Window guide to the energy certification of buildings

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How to recognize a window. Window guide in real estate certification.

One of the most important aspects when we certify a property is the envelope and the gaps within it. In particular, the questions that we could ask ourselves … Do you know all the aspects of windows? Do you know their typologies? Would you know how to determine a window if it is from the 50s or the 80s?… .etc. In short, a series of characteristics of window joinery that many of us have forgotten and as technical professionals in the architecture sector we should remember and recognize.

Windows on the facade. Most common types used:

Of course, the variety is abundant and with current technology, new types of windows are appearing that reinvent the current ones, substantially improving all their aspects, including carpentry with smart glass, but in a generic way we can identify:

Materials and components of a window:

It is basically made up of glass supported by frames of very high different materials such as steel, aluminum, wood, PVC, polyurethane or mixed, along with possible sun protection.

• If we look at the aluminum profiles, we will find basically two distinctions on the market:

1. Aluminum profile without thermal break. Profile does not offer any resistance to the passage of heat flow between the exterior and interior of the space.
2. Aluminum profile with thermal break. These are profiles made up of two or more metal sections joined by at least one thermal insulating component (non-metallic).

• If we focus on PVC profiles:

PVC is a chemical combination of carbon, hydrogen and chlorine (More info HERE). Its components come from crude oil and salt. They are obtained by polymerization of vinyl chloride, the manufacture of which is carried out from chlorine and ethylene. The PVC profiles for the manufacture of windows they are obtained by extrusion and their parts are:

• Wood profiles.

As for wood in the architecture sector and focused on carpentry, its crucial evolution has been to be able to combine it with different materials.

1. Mixed wood-aluminum profiles: to the wood profile of different dimensions, depending on the need of the project, an aluminum profile is incorporated on its outer face, with a multitude of possibilities and designs based on aesthetic and constructive needs.
2. Mixed profiles of wood, aluminum and thermal insulation: the incorporation of thermal insulation, high-performance EPS insulation, to the window assembly improves thermal insulation.

• Glazing

1. Annealed glass. It is the flat glass for construction obtained in the melting furnaces. The controlled cooling process of the glass mass once it has been shaped in thickness and width that allows stress relaxation avoiding breakage is called glass annealing. It should not be confused with another type of heat treatment such as thermosetting or tempering.
   Annealed glass can be cut, manufactured and processed to obtain different glazing products. Depending on the procedure for obtaining the glass sheet, one can speak of float glass or glass printed by lamination.
2. Float glass. Float glass consists of a sheet of glass made by floating molten glass on a layer of molten tin. This method gives the glass a uniform thickness and a very flat surface, making it the most commonly used glass in construction. It is also called flat glass, however not all flat glass is glass made by the flotation system.
3. Printed glass. It is the glass obtained by laminating the melt or melt in a plastic state between two rollers, which is subsequently cooled in a controlled way in the annealing process to its final state. Lamination rollers are commonly used to print raised patterns on the glass surface. For this reason, it is commonly known as printed glass.
4. Coated glass. It is defined as a vitreous substrate on which a layer is deposited, usually of a metallic nature, in order to modify one or more of its luminous, solar or thermal properties. Mirrors, enameled glasses and glasses on which a plastic film adheres are not included in this denomination. Coated glass and its classification according to its properties and possibilities of use are included in the European standard UNE-EN 1096. Glass for building. Coated glass.
5. Low Emissivity Glasses. They reduce heat losses from inside the building through the glazing. Its placement can be on the inner or outer sheet of the double glazing, without varying its insulation performance (U W / m2 K value). They are particularly effective in unexposed orientations since, apart from saving energy, they avoid the “cold wall effect” or sensation of “heat theft” that the human body experiences in the presence of the cold surface of a normal glazing with low outside temperature. .
6. Solar Control Glasses. They reduce the inputs of heat produced by sunlight, reducing the greenhouse effect. They must be placed in joinery that can receive direct solar radiation. The loss of heat gains in cold seasons must be calibrated or supplemented with low-emissivity glass to reinforce insulation in winter. Among the solar control glasses, the highly selectivity glasses stand out. This is the name given to those solar control glasses that allow large percentages of light to pass through. In other words, they slow down radiation with a high energy content and yet allow the passage of radiation corresponding to the visible spectrum, thus making a "selection" of the wavelengths that cross them. Selectivity is defined by the TL / g ratio, the more selective being.

As information we can access this summary in PDF of a congress of Energy Efficient Glass and Frames. and we can also consult information on the advantages and types of awnings as well as their energy characteristics.

• Blind drawers:

The Thermal transmittance of the opening must be evaluated for the entire assembly, including the blind box if it is incorporated. In the same way, the tests of air permeability, watertightness, wind resistance or acoustic insulation must evaluate the window and box assembly, if it is incorporated. In other words, the incorporation of the blind box affects all the properties that are evaluated in the window.

In the case of thermal insulation of the whole, for the obtaining the value of the thermal transmittance Uw / sb of the entire window with blind box, it is possible to calculate it as follows:

On the other hand, how do we remember the post… «Improvement of façade openings via CE3X«.

Carpentry in energy certification and its evolution:

We must recognize the evolution of the materials in order to determine the type of window that we have in the property to be certified:

Aluminum carpentry evolution: Although it depends on each case, in general it can be indicated that in the 60s 40mm wide series were used in practicable systems and 55/65 mm in sliding systems. It is from the 70s when the sliding aluminum series became 70mm. The 40 / 45mm practicable series without thermal break remained until the 90s when RPT systems appeared (about 60mm), but these systems did not become general until the 2000s and onwards (with systems from 45mm to 120mm). ).

Wood carpentry evolution:

• From traditional architecture to the 1950s: 80 / 90mm wooden sections are used (with 3mm monolithic glazing, seamless). Examples of these carpentries are found in hotels and homes in the centers of large cities such as Madrid or Barcelona.
• In the 60s - 70s and 80s: wooden sections of around 45mm are used (with monolithic glass), these tend to present problems with recesses and the absence of rubbers (problems of permeability are identified in windows built in the 70s) .
• From the mid-80s to the 90s: windows with sections of approximately 57mm and gaskets are used.
• In the 90s: the mixed systems, wood-aluminum and carpentry from 68mm are introduced.
• From 2006 to the present: larger sections, from 78/88/92, and improved glazing.

PVC carpentry evolution:

Glazing evolution:

After this scheme as technicians we can already recognize the qualities and typologies of a window that we can meet in the day to day of our work. We can already identify them both in their characteristics and in time. I highly recommend reading the Window guide in the energy certification process… HEREprovided by ASEFAVE (Spanish Association of Manufacturers of Light Façades and Windows). Where in addition to finding more information than the one previously summarized, we can see a practical case of transmittance calculation and other aspects that can improve our knowledge in the world of carpentry.

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Links of interest:

• Infoxication and decline of the energy certificate
• Architecture and crisis
• Conscious recycling before the consumer.