HVAC systems in large plants: solving 5 common issues
Large structures such as warehouses and manufacturing facilities present unique HVAC challenges. Large open spaces can be difficult to heat and cool and to maintain appropriate air quality and moisture control. However, working through these challenges is well worth it for the outcomes: improved occupant safety, comfort and increased productivity, preservation of the structure and increased energy efficiency. The first step to solving large facility HVAC problems is to identify them. Here are five of the most common ones you are likely to find:
- Unwanted thermal stratification. In a large open space, it is difficult to achieve ideal air distribution. Cold air tends to settle while warm air rises, resulting in stratified layers that tend to stagnate. In addition, it is not uncommon for the temperature difference to result in the formation of cold downdrafts along vertical surfaces. These can cause uncomfortable cold spots in the building. Conventional HVAC cooling systems can intensify the problem by introducing large volumes of cold air into the space at once. For this reason, it is often a good idea to incorporate an air distribution solution, such as large industrial ceiling fans, into the design.
- Fluctuating need for fresh air intake. In buildings where occupancy rates vary considerably (such as concert venues or sports arenas), it may be necessary to adjust air intake and distribution accordingly. When the structure is filled to capacity, more air may need to be brought in to satisfy fresh air requirements. During times of relative vacancy, the air turnover rate may not be so critical. Where the need for air intake varies, it is important to design the HVAC system in such a way that these variations can be easily and quickly accommodated.
- Moisture condensation. Large buildings, especially uninsulated ones, are prone to moisture condensation. When large quantities of warm moist air trapped near the ceiling become exposed to cooling surfaces such as walls or windows, moisture is released that can accumulate on interior surfaces. Like all moisture issues, this can lead to problems with fungal growth as well as damage to the building structure. Condensation can also be a serious safety issue. Moisture can accumulate on floors, railings and metal stairs, where it can cause occupants to slip and injure themselves. Metal buildings are especially prone to this problem. Condensation can be controlled through improved insulation, reducing sources of humidity and effective ventilation. Cooling fans that provide an evaporative cooling effect can be especially useful.
- Uncontrolled energy costs. Large doorways, inadequate air sealing and insulation and poor heat distribution all contribute to energy loss in large buildings. Buildings that demonstrate excessive outside air infiltration are especially prone to high energy costs. This is sometimes unavoidable, as in the case of warehouses with large loading docks. Devices such as vinyl strip curtains can help separate indoor from outdoor air. In cases where this is not practical, a series of high-volume low speed fans can create an "air curtain" that achieves a similar effect, without obstructing the movement of people and equipment through the space. Techniques and devices such as space heating and cooling, air destratification, natural ventilation, programmable controllers and heat recovery can greatly improve large building energy efficiency, as can upgrading to more efficient HVAC equipment.
- Sick building syndrome. Inadequate air flow, air stratification and moisture buildup in large buildings can all conspire to create ideal conditions for the growth of toxic mold. In addition, stale air is an excellent medium for harboring viruses, bacteria and other airborne contaminants. Any time illness rates and absenteeism appear higher than normal, a large building’s HVAC system should be inspected to be sure acceptable indoor air quality standards are being maintained.
If you are experiencing these or similar problems in your large building, it is important to diagnose exactly what is causing the issue. HVAC problems can be complex to troubleshoot, especially in buildings that incorporate many integrated HVAC components. Fortunately, there are many diagnostic tools and methods available today, including portable methods. Hiring a consultant familiar with air flow issues in large buildings can be an excellent investment. Most problems of this sort can be solved, sometimes in surprisingly simple ways, thus greatly increasing comfort, safety, productivity and energy savings in the buildings involved.
Nikki Heinkel is Marketing Manager at Go Fan Yourself, a company that manufacturers patent-pending, industrial, high-volume, low-speed.