By Steve Mauro, Kingspan Insulated Panels
So where should designers and specifiers start when looking to reduce energy usage in refrigerated facilities? Focus on the equipment, the walls, the doors? The correct answer is all of the above...and more.
Those involved with existing facilities should begin with an energy audit while new projects should make energy efficiency an integral part of the design process. In either instance, below are some key areas where refrigerated facility owners, designers and specifiers should focus.
Compressors use more energy than any other component of a refrigerated system. Compressors must run constantly to maintain temperatures in environmentally controlled areas. Types of compressors, configurations, housings and an array of other factors can be tweaked or improved. Understand at the onset, that more efficient equipment will require a greater monetary investment upfront. The key will be accurate ROI calculations to ensure the savings justify the costs.
The first important decision will be the use of refrigerated or unrefrigerated shipping docks. The choice will depend on operational procedures, good manufacturing practices, and product supply chain requirements.
Refrigerated docks prevent the entry of moisture into your cold storage room, thus reducing the enormous load moisture puts on refrigeration equipment. Additionally, refrigerated docks help to reduce the risk of temperature abuse, thereby reducing risks related to food safety.
The envelope design for the refrigerated sections of a facility serve an important role. These envelopes reduce heat transfer and control moisture infiltration and condensation. Heat transfer through refrigerated space walls and the outside ambient environment creates a greater load.
Moisture in refrigerated spaces comes with a litany of disadvantages:
- Increased Energy Costs
- Diminished Insulating Effect
- Structural Damage
- Biological Growth
- Ice/Frost Formation
About one third of cold storage heat gain is through the envelope. Insulation of the envelope surrounding the refrigerated space and the external building shell will both be important. The most effective type and amount of insulation must be determined through modeling and life cycle cost calculations.
The building envelope should be compliant with ASHRAE Standard 90.1-2007, (check your local jurisdiction on each individual state's adoption) utilizing the 2010 ASHRAE workbook for Refrigerated Warehouses and Chapter 8 of the Title 24 California Energy Code. The warehouse can be modeled with the incremental improvements in varying thickness of insulation in wall, floors and roof systems.
Each type of insulation delivers unique performance characteristics. Research all available options thoroughly to ensure maximum benefit.
The critical failure points for roofs will be water and vapor leaks. The roof serves an important structural role. There are three important considerations when designing a successful roof system:
- Maintaining structural integrity at all times.
- Sealing all joints to prevent air and moisture infiltration.
- A required uninterrupted vapor retarder.
Types and designs of walls will be important. The current trend in the industry is to use preformed materials such as insulated metal panels or insulated concrete.
External walls must accommodate loads incurred as a result of the physical environment (i.e. wind and rain). Vapor and heat transfer control must also be included. External walls contribute to energy efficiency for the facilities' entire heating and cooling load, not just refrigerated spaces.
Internal wall design and configuration will vary depending on facility layout. If cold storage spaces sit adjacent to one another, no need exists to insulate the adjoining walls. If a refrigerated space will be individually insulated, then different design specifications must be considered. The internal walls of refrigerated rooms must also adhere to food safety regulation. With that in mind, wall materials or surfaces must be washable in addition to sealed and vapor retardant.
Air infiltration through open doors can represent 50 percent or more of the total refrigeration load. Cold storage doors come in a myriad of choices—all with varying aspects that affect energy use and functionality. Modern cold storage doors may need to accommodate products handled by automated processes at high volume with rapid turnover.
Three important factors will influence design and choice concerning doors:
- How the door will be used
- How often it will be used
- The space required for a forklift, its load, and the mast to pass through without hitting the door
Designers will also need to consider:
- Door Activation methods
- Life cycle costs