Dynamic facades save energy.
Recent studies have shown that the correct distribution of window openings in a room, in combination with the operation of lighting control systems, as well as heating, ventilation and air conditioning, can significantly reduce peak loads on the air conditioning system. This measure also makes it possible to reduce energy costs spent on lighting and ventilation, while maintaining comfortable indoor conditions, both in terms of lighting and indoor air quality.
Technologies do not stand still and today transparent facades are appearing — a necessary component of environmentally friendly buildings. The facades of such buildings are dynamically rearranged by a shading system to provide an optimal combination of artificial and natural lighting. The concept of dynamic facades (the idea of which is to install shading elements on the surface of the building) is not new. But its active development began only in recent years. Engineers and architects have only recently begun to “trust” such systems and use them in construction.
Dynamic shading elements are made possible by advances in window technology. The result was the emergence of technologies for dynamic placement of window openings through automated control of the shading system. All this characterizes a new generation of “smart” buildings, the hallmark of which will be an efficient heating, ventilation and air conditioning system. The idea itself seems wonderful, but its implementation is not as simple as it seems at first glance.
Each building requires an individual approach to design depending on its purpose, outdoor climate conditions, spatial orientation and the degree of transparency of the facade. Already at an early design stage, the development team is faced with a choice of solution options. However, it can be difficult to definitively assess the merits of options, especially if innovative technologies are used. As a result, the final choice is often subjective. The disunity between the stages of the construction process, in which none of the team members takes on the task of fully optimizing the microclimate, is the main problem in “fine-tuning” the project. Therefore, very often, at the last stage of construction, traditional “passive” systems are offered as a “safe” alternative.
Despite all the difficulties that arise, the advantages of dynamic shading elements are obvious. For example, you can effectively reduce your exposure to direct sunlight. To do this, it is necessary to place an automated shading system along the external perimeter of the offices. Shading elements placed on rollers can automatically move to block direct sunlight so that diffuse light enters the office. This measure allows you to combat glare and create a comfortable light feeling in the rooms. Horizontal (“Venetian”) blinds redirect natural light into the room space and allow you to create uniform illumination even in open office spaces. Automatically controlled windows allow for natural ventilation, facilitating the flow of fresh air and preventing overheating.
It is no secret that a dynamic façade that would cover the entire perimeter is difficult to construct, and not every building can be equipped with such a system.
The effectiveness of shading systems directly affects various aspects of building performance (heating, air conditioning and lighting), as well as comfort (thermal and visual), so an integral approach is necessary from an early design stage. This measure will allow achieving optimal results from the joint work of architects and civil engineers. The contribution of consultants and energy saving specialists is also important.
Research has shown that a dynamic façade design with automated control, together with lighting control systems and HVAC components, can significantly reduce the peak load on the ventilation system and optimize overall energy consumption. In this case, lighting and ventilation conditions will be sufficient to maintain the desired microclimate and lighting comfort.
When considering the benefits of using building automation to control shading elements, the following should be noted: When automating office and government buildings, the designer must first of all provide protection from bright light. This means that blinds should be positioned to prevent direct sunlight from entering work areas. This measure also prevents the internal air from overheating. If there is no automation, then the person himself is forced to move the “shade” (curtains, blinds), but in this case, this would not contribute to the reduction of daily energy consumption for lighting and air conditioning, because a subjective factor would interfere with the process. It has been observed that at least 30% of people prefer to shade their windows on cloudy days (this reduces natural light and increases lighting costs), and open them on clear days (this increases air conditioning costs). What can we say about the hours/days when no one is in the offices (lunch time, weekends)?
An automated system can solve these problems without compromising comfort (with proper controls). Automation can also take into account the individual needs of the user.
Then the question naturally arises: “What should be the shading parameters?” After all, we love natural light (and also looking outside), but we don’t like it when the sun is too bright. That is why automatic blinds must diffuse sunlight, preventing direct rays from entering the room. The main thing is to establish a balance between the positive and negative effects of sunlight. It is known that in very clear skies the transmittance should be above 5%, so recommendations often state a figure of 5% as a threshold.
The color shade of the shade is also important, as it affects the appearance outside the window and the degree of absorption of solar energy. Dark shades of blinds improve the appearance of the office, but such shades increase the air temperature in the room. Keep in mind that the color choice of shade of curtains or blinds can improve the aesthetic impact, but your room will be hotter. There is a solution to this problem: there is a special fabric that is dark on the inside and light on the outside (so it reflects the rays better).
Of course, the possibility of horizontal blinds that automatically rotate depending on the height of the sun , can provide effective protection, but such a system requires careful design.
It is also important to consider the location of shading screens. External shaders always outperform internal ones, but screens are still preferred to be placed inside for aesthetic reasons and for ease of maintenance.
When the problem of controlling the shading system was solved (at least partly at an early stage of development), the problem remained: perhaps on a larger scale: implement the project.
Currently existing lighting control systems make it possible to automatically regulate illumination at low cost. The lamps are turned off (or dimmed to a minimum) when daylight becomes bright enough. When artificial lighting is required, the lamps will turn on accordingly. Occupancy sensors in the workplace will ensure that the lights in the room are not on when an employee is absent. Photoelectric sensors are currently controlled by “smart” algorithms, so no more than two or three sensors (per side) will be needed on the building façade. Lighting can be adjusted depending on the task and preferences of the owner of the room.
The issue of integrating lighting control systems with automatic shading systems is increasingly becoming relevant. The goal of such integration will be to achieve the best possible energy savings. How to achieve it? Let's consider shading and lighting systems as a “single lighting system”. This system will become an integral part of the office premises (especially the external perimeter) and will be developed at an early design stage. The position of the shades will be continuously adjusted depending on the ambient lighting conditions, and the lights will only turn on when needed. There is no need to use separate systems. The idea itself sounds simple and clear, but its implementation may require interaction between two systems, and technologically we are ready to solve this problem.
The last point of integrating dynamic facades into a building automation system is the need to interact with the heating, ventilation and air conditioning system. The impact of an integrated lighting system on an air conditioning system is aimed at two goals:
• a reduction in cooling capacity due to the use of shading (this reduces the capital cost of a less powerful system),
• a reduction in cooling energy consumption, which reduces the need for “heating” effect of lighting (both solar and artificial).
These two points must be thought through at an early design stage, when fundamental decisions are made. In addition to reducing the power required from the air conditioning system, dynamic temperature control around the perimeter of an office building will significantly reduce overall energy consumption.
Other perimeter automation options (such as automatically opening windows for natural ventilation) are also important and should be considered. attention when designing the facade of a building.
Experience in developing dynamic facades has shown that for an average building with a height of 10-15 floors and an area of 4500 sq. m. with glazed facades, energy savings due to the automatic shading system are 40%. Energy consumption can be reduced by more than 60% (compared to passive climate systems). The peak load of the air conditioning system can be reduced by 20-40%. These facts make the technology very attractive, promising to reduce energy consumption, greenhouse gas emissions and create healthier microclimates.
About the author
Thanos Tzempelikos – M.A., Ph.D. He is an independent consultant and works within the framework of the “Solar Energy in Civil Engineering” project. For 5 years he has been conducting research on optimizing the microclimate of office premises (dynamic facades, natural lighting, development and control of shading screens). Also deals with their integration with artificial lighting and air conditioning systems.
based on materials from the AutomatedBuildings website