With our ability to mount operating lever handles at either the head or jambs, Hopper units are versatile and convenient to operate whether oriented horizontally and mounted at the floor or with vertical orientation. They can be adjusted for variable tilt into the space and can include releasable hinge stops, enabling the window to open to a horizontal position for ease of cleaning.

Wood Species & Finishes

Duratherm sources all its materials by project, only from providers we know and trust. Many of our woods come from Forest Stewardship Council® (FSC- C108949) certified sources. We obtain others from sustainably-harvested plantations. Fourteen domestic and exotic wood species offer a wide range of colors, grains, and textures.

Please contact us for information about finishing options (including paint, Sikkens, clear laquer, stain, bleach stain, oil, etc.) and to discuss the use of a species not on our standard menu. We consider availability, durability, machining, and gluing characteristics to determine the feasibility of your choices.




We offer dry or wet weeped

glazing compounds.

Specially developed extruded silicon gasket sets the glass by compression. Our proprietary system is long-lived, has low maintenance, and stays waterproof.

Our special silicon wet glazing compound bond to the glass for long-lived sealing. Plus our continuous extruded silicon weatherstrip runs around the frame perimeter, and the seal is not compromised by seasonal expansion and contractions of the sash and frame.




We use only the highest quality hardware. Our standard hardware finishes for most window operators are lacquered Red Bronze (US 20) and White Bronze (US 25). Other finishes are available on request.


KEY (mouse over #s to view details)





Zinc chromate shoot bolt connected to lever handle controls. For tall, narrow units, shoot bolt is rebated into sash stiles (one each stile); short, wide units have shoot bolt rebated into top rail. Turning the lever handle engages the shoot bolts into strike plates at the head or jambs depending on configuration.

Egress: Properly-sized units meet egress requirements using standard hardware configuration.

Lever Handle

Operating hardware accepts any lever handle with 43mm attachment spacing and 7mm square spindle. A wide variety of styles and finishes is available from various manufacturers.

Optional Hardware

Custodial locks, sash restrictors, removable handles, remote pole operation.

Insect Screens

1" x 1/4" tubular extruded frames in anodized bronze, mill finish aluminum or custom color painted aluminum. Mesh of 18 x 16 screen cloth held with vinyl spline, available in charcoal finished aluminum, mill finish aluminum, stainless steel or bright brass. Maximum width of screen mesh is 72". Wood-framed screens are available.


All glazing is per project specifications. Duratherm can accommodate most configurations and make-ups from 1/8" single glazed to a maximum of 1 3/4" security glass.

Clear glass opening: Unit height minus 7 3/4", unit width minus 6 3/4".


Double continuous extruded silicone flap gasket set in rebate around the perimeter of the sash. Engaging the lever handle compresses the weather-strip to ensure a tight seal.


The minimums and maximums shown are intended as guidelines. For applications that exceed these ranges, please contact the factory for assistance.


Minimum: 18”

Maximum: 72"


Minimum: 18”

Maximum: 96"

To ensure smooth and troublefree operation over time:

At maximum width of: 72", limit height to: 36"

At maximum height of: 96", limit width to: 28"


Based on:

20" clear width

24" clear height

5.7 sq ft clear opening

Minimum unit width: 25"

Minimum unit height: 72"

To meet egress requirements:

At minimum unit width of: 25", height must be at least: 72"

At minimum unit height of: 72", width must be at least: 25"

Frame Depths

Standard: 6 1/4”

Minimum*: 5 1/2”

Maximum: 10”

(*Contact factory for frame depths less than 6 1/4")



Static Air Infiltration:
ASTM E283 cfm/ft2 @ 1.57 psf

Allowed 0.30 Test Result 0.016

Water Infiltration:
ASTM E547-cyclic ASTM E331-static at 8 psf

Allowed 0.0 Test Result 0.0

Load Deflection:
ASTM E330 10 sec at +60 and -60 psf


Sash Torsion:
AAMA/WDMA/CSA 101 / I.S.2 / A440


Vertical Deflection:
AAMA/WDMA/CSA 101 / I.S.2 / A440


Forced Entry:

Thermal TransmissionResults

Center of Glass:

ASTM C-236 U-value using Viracon VE1-2M Low E glass and Lawrence Berkeley Laboratories Winow 5.2 analysis program.

1": 0.29 with Argon: 0.24

Total Unit:

1": 0.35 with Argon: 0.31
Hurricane ImpactResults

Large Missile Impact and Cyclical Air Pressure:
- ASTM E1996-05, ASTM E1886-05
- Tested at 42 psf
- Wind Zone 3, not including Dade County, FL
- Missile Level D

Note: Contact factory for size limitations
and detail modification required for
hurricane certified units.


© 2021 Duratherm Company | 720 Main Street, Vassalboro, ME 04989 | T 207.872.5558 / 800.996.5558 | F 207.872.6731