PVC / Aluminium Composite window system offering the best of both worlds.

Product Information



This specification defines materials, construction, finishes and hardware for the Duotherm elite Casement Window, which conforms generally with BS 4873 specification for aluminium alloy windows. Windows described in this specification are suitable for both replacement windows into existing buildings and installation into new building work, and are designed to allow for fixing direct to masonry or into conventional sub frames of timber or PVC-U.


Aluminium Profiles

  • Profiles are extruded from 6063 T6 alloy and comply with the recommendations of BS 1474.
  • Sections are pre-treated and finished:-
  • anodised to BS 3987, Grade AA25 to a natural self colour and other agreed colours.
  • polyester powder organic coating to BS 6496 in White 9910 high gloss finish.
  • polyester powder organic coating to BS 6496 in Havana Brown 8912 satin finish.
  • polyester powder organic coating to BS 6496 in Black 9005 matt finish.
  • polyester powder organic coating to BS 6496 in agreed colours, matt or gloss finish
  • woodgrain effect finish in mahogony and light oak colours.

PVC-U Profiles

  • Profiles are multi-chambered offering marvellous insulation properties and are extruded from high grade window material.
  • Sections are finished either in a solid white high gloss or woodgrain efect in mahogony and light oak colours.
  • Bearing Devices and Hardware
  • All opening vents are hung on concealed stainless steel variable angles friction stays and fitted with (1) cockspur or (2) espagnolette or (3) espagnolette shootbolt locking mechanisms.
  • To limit the opening, restrictor stays shall be fitted. The above shall be manufactured from material meeting the requirements of BS 4873.


  • Weatherstripping is Q-lon set in undercut channels


  • All fixings used in construction shall be either stainless steel or other suitable corrosion resistant materials as prescribed in BS 4873.


  • Glass shall conform to the requirements of BS 6262 and Part ā€˜Nā€™ of the Building Regulations for both thickness and type.
  • Glazing materials such as gaskets shall comply with the requirements of BS 4873.


  • Frame members are mitre cut at 45Ā° and faces coated with a suitable frame joint sealing compound. Using internal extruded aluminium corner cleats, members are abutted and securely jointed by mechanical means.
  • Transoms and mullions are end milled to shape and mechanically secured to each other or other frame members with self tapping screws driven into screw receptacles in the profiles.
  • All mechanical joints shall be sealed against entry of moisture.


  • External or internal, whichever is relevant to the window type chosen, aluminium glazing beads and flexible gaskets inside and out meet the requirements of BS 6262, Code of Practice for Glazing for Buildings.
  • Beads and gaskets will accommodate single thickness glass 6mm and double glazed units of thickness 20mm, 24mm, 28mm and 32mm.

NOTE: The internally glazed vent frame will accept 24mm double glazed units only.


*Windows having been tested in accordance with the requirements of BS 6375 : Part 1 have achieved the following classification for weather tightness.

  • Air permeability Class C 600 pa
  • Water Tightness 600 pa
  • Wind Resistance 2000 pa
  • Test Report 3187

Product Range

  • Windows are manufactured to required design to within the following maximum limitations (subject to location and conditions).

Single opening vents

1.Side Opening

  • max.width 700mm

2.Top Opening

  • max.height 1200mm

Subject to the agreement of Smart Systems Ltd, it is possible, in some circumstances, to exceed these limitations depending on the design criteria for weather performance and recommendations of the friction stay manufacturer.

Please contact the Research and Development Department at Smart Systems Ltd for advice.

Multi opening vents

Dependent on the design of the window and subsequent calculation results based on the mechanical strength of the profiles, type of glazing used, location and height of building.

Document Downloads

File Type Document Description Download Document
Adobe PDF Duotherm Windows & Doors Brochure
Product brochure
Download (2.1 MB)

Technical Specification


Product Type Windows
Material Aluminium / PVC
Dual Colour Yes
Thermally broken Yes
NBS available Yes


Max width 1300
max height 1500
Max weight 50
Weather suitability Best
Acoustic suitability Best
Thermal suitability Best
Min Glazing 6
Max glazing 32
serurity rating Best


BS6375 Pt 1 Yes
BS6375 pt2 Yes

Locking options

Espag (or two point lock) Yes
Cockspur (or single point lock) Yes
Shootbolt (or multi-point lock) Yes

Frame options

Odd leg Yes
Even leg Yes
Ovolo Yes
Square Yes
Direct Fix Yes


Crimp Yes

Building suitability

light duty Yes
medium duty Yes