How can a building be more efficient? It is a concern that architects face on a daily basis, as they try to keep up with the demands of an industry that is increasingly aware of its environmental impact. Today more than ever, there is an effort to design buildings that integrate sustainability, efficiency and thermal comfort, which are fundamental pillars of a healthier built environment.
Having an effective solar control strategy is crucial to achieving a more efficient architecture. In addition to providing solar protection and economic savings, these strategies also carry benefits in terms of aesthetics, acoustics, thermal comfort, durability and maintenance.
This article will focus on the main outcomes of a study carried out by Bandalux, a company that specializes in manufacturing efficient and sustainable solar protection products. We will see how designing with exterior technical blinds means that architects don’t have to opt for the most expensive glass on the market in order to have a properly climatized and energy-efficient building. These are the types of decisions that can lead to zero energy buildings.
The search for an effective solar protection solution for thermal and visual comfort
Considering that, in 2020, 75% of the available real estate in the European Union was deemed inefficient from an energy consumption perspective, it is extremely important to find an effective solution to control the heat gains that occur through openings.
Among the most common solar protection systems is solar control glass, which prevents excess heat in summer, but simultaneously limits heat gains in colder months. Another alternative is the use of opaque materials (such as in curtains and exterior shades), however, these restrict visibility and lighting despite being mobile. Cooling systems are also a widely used alternative, but the cost they entail in the long run tends to be excessive, both in hot and temperate climates.
Technical blinds, in turn, have emerged as an optimal and effective solution to achieve both energy and economic savings. This may be surprising to some, but based on a number of simulations carried out by the aforementioned study (which we will review below), it was possible to verify the energy efficiency that is achieved when taking into account both the positioning of technical blinds and their combination with different types of glazing.
Heat gains according to different types of glass in static façades
A static façade is when a building’s envelope cannot be adjusted according to solar movements throughout the day. One of its components is thermally treated glass, which is used to manage sunlight and maintain appropriate insulation, hence achieving a stable and comfortable indoor temperature. Nevertheless, as we will explore later, this is not always the most efficient solution in terms of energy and economic savings.
The study, which includes data from three countries –Spain, the United Kingdom and Mexico, with Mediterranean, temperate and desert climates respectively–, evaluates four standard types of glass:
- Glass Type A – single-glazed
- Glass Type B – standard double-glazed
- Glass Type C – low-emissivity double-glazed, which has one of its inner faces coated with a material that reflects solar energy and enhances thermal insulation
- Glass Type D – solar control double-glazed, which includes a filter on the exterior face that prevents excessive radiation from entering the building (without obscuring the glass too much)
These can be seen in the graph below, arranged by degree of solar protection (solar gain coefficient, solar and light transmittance, and U-value) and from most affordable to most expensive (from left to right).
A dynamic and intelligent façade can lead to up to a 98% reduction in solar energy transmission
Unlike the static façade, a dynamic façade is created by adding adjustable technical blinds that can respond to the sun’s movements and the needs of each user. It adds to the building’s skin the necessary intelligence to capture or protect residents from the sun throughout the year, thus achieving a higher level of efficiency and thermal comfort. Motorized blinds, such as the Z-Box roller shades, allow users to automate and control them remotely.
The study considers mainly exterior roller blinds that, unlike interior blinds, also avoid the heat transmission that can be caused by the blinds themselves. By adding an exterior solution to the previously listed types of glass, the reduction in energy transmission is significant in each of the different climates: in Madrid (Spain) it is reduced by 88%-94%; in London (United Kingdom), by 95%-97%; and in Hermosillo (Mexico), by 67%-98%.
Can an exterior blind substitute a double-glazed solar control glass? The answer is yes
Adding an exterior blind can noticeably decrease heat transmission, but we also know that architects tend to only opt for a good quality solar control glass, due to its high performance in comparison to other types of glass. In Madrid, for example, the use of Glass Type D would translate into 54% less heat energy per year. However, in addition to preventing overheating in the warmer months, it also blocks heat from entering during winter, when buildings do need to be warmer. It is therefore necessary to have a system that allows users to control the flow of energy and heat, whether to darken a room during resting hours or to regulate the entry of natural light in an office.
In every case analyzed by the study, a dynamic or closed exterior blind significantly reduces heat gains, achieving practically zero consumption during some periods of the year. In addition, as can be seen in the previous diagram, using a Glass Type C with an exterior blind results in a higher performance than a Glass Type D on its own. Likewise, a Glass Type C with an exterior blind has nearly the same thermal performance as a Glass Type D with an exterior blind – all while having a lower cost.
Although a Glass Type C with an exterior blind requires a larger initial investment than simply using a Glass Type D, in many cases, it is more cost-effective in the long term due to the savings in energy consumption that it will generate, whether in terms of heating or cooling. In turn, a Glass Type C –which usually requires a lower initial investment than a Glass Type D– will achieve a lower total consumption if it is paired with an exterior blind. The study therefore shows that this is a convenient combination both in terms of energy and economic savings, even if we compare it with a higher performing glass.
Another conclusion of the study is that even solar control glass (Glass Type D) can become obsolete as an efficiency solution. That is, it is not necessary to always opt for the most efficient and costly glass type available, as even the use of a simple glass will have a similar or better behavior once it is paired with exterior blinds.
Blinds are effective regardless of the quality of the glass used, so much so that they can make up for some of the deficiencies of glass in building façades. Exterior technical blinds are therefore a mechanism that can bring buildings closer to achieving zero consumption, whilst providing flexibility, comfort, health and well-being to users. It is hence crucial to anticipate and include blinds during the design phase in order to help buildings achieve full energy efficiency.
For more information on Bandalux products, visit their website or product catalog.
This article was elaborated based on: Informe Prescripción Ahorro Energético. Bandalux (2023).
