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An HVAC system is one of the most important systems in a hotel property. While designing a HVAC system, there are many details to be considered. Among them are the three most important elements -energy conservation, water conservation and indoor air quality. Besides heating, ventilating, and air conditioning equipment, the whole HVAC system can also be combined with other systems especially control systems to ensure its efficiency. Several processes in planning a successful HVAC system include designing, purchasing, operating and maintenance.
As hotels are businesses, the overall mission is to make profit. The basic principle of designing an HVAC system is to make it efficient. On one hand, hotels have to ensure guests' satisfaction and provide a comfortable work environment for employees. On the other hand, hotels also need to cut cost because HVAC system is a big energy consumer.
Although retrofit of an HVAC system can be expensive, it is worth it for hotels with old equipment. The investment will actually be covered in just few years and bring hotels many long-term benefits. In addition, a new HVAC system helps hotels to be socially responsible and protect our environment.
HVAC (Heating, Ventilating, and Air Conditioning) refers to the technology of indoor or automotive environmental comfort (Wikipedia). HVAC systems in hospitality buildings provide control of the interior temperature, humidity, air movement, and air quality within the structure (Hotel Mule Wiki). A well-designed HVAC system is comprised of a number of components including boilers, chillers, centralized and decentralized guestroom HVAC units, large roof mounted PTAC units, air handling units, and cooling towers. As service is core of the hospitality industry, an HVAC system directly influences guests' satisfaction and therefor plays a big role in ensuring hotels' success.
The needs of an HVAC system can be very different depending on the size, location, structure and style of the hotel property. A small B&B may only have a heating unit while a big luxury hotel may apply a huge temperature control system. With the development of technology, some HVAC systems are very high-tech and efficient. Besides, the renovation of an HVAC system in some old properties can be highly expensive and complicated. When planning an HVAC system, any small mistake may lead to a big failure and potentially a hotel disaster.
As HVAC system is a big consumer of energy, the more efficient they are, the more costs a hotel can cut. A "green" system can also help a hotel to build a good reputation. In this paper, some suggestions and analyses of how to design a hotel HVAC system will be discussed.
According to Pradeep (2005), although designing an HVAC system for a hotel is a huge project and consists of many key steps, the following three are the most important:
* Energy conservation
* Water conservation
* Indoor air quality
Unlike office buildings, HVAC systems have to be operated for 24 hours a day, seven days a week in hotels. As Hu, Kwong, and Chao (2006) argued, there is room to save energy in hotels. Choosing a chilling unit, pumping system and cooling tower is crucial to the control of energy use. Although chillers with higher Coefficient-of-Performance (COP) are more expensive, they are suitable for hotel applications and the payback period is reasonable (Hu, Kwong & Chao, 2006). Based on this consideration, water cooled chillers should replace air cooled chillers.
Another way to improve cooling system efficiency is installing variable-frequency drives on chillers, pumps and cooling towers (Fypower). With the help of these drives, cooling system power loads can be controlled to fit hotels' specific needs; for example, the cooling load in summer could be much high than in autumn, the cooling load could also be different between day and night. Therefore, sometimes it is not necessary for chillers to run on a full load all the time. Hotels can save energy during the low cooling load period. Furthermore, larger hotels or convention centers may have another problem: the occupancy level can fluctuate significantly within a short period of time. As Hu, Kwong, and Chao (2006) mentioned in their study, "Manual control may not respond fast enough and may result in waste of energy." To deal with this, building automation systems (BAS) can be used. They can integrate, control and monitor HVAC equipment in a most effective way with minimum human errors (Pradeep, 2005).
Another part of the system is to use the free cool air from outside to save energy. If a temperature sensor or web-based control system (Scarpa, 2009) can be used by a hotel, it is even possible to get free cooling during the morning and evening.
Water conservation in an HVAC system is not as important as in other functional usage such as cooking, washing, bathing, flushing, laundry and boilers, etc. (Pradeep, 2005). If hotels use water cooled chilling units instead of air cooled chillers, they will consume a large amount of water. But as the quality of water for cooling towers is much lower than potable water, hotels can resolve this problem by using a gray water system or properly reusing sewage water.
Indoor Air Quality
The "V" in HVAC system refers to ventilation. Through the process of ventilating, air can be changed or replaced in any space to control temperature or remove moisture, odors, smoke, heat, dust, airborne bacteria, carbon dioxide, and to replenish oxygen (Wikipedia). According to this, the importance of ventilating is not only related to guests' comfort but also related to the safety and health of whoever stays in the hotel property. However, different rooms and spaces may have different requirements for air ventilation. Guests will feel uncomfortable when there is no ventilation while they are sleeping. Kitchens and bathrooms need mechanical exhaust to control odors and sometimes humidity (Handbook, A. 2001). In all public spaces fresh air needs to be ducted from the outside and exhaust air must be removed. Besides fans, a well-designed HVAC system can also ensure effective natural ventilation. The layout of windows, doors and vents needs to be planned carefully.
As recognized by the American Society of Heating, Refrigeration and Air-conditioning Engineers (ASHRAE), ineffective HVAC systems can cause, or help the growth of mold in hotels. 50 percent of all illnesses are caused by polluted indoor air (Freed, 2009). Because of this, mold protection products like air purifier are worth installing (Martin, 2005). Evaluating HVAC systems regularly and implementing proper operation and maintenance procedures are very important.
HVAC combined with other systems
By using infra-red technology in guestrooms, the HVAC system can be automatically turned on when a guest enters a room. The air-conditioning will start to control the room temperature and the ventilating system will also start to work. If the guest wants to alter the room temperature by him or herself, manual control devices should also be available. "Once the guest leaves the room, the temperature can be adjusted to the level pre-set by the hotel to keep energy costs down and provide a more comfortable environment for the guest when he or she returns (Worcester, 1998)." Some similar control systems can be as simple as key card system or as high-tech as a sound-activated system or even biosensors. To detect occupancy in the guestroom is now the most effective way to control energy output.
Furthermore, as mentioned before, with the help of a building automation system, a hotel will be able to control the whole property automatically. In addition to regular operations, time scheduling, limiting demand and an early warning system failure can be implemented in an HVAC system (H&MM, 1996). This can significantly help hotels to reduce labor cost, save energy and enhance guest satisfaction.
Another trend is the use of a raised floor with under-floor HVAC system. According to Alwine (2010), an under-floor pathway created by panels can provide a property with a service distribution system. Such service distribution systems include modular wiring, passive or active zone cabling and heating and ventilation and air conditioning. Using this system, fresh air can be supplied by air diffusers from below the floor directly into the occupied space. As a traditional overhead service distribution design uses walls and columns to place cables and HVAC systems, an under-floor system can save more space and support more facilities. Furthermore, Alwine (2010) also argued that "raised access flooring affords operators more flexibility to respond to equipment layout and technology changes quickly, easily and cost-effectively because updating the interior design does not demand expensive facility investment and construction expenditures." This is extremely important for hotels because hotels are running 24 hours a day and are cost-sensitivity. This design has been proven very successful in casinos and will also be applied by more and more hotels.
After a system design, a hotel needs to consider some key issues when buying the system (Higgins, 2009). First of all, the performance of the HVAC system needs to be ensured. The hotel should do some research on the company and its products. If possible, they should also try to check the performance of systems in other hotels. After this, a hotel needs to consider the utility cost and performance cost. Although some systems may be expensive at purchase, they can save a lot of energy and bring the hotel more benefits in the long-term. The sound level and equipment size are also important considerations. Gloede (2007) argued that a property needs to determine exactly what heating and cooling load is needed and then spec the system accordingly. Finally, hotels should assess the value of the whole HVAC system to find the most suitable one for their property.
As an HVAC is a continuous operating system, the hotel cannot disregard it after purchase and installation. A maintenance plan for the HVAC system needs to be established to ensure the success of operation. According to Freed (2009), air conditioning comprises 50-70% of a hotel's energy consumption. By properly cleaning the HVAC system, a hotel can save 20-30% on an energy bill. Furthermore, "the number one cause of heating/cooling system failure is dirt and neglect (Freed, 2009)". Based on these factors, hotels should follow strict maintenance standards and schedules. The benefit of this is that equipment is efficient and less likely to break down. The breakdown of an HVAC system not only affects a hotel's revenue, but also results in a health risk.
Hotels can develop a training plan for employees so they can handle most of the regular maintenance. On the other hand, hotels also need to outsource experts to do the deep cleaning and preventive maintenance annually. If necessary, large hotels can assign someone to do HVAC energy audits. This person is responsible for operating, maintaining, and controlling the cost of the HVAC system and reports to the executive engineer. In order to deal with emergencies, hotels need to develop an emergency response plan. Certain information such as detailed equipment layout drawings and emergency contacts should be prepared to save time and money (Doring, 2000).
By upgrading a hotel's HVAC system, employees' productivity can be increased because of an improved working environment (Gann, 1998). According to 1992 Means Construction Data, the installed cost of the HVAC system is approximately 10 percent of the total building construction cost. According to this, a 50,000-square-foot building needs about $200,000 to upgrade its system in 1995 (Gann, 1998). If we assume this percentage stays the same and calculate inflation, the amount will be larger today. This seems to be a huge expense if a hotel wants to retrofit its HVAC system. The hotel management also needs to decide whether it is worthwhile, considering the impact on revenue during the renovation period. Based on Gann's calculation, the return on investment will be around 71% and simple payback will be 17 months (based on the statistics in 1995 for a 50,000-square-foot building). With the development of technology, HVAC systems are becoming more and more affordable and efficient. Now, more than ever, a new HVAC system is worth retrofitting in a hotel.
The renovation of Marriott Mission Valley's HVAC system saved the hotel more than 700,000 kWh per year (Fypower). Another case study done by Mode: Green showed that a hotel in Chicago, which installed new thermostats and controllers, could save approximately 22% of the heating and cooling costs with a return on investment under three years.
In order to plan a successful HVAC system, three major elements should be first defined. In energy conservation, water cooled chillers with higher Coefficient-of-Performance (COP) are preferred. Chillers, pumps and cooling towers should have variable-frequency drives installed. This can help the hotel to save energy and cut costs. A central control system such as BAS, is suitable for large properties. In water conservation, hotels can use a gray water system, or a purification system to reduce water waste and reuse sewage water. Ventilating systems should be designed to safeguard customers' health. Depending on their needs, hotels can choose to combine HVAC systems with other control systems to micro control each device in the property. Under-floor HVAC systems have become more and more popular.
It is a good strategy for the engineering department to cooperate with other departments such as rooms division and the human resources department to ensure the consistency and success of the HVAC system plan. When the management team decides to renovate the HVAC system, a long-term view should be taken. Saving energy, cutting costs, being environmentally-friendly - they are the "Trinity".