Can VIG fit in original historic window frames?

Yes. VIG starts at just 6.2mm thick, which fits directly into original single-glazed window profiles without modification. No other high-performance glass is thin enough for this application.

Is VIG compliant with historic preservation requirements?

Yes. VIG preserves original sightlines and architectural character, meeting SHPO (State Historic Preservation Office) guidelines. It is a like-for-like replacement that upgrades thermal performance without altering the building exterior.

What tint options are available for historic buildings?

VIG is available in historic tints including Gray, Bronze, Green, and Blue, as well as multiple Low-E coating options. This allows matching the original glass appearance of landmark buildings.

How does VIG compare to standard IGU for historic retrofit?

Standard double-glazed IGUs are 24-32mm thick, far too wide for original single-glazed frames. VIG at 6.2mm is 4-5x thinner while delivering R12-R20 insulation versus R3-R5 for standard IGU. VIG is the only option that fits without frame modification.

Historic Preservation

Same Sightlines — 6.2mm Thin.
3–4x More Efficient Than IGU.
Thin Enough to Fit
Where IGU Can’t.

VIG is the only high-performance glass thin enough for original single-glazed window frames. Preserve the character. Modernize the performance.

The Challenge

Historic Frames Were Not Built for Modern Glass

Most high-performance glazing is too thick for landmark buildings. Standard double-glazed IGUs start at 24mm — far too wide for original single-glazed profiles that typically accept 3–6mm glass. Building owners face an impossible choice: preserve the architecture or upgrade the performance.

VIG eliminates that tradeoff. At just 6.2mm, it drops directly into existing frames. No new mullions. No altered sightlines. No compromise on the architecture that earned the building its protection.

6.2mm

Thin Enough for History

Original single-glazed frames accept 3–6mm glass. VIG at 6.2mm is the closest any high-performance glass has ever come to matching that profile.

Head to Head

VIG vs. Standard IGU for Historic Retrofit

Metric	Standard Double-Glazed IGU	VIG
Profile thickness	24 – 32mm	6.2mm
Fits original single-glazed frames?	No — requires new frames	Yes — direct drop-in
R-value (center of glass)	R-3 to R-5	R-12 to R-20
U-value (W/m²·K)	1.2 – 1.8	0.3 – 0.5
Condensation	Possible (gas seal degradation)	Zero — no air in cavity
Sound attenuation	28 – 32 dB	39+ dB
Sightline alteration	Significant — wider mullions required	None — original profiles preserved
SHPO compliance	Often rejected	Compliant — preserves character
Historic tint options	Limited	Gray, Bronze, Green, Blue + Low-E
Gas fill degradation	Yes — argon leaks over time	None — vacuum is permanent
Tested lifespan	20 – 25 years	40+ years

Why VIG Wins

Near-Zero Competition

No other glass technology can match VIG's combination of thin profile and high performance for historic buildings. This is the most defensible position in the glazing market.

✓6.2mm profile fits original single-glazed frames without modification

✓SHPO compliant — preserves original sightlines and architectural character

✓3–4x more efficient than IGU — in a profile thin enough to fit where IGU cannot

✓Historic tints available: Gray, Bronze, Green, Blue

✓39+ dB sound attenuation — meaningful upgrade for urban landmarks

✓40+ year tested lifespan — outlasts standard IGU by decades

✓No construction disruption — like-for-like swap, no frame modification

Ideal For

Who Specifies VIG for Retrofit?

VIG is specified by preservation architects, building owners, HOAs, and facilities managers working with:

•National Register-listed buildings

•State and local landmark properties

•Historic districts with design review requirements

•University and institutional buildings with original fenestration

•Churches, courthouses, and civic buildings

•Residential historic homes and estates

Same Sightlines — 6.2mm Thin.3–4x More Efficient Than IGU.Thin Enough to FitWhere IGU Can’t.