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Recent studies have shown that proper distribution of window openings in a room, in combination with the operation of lighting control systems and heating, ventilation and air conditioning, can significantly reduce peak loads on the air conditioning system. This measure also allows you to reduce energy costs for lighting and ventilation, while maintaining comfortable conditions inside the room, both in terms of lighting and indoor air quality.
Technologies do not stand still and transparent facades are already appearing today – a necessary component of environmentally friendly buildings. The facades of such buildings are dynamically rebuilt 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 a building) is not new. But its active development has only begun in recent years. Engineers and architects have only recently begun to “trust” such systems and use them in construction.
Dynamic shading elements have become possible thanks to advances in window technology. The result is the emergence of technologies for dynamic placement of window openings due to 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 great, 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 degree of transparency of the facade. Already at an early stage of design, the development team is faced with a choice of solution options. However, it can be difficult to finally evaluate the merits of the options, especially if innovative technologies are used. As a result, the final choice is often subjective. The disunity of the stages of the construction process, in which no one member of the team takes on the task of fully optimizing the microclimate, is the main problem in the “finishing” of 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 the impact of direct sunlight. To do this, you need to place an automated shading system along the outer perimeter of the offices. Shading elements placed on rollers can move automatically, blocking direct sunlight so that diffused light enters the office. This measure helps combat glare and create a comfortable lighting sensation in the premises. Horizontal (“Venetian”) blinds redirect natural light into the room space and allow for uniform illumination even in open office spaces. Automatically controlled windows allow for natural ventilation, promoting the flow of fresh air and preventing it from overheating.
It is no secret that a dynamic façade that would cover the entire perimeter is difficult to design, and not every building can be equipped with such a system.
The efficiency of shading systems directly affects various aspects of building operation (heating, air conditioning and lighting) and also creates comfort (thermal and visual), so an integrated approach is necessary already at an early stage of design. This measure will allow achieving optimal results of the joint work of architects and civil engineers. The contribution of consultants and energy saving specialists is also important.
Research has shown that the design of a dynamic façade with automated control, together with lighting control systems and HVAC components, can significantly reduce the peak load on the ventilation system and optimize energy consumption as a whole. At the same time, lighting and ventilation conditions will be sufficient to maintain the desired microclimate and lighting comfort.
If we take into account the advantages of using building automation in controlling shading elements, then it is necessary to note the following: when automating office and government buildings, the developer must, first of all, provide protection from bright light. This means that the blinds should be positioned so as not to allow direct sunlight to hit the workplaces. This measure also prevents overheating of the indoor air. If there is no automation, then the person himself is forced to move the “shader” (curtains, blinds), but in this case, this would not contribute to reducing the daytime energy consumption for lighting and air conditioning, because the subjective factor would interfere with the process. It has been noted that at least 30% of people prefer to shade the windows on cloudy days (this reduces natural light and increases lighting costs), and on clear days, on the contrary, they open them (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 (if there is proper control). Also, automation can take into account the individual needs of the user.
Then the question naturally arises: “What should the shading parameters be?” After all, we love natural light (and also looking outside), but we don’t like it when the sun is too bright. That’s why automatic blinds should 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 with a very clear sky, the transmittance coefficient should be higher than 5%, so the recommendations often voice the figure of 5% as a threshold.
The 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 the 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 capabilities of horizontal blinds that automatically rotate depending on the height of the sun can provide effective protection, but such a system requires careful development.
It is also important to consider the placement of shading screens. External shading is always better than internal shading, but screens are still preferred to be placed inside for aesthetic reasons and ease of maintenance.
Once the task of managing the shading system has been solved (at least partly in the early stages of development), there remains a problem of perhaps greater scope: implementing the project.
Existing lighting control systems allow automatic, low-cost regulation of lighting. Lamps are switched off (or dimmed to a minimum) when daylight becomes bright enough. When artificial lighting is required, the lamps are switched on accordingly. Presence sensors at the workplace will ensure that the light in the room is off when the worker is absent. Photoelectric sensors are currently controlled by “smart” algorithms, so no more than two or three sensors (per side) will be required on the building façade. Lighting can be adjusted depending on the task at hand and the preferences of the owner of the premises.
The integration of lighting control systems with automatic shading systems is becoming increasingly important. The goal of such integration will be to achieve the best energy savings. How can this be achieved? Let's consider shading and lighting systems as a «single lighting system». This system will become an integral part of office premises (especially the outer perimeter) and will be developed at an early stage of design. The location of the shades will be continuously adjusted depending on the external lighting conditions, and the light will be switched on only when necessary. There is no need to use separate systems. The idea itself sounds simple and clear, but its implementation may require interaction between the two systems, and we are technologically prepared to solve this problem.
The final point of integration of dynamic facades into the building automation system is the need for interaction with the HVAC system. The influence of the integrated lighting system on the air conditioning system is aimed at two goals:
• reduction of cooling capacity due to the use of shading (this reduces the capital costs of a less powerful system),
• reduction of energy consumption for cooling, which reduces the need for the “heating” effect of lighting (both solar and artificial).
These two points should be considered early in the design process when major decisions are being 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 automatic opening of windows for natural ventilation) are also important and should be taken into account when designing the building's façade.
Experience in the development of dynamic facades has shown that for an average building of 10-15 floors and an area of 4,500 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 a healthier microclimate.
About the author
Thanos Tzempelikos – M.A., Ph.D. is an independent consultant and works within the framework of the project «Solar Energy in Civil Engineering». For 5 years he has been conducting research dedicated to the issues of optimization of the microclimate of office spaces (dynamic facades, natural lighting, development and control of shading screens). Also involved in their integration with artificial lighting and air conditioning systems.
based on materials from the AutomatedBuildings website |
