Run to success
Rationel Forma FormaPlus Triple Glazed Chop Sample

Forma & FormaPlus

Designed for a more traditional style of building, the Rationel FORMA window has an all-timber construction with slim, non-continuous bars. Featuring an ovolo moulded profile and angled glazing bead, FORMA is perfect for older, classic and country style houses. The aluminium external cladding also has a unique curved edge.
In terms of frame construction, the Rationel FORMAPLUS window is identical to FORMA. The only difference between them is the addition of external aluminium cladding included on the FORMAPLUS window. This inclusion ensures both minimum and easy maintenance characteristics.

Full Details

Rationel Windows is a manufacturer with more than 60 years’ experience. Rationel employs 1,050 people in Denmark, England, Ireland and Poland, manufacturing premium-quality, durable and stylish windows and doors.

We are a FENSA-registered Rationel distributor and approved installer. When we supply and install, we offer this as a single contract: the product itself, transportation, survey and installation are all included within your order.

Rationel Forma and FormaPlus Options

Both Forma and FormaPlus have a wide variety of opening designs, glazing options and configurations. Along with the typical styles, Rationel FORMA and FORMAPLUS can be manufactured in bespoke shapes to correspond to an assortment of openings. Featuring fully adjustable and secure ironmongery (Secure by Design part Q compliant hardware), two gaskets and the option of trickle vents, FORMA and FORMAPLUS are carefully engineered with the customer in mind. Furthermore, all Rationel products prioritise energy efficiency. The slim design naturally takes advantage of the solar heat from daylight, and their exceptional insulating qualities reduce CO2 emissions significantly.

Due to their energy efficient characteristics, both Rationel FORMA and FORMAPLUS are suitable for Passiv Haus buildings.

Thanks to constantly enhancing efficiency and optimising their products, Rationel windows are designed to withstand all weather types, attempted break-ins, and the constant wear and tear of opening and closing windows year after year.

Marine Suitability

Rationel aluminium profiles are coated with a minimum of 60 microns thickness and are pre-anodized so can be called marine grade. The windows and doors will require regular maintenance as per the OE manual shown in the downloads tab of this page.

Efficiency, Solidity, Dependability

The Rationel product development is primarily based on the Danish market and climate which is predominantly coastal – similar to northern Scotland – so the products are suitable for coastal locations. We treat the aluminium for filiform corrosion prior to powder coating, and the products are also salt-spray tested at R&D stage. Furthermore, salt-spray batch testing is completed on all metal components, from cladding to hinges.

“We basically offer a complete service. For over 60 years, our company has been based on excellent craftsmanship. This is still the case. At Rationel we take pride in delivering high quality,” Rationel CEO, Thomas Tvedergaard Larsen.

Typical LifespanFORMA: 60 years
FORMAPLUS: 85 years
Lead Time8-10 weeks from sign off
Best U-Value0.78 W/m^2k
Finishes Any RAL Colour
for both timber and aluminium (FORMAPLUS only)
GlazingDouble, Triple, Obscure, Solar, Laminated, Toughened
Performance and
Air Permeability: 600 PA
Wind Resistance: 1600 PA
Operation: 10,000 cycles
Water Tightness: 600 PA
Manufactured inPoland
Opening Configurations

Fixed Frame

Fixed Frame Configuration

Side Guided

Side Guided Configuration

Side Hung

Side Hung Configuration

Top Guided

Top Guided Configuration

Our Configuration Options for Bespoke Windows page contains additional information about each of the options shown above, it may also be helpful in choosing how to configure your windows to best suit your needs.


Single Door

Entrance Door Configuration

Double Doors

French Doors Configuration

We have and extensive range of doors available in Rationel Forma and FormaPlus, the images above show some of the general configuration options available. For more information about the opening types and how each can best be used see our Bespoke Doors page.

For more in-depth options on the look of single or double doors our Choosing a Panelled Door and Choosing a Glazed Frame-Door pages will go into more detail.


Window handles

Rationel Window Handle Non-Locking
Rationel Window Handle Child-Lock
Rationel Window Handle Key-Lockable

Entrance and Panel Door handles

Rationel Rose Handle with Key Lock Both Sides
Rationel Rose Handle with Thumbturn
Rationel Backplate Handle with Key Lock Both Sides
Rationel Backplate Handle with Thumbturn

Terrace Door handles

Rationel Terraced Door Handle

Our Hardware and Security of Rationel Windows blog post goes into greater detail about the handles used on our rationel products and how they relate to it’s security.


RAL Colour options in the standard range for Rationel products

RAL Classic colours outside Rationel’s standard colour range will be subject to additional costs and lead times.
For clear lacquer and granite textured colours (FormaPlus & AuraPlus only) please see page 7 of the Rationel Aura & AuraPlus Brochure.

RAL1035 – Pearl beige

RAL7001 – Silver grey

RAL7003 – Moss grey

RAL7013 – Brown grey

RAL7021 – Black grey

RAL7022 – Umbra grey

RAL7037 – Dusty grey

RAL7044 – Silk grey

RAL8017 – Chocolate brown

RAL8019 – Grey brown

RAL8022 – Black brown

RAL9002 – Grey white

RAL9004 – Signal black

RAL9007 – Grey aluminium

Where you see a next to a colour, clicking on it will take you to a page of our client galleries that use that RAL Colour.
Some colours are subject to additional lead time from Rationel.
Colours shown should not be used in place of an official RAL colour sample. We cannot guarantee colour-accuracy when viewed on-screen or printed out.
Chop Sample

Below are some of our recent galleries which include Rationel Forma and FormaPlus