These retail stores offer a wide array of merchandise, fish, birds, pets, plants, and often include eating facilities, auto service, and garden shop. There are also stockrooms, offices, restrooms, and special storage rooms for perishable commodities -- all of which affect the energy system design.
These stores typically have one large open sales area with a relatively small glass storefront. The heat in the lighting system typically offsets the roof heat loss during the colder times of the year, so the interior of the store typically needs cooling all year long during business hours. This is extremely important in the design since some stores are open 24-hours a day. The perimeter, storefront, checkout and entrance areas have highly variable heating and cooling needs. So, proper zone design and control are essential for satisfactory comfort in these areas.
Some of the national chains, such as Wal-Mart, have pre-specified construction plans, including the HVAC and lighting systems. In these cases, the ability to work with them in the expeditious construction of the facility is most meaningful.
Discount and variety stores vary in size, type, and location. Each store should have an air- conditioning system design that meets its particular needs. Sufficient outdoor air must be supplied to minimize or eliminate odor problems. Basic features of a quality system include:
- An automatic control system to handle changing loads
- Main sales areas zoned for air distribution to maintain comfort conditions with varying loads
- Use of an economizer system for cooling during intermediate seasons and peak sales periods
- Design the system to maintain relative humidity at 50% or below with a corresponding dry-bulb temperature of 78°F
This humidity limit eliminates musty odors and retards perspiration, particularly in fitting rooms. It is also desirable to adjust indoor temperatures for variations in outdoor temperatures, to avoid temperature shocks as customers enter and leave the store. Winter humidification is seldom used in-store air conditioning.
Multiple single-zone unitary rooftop equipment with prefabricated and matching curbs simplify installations common in-store air conditioning. The use of multiple units to condition larger stores involves less ductwork and can maintain comfort in the event of partial equipment failure. These HVAC units may be either heat pumps or gas heating/electric cooling packages. This equipment is air-cooled and has a low first cost and ease of operation, which readily adapts them to these applications.
Water-cooled cooling equipment is available but many communities have restrictions on the once-through use of city water and require the installation of a cooling tower or other water-conserving equipment. Water-cooled equipment generally operates more efficiently and economically, but higher first cost with a tower and higher maintenance limits its application.
Retail facilities often have a high sensible heat gain relative to the total heat gain and equipment should provide the necessary sensible heat removal. Average air quantities range from 350 to 450 cfm per ton of cooling in accordance with the calculated internal sensible heat load.
Larger stores may use either unitary or central-station air-conditioning systems. Central-station systems, when used, consist of air-handling units having chilled water cooling coils, hot water heating coils, fans, and filters. Air systems must have adequate zoning for varying loads, occupancy, and usage. As there are wide variations in people loads, variable volume air distribution systems are often used. The water chilling and heating plants distribute water to the various air-handling systems and zones and may take advantage of some load diversity throughout the store. Air- conditioning equipment should be located in ceiling, roof, and mechanical equipment room areas whenever practicable. The noise and expense are less than when placed in the sales area. Maintenance and operation of the system are important considerations in the location of equipment.
Larger stores may contain restaurants and lunch counters. These special areas may operate during all store hours. They may be met by the portion of the air conditioning system serving or by a separate air-conditioning system. For control of odors, a separate air-handling system should be considered.
Energy Saving Recommendations
- Older inefficiency cooling and heating systems should be investigated for upgrading or replacement, particularly if CFC refrigerants are used.
- Where demand and/or on-peak energy costs are high, investigate thermal storage.
- Add Economizer cycles if they are not installed or in use.
- Upgrade antiquated or inappropriate control systems.
Water heating is not a major energy user with uses typically for hand washing and cleaning purposes. Most water heating is done separately from the building heating system using direct resistance or gas heaters, and in some cases, point-of-use heaters. Larger stores may use central distribution systems with storage and constant recirculation where it is desirable to have hot water available continuously at the fixtures.
Energy Saving Recommendations
If existing systems are inefficient or inadequate, replace with modern efficient equipment. If a source of waste heat (i.e. tower water) is available, consider a water-to-water heat pump heater.
Larger stores may contain restaurants and lunch counters. Their cooking needs should be handled as appropriate.
In retail situations, the obvious function of lighting is to enable the shopper to examine the products offered and read any packaging information. More importantly, the lighting helps the shopper to identify with the level of merchandise and service. So lighting designed to communicate these values between retailer and shopper is an indispensable part of gaining a competitive edge.
Each retail establishment has distinctive features that hopefully make it attractive to a specific customer and reinforce its sales strategy. These include the range of products, style of service and the interior design, including the lighting design.
Variety stores typically use fluorescent strip lighting - either recessed or open bottom - for their general lighting. Some will use metal halide due to high ceilings. In most cases, there is little or no highlight lighting in variety stores.
Energy Saving Recommendations
All T-12 fluorescent lamps and magnetic ballast should be replaced with T-8 fluorescent lamps and electronic ballast. Metal halides should be replaced with pulse-start metal halide is some cases. Conversion from metal halide to fluorescent is also justified in many cases because of maintenance cost.
Larger stores may contain restaurants and lunch counters, or specialty departments that require refrigeration. Their refrigeration needs should be handled as appropriate.