Smart Glass and Motorized Windows: What Is Realistic for a Replacement Project

"Smart windows" is a marketing umbrella over four different things: glass that changes tint, windows that open and close by motor, sensors that report whether a window is open or locked, and blinds built into the glass. They differ enormously in cost, maturity and how well they fit a replacement project. This page takes each in turn. It is part of our California window guide.

Our position up front: for most houses, none of this beats a well-chosen ordinary window. The exceptions are specific openings with a specific problem.

Dynamic glass: electrochromic, thermochromic and photochromic

California's Energy Code has a name for glass that changes its properties: chromogenic glazing. The family has three members.

• Electrochromic glass tints when a small voltage is applied and clears when it is reversed. It is controlled by a switch, a schedule or sensors.
• Thermochromic glass tints by itself as the glass warms in the sun. No wiring, and no control either.
• Photochromic glass darkens in response to light, like transition lenses in eyeglasses.

What electrochromic glass can do

The appeal is real. A window that can go from clear to deeply tinted removes the need to choose between a view and a cool room. SageGlass, one of the long-established manufacturers, publishes a range for a typical double-glazed unit of 60 percent visible light transmission when clear down to 1 percent when fully tinted, with the solar heat gain coefficient moving from 0.41 to 0.09. For comparison, the fixed SHGC maximum for replacement windows across most of California is 0.23. Fully tinted, electrochromic glass blocks far more solar heat than conventional glass, and when clear it admits far more.

Why you rarely see it in houses

• The market is commercial. The major electrochromic manufacturers build for offices, hospitals, airports and multifamily buildings. They sell through architects and glazing contractors, not through the residential window dealers a replacement project uses.
• Every pane needs wiring. Electrochromic glass runs on low-voltage power, with a cable to each insulating glass unit and a controller somewhere in the building. In new construction that is planned in. In an existing house it means fishing wire to every opening.
• It has to fit a frame. The glass is one component. It has to be glazed into a window frame designed to route the wiring, by a manufacturer willing to warrant the combination.
• It is one more system. Controls, power supplies and software all have to keep working for the life of the window, and a window is expected to last decades.

We are deliberately not quoting tint speeds or prices. They vary by product and size and we have not verified current figures.

Where dynamic glass can make sense

A custom home or a major remodel with a wall of west-facing glass and a view worth keeping, where exterior shading is not possible and the wiring can be designed in. That is a project with an architect and a specialty glazing contractor. It is not a like-for-like window replacement.

What gets you most of the benefit for less

For the same hot west-facing room, in order of how often we would recommend them:

1. Low solar gain Low-E glass. It is what the Energy Code already requires in most zones. See the best windows for cooling.
2. Exterior shade. An awning, a trellis, a deciduous tree or exterior solar screens stop the heat before it reaches the glass.
3. Motorized interior shades. Not as effective as shading outside, but simple to retrofit and battery-powered versions need no wiring.
4. Window film on glass you are not ready to replace. Our page on window film versus window replacement covers when it works and when it puts the glass warranty at risk.

Motorized windows

A motorized window uses an electric operator in place of the crank or the hand. Motors suit windows that swing on hinges, which is why the products that exist are mostly casements, awnings and skylights, plus large sliding doors.

What is on the market

The clearest current example from a mainstream window manufacturer is Marvin's Connected Home line: an automated casement, an automated awning and an automated multi-slide door, all in Marvin's Modern collection. Marvin says integrated sensors close the windows automatically when moisture is detected or power is lost, that pinch detection stops a window closing on an obstruction, and that the units can be run from on-unit controls, an app, a wall switch, a voice assistant or a home automation system such as Crestron or Control4.

That list tells you who the product is for. It is a premium line, offered in one collection, aimed at new custom homes with an integrator on the project. Other manufacturers sell add-on power operators for particular awning and casement windows, and some of those carry restrictions on older units or on installations near the coast.

Where a motor earns its place

• Windows you cannot reach. High awning windows in a stairwell, clerestories above a vaulted living room, operable skylights. A window that is never opened because it needs a ladder is a fixed window you paid extra for.
• Accessibility. For someone who cannot work a crank or lift a sash, a motor is a genuine improvement.
• Night ventilation. Across much of the Sacramento Valley and the Bay Area, evenings cool off quickly after a hot day. High windows that open on a schedule or a temperature signal can flush heat out of a house.

What to ask before buying one

1. How does it get power, and who runs it? Each unit needs a cable. Find out whether it is low-voltage from a central power supply or line voltage at the window, and who is responsible for the electrical work and its permit.
2. What happens when the power fails? Closes, stays put, or needs a manual override?
3. How do I open it by hand? This is the question that matters for bedrooms.
4. What does the warranty say about the motor and electronics? Electronic components commonly carry shorter coverage than the window itself.
5. What happens when the app is discontinued? A window outlives several generations of phone. Prefer products that still work from a wall switch with no network.

Bedrooms and escape openings

Sleeping rooms generally need an emergency escape and rescue opening, and for most houses that opening is a window. The 2025 California Residential Code, Section R319 (formerly R310), requires that such openings be operational from the inside of the room without the use of keys, tools or special knowledge.

A motorized window that opens fully by hand as well satisfies the plain reading of that. One that needs power, a code or an app to open is a problem. We would not put a motorized unit in a required escape opening without the building department's agreement in writing. The same goes for any motorized shade or screen that covers one.

Sensors

This is the modest, useful end of smart windows. A contact sensor reports whether a window is open or closed; some also report whether it is locked. They come two ways: built into the window at the factory, or as small wireless add-ons stuck to the frame of any window.

The value is practical. You can check from bed whether the downstairs windows are shut, and an alarm system knows what is open. Sensors do not make a window harder to force, though. The lock, the glass and the frame do that, and they are covered in window security in California.

One caution: do not let anyone drill into a new window frame to mount an aftermarket sensor without checking the window warranty first. Adhesive-mounted sensors avoid the question.

Blinds and shades between the glass

Several manufacturers build a blind or shade into the window, behind a pane of glass where it cannot be touched. Pella, for example, offers between-the-glass blinds and shades on its Lifestyle Series, promoted as cordless and protected from dust and damage.

The real advantages are the ones Pella lists: nothing to dust, nothing for a pet to shred, and no cords. That last point is a safety feature in a house with small children; see window fall prevention and child safety for why cords matter.

The trade-offs are just as real:

• You are choosing the window by its blind. The feature exists in a few product lines, so it decides the brand, the frame material and the price tier.
• Repair is the manufacturer's. A broken ordinary blind is a trip to the hardware store. A broken built-in blind is a service call, and how accessible the blind is varies by product.
• It is most useful on doors. A blind that cannot swing or bang on a patio door is the best case for the idea.
• It is not an energy shortcut. Title 24 compliance rests on the NFRC-certified figures for the window. Read the label for the configuration you are ordering.

Title 24 and NFRC: how the code sees all this

Replacement windows in California have to meet a maximum U-factor and, in most climate zones, a maximum SHGC, shown by the NFRC label on the product. Our page on Title 24 requirements for replacement windows has the figures by zone.

For dynamic glass, the 2025 Energy Code has a specific provision. It defines chromogenic glazing, and an exception in the residential prescriptive requirements (Exception 4 to Section 150.1(c)3A) provides that for fenestration with chromogenic glazing the lower-rated labeled U-factor and SHGC are used, on condition that the glazing has automatic controls to modulate solar gain and light. Chromogenic glazing is considered separately and may not be area-weighted with ordinary windows.

Two practical consequences. First, the benefit depends on automatic control: glass you tint by hand when you remember to does not get credit as if it were always tinted. Second, this is a compliance question for whoever prepares the energy documentation, and a project with dynamic glass should have that person involved before anything is ordered.

Motors and sensors do not change the label figures at all. A motorized casement is rated like the manual one.

What is realistic, by project type

The difference between the first two columns is explained in retrofit windows. If smart features matter to you, they are a reason to decide the installation method early.

Sources

• SageGlass (Saint-Gobain): How Electrochromic Glass Works
• Marvin: Connected Home
• Pella: Between-the-Glass Blinds and Shades
• California Energy Commission: 2025 Building Energy Efficiency Standards (Title 24, Part 6), Sections 100.1 and 150.1(c)3A
• 2025 California Residential Code, Chapter 3, Section R319 (emergency escape and rescue openings)
• Lawrence Berkeley National Laboratory: High Performance Windows research
• National Fenestration Rating Council: The Energy Performance Label

Working with Heritage Exteriors

We install windows, not home automation systems, and we will say so when a request needs an integrator or a glazing specialist we are not. What we can do is tell you which openings would justify a motor or a built-in blind, plan the installation so the wiring is possible, and make sure the windows themselves meet the code without relying on the gadgetry. Licensed in California, CSLB #1055919. Call (916) 546-2991.