental where you cannot touch the exterior, or in any house where the windows are structurally fine and simply leaky. A full window replacement runs into the thousands per opening. A good acrylic insert is a fraction of that, and a DIY panel is a fraction of that again.

This guide covers the five products we would actually put in our own windows, ranked by how well they seal, how they mount, what they cost, and how much of the work falls on you.

Our picks at a glance

How we evaluated

We have not run these panels through a thermal chamber. Our rankings are built from manufacturer specifications, published acoustic and energy data, independent reviews, and owner reports, weighed against five questions:

• How airtight is the seal? Drafts, not glass, are usually the biggest heat loser in an old window. A compression or magnetic seal beats tape and cleats every time.
• How thick is the acrylic? 1/8 inch is the standard for insulation. 1/4 inch is what you want for serious noise reduction.
• What does it look like from the street and from the couch? Frames, magnets, and visible hardware count against a product.
• Can you take it out? Seasonal removal for cleaning, ventilation, or egress matters.
• What does it cost per window, all in? Including measurement, shipping, and your own time.

Prices below are what manufacturers and independent pricing guides published as of September 2026. Custom products are quoted per window, so treat every figure as a starting point.

1. Indow Window Inserts

Best Overall. Indow makes the insert most people picture when they hear "interior storm window." Each panel is a sheet of clear acrylic edged in a patented silicone compression tube. The company laser-measures your window opening, cuts the panel to match, and you press it into place. There is no frame, no magnet strip, no screw hole, and from a few feet away the insert is nearly invisible.

The compression tube is the whole trick. It squeezes against the inside of the frame to make a seal that Indow describes as airtight, and it forgives the out-of-square openings that every old house has. Removal is a matter of pulling one corner.

Grades. Standard Grade uses a nominal 1/8-inch acrylic and is the pick for drafts and heating bills. Acoustic Grade doubles that to 1/4 inch for noise. Museum Grade blocks 98 percent of UV to protect furnishings and art. Commercial Grade adds an abrasion-resistant coating for high-traffic buildings. There are also Sleep and Shade options with tinted or opaque acrylic.

Performance. Indow publishes a 50 percent noise reduction (10 to 12 dBA) for Standard Grade over single-pane glass and 70 percent (18.9 dBA) for Acoustic Grade. On energy, a field study the company cites found heating costs fell an average of 19 percent after installation. Those are single-pane numbers. Over a double-pane window the gains are real but smaller.

Pricing. Independent pricing guides put Standard Grade at roughly $20 to $28 per square foot, the Acoustic, Museum, and Shade tiers at $25 to $36, and Commercial Grade at around $40. A typical 3-by-4-foot window in Standard Grade lands in the $250 to $400 range. Indow raised prices by 10 percent in July 2026, so older quotes you find online will run low. Professional measurement and installation, if you do not do it yourself, adds a few dollars per square foot.

Warranty. Lifetime on the acrylic panel against defects. Five years on the compression tubing against heat, cold, and UV damage.

Read our Indow review or get a quote from Indow.

2. Climate Seal Thermal Series

Best for Noise. Climate Seal takes the magnetic route. A thin steel subframe is fixed to the inside of your window casing, and the acrylic panel carries a magnetic perimeter that snaps to it. The seal is described as virtually airtight, and because it is magnetic you can lift the panel off in seconds for cleaning or summer storage and put it back without tools.

The detail that sets Climate Seal apart from a generic magnetic panel is the bellows built into the molding. Acrylic expands and contracts with temperature more than glass does, and on a big panel that movement can bow the sheet and pop a magnetic seal loose at the corners. The bellows lets the sheet move in its own plane without deforming.

Series. The Thermal Series is the everyday product, using standard 1/8-inch acrylic and aimed at heating and cooling savings. The Acoustic Series steps up to 1/4-inch acrylic with acoustically rated weather stripping and claims an STC rating of up to 49 and up to 80 percent sound reduction. There is also a Preservation Series designed for historic buildings and a Pro Series at the top of the range.

Performance. Climate Seal claims up to 60 percent sound abatement even from the Thermal Series, which is competitive with Indow's Acoustic Grade on paper. Its energy claims are framed around draft elimination and the dead-air space rather than a percentage.

Pricing. Climate Seal does not publish prices. Everything is quoted per window through the company or a dealer. Expect it to land in the same broad band as Indow, with the Acoustic Series higher.

Read our Climate Seal review or learn more at Climate Seal.

3. Magnetite Interior Windows

Best Professionally Installed. Magnetite has been around long enough to have appeared on television and to claim a presence in more than 100,000 homes. The system is a sheet of optical-grade acrylic with patented magnetic edging that holds against a frame installed on the window jamb. It works the way a refrigerator door does, and it is sold and fitted through a network of local dealers rather than shipped to your door.

That dealer model is the point. A trained installer measures, orders, and fits the panels, and Magnetite makes a point of handling non-standard shapes: arches, circles, angled attic windows, and very large openings that a mail-order compression insert would struggle with.

Performance. Magnetite claims up to 90 percent noise reduction at some frequencies, which is a carefully worded figure; real-world broadband reduction will be lower. On energy, it claims to double resistance to conductive heat loss and virtually eliminate air infiltration, which is consistent with what any sealed 1/8-inch acrylic panel over single glazing should do.

Pricing. Quoted by the dealer, and it includes installation. Independent guides put custom-fitted magnetic inserts in the $80 to $250 per opening range for materials, with professional installation on top. Expect Magnetite to be competitive with Indow once you include labor.

Find a Magnetite dealer

4. Window Savers Kit

Best DIY Kit. Window Savers has been selling the same idea since 1994: a kit of flexible magnet strip, vinyl-covered steel strip, and peel-and-stick adhesive that turns a plain sheet of acrylic into a magnetic interior storm window. You mount the steel strip to the window molding or to small cleats inside the jamb, stick the magnet strip to the edges of the acrylic, and the panel snaps on.

The kit is $229 direct from the company and, per This Old House, makes about seven average 3-by-4-foot windows. It does not include the acrylic. You buy that cut to size from a plastics distributor or a home center. Window Savers recommends 1/8-inch sheet for insulation and 3/16 or 1/4 inch if noise is the goal. Thinner sheet exists but only works on small windows.

What you get versus a custom insert. This Old House judged that the finished panels equal the best custom interior storms in appearance and performance at about a quarter of the cost. The trade-off is that the finish depends on how carefully you cut and align. A crooked steel strip means a leaky corner.

Warranty. Window Savers offers a 60-day return window rather than a product warranty: 90 percent refund on an unused kit, 50 percent on a used one.

Read our full Window Savers review or shop the kit.

5. DIY Acrylic Sheet Build

Best Budget. If you have a handful of small windows and a tight budget, you can skip the kit entirely. Buy 1/8-inch clear acrylic sheet from a home center (OPTIX is the house brand at Home Depot; Plaskolite makes it) or a local plastics shop, have it cut to your opening, and mount it with adhesive-backed magnetic tape against steel tape on the casing, or with simple turn-button cleats.

Independent guides put materials for a standard double-hung window at $30 to $120 depending on size and thickness. A 24-by-48-inch 1/8-inch OPTIX sheet retails around $50, and a full 48-by-96-inch sheet yields several small panels.

Where it falls short. Off-the-shelf magnetic tape is weaker than the strips in a Window Savers kit and much weaker than a compression tube, so the seal on anything larger than a small window is unreliable. Sheet from a home center is usually extruded rather than cast acrylic, which is fine optically but scratches more easily. And every part of the appearance is on you.

Browse 1/8-inch OPTIX acrylic sheet

How to choose

Start with the seal. The difference between a good interior storm window and a bad one is almost entirely the perimeter seal. Compression tubing (Indow) and engineered magnetic systems (Climate Seal, Magnetite) are both excellent. Kit magnets (Window Savers) are good if you install them carefully. Hardware-store magnetic tape is the weak link.

Match thickness to the problem. For drafts and heating bills, 1/8-inch acrylic is the standard and anything thicker is money wasted. For noise, go to 1/4 inch and look for a product with an actual STC rating or dBA figure rather than a percentage.

Count your windows. For one to four windows, a custom insert from Indow or Climate Seal is the easy answer. For a whole house of fifteen or twenty, the Window Savers kit's per-window cost is hard to argue with.

Think about removal. If you open windows in summer or need egress from a bedroom, a magnetic or compression panel you can pull in seconds is essential. Screwed or cleated DIY panels are a chore.

Check your existing windows first. Inserts stop drafts and add an air gap, but they cannot fix rotten sashes, broken glazing putty, or a window that leaks water. Repair first, then insert.

Frequently asked questions

Do interior storm windows cause condensation? They can, if warm indoor air reaches the cold glass behind the panel. A tight seal prevents that, which is one more reason to prefer compression or magnetic mounting. If you see condensation between the panel and the glass, the seal is leaking somewhere.

Will acrylic yellow over time? Modern cast and extruded acrylic is inherently UV-stable and does not yellow the way polycarbonate does. It does scratch more easily than glass, so clean it with a soft cloth and a plastic-safe cleaner, never a dry paper towel.

Are they better than exterior storm windows? Interior inserts are easier to install, easier to remove, and invisible from the street, which makes them the default for historic homes. Exterior storms protect the primary window from weather, which interior panels do not. Many old-house owners run both.

What about the plastic film kits? Shrink film taped to the frame creates the same air gap for a few dollars, and it works. It also looks like plastic film taped to the frame, lasts one season, and cannot be removed and reused. Rigid acrylic is the permanent version of the same idea.

Sources

• Indow Window Inserts: Standard Grade, Acoustic Grade, Museum Grade, and 2026 pricing update
• Indow Windows Cost 2026 and Indow Window Inserts: Performance, Cost, and Reviews
• Climate Seal Thermal Series, Acoustic Series, and Magnetic Window Insulation
• Magnetite: Our Product
• Window Savers: Shop and FAQ
• This Old House: All About Storm Windows
• Bob Vila: Interior Storm Windows Save Homeowners Money in Two Ways
• Home-Adviser: Magnetic Interior Storm Window Inserts
• OPTIX acrylic sheet at The Home Depot