Free in-home measure and quote - PGT, CGI and CWS impact lines compared on your actual openings, style by style
Fast, Reliable Energy-Efficient Windows Across Marathon
Energy-efficient window replacement in Marathon, FL typically runs $850 to $2,400 per window installed, depending on whether you’re upgrading from old jalousies to impact-rated double-pane units or going full triple-pane with low-E and argon. Our crews are in Marathon every week, and we schedule window energy audits within three to five business days. If you live off Sombrero Boulevard, along US-1, or back in a canal-front neighborhood, call (813) 320-9346 and a live person will answer. That’s not a callback service. That’s us.
Here’s the thing about Marathon most window companies on the mainland don’t plan for: every replacement window here must carry a Miami-Dade Notice of Acceptance (NOA) or equivalent HVHZ approval. Standard non-impact windows are not a legal option. That changes how energy efficiency gets specified, priced, and installed, and it’s why we spec marine-grade stainless fasteners and neoprene seals as a default, not an upgrade.
Why TruePane Windows & Doors Is Marathon’s Preferred Energy-Efficient Windows Company
TruePane Windows & Doors was founded by Dale Kessler, a second-generation glazier, and the company has served local communities since 2008 through a craft tradition, not a franchise playbook. Marathon homeowners call us because we answer the phone, show up when we say, and write both manufacturer warranty layers into the contract before the truck leaves the driveway, a practice we call The Keystone Standard. No paperwork fights. No arguing about what’s covered.
We’re an authorized installer for more than a dozen manufacturer lines, including PGT, CGI, and Simonton. That means when a Marathon customer asks us to compare a PGT impact-rated low-E window against a CGI equivalent, we print both quotes side by side on paper. You see exactly what you’re buying, including U-factor, SHGC, and the NOA number for each unit.
Our technicians are background-checked and uniformed. They measure every opening twice, and they work in your home the way they’d work in their own mother’s. Every job is covered by our 90-Day Done Right Promise: if it’s not done right, we make it right. Dale’s rule on the whiteboard hasn’t changed: if the pane is not true, the job is not done.
Dispatch and scheduling for Marathon are coordinated from our South Florida office, and technicians drive down to Marathon with the materials they need on the truck, not a promise to come back next month. A live person answers the phone 24 hours a day, 7 days a week. Call (813) 320-9346 and you’ll get us.
Our Energy-Efficient Windows Services in Marathon
Low-E & Argon Gas Glass
Low-E coatings in Marathon do double duty: they reflect solar heat while allowing visible light through. Argon gas between the panes slows thermal transfer. Pair those with impact-rated glass and you’ve got a window that cuts AC load and meets Monroe County code. Low-E and argon fill add roughly $60 to $140 per window over standard impact glass. In Marathon’s salt-air environment, the edge seal quality matters just as much as the glass itself. Cheap edge seals on budget impact windows fail within a few years, fog between the panes, lose the argon fill, and the efficiency gain disappears.

ENERGY STAR Replacement Windows
ENERGY STAR certification is a starting point, not the finish line. A window that carries the ENERGY STAR label for South Florida must meet specific U-factor and SHGC thresholds for our climate zone. But in Marathon, the label doesn’t override HVHZ code. The window still needs a Miami-Dade NOA. We spec ENERGY STAR-rated impact windows from manufacturers whose products carry both certifications in the same unit, so you don’t choose between the rebate and the building permit.

Double & Triple Pane Windows
Most Marathon replacements we install are double-pane impact units with low-E and argon. They run $1,100 to $2,000 per window installed, depending on size and opening type. Triple-pane is available and adds roughly 25% to 40% to the per-window cost, with marginal additional energy savings in our climate. For canal-front homes exposed to salt spray from three directions, double-pane impact glass with quality edge seals and marine-grade hardware outperforms triple-pane with standard hardware that corrodes in five years.

UV-Blocking & Fade Protection
Marathon’s sun works on everything: furniture, flooring, artwork, and window frames themselves. Low-E coatings block a meaningful percentage of UV light, and some low-E formulations are tuned specifically for fade protection while still meeting hurricane impact standards. For homes facing east or west with unshaded windows, we recommend low-E coatings with higher UV-blocking performance on those elevations. Expect to pay $40 to $90 more per window for upgraded low-E coatings with stronger UV rejection.

Window Energy Audits & Ratings
Before we quote a replacement, we can perform a window energy audit on the existing openings. We check the condition of edge seals, look for fogging between panes, test the operation of the sashes, and evaluate whether the current windows still carry a valid NOA. Many Marathon homeowners learn their 1990s impact windows have lost their argon fill or were installed with standard fasteners now corroding. An audit means you replace what actually needs replacing, not what someone thinks you should replace. Audits run $149 to $350 depending on the number of openings and access.

What happens when you call
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A real person answersNo phone trees - you reach a local pro.
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You get an upfront price rangeHonest numbers before anyone is dispatched.
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A background-checked tech heads outLicensed & insured, dispatched right away.
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You approve before work beginsNothing starts until you say go.
Trusted Brands We Service in Marathon
We install and service windows from PGT, CGI, Simonton, and Ply Gem, among others. PGT and CGI both manufacture impact-rated lines specifically tested for Florida’s HVHZ counties, and we’ve installed both extensively across Marathon. If you already have PGT or Simonton windows that are fogging or binding, we can evaluate them and order replacement sashes or insulated glass units without tearing out the frame. For Marathon customers, we keep common replacement parts and marine-grade hardware in local stock so we’re not waiting on a mainland shipment to finish a job. Visit our Energy-Efficient Windows page for more details on manufacturer lines and options.
Common Energy-Efficient Windows Problems We See in Marathon Homes
- Fogged glass from salt-air edge seal failure. The insulated glass unit’s edge seals pit and degrade quickly in Marathon’s salt spray. Once the seal fails, the argon leaks out, and the window’s thermal performance drops to single-pane levels even if the glass still looks fine.
- Weep holes clogged with salt scale. Canal-front and bayfront homes off Sombrero Boulevard and along the water get salt spray from below as well as the sides. Weep holes clog, water sits against the sash, and the jamb rots. Regular cleaning helps, but marine-grade hardware and neoprene seals slow the corrosion cycle.
- Impact-rated glass with standard fasteners. A window can carry a valid NOA and still be installed with hardware that corrodes within a decade. Post-storm inspections have failed windows where the glass held but the fasteners didn’t. We spec marine-grade stainless fasteners as a default on every elevation in Marathon.
- Original jalousie windows that can’t be upgraded. The louvered jalousie style once common across the Keys provides almost no wind resistance, no thermal barrier, and no sealing surface for energy-efficient glass. If your home still has them, replacement is the only code-compliant path forward, and it will be an impact-rated unit by default.
Pricing for Energy-Efficient Windows in Marathon, FL
Here’s what Marathon homeowners should expect to pay for installed energy-efficient windows. A standard double-pane impact window with low-E and argon runs $1,100 to $2,000 per opening. Triple-pane adds 25% to 40%. Upgraded low-E for stronger UV protection adds $40 to $90 per window. Window energy audits run $149 to $350. Larger openings, second-story work, or full-house projects can shift these numbers, and we write every quote as a fixed line-item price. No change orders unless you approve it in writing first. Call (813) 320-9346 for a free estimate, and we’ll put the numbers on paper before you decide anything.
We Also Serve Cities Near Marathon
TruePane installs Energy-Efficient Windows in Marathon and the surrounding Keys communities, including Key Colony Beach, Big Pine Key, Tavernier, and Key Largo. Our crews drive the Overseas Highway weekly, so scheduling doesn’t require a mainland company’s logistics. If you’re in a neighboring town, the same pricing, warranty registration, and 90-Day Done Right Promise apply.
Serving Marathon, FL - Our Local Coverage Area
We’re based in the Marathon area and know this community well. Use the map below to see our service coverage - if you’re nearby, we can almost certainly help.
FAQs - Energy-Efficient Windows in Marathon
No. Every replacement window in Marathon must carry a Miami-Dade Notice of Acceptance (NOA) or equivalent HVHZ approval. An energy-efficient non-impact window can meet every ENERGY STAR threshold and still fail Monroe County code. The energy-efficient path here starts with impact-rated glazing as the code floor. Call (813) 320-9346 and we’ll quote what’s legal first, then efficient.
Jalousie, or louvered, windows cannot be upgraded to meet current code or provide meaningful insulation. The individual glass slats don’t seal against each other, so air, water, and wind pass through by design. You’ll replace them with impact-rated windows. If you want airflow, fixed louver shutters next to a proper impact window can give you the breeze without the code violation. Call (813) 320-9346 to talk through options for your specific openings.
Impact rating is about wind resistance. Argon is about thermal performance. The two are separate systems in the same window. Argon between the glass panes slows heat transfer, lowering your AC load. In Marathon’s salt air, the edge seal protecting that argon fails faster than it would on the mainland. A quality edge seal and a registered warranty matter as much as the gas itself. Call (813) 320-9346 for a free estimate with argon spec’d in writing.
Yes. An energy audit checks the edge seals for fogging or pitting, tests whether the argon fill is still intact, and evaluates the condition of hardware and weep holes. Many Marathon homeowners find their 1990s impact windows are structurally sound but thermally dead. It’s cheaper to replace the insulated glass unit than the whole window when the frame is still good. Audits run $149 to $350, and that cost is credited toward replacement work if we do the job.
Yes. Canal-front and bayfront homes in Marathon get salt spray from below as well as from the sides. Standard window fasteners and weatherstripping corrode much faster on those elevations. We spec marine-grade stainless fasteners and neoprene seals on every canal-front installation, even when the manufacturer’s default hardware would technically pass code. It costs a bit more up front and lasts twice as long. Call (813) 320-9346 and we’ll show you the difference on paper.
Written by Dale Kessler, Owner at TruePane Windows & Doors, serving Marathon and the Florida Keys.
Six Reasons Homeowners Choose TruePane Windows & Doors
Impact systems engineered to design pressures up to +/-100, matched to your wind zone - your openings hold when the storm arrives.
Low-E insulated impact glass from our manufacturer lines commonly cuts monthly cooling bills 20-30%.
Laminated impact glass shuts out up to 40% of outside noise - traffic, neighbors, weather.
Monitoring services run $30-90 a month. Laminated impact glass resists forced entry around the clock, with no subscription.
Florida homeowners average around 25% savings on the windstorm portion of their policy after protecting every opening - some homes qualify for more.
A full impact package upgrades curb appeal, buyer confidence and appraised value in one project.



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