There is no such thing as a simple decision when it comes to choosing a commercial HVAC system. Each building – and sometimes each part of a building – has different requirements for indoor air quality (IAQ), which is influenced by the building’s design, occupancy, location, and purpose. Additionally, HVAC systems typically account for 39% of the energy used in any commercial building.
Improving the controls in an HVAC system or upgrading equipment can sharply reduce energy use by 10% – 40%. Whole building design with extended comfort zones can realize even deeper energy savings, typically between 40% – 70%. Improved HVAC systems also provide more comfort for occupants, better IAQ, and can also affect water consumption and acoustics (various mechanical noises and how sound reflects off walls, ceilings, and floors).
What makes up a commercial HVAC system?
Your building’s HVAC system is sophisticated. It includes all your heating, ventilation, and cooling equipment, including furnaces, boilers, chillers, cooling towers, air handling units, heating coils, air filters, steam or hot water piping, exhaust fans, ductwork, air handling units, and associated equipment. Your HVAC system also includes controls for this equipment which impact the entire system’s performance and ensure its safe operation.
So if you’re retrofitting your current HVAC system or getting bids for a system in a new building, here is what you need to know to have an intelligent discussion with your HVAC contractor. Choosing the right HVAC system is the best decision you’ll ever make. Choosing the wrong one leads to complaints and problems all day every day.
Tips for choosing a commercial HVAC system
“According to the Consortium of Energy Efficiency, at least 25% of all rooftop HVAC units are oversized, resulting in increased energy costs and equipment wear. Properly sized equipment dramatically cuts energy costs, increases the life of the equipment, and reduces pollution.”EnergyStar.gov
The single most important factor for energy-efficient operation is choosing an HVAC system of the right size. Oversized equipment operates less efficiently and costs more to install than properly sized equipment. For instance, an oversized cooling system may not dehumidify the air properly, creating cool but damp rooms. If you have an oversized constant air volume system (CAV), fan energy use will be high because the fans will run constantly to provide ventilation. In an oversized variable air volume system (VAV), fan and reheat energy use will be higher because the turndown of oversized zone boxes is limited.
Can the system be upsized later? New technologies and building renovations change the demand for heating and cooling. Plan mechanical rooms to be an adequate size to house more equipment when necessary and consider modular HVAC systems which can be added onto later. Instead of oversizing your equipment now in anticipation of an expansion, add that capacity only when it’s needed.
Consider the whole building. HVAC systems interact with lighting systems, daylighting, natural ventilation, and your building’s design. Each of these affects the heating, cooling, and energy requirements of the building. For instance, natural and mechanical ventilation is largely dependent on the activities of the building and its location (is the outdoor air clean or polluted?). If your HVAC system is chosen without considering every system, your building won’t be even close to energy-efficient and you’ll struggle to maintain IAQ.
What is the HVAC system’s part-load performance? Your heating and cooling system is designed to keep your building comfortable and safe on the hottest and coldest days of the year – this is referred to as running full load. But what about the other 330 days? Part-load performance is used when the system doesn’t have to meet those expectations and it’s where a lot of energy is wasted. In some facilities, the situation is reversed – the system works at full load most of the time with the system on part load during non-working hours. Learn how your new HVAC system will perform when demand is low.
Can the system be designed to shave or shift electric loads during peak demand? For instance, building controls can be programmed to run certain tasks at night when rates are lower, taking advantage of Time of Use (TOU) plans. This load shifting might include running chillers at night in an ice thermal storage system. The cold supply water from the ice is then used for cooling the building the following afternoon when rates are higher.
What are your local and federal guidelines for HVAC performance? Your new HVAC system must conform not only to local building codes but state and federal guidelines for your business sector (such as pharmaceutical manufacturing). Your HVAC contractor and building engineer should have a good handle on these criteria and your system must strictly adhere to them to avoid inspection problems, construction delays or fines down the road.
What are the requirements for air filtration? Filtering atmospheric dust, pollen, molds, animal dander, lead, bacteria and viruses; and ventilating indoor air contaminants all must be considered. What is required to be filtered and at what level depends on your building’s use.
What are the requirements for humidity control? An office building simply needs to be comfortable, but a manufacturing facility must be comfortable and meet strict standards to maintain the integrity of the products.
Don’t be afraid to ask your HVAC company these questions and more when choosing a commercial HVAC system. Healthy indoor air quality contributes to productivity, comfort, and a sense of well-being for everyone who works or lives in the building.
Do you have questions about upgrading or installing a new HVAC system? We’re happy to answer them.