Rationel FORMA® Windows


A range of energy efficient, solid timber windows which combine a natural look with a traditional design. Design of Rationel FORMA® is slim and traditional and is suitable for new-build or refurbishment projects. The angled glazing bead and ovolo-moulded profile make it a suitable choice for country-style and traditional designs. The slim and well-insulated construction makes it possible to let in more solar heat during winter than it lets out, resulting in a much lower heating bill and significant CO2 savings.

Rationel FORMA® is available in many different opening functions and designs and the product range is available in a wide range of RAL colours and selection of energy efficient panes, depending on the desired function of the windows. The window includes security ironmongery as standard.


  • BM Trada Q-Mark Scheme for: Security and general windows (Denmark).
  • CE marked.
  • DVV (Danish Window Verification) certified.
  • FSC certified timber.
  • SBD Certification.
  • Five year warranty.
  • For new-build and refurbishment projects.
  • U-value as low as 0.78 W/m²K (European standard size window 1.23 x 1.48).
  • Net energy gain of 500 kWh/year (typical Passivhaus project).


  • CE-marked and resistance tested to wind load as well as wind and watertightness.
  • The total thickness of double-glazed units is 32 mm with a centre U-value maximum of 1.2 W/m²K and the total thickness of triple-glazed units is 52 mm with a centre U-value maximum of 0.52 W/m²K.
  • The documented sound reduction of a double-glazed ‘reference windows’ is a minimum of 35 dB Rw, and triple-glazed ‘reference windows’ is a minimum of 42 dB Rw.
  • The window construction is tested for burglary protection. Secured by Design, Part Q-compliant.
  • Air permeability: 600 PA.
  • Watertightness: 600 PA.
  • Wind resistance: 1600 PA.
  • 30 years' life expectancy.

General information


As drawing

As schedule


BM Trada Q-Mark Scheme for: Security and general windows (Denmark)

CE marked

DVV (Danish Window Verification) certified

FSC certified timber

SBD Certification

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Uniclass 2015

Pr_30_59_98_96 Wood window unitsPrimary


L10/10 Wood windows

L10/210 Wood windows

Specification data - Wood window units

Product Reference

Rationel FORMA® Window


As drawing

As schedule


Fixed light

250-3000 x 250-3000 mm (w x h). Maximum area 5 m².


450-1000 x 440-1800 mm (w x h).


350-950 x 360-1800 mm (w x h).


360-1800 x 380-1600 mm (w x h).

Top swing

550-1600 x 550-1600 mm (w x h).


System 2 ECO coating

Insert colour requirement.

Special order

Insert requirement.




Rationel Energy

Insert requirement.

Rationel Obscure

Insert requirement.

Rationel Safety

Insert requirement.

Rationel Secure

Insert requirement.


32 mm, double-glazed

48 mm, triple-glazed

Glazing bars

Insert requirements.


Not applicable

For Fixed light.

ID handle

ID handle with key

ID handle with childproofing

Factory fitted restrictor (optional)


Manufacturer's standard

Secured by Design standards

Standard product features


- Timber:

The timber used in the manufacture is supplied from FSC-certified North European coniferous trees from selected sawmills with sustainable forest management. The proportion of heartwood is at least 90% for exterior rebates and surfaces. In general, knots and small cracks are cut off and the wood finger-jointed. However, minor knots will be permitted. All softwood sections are laminated and their edges rounded.

Timber surface treatment:

The surface treatment uses the System 2 Eco, which involves:

  • Impregnation in a flow coat system.
  • Primed with a flow coat system.
  • Topcoat with a water-based paint, gloss 20.

Weather strips:

All windows are constructed with two sealing faces. The weather strips are grey EPDM and are fitted in a groove in the sash in the same face.


  • Double and triple-glazed units, respectively, are manufactured with 32 mm and 48 mm insulated glazing and covered by the glass supplier's standard five-year guarantee.
  • All the glazing units are safety sealed.
  • All panes are approved to BS EN 1279 and have a warm-edge spacer.

Glazing gaskets:

Glazing gaskets are manufactured from a grey thermoplastic (PVC-free) material that does not rub off when washed. The removable gasket must be fitted in a groove in the sash.

Glazing beads:

Aluminium alloy EN AW-6060 or EN AW-6063 in accordance with EN 755-2, gloss 30 on all four sides, mitre-cut in the corners.

- Aluminium surface treatment:

The aluminium glazing beads are finished polyester powder-coated to a coating thickness of 60–120 microns. Standard gloss 30.

Product Options


- Fixed light:

Ideal wherever maximum internal light is required or for glass sections overlooking gardens or attractive views. Dummy sashes available to give consistent sight lines with opening sash windows.

- Side guided:

Controlled by tracks and slides. When opened, the hinge side of the sash moves towards the middle to create an opening that allows the glass to be cleaned from the inside. Side guided windows can also be used for emergency exits and are fitted with night vent position.

- Side hung:

Sash is hung on visible butt hinges. On windows over 430mm wide and 530mm high, the handles controlled brake allows the window to be fixed in any open position. Can also be used for emergency exits and is fitted with a night vent position. The frame is fitted with an adjusting screw for easy adjustment of the position of the sash in the frame.

- Top guided:

A simple, elegant and user-friendly design. Opening is controlled by tracks and slides.

As the window opens, the top of the sash slides downwards as the bottom opens outwards. Adjustable friction ironmongery allows an infinite choice of open positions. Fitted with a night vent position.

- Top swing:

An outward opening window, in principle it works like a top guided window and is particularly suitable for multi-storey buildings where there is no access to the window from the outside. The sash can be turned 180° outside the frame for easy cleaning of the outside of the window. It can be used as a rescue opening, fitted with night vent position. Each jamb is fitted with an adjusting screw for easy adjustment of the position of the sash in the frame.

Mullions and transoms:

68 x 115 mm.

Frame/ sash colour:

System 2 ECO coating available in standard RAL colours, other RAL colours are available for an additional cost, consult manufacturer's literature for more information.


Glazing options are available in different configurations, with variations such as pane thickness, gas infill and pane spacing. Consult manufacturer's literature for more information.

- Rationel Energy:

Energy-efficient panes where the space between is filled with argon and the inner glass layer has a thin metal Low E coating that reflects the heat back into the room.

- Rationel Obscure:

Used to restrict the view into bathrooms, etc. Available in different patterns.

- Rationel Safety:

Available in toughened or laminated versions.

- Rationel Secure:

Contains toughened and laminated glass.


- Manufacturer's standard:

Rationel FORMA® windows are SBD certified as Standard. Special security features are built into Rationel FORMA® windows as default. There are several locking points around the sash/ frame construction operated from a single architect-designed handle per sash. The windows are also secured with reinforced fittings as standard and espagnolette with three locking points.

Laminated pane of glass may be required, depend on project specific requirements.


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