The HVAC Factor: Cleaning The Systems

By Pete Haugen
Published in the June 2008 issue of Today’s Facility Manager

The goal of cleaning a heating, ventilation, and air conditioning (HVAC) system is the removal of the dirt, debris, and other contaminants that accumulate there. Like facilities themselves, HVAC systems come in a wide variety of shapes and sizes, and some are simple while others are complex. An effective cleaning approach will go a long way toward efficient operations.

In general, HVAC systems incorporate all of the components that heat, cool, filter, humidify, dehumidify, and distribute the air. These include: return air grilles, return air ductwork, air handling units (mixing box, coil components, drain pan components, fan components, filter components, and humidifiers and/or dehumidifiers), supply ductwork, turning vanes, reheat coils, VAV boxes, supply registers, and other dedicated supply or exhaust systems (such as make up air systems and restroom exhaust systems).

Facility managers (fms) will find two major benefits to cleaning their HVAC systems: improved indoor air quality (IAQ) and lower energy consumption.

A dirty HVAC system can be a breeding ground for microbial contamination. All that is needed for this to occur is the presence of a food source (dirt), moisture (high humidity or water intrusion), and time. Given the right conditions, the microbial contamination will amplify and be distributed throughout the building by way of the HVAC system. This can adversely affect building occupants, possibly resulting in lower productivity, higher absenteeism, and even litigation. In severe cases, this is called Sick Building Syndrome.

Proper HVAC system cleaning serves to remove the food sources essential for microbial contamination to occur. It also gives the fm a baseline against which to compare future conditions and sets an example of proactive building maintenance.

HVAC systems generally consume 60% to 70% of a building’s energy. A recent Department of Energy (DOE) study states: “Dirty coils can increase compressor energy consumption by 30%.”

By cleaning the evaporator and cooling coils regularly, fms can save that 30% increase in energy consumption. In fact, many fms have service maintenance contracts that include coil cleaning and filter changes.

If only the coils are cleaned (and not the rest of the HVAC system along with them), they will get soiled again very quickly as the dirt, debris, and other contaminants from the rest of the system pass over the coils during operation. It is essential for the entire system to be cleaned to achieve maximum energy savings and optimum IAQ improvements.

An HVAC system should be cleaned when enough dirt, debris, and other particulates have settled into that system to pose the threat of microbial contamination and/or when a system’s energy consumption has increased, decreasing energy efficiency. The best way to determine this is to inspect the HVAC system on a regular basis.

The National Air Duct Cleaning Association (NADCA) recommends the air handling unit in most buildings be inspected once a year and the supply and return ductwork be inspected every two years. For healthcare and industrial buildings, it is recommended that all components be inspected once a year.

ASHRAE Standard 180P also recommends annual inspections for most components. These inspections, which usually include photo or video documentation, will provide the information needed to determine when system cleaning is necessary.

Good results start with the development of a good cleaning specification. The specification is a plan of action that outlines the scope of work, the schedule, required worker qualifications, acceptable cleaning methods and equipment, acceptable chemicals for use in the cleaning, health and safety plans, and verification protocol for the system cleanliness.

HVAC cleanliness
The cleanliness of an HVAC system has an effect on occupant health and energy efficiency in a building. The dirty insulated ductwork above poses a higher threat to health and energy efficiency than the cleaned insulated ductwork at bottom left. (Photos: VacSystems International)

NADCA has developed a document titled, “Assessment, Cleaning and Restoration of HVAC Systems” (or “ACR 2006”). Fms can use this document by itself as a cleaning specification, or it can be used as the basis for a specification developed for a particular building. Fms can also work with an environmental consultant and/or an HVAC system cleaning contractor to assist with the development of a cleaning guideline.

After the cleaning specification is finalized, the fm will need to select a contractor to do the work, unless in-house staff members have the training and equipment to do so.

If the fm opts to hire a contractor, s/he will want to verify that the firm has several years of verifiable experience, is a member of NADCA, and has at least one Air Systems Cleaning Specialist (ASCS) on the project. Generally, the selected contractor will meet the qualifications spelled out in the cleaning specification and will be awarded the project through a bidding process.

HVAC cleanliness

However, if an fm is responsible for a number of buildings, such as in a hospital complex, college or university, or large corporate campus setting, it may be more cost-effective to use in-house staff. Appropriate equipment would have to be purchased, and staff would have to be trained, but this can be a wise investment. This is because the fm will have the capability to clean the HVAC systems at a lower cost per hour than with an outside contractor. The fm will also have direct control over scheduling and quality of the work. Eventually, the investment in equipment and training will pay for itself.

Fms can improve the IAQ in their buildings and reduce energy consumption by maintaining clean HVAC systems. An initial inspection will provide a baseline for future comparisons. From there, a well thought out cleaning specification and a qualified contractor or in-house staff will lead to quality results for the facility.

Haugen ( is president of Vac Systems International, a Burnsville, MN-based supplier of equipment, products, and training for HVAC system inspection, cleaning, and maintenance. What HVAC cleaning strategies have you implemented to improve the quality of your facility?