How to choose window frames? What are the important features that window frames must have? Complete guide to the functions of windows in relation to the building.
Have you ever wondered what are the most important features that windows must have?
This question is fundamental in the choice of window frames. Here is the complete guide by Windowo dedicated to the role of window frames as a fundamental architectural element within the building envelope .
Window features: the relationship with the building
The window plays the very important role of creating a contact between the internal and external environment of the building. The need to create a passage of people, the view, the ventilation of the interior, and many other functions (which we will see in this guide) have made the moving parts that can accommodate the total or partial opening of the window itself essential.
The characteristics of external frames allow the user to control the passage of air, light, sounds, odors and the passage of people or animals. Furthermore, the frame allows the maintenance of an optimal internal microclimate by limiting heat loss (in winter) and heat input (in summer). The behavior of a frame depends on the context in which it is inserted and the technologies with which it is made.
Which window frames to choose? Here are the most important features
Click on the links to directly choose the window feature.
1. Visual well-being of windows and doors: control of light in rooms
This type of requirement is linked to the control of the light flow : the input of natural light should be adequate for the performance of the activities planned inside the rooms. Furthermore, it should also be possible to adjust the light based on the time of day (and in relation to the position of the sun).
The size of the window in proportion to the surface of the interior determines the amount of natural light that is introduced into the building. Furthermore, the height of the opening in relation to the floor also influences the amount of light introduced. Another factor that has an impact is the height of the opening in relation to the floor level. Finally, the presence of darkening screens can regulate the entry of light or the achievement of complete darkening.
2. Ventilation and cooling of windows: the role of windows in the correct circulation of air
By ventilation we mean the formation of air currents inside the rooms. It is a phenomenon influenced by the context in which the building is inserted, by its confirmation, by the number/location/sizing of the windows.
To have good air circulation, two openings are needed, positioned so that one is the inlet and the other the outlet of the air flow. The flow rate of the air flow generated by a pair of windows corresponds to the difference in wind pressure at the inlet and outlet, together with the size of the openings. In the case of homes without more than one view to the outside, ventilation is achieved by involving several rooms (therefore, the movement of fumes, vapors and odors between the reference rooms must also be taken into account).
3. Thermal insulation of windows: how to contain heat loss
A house loses about 30% of its energy through its windows: for this reason it is important to evaluate this important aspect. Thermal insulation means the ability to contain heat losses that occur through radiation, conduction and air exchanges between the internal and external environment.
All the parts that make up the window frame (glass, frame, hinges, gaskets), but also the conditions of the wall cavity and the presence of screens or any box, contribute to the more or less efficient thermal insulation of the home. To have a good result on this front, it is therefore necessary to use the appropriate hardware , use the right elements for fixing to the cavity and use suitable insulating materials. Depending on the materials used, thermal bridges are physiologically created due to various factors (penetration of materials with different conductivity, variation in the thickness of the construction, difference in surface air that disperses on the internal side and on the external side, etc.). In general, it is good to position the window frame in such a way as to form continuity with the insulating layer of the wall (in order to eliminate such thermal bridges). In any case, the part that connects the window frame to the wall must be filled with insulating material and hermetically sealed.
The variation in the thickness of the glass has almost no impact on the thermal resistance, but is determined by the mere existence of a glass (in fact the thermal resistance of a glass is proportional to its thickness and varies by 1 to 1000). To calculate how much energy a window frame disperses through the surface, the thermal transmittance coefficient is used: Uw . The lower Uw is, the greater the thermal insulation will be. To improve environmental comfort, it is possible to opt for low-emissivity glass or elements such as roller shutters and blinds (for the winter) that reduce heat dispersion, or for selective glass (for the summer) capable of blocking the solar light that heats.
4. Control of solar radiation of windows
The screen (such as roller shutters or blinds) is the element responsible for controlling direct solar radiation . There are also reflective glasses that also allow the window frame itself to limit the passage. The frame should also be made up of elements that allow the user to regulate the radiation, without excessively compromising visibility.
5. Air tightness of windows and doors: the rebate planes and the gaskets
This feature essentially concerns the "stop" between the opening parts of the window and the fixed parts . In fact, the window is one of the few building elements that makes movement its essential characteristic, hence the difficulty in maintaining the seal of the joints over time. In the areas where the stop planes do not adhere perfectly, the gaskets are not compressed perfectly and therefore do not guarantee the seal itself.
6. Water tightness of windows and doors: the importance of the joints between the sill and the lower crosspiece
Even for water tightness the criticality is constituted by the openable joints. In this case it is necessary to pay particular attention to the joints between non-homogeneous elements . Normally the frames today guarantee excellent performances on this front even in case of heavy rain. It is however necessary that the frame and the sill help the water to flow out.
7. Control of window condensation through temperature control
It is essential to avoid the formation of condensation on window frames . This is mainly for three reasons: one because the fogging of the glass is annoying, two because a wet window frame is unpleasant to the touch, three because water can accelerate the deterioration of the window frame itself. The internal surfaces of a window frame are colder the lower the insulating capacity of the elements that constitute it. To block the formation of condensation, which occurs when the surface temperature of the perimeter walls is lower than the dew point, the use of double glazing and insulating materials is recommended.
8. Natural air exchange in high-performance windows
In the past, air exchange was guaranteed by poor air tightness of the frames and inadequate sealing of the frame/wall joint. All characteristics that in turn led to uncontrolled heat loss, dust infiltration and noise passage. Today, frames with high air tightness performance eliminate these inconveniences but leave the burden of periodically opening the window to the user.
9. Hearing comfort of windows and sound insulation from external noises
Normally a window offers lower guarantees of acoustic insulation than the wall part. For this reason it would be necessary to act not only limited to the window frames, but also on the sources of emissions of such noises and making adequate design choices relating to the location of the building.
The acoustic performance of a window frame is assessed by referring to the sound insulation powerRw . External window frames must have a specific acoustic performance class in relation to the intended use of the rooms and the noise level of the area where they are installed.
10. Block noise and vibrations of the windows
Shutters or roller blinds, as a screen element, can generate noises if subjected to the impact of rain or hail or to the flapping of the wind. To reduce these noises, it is possible to use heavier slats or slats filled with polyurethane foam that increases their mechanical resistance and soundproofing.
11. Wind resistance of windows
External vertical frames must be able to resist the action of the wind in order to guarantee safety for users and ensure functionality over time. They must also prevent the wind from generating too much noise, vibrations and banging.
12. Protection from falling windows
The "fall protection" feature is only important for openings facing external height differences of more than one meter. If the height exceeds 0.9 m, additional safety devices such as parapets or railings should be installed.
13. Fire resistance of windows and doors
Fire resistance consists in the ability of the window or door frame to maintain, in whole or in part, within a certain period of time and despite the action of fire, the stability R (from the French Résistance ), the tightness E ( Etanchement ) and the thermal insulation I ( Isolement ). The symbols REI, RE and R followed by a measurement (in minutes) identify a construction element that maintains stability, tightness and insulation for a certain period of time.
14. Intrusion resistance of windows and doors
The location of the different openings of a building determines the greater or lesser importance attributed to this requirement. The components of a window that can influence the level of security are: the locking hardware with at least one burglar-proof locking point, the handle with a safety button or key, shatterproof glass, the frame fixed with anchor screws, hinges adequate for the weight of the window.
15. Limitation of space inside the premises
This feature depends on the size of the window and its position in the wall of the opening. The type of opening determines the portion of the floor occupied for the maneuverability of the frame.
16. Simplicity in the movement of window frames
It concerns the movement and maneuvering organs of the moving parts of the window frames.
17. Possibility of integration with roller shutters, blinds or other screens
This feature concerns windows with screens, which must allow for mutual completion (without losing functional capacity or technical characteristics).
18. Cleaning window glass: easy and safe
This is an important feature that a window frame must have, especially if you want to maintain the transparency of the corresponding glass surfaces.
19. Resistance to false or violent movements of the window frames
A window must guarantee robustness to cope with significant stresses that act on planes or directions other than those normally expected. This is because users can also perform incorrect maneuvers, especially in the case of operations that are not immediately understandable.
Fixtures how to choose? If you still have doubts contact us!
We hope that this guide on window features will be useful to you in understanding what features each window should have.
Do you have doubts in choosing the frames? Contact us, the Windowo staff is at your disposal.
Elia Caneppele
I'm Elia Caneppele, author of this article and founder of Windowo, the Italian shop specialising in the online sale of products for windows. My speciality is doing SEO for ecommerce, which, in simple terms, means getting people to find us on the Internet.
Since 2014 I have been a digital entrepreneur and, in addition to managing Windowo, I also deal with the communication of Autismo.it. I create content trying to convey as much value as possible to our customers.
Want to improve your e-commerce ranking? Once a month, I offer SEO consulting for struggling online stores. Contact me on my social media to schedule a free call.
