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Technical details: (Technical Building Code) and the wooden window

Basic element in sustainable building which complies with thermal and sound insulation requirements.

Building has finally committed to energy savings. The new Technical Building Code (C.T.E.) demands that new constructions are safer, and more liveable and sustainable. This will contribute to increase the quality of the spanish window, a constructive element which is essential in order to comply with the two basic requirements for buildings: energy savings and sound attenuation.

The wooden window has incorporated a state-of-the-art technology which has lead, for example, to the making of laminated profiles, with sophisticated designs which improve their conditions of durability, water-proof-ness and insulation. It has lead, overall, to a better protection and finish. On top of this, one may add that wood already stands out as being a durable, available, adaptable and versatile material. It is healthy and pleasant, and maintains thermal conditions in the buildings, regulates moisture fluctuations, and reduces energy requirements in buildings.

What is the window?

From an architectonic point of view, the window is the transparent element of the facade which allows for an inside-outside relationship, including the flow of fresh air, light, solar energy, and vision in both ways. It is therefore mostly a glass surface, in approximately 90%, and is held by a frame made of different materials such as aluminium, wood, PVC, polyurethane or mixed. This allows for the aperture and closing of the window and protects the interior from weather agents.


Windows have six main characteristics, no matter which material their profiles are made out of:

  • Permeability to air
  • Water tightness
  • Resistance to wind load
  • Sound insulation
  • Thermal insulation                  
  • Optical properties

The first three depend basically on the joinery systems. The ones referring to insulation depend both on the profiles and on the glazing, whereas the last characteristic rests solely on the glazing.

Air Permeability

Air permeability is the property of a closed window to let air flow when subjected to a pressure differential and it is fundamental in order to satisfy the basic requirements of habitability of the LOE – Law of Building Regulations – in relation to energy savings and thermal insulation. This is because the energy used in heating up the air leaking in is usually much higher than the loss of energy transmitted through the window.

On the other hand, air renovation inside buildings is fundamental for comfort and it can be partially owed to windows permeability to air. A low permeability is also important for sound insulation through the window.

Water tightness

Water tigthness is the capacity of a closed window to stand against water leaking in. This property is essential in order to satisfy the basic habitability requirements of the L.O.E. in relation to hygiene, health and environment.

Resistance against wind load

Wind action on buildings is transformed into pressure forces over the glazed surfaces, which are then transmitted to the facade through the sash profiles and casing of the windows. The resistance of a window against wind action is essential in order to comply with the basic security requirement of L.O.E. in relation to safety.

Sound Insulation

It is the capacity to prevent sound from entering the building. The appropriate acoustic performance of the window is essential in order to comply with the basic requirement of L.O.E. in terms of habitability

Thermal insulation

It is the capacity to prevent the entry of heat and cold into the building. Windows have a large influence in the energy performance of the building. They play a crucial role on the optimization of energy consumption and on the reduction of CO2 emissions to the atmosphere.


Joinery manufactured with a material as warm and pleasant as wood becomes not only a functional building element but also an alternative in-line with the current tendencies in decoration. Currently, the main wood window manufacturers in Spain use pine, iroko, oak, niangon or framire, amongst other species.

For new buildings or rehabilitation, either using straight lines, round or trapezoidal arches; in an infinite scope of measurements and finishes, and with accessories and models such as shutters, grilles, sliders, panels, etc, wood window manufacturers in Spain today have the appropriate technology, means and staff to adapt the product to the specific needs of any project, depending on the geographic area and the technical demands of the work at hand.

A thermal-acoustic sealing gasket, positioned all along the perimeter of the profile, ensures a permanent contact between the frame and the sash and absorbs any potential variations in wood dimensions that may occur, being wood a living and natural material.

Current technology allows for the design of profiles with overlaps and drainage holes, with thicknesses allowing for the use of simple or double glazing. Finished with ecological water borne coatings, nowadays the wooden profiles of the windows are treated in autoclaves in order to protect it from atmospheric agents and from the attack of insects and other xylophages.

The window and the environment

Wood materials store carbon. Wood presents a closed carbon cycle. An increase in the use of wood windows would involve increasing the stocks of stored carbon, and therefore a step towards supporting the Kyoto Protocol commitments. Wood is a renewable and recyclable material. In Spain the percentage of wood recuperated after its use and re-integrated into the production chain is very high, up to 70%.

CCertification and quality in the new CTE

The Permanent Building Committee (formed by representatives from the 25 European Union countries and created by the new Directive “Construction Products”) accepted to extend the period of co-existence to 24 months. This decision has and will have important ramifications in relation to the obligatory CE Marking.

The implementation of this European Norm will be as follows:

  • Availability date (DAV): 22nd March 2006
  • Date of publication in the DOCE (DOP): 30th September 2006
  • Beginning of the period of co-existence (CE Marking voluntary, not compulsory): 31th December 2006
  • End of the period of co-existence (Compulsory CE Parking): 31st December 2008

* DAV means the date of availability, which is the day in which the Central Secretariat of the CEN distributes the final text of a CEN / CONELEC publication approved in versions corresponding to the official languages (English, French and German)
* DOP is the date of the publication of the norm in the European Union Oficial Diary (DOCE) and represents the end date for the adoption of a European normative at the national level, both through the publication of an identical National Norm or through ratification.


Whilst PVC reigns in Europe and wood covers just one fourth of the window manufacturing market, to which one may add an 8% of wood/aluminium windows; in Spain aluminium rules the market. From the 12,5 million windows manufactured in Spain in 2005, 70% are aluminium, 18% wood, 10% PVC and 2% mixed.

The coming of the C.T.E. places Spain as one of the most innovative nations in terms of building, complying with the European directives in terms of quality and energy efficiency, and promoting innovation and technological development. This Code includes the regulation of new buildings and of rehabilitation of existing buildings in a wide use range: dwellings, commercial use, educational, heath system, industry, socio-cultural; and introducing new elements in relation to materials and construction techniques. Given all this we trust that the adaptation of the building industry to the strategy of economic, energetic and environmental sustainability will broaden the possibilities of growth of the wooden window in Spain .

Source of text: AITIM

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