A traditional window with a sliding lower sash, with great weather-tight integrity and versatile in size. The upper sash is fixed.

Photo © Cannon Design

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.



KEY (mouse over #s to view details)

Detail: Head



Meeting Rail Latch

Oxidized bronze alloy. Located at the center of the meeting rail, the latch’s cam action manually draws the sash into a locked position.
Finishes: Oil-rubbed Bronze (US10B), Lacquered Red Bronze (US20A), White Bronze (US26D).


Standard: Ultralift 88L series 670 heavy duty tube / spring balances, Heavy Duty BSI, or Amesbury Group fully concealed block and tackle balances mortised into the stiles of the operable sash.

Custom: Traditional weight and chain or clock spring balance systems are available on a custom basis. Contact factory for more information

Sash Locks (Included for oversized units)

Oxidized bronze alloy at midpoint of sash stiles. Turning the side latch compresses the weather-strip and locks the sash at each jamb.
Finishes: Oil-rubbed Bronze (US10B), Lacquered Red Bronze (US20A), White Bronze (US26D).
Egress: Properly-sized units meet egress requirements using standard hardware configuration.

Optional Hardware

Custodial locks, sash restrictors.

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: 36”
Maximum: 96"


Based on:
20" clear width
24" clear height
5.7 sq ft clear opening
Minimum unit width: 25"
Minimum unit height: 68"

To meet egress requirements:
At minimum unit width of: 25", height must be at least: 68"
At minimum unit height of: 68", width must be at least: 25"

Frame Depths

Standard: 6 1/4”
Minimum*: 6 1/4”
Maximum: 10”




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

Allowed 0.10
Test Result 0.007

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 Transmission


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": 0.34
with Argon: 0.30

Hurricane Impact


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.