Fiberglass Window Replacement — Stiff Frames, Dark Colors, Paintable
You want a black or dark exterior, a slimmer frame, or a window you can paint later. Fiberglass handles all three; we measure, order and install it.
JMB Builders does fiberglass window replacement across the Twin Cities metro. We quote from photos, measure each opening in your home, order fiberglass windows in the style, color and glass you choose, remove the old units, set the new frames in a sill pan or into the old frame, foam, seal and trim them inside and out. Priced per window, written quote within one business day.
- Priced per window, fiberglass windows supplied
- Dark exterior colors available
- In-home measure before the order
- Licensed MN contractor BC809005
Fiberglass frames are made from glass fibers in resin, so they expand and contract at close to the same rate as the glass they hold. That is why fiberglass stays straight in a dark color on a south wall and why the frames can be narrower than vinyl for the same size opening. The frame can also be painted, now or years from now.
A stiffer frame is less forgiving of a bad opening. It will not flex to hide a sill that slopes the wrong way or a rough opening out of square; the sash will just rub. So we check the opening at the measure, fix rot in the sill or jack studs when the old unit is out, set the new frame in a sill pan, shim it square, and fill the gap with low-expansion foam.
You pick the style, colors inside and out, glass and grilles. Some fiberglass lines offer a wood interior you can stain. We handle the order, the install, haul-away and trim. Painting is quoted as a separate line — or leave it primed and caulked and paint it yourself.
What you supply
- Your pick of style, interior and exterior colors, glass package and grilles
- Clear access: furniture pulled back and window coverings down
- Photos of each window from inside and outside and a close-up of one sill
What JMB supplies
- In-home measure of every opening
- The fiberglass windows, ordered to those measurements
- Removal and haul-away of the old windows
- Sill pan, flashing tape, shims, low-expansion foam, backer rod and sealant
- Interior casing or stops and exterior trim or capping
- Photos of the finished windows in your job folder
How it is priced: per window
Quoted in writing from your photos within one business day. What moves the number:
- Window size and style
- Exterior color: standard vs. a dark or custom color
- Wood interior vs. a painted or plain fiberglass interior
- Glass package: double or triple pane and coatings
- Insert into the old frame vs. full-frame tear-out
- Rot repair found once the old window is out
- Second-story openings and exterior trim type
Send photos of each window inside and out. Tell us the exterior color you want; dark colors can change lead time.
How long it takes
One to three full-frame fiberglass windows a day depending on size and siding; inserts go faster. Lead time on the order depends on the color and the maker.
How your project works
- 1
Send photos, get a written quote
Send three photos of the space and a sentence about what you want. You get a clear, itemized quote within one business day. We only come out to measure first when the job needs a tape measure — no pressure, no games.
- 2
Pick materials, or bring your own
We help you choose profiles and materials that fit the house and the budget, or match your existing millwork exactly — or you buy the door or trim yourself and we install it. Everything is confirmed before the crew is scheduled.
- 3
Clean, precise installation
The crew shows up on time, protects floors and furniture, and installs with tight joints and consistent reveals. Photos of the finished work go in your job folder.
- 4
Walkthrough and invoice
We walk the finished work with you. If anything is not right, we fix it before we call the job done. Then one invoice, paid by check or direct deposit — no card fees, no payment links.
Situations and options
Dark exterior fiberglass
Black, bronze and other dark colors hold their shape on fiberglass because the frame does not soften in sun the way vinyl can. The interior can be a lighter color or wood.
Paintable fiberglass
A factory-painted frame you can repaint later with the paint the maker lists. Useful if you think you may change the house color.
Fiberglass insert
A fiberglass window sized to set inside the old frame so the interior trim stays. It works when the old frame and sill are sound and square.
Fiberglass Window Replacement — Stiff Frames, Dark Colors, Paintable: questions, answered
Why choose fiberglass windows over vinyl?
Fiberglass frames move with temperature about as much as glass does, so they stay straight in dark colors and in full sun. The frames are stiffer, so they can be slimmer for the same glass size, and they can be painted. Vinyl costs less per window; we price both when you ask.
Can fiberglass windows be black on the outside?
Yes. Dark exterior colors are one of the main reasons people pick fiberglass. The color is chosen when the window is ordered, and dark colors can take longer to arrive.
Can you paint fiberglass windows later?
Most fiberglass frames can be painted with the paint type the maker lists, which vinyl frames generally cannot. We tell you what the maker of your window allows so you do not void the finish.
Are fiberglass windows harder to install?
They are heavier and stiffer, so the opening has to be right. A stiff frame will not bend to cover a sloped sill or an out-of-square rough opening; the sash rubs instead. We fix the opening first, then shim and fasten the frame square.
Do fiberglass windows come with a wood interior?
Some fiberglass lines offer a wood veneer or wood interior you can stain to match your trim. Others are fiberglass inside and out in a factory color. We go through what is available at the measure.
How long does a fiberglass window replacement take?
One to three full-frame windows a day depending on size, siding and floor; inserts go faster. The wait before that is the order, which depends on the color and the maker. Each opening is closed up the same day.
Recent JMB work, from our job log
59 installs recorded across 30 Twin Cities communities since Dec 2025. Window and door installs for homeowners and for the builders and dealers we sub for. Counts come straight from our job log; no customer names.
Get a written quote for this job
Three photos and a sentence is enough. You hear back within one business day. Or text the photos to 763-204-2099.
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Read morePage reviewed September 26, 2026 · JMB Builders LLC, MN license BC809005 · All windows pages
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Based in Zimmerman, scheduling across the Twin Cities metro. Closest first: