Glass walls that slide away are showing up on condo balconies and restaurant patios all over the region. We asked a local installer to explain what’s actually going on inside them, and why the gaps are there on purpose.
Walk through Belltown on a rainy afternoon and look up. You’ll probably spot a few balconies closed in with what looks like a single sheet of glass, no frames anywhere. Come back on a warm day and the same balconies are wide open, the glass folded away as if it was never there.
These retractable glass systems get called sunrooms, though they have little in common with the insulated rooms people add onto houses. To find out how they work, and how they hold up in a climate this wet, we talked with Ruslan Bencheci, owner and CEO of Star Construction WA. The Bothell company installs Lumon retractable glazing along with decks and patio covers across King and Snohomish counties.
The conversation has been edited for length and clarity.
“People expect a window. It’s closer to a weather shield.”
When someone asks you what a retractable glass sunroom is, what do you tell them?
I tell them to picture a covered porch with walls you can put away. That’s closer than “sunroom,” honestly. Most people hear sunroom and imagine a room you heat, with insulated walls, part of the house. This isn’t that. It’s single-pane tempered glass that keeps the rain and wind off, and when the weather’s nice you slide it all out of the way.
So what’s physically there?
Less than people think. There’s an aluminum profile along the top, attached to the ceiling or the balcony above. There’s a track along the bottom, usually on the railing. And then the glass panels in between, with no frames on the sides. Each panel sits a couple of millimeters from the next one, so from the street it just looks like one piece of glass.
Which part matters most?
The tracks, by a lot. If a track is even slightly out of level, the panels start to drag, and within a season the customer is annoyed every time they open it. So we spend way more time on the tracks than on the glass. On balconies we install from inside the railing, which helps. You’re standing on the balcony doing careful work instead of hanging off scaffolding on the sixth floor.
“It Takes About as Long as Opening French Doors.”
Walk us through opening one.
Most frameless systems, including Lumon, use a slide-and-turn. You unlock the first panel and slide it to the end of the track. There it pivots, like a door, and swings in against the wall. Then you bring the next one over, turn it, and lay it against the first. By the end you have a neat stack maybe a foot deep, and the whole opening is clear.
When I explain it that way it sounds complicated. Then people try it once and they’re done in under a minute.
Anything people don’t expect?
The window cleaning. When the panels are turned open, you can reach both sides of the glass from inside. For someone on a high floor, that’s a bigger deal than you’d think. They were paying someone to clean those windows, and now they don’t have to.
“It’s Not Watertight. It’s Not Supposed to Be.”
Do these leak?
A little, and on purpose. That’s usually the moment in a consultation where people look at me funny. In a real sideways rain, some water gets past the gaps between panels. And on cold mornings you’ll get condensation running down the inside of the glass. The bottom track is designed to catch all of it and send it back outside through small channels under each panel. So the water gets into the track, not onto your floor.
Why not just seal it?
Because in Seattle, a sealed glass box is a mildew box. Single-pane glass in this climate makes condensation all winter. If the room can’t breathe, that moisture sits there, and in a couple of years you’ve got mildew in the corners and rot wherever there’s wood. On a balcony it can even trap water against the building wall, which is a much bigger and more expensive problem than a damp balcony.
The Lumon panels leave gaps of about 2 to 3 millimeters. That’s small enough to keep out rain and most of the wind, and big enough that air keeps moving even with everything closed. On a dry day you open a few panels and the whole space airs out in minutes.
What should people ask when they’re comparing products?
Ask the installer to show you where the water goes. Literally point at it. Where does it go when it gets into the bottom track, and how does it get out? Anyone who’s done this a while answers that in ten seconds. If you get a vague answer, keep shopping.
“It Won’t Be Your Living Room in January.”
Can you heat one?
A little. A small infrared heater or an electric fireplace works fine for the cold weeks, and a lot of our customers have one. On a sunny winter afternoon it can feel great out there without any heat at all. But at night it drops toward the outside temperature, because it’s single-pane glass with air gaps. If someone tries to heat it like a bedroom, mostly what they get is fogged-up glass.
Does it add square footage?
Not in the way an appraiser counts it. It’s unheated and ventilated, so it’s treated more like a covered patio, an amenity. If someone tells me square footage is the goal, we’re talking about a real sunroom addition, with insulated walls and a different permit. I’d rather have that conversation in the first ten minutes than after they’ve fallen in love with the glass.
Is it the same as a retractable roof?
No, and that’s a common mix-up. These are walls. They need something solid overhead, like the balcony above, an existing roof, or a patio cover we build first.
“Most of the Waiting Happens Before We Show Up.”
How long does a project take?
The install is fast. Most single balconies go in within a day, and a full sunroom built with the system takes three to five days on site. The wait is mostly production. Every panel is made to the exact measurements of your opening, so it’s typically four to six weeks from order to delivery.
And cost?
For a residential balcony, most jobs land somewhere between $12,000 and $28,000. It mostly comes down to how much glass you need, plus corners and whether the railing has to change. Sunroom additions are a different project and start around $45,000. (Star Construction WA publishes its typical prices and warranty terms for the Lumon systems it installs.)
What should buyers look at beyond the price?
Parts. Lumon’s warranty covers materials for five years. Spare parts stay available for ten years, and the functional and safety components for twenty. People skim over that, but rollers and seals are what wear out. Fifteen years from now, you want to be able to call someone and get a roller, not replace the whole system.
I’ll also say this: Lumon isn’t the only option. They’ve been making this since 1978 in Finland, and it’s what we install, but there are other manufacturers, and framed systems can cost less. Whoever you talk to, get the quote itemized and in writing, and ask about parts and drainage.
“Vacuum the track. That’s most of it.”
How much maintenance are we talking about?
Not much. The bottom track collects grit and leaves, and if you’re under fir trees, a lot of needles. That’s what makes panels stiff. Vacuum the track every month or two, more in the fall. Wipe the rollers and seals once in a while. If something sticks, use the lubricant the manufacturer recommends, not whatever’s sitting in the garage.
And if a panel starts dragging anyway?
Call us before you force it. It’s usually a quick adjustment. Forcing it is how rollers break, and then it’s a service call instead of a two-minute fix.
Last question. Who’s this a good fit for?
Honestly, anyone who looks at their balcony or covered deck in November and thinks, “I haven’t sat out there since September.” That’s who it’s for. It won’t give you a new room. It gives you back the one you already have for a lot more of the year.
Robert Thompson, a proud alum of the University of Oregon with a degree in Landscape Architecture, has been a leading figure in outdoor space enhancement for over 17 years. He started his career with a landscape design firm, gaining invaluable experience creating functional and attractive outdoor living areas. Robert joined our website in 2018, where he quickly became known for his innovative yet practical advice on outdoor renovations. He has been the chief editor of our deck and patio section ever since then, helping readers transform their outdoor spaces into personal retreats. When not drafting designs or writing, Robert is an avid kayaker, often drawing inspiration from nature for his creative projects.
