Innovations in Comfort, Efficiency, and Safety Solutions.
Thomas Hartman, P.E.
The development of low cost wireless data transmission technologies demands a new look at how building control systems can effectively employ such technologies. However, most such considerations envision employing wireless technologies to replace connections and communication links that are already part of building controls. The real opportunity for wireless technologies is to implement a communication link that is only rarely employed in building controls and when it is not, is sorely missed - connecting the building occupant to the building comfort system.
WHY AN OCCUPANT CONNECTION?
In commercial buildings, occupants are more disconnected from the means intended to maintain their comfort than ever. In the first half of the last century, nearly all commercial building occupants had direct control over both their source of heating - a valve on a radiator, and cooling - an operating window. And great pains were made to keep everyone as near as possible to a radiator and a window. As mechanical air conditioning became popular, buildings were designed with much larger floor plates and configured be populated more densely. The idea of a "hermetic" building emerged in which heating, cooling, and ventilation would be carefully controlled automatically to ensure both comfort and operating economy. Precise control would eliminate the need for occupant adjustment in this concept; in fact any adjustment could adversely affect the careful balance of the system and was generally discouraged. Though not well accepted by building occupants, this basic building design philosophy endured and continued to predominate HVAC designs up through the end of the century. Despite the proliferation of low cost digital controls, occupant control actually decreased during this time as operable windows disappeared and adjustable thermostats were replaced with temperature sensors, most of which did not permit any occupant adjustment.
Because occupant control of windows and steam valves was not particularly effective in maintaining good comfort, and because modern buildings are so unlike the earlier buildings, it is unfair to call the change a backward step in occupant control of comfort. In retrospect, it should probably be considered a transitional step toward better buildings. In fact building and mechanical systems have improved so much that the basic approach toward conditioning commercial buildings has changed. However, in all this time, surveys have shown that building occupants have not become happier with their buildings' comfort level. It is becoming clear that the only way to improve building comfort to a satisfactory level is to provide a means of individual thermal control to every building occupant, and to accomplish that each occupant must have some connection to the building's comfort system.
IMPROVED COMFORT CONTROL
As the need to address direct occupant control of indoor environments is becoming more widely acknowledged, a whole new approach to comfort control is being developed. The use of mechanical valves or thermostats to control comfort is enormously out of date and most certainly should not be revived. It is now understood that human comfort is an interaction of a number of environmental factors, and we now know that a careful management of various components of human comfort allows low cost personal comfort systems to provide perceived thermal comfort gradients of from four to ten degrees Fahrenheit between adjacent workstations in open office configurations. With low cost sensors and controls, occupants can communicate preferences to such an individual comfort system. The comfort system can then automatically adjust elements of the local environment in accordance to occupant preferences in such a manner as to optimize the system's effectiveness and operating economy without adversely affecting the preferences of adjacent occupants.
BETTER OCCUPANT INTERFACES
As the need for individual occupant control is becoming more widely acknowledged, new approaches to occupant interface have been developed. A serious problem with thermostats, and one that continues to plague many individual comfort system is the problem associated with any "direct control." Direct mechanical control of any device to adjust comfort means that additional direct mechanical control will be required to reset the adjustment to a neutral state.. When mechanically or electrically linked levers, knobs or slides are employed for occupant adjustment, then resetting the adjustment also requires direct action. This limits the ability of the system to automatically adjust to changes. For example, if a space temperature sensor is adjusted downward during late in the afternoon because of increased solar or occupant load, then unless the occupant(s) remember to reset the unit before leaving, it is likely that the following morning the space will be uncomfortably cool. However, if the device is provided with "indirect" controls such as "Warmer" and "Cooler" pushbuttons and a display that shows the occupant adjustment, such adjustment can be automatically reset at the end of occupancy by the controlling system. The greater logic of digital control system can also be employed to anticipate a need for adjustment and reduce the discomfort that leads occupants to adjust comfort levels in their spaces.
THE ROLE OF WIRELESS COMMUNICATIONS IN OCCUPANT CONTROLS
There are three basic approaches to bringing occupant control back to building comfort systems. The simplest is a wired interface. While this is still the simplest and may be the lowest cost approach in some systems, the use of wired control needs to be carefully considered because as outlined in the previous section such interface must be applied only indirectly so that the control system can provide automatic reset and incorporate "smart" learning features. The second approach is to employ a network interface. In commercial buildings, most workstations have Internet connections. In such spaces, occupants can be set up to request adjustments in their workstation environments with pop-up menus, similar to how one changes the settings on their computer. When an occupant has entered an adjustment request, it is sent to the building control system which is also connected to the Internet or a specifically developed building network.
While the wired and network connections each have potential applications. There is a strong potential role for wireless occupant interface. In the longer term, a wireless approach has the advantages of allowing the comfort system to follow occupants through the building and to automatically adjust occupancy, ventilation, lighting and thermal levels to meet personal preferences wherever the occupant travels through the building. Though this may seem like a futuristic vision for occupants who today do not even have a temperature sensor near their workstation, the industry is readying itself for an enormous revolution in occupant connectivity and the improvements in environmental comfort it will bring. Enabling technologies have already been developed and are ready for implementation. It is not unreasonable to consider occupant connectivity as the next great step in building operations, and it is a given that wireless communications will play an important role in that giant step forward.
Additional information on technologies discussed in this article is available at http://www.hartmanco.com. Comments and questions about the article may be addressed to Mr. Hartman at firstname.lastname@example.org.
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