Larson specializes in storm windows and security products engineered for harsh weather conditions. Their product line includes exterior storm windows rated for 90 mph winds, interior storm windows for historic preservation, and security panels that combine stainless steel mesh protection with energy efficiency features.
The company positions itself as the largest storm door and storm window manufacturer in the United States, with over 65 years in business and 20+ patents. Their focus remains on residential products that protect homes from weather extremes while improving energy efficiency.
SecurePRO Window Protection: Measurable Security Without Bars
The SecurePRO series uses stainless steel wire mesh (0.028” diameter, 12 weaves per square inch) that exceeds 1,000 lbs of impact force. Frame compression testing shows 15,000 lbs of force rating, with tensile strength at 800 lbs per linear inch. Those aren’t marketing numbers — they’re tested to SMA 6001-2002 industry standards.
The mesh design solves the visibility problem that traditional security bars create. You get break-in protection with unobstructed views, plus UV filtration that reduces fading on interior furnishings. Self-storing glass panels slide up and down seasonally — security mesh in summer for ventilation, glass panels in winter for insulation.
Emergency release systems come standard for code compliance — occupants can escape quickly if needed. Installation uses tamper-proof, one-way screws that can’t be removed from the outside. Size range runs from 24 1/8” to 54” wide and 14” to 90” tall.
Glass options include standard double-strength tempered, laminated glass for additional security, or Low-E coated panels for energy savings. The Low-E coating becomes particularly valuable in Montana’s temperature extremes — reducing heat loss in winter and heat gain in summer.
Premium Exterior Storm Windows: Built for Wind and Cold
The L603/L603E Performance Series handles winds up to 90 mph with air leakage at just 0.7 cfm/ft² — approximately 75% better air infiltration reduction than no storm window and 4x lower than standard performance series. For Montana’s chinook winds and winter storms, those numbers translate to real energy savings and draft elimination.
| Specification | L603/L603E Performance Series |
|---|---|
| Wind Resistance | Up to 90 mph |
| Air Leakage @ 75 Pa | 0.7 cfm/ft² |
| Noise Reduction | Approx. 50% of outside noise |
| UV Protection (Low-E) | Up to 60% UV radiation blockage |
| Low-E Emissivity | 0.15 |
| Solar Transmittance | 0.69 |
The frame uses double-wall aluminum construction with marine-grade wrap-around glazing — critical for moisture resistance in freeze-thaw cycles. High-performance wool pile weatherstripping combines with double weather-strips on inserts and interlocking meeting rails. That’s multiple barriers against air infiltration.
Size range covers 25.5” to 90” width and 14.5” to 63” height, with restrictions above 74” wide by 58” tall. Installation takes about 10 minutes with the no-cut, quick-install system — pre-punched mounting holes mean no custom drilling.
Color options include white, almond, brown, and sandstone. Standard configuration includes left-half screen with optional full-screen or right-half operation. Integrated weep holes manage moisture that gets past the primary window — preventing the rot and mold problems common in Montana’s wet spring seasons.
Interior Storm Windows for Historic Preservation
The I900/I900E interior mount series fills a specific niche — historic buildings where exterior modifications aren’t allowed. Montana has plenty of these in Butte, Helena, and other historic districts where preservation committees control exterior aesthetics.
Performance data shows meaningful improvements without touching the exterior:
| Specification | Clear Glass | Low-E Glass |
|---|---|---|
| Draft Reduction | Up to 48% | Up to 62% |
| U-Factor Improvement | Up to 50% | Up to 62% |
Maximum size reaches 80” x 80” or approximately 23 square feet — large enough for most historic window openings. The system tolerates up to 1/8-inch out-of-square openings, which matters in century-old buildings where nothing’s plumb anymore.
Glass thickness varies by size — 1/8” float glass for united inches up to 95, stepping up to 3/16” glass for larger sizes. Tempered glass options available for sizes over 95 united inches. Color choices include white, antique white, brown, and champagne to match historic interiors.
The mounting system requires just 1-inch depth (actual window depth 5/8-inch), shallow enough for most historic window sills. No exterior work means no scaffolding, no historic committee approvals, no exterior paint matching — just interior installation that preserves the building’s character while cutting drafts by half or more.
The Verdict on Larson
Larson delivers on performance specifications that matter for Montana conditions. Their 90 mph wind ratings address real chinook wind concerns. The 75% air infiltration reduction translates to lower heating bills. Security mesh that stops 1,000 lbs of force provides genuine protection for ground-floor windows.
The mixed customer reviews suggest quality varies by product line — a common pattern when manufacturers offer both premium and budget options. Their storm door products face more complaints about moisture trapping and component failures, while the storm window lines show better durability ratings.
For contractors, Larson’s value proposition centers on measurable performance gains you can demonstrate to customers. Show them the air infiltration numbers. Point to the wind ratings. Explain how Low-E coatings with 0.15 emissivity cut energy loss. Those specifications justify the premium over basic storm windows.
Skip Larson if you’re looking for budget solutions or if the project doesn’t require their specific performance features. But for historic preservation work, security upgrades, or serious weatherization projects, their engineered approach delivers results contractors can stand behind.
Frequently Asked Questions
What makes Larson storm windows different from standard replacement windows?
Storm windows install over existing windows rather than replacing them. Larson’s L603 series reduces air infiltration by approximately 75% while maintaining the original window. This approach costs less than full window replacement and preserves historic windows that can’t be changed. The combination also cuts outside noise by about 50%.
How do SecurePRO panels compare to traditional security bars?
SecurePRO panels use stainless steel mesh that exceeds 1,000 lbs of impact force while maintaining visibility. Traditional bars block views and make homes look fortified. The mesh design allows ventilation when glass panels are stored, and the emergency release system ensures occupants can escape — something fixed bars don’t offer.
Which Larson products work best for Montana’s weather extremes?
The L603/L603E exterior storm windows handle 90 mph winds and reduce air leakage to 0.7 cfm/ft². For temperature swings, Low-E glass options provide 0.15 emissivity and block up to 60% of UV radiation. Interior storms work well where exterior installation isn’t practical — they reduce drafts up to 62% with Low-E glass.
What’s the real energy savings from adding Larson storm windows?
Larson claims approximately 75% reduction in air infiltration versus no storm window. With Low-E glass reducing energy loss up to 60%, the combination significantly cuts heating and cooling costs. Actual savings depend on your existing windows’ condition and local energy costs, but the measurable air infiltration improvement provides real benefit.
Do Larson products require professional installation?
The L603 series features a no-cut, quick-install system that takes approximately 10 minutes with pre-punched mounting holes. Security panels use tamper-proof, one-way screws for permanent installation. While DIY installation is possible, professional installation ensures proper weatherstripping alignment and maximum energy efficiency.
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