As our clients navigate HVAC system design for high bay facilities such as distribution centers or industrial manufacturing plants, they are often asked to recommend a design that accomplishes 3 key deliverables. 1.) Meet variable ventilation requirements 2.) Meet heating requirements / (Consider air load and conductive load and comfort requirements) 3.) Evaluate redundancy to eliminate production and/or service interruptions 
As a manufacturer of high efficiency heating technologies (S-Series, SA-Series, Infrared) and ventilating technologies (M-Series, M-Series w/Cooling) we first seek understanding regarding how the building will be operated in order to recommend a heating platform, a ventilation platform, or both. While the core technologies are both 100% outside air, direct fired gas heaters, there are differences in system performance that will impact EE (energy efficiency), thermal comfort, and system installation cost. When there is a high level of CFM being exhausted due to processes inside a manufacturing facility, making up that building air loss with mechanical ventilation or inbound CFM is critical to balancing the air load of the building. Direct Fired Make-Up air systems with variable air flow capabilities utilizing a Variable Frequency Drive help to ensure better indoor air quality, better thermal comfort, and in some cases reduce safety incidents caused by negative environments and back drafts with non-powered combustion devices. When high CFM needs are identified (VENTILATION DRIVEN APPLICATION) due to process exhaust in either a manufacturing facility or distribution facility, engineers will first seek to design a VENTILATION (M-Series) system to bring the building to a neutral or balanced position with proper relief. According to the International Mechanical Code and the International Fuel Gas Code Section 611.7 Relief opening - The design of the installation shall include provisions to permit non-recirculating direct-fired industrial air heaters to operate at rated capacity without over-pressurizing the space served by the heaters by taking into account the structure’s designed infiltration rate, providing properly designed relief openings or an interlocked power exhaust system, or a combination of these methods. Depending on the application, achieving a neutral or even slightly positive pressure can be advantageous to keep natural infiltration in check and to avoid severe over pressurization, or adding to the required air load in the building. ANSI/ASHRAE Standards 62.1 is the recognized standard for minimum ventilation rates to meet acceptable Indoor Air Quality. As the complexity of a building’s air load increases with variable exhaust due to intermittent processes, variable ventilation solutions are required to maintain fresh air and neutral to slightly positive pressure in the building. Now that the ventilation is addressed in this high CFM building scenario, the designer then seeks to understand the heat load of the building and evaluate if the ventilation solution carries enough BTUS to cover heat requirements on design days. The warehouse or manufacturing facility in this case is built to FIRST satisfy the ventilation requirement and then “stack” any supplemental heating technologies to cover the heat load (air load + conductive load = total heat load.) In order to maximize efficiency, the designer can utilize a low CFM, high BTU heating technology to build the comprehensive system if the ventilation technology does not deliver the needed BTUs on design days for that particular city or location. In this scenario, designers would utilize the M-Series ventilating and heating technology and consider supplementing with S-Series (low CFM, high BTU) heaters if necessary to deliver efficiently, any remaining BTUS required. When there is not a significant process call for CFM or ventilation beyond basic ASHRAE 62.1 requirements for indoor air quality, High Temperature Heating and Ventilating (HTHV) technologies like the Cambridge S-Series offer the most effective solution. These offer the highest btu/cfm outputs of any make up air technology in the industry. In a HEATING DRIVEN APPLICATION, the designers seek to understand the heat load for the building and design a system that accounts for infiltration and brings the building to neutral, but does not over pressurize the building again addressing proper relief per the IFGC. This leads me to my last deliverable. Reliability and redundancy of ventilation and heating systems in an industrial manufacturing plant is central to productivity, output and plant productivity measurements. Failure of systems or lack of redundancy of system design is not an option. Deploying systems that are designed to exacting specification, that are built to last, that are reliable and that are easy to service are minimum expectations in the plant production arena. Designers choose quality manufacturers and consider redundancy in their designs to meet the unique demands of these applications. When designing a ventilation and heating system or a heating and ventilation system for your high-bay building, explore the advantages that two different equipment platforms may provide you in the areas of thermal comfort and operating costs (or EE.) Cambridge Engineering, Inc. manufactures both MAU (Make Up Air/Ventilating) and HTHV (High Temperature Heating & Ventilating) types of equipment. While we are most known in the industry for our HTHV heating & ventilation technologies, we have been delivering outstanding product, design service and post installation support within the MAU space for over 15 years. Let us know how we can support you with your system design. Is it a ventilation or heating requirements based system design? Please share your thoughts on your design approach or system considerations as you navigate the nuances of heating and/or ventilating high bay buildings.