Strengthening the “V” in HVAC
Heating, ventilation and air conditioning (HVAC) systems are often sold with slogans that revolve around comfort. You might hear, “Comfort, it’s what we do best” or “You’re always comfortable with us.” Unfortunately, these catchphrases omit an integral part–and one quarter of the initialism–of understanding a proper HVAC system: ventilation.
We focus our efforts on delivering comfort and forget that good indoor air quality is part of our job. This lack of representation is also found in most HVAC technician education and residential state license exams. Gone are the days of just providing heating and cooling. To stay in the comfort business, we must learn new building materials, code changes and above-code program standards that include installing ventilation in homes that used to breathe on their own. What do we do now? With ventilation a key component to comfort and safety in all HVAC systems, we need to promote it to the same extent as its surrounding letters.
Most technical education institutions focus on the fundamentals of electrical systems, gas characteristics and air properties as well as troubleshooting system components. And for good reason. If a 6-year-old comfort system is not operating, the problem is likely unrelated to the ventilation system, and the diagnostic will center on what changed since yesterday. Little or no time is spent on ventilation calculations or design because it will typically not be needed to repair the system. However, sometimes ventilation is needed.
Residential state license exams also have reasons for not testing on the subject. Their focus tends to be on proper gas line sizing, manuals needed for correct system sizing or legal matters, such as how much time you have to renew your license if it expires. The goal is to cover topics dealing with safety and administration questions. If any emphasis is placed on ventilation calculations, systems or components, it is brief. In addition, some states don’t mandate that HVAC contractors attend continuing education classes to maintain their mechanical license. This can quickly lead to a situation in which adopting new building codes requires us to design and install ventilation systems, and in most cases, we are unprepared to do so.
Today’s HVAC contractor is responsible for far more regarding ventilation than previous generations for two reasons: tighter buildings and indoor air quality. With new building materials, techniques and above-code programs, buildings are becoming tighter. As these homes are no longer able to “breathe” on their own, smells, excess moisture and contaminants (in the form of volatile organic compounds, particulates and other ingredients) may build up inside.
Left unaddressed, these issues can lead to comfort complaints such as “sick home syndrome.” Because of this, national above-code programs like ENERGY STAR® and Environments for Living® not only make the installation of ventilation mandatory but also require documentation to prove it and detail the type, location, rate, frequency and duration used.
Considerations such as climate zone should also be included because it can influence the effectiveness of a ventilation strategy (e.g., positive pressure, negative pressure, balanced). For instance, exhaust-only ventilation is not recommended for hot-humid climates because raw-humid outdoor air may contribute to indoor moisture problems due to the house being under a negative pressure. Supply-only ventilation is not recommended in cold climates because humidity in the indoor air may lead to moisture problems inside exterior walls due to the house being under a positive pressure. Balanced ventilation may be skipped in any climate because it may be more expensive to install. If you are unfamiliar with the requirements, the calculations, considerations and paperwork for a design can be exhausting and time consuming.
The American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) created the calculations for determining the minimum ventilation rate needed in a home. Currently, there are two standards to follow: ASHRAE 62.2-2009 or ASHRAE 62.2-2012. These calculations are not only different, but the 2012 version provides optional ‘’ventilation credits’’ for having certain items in a room, such as an operable window. While this is great for flexibility, it can become a mathematical nightmare in practice.
After the strategy is chosen and the correct ventilation CFM is determined, most of the paperwork is completed. Unfortunately, our job is not done. We now begin the design phase. We must install a one-of-a-kind ventilation system to deliver the needed rate consistently and reliably while keeping in mind access to filters, ventilation inlet locations and construction. With the large number of products and controls available, it can be difficult to decide which one is best for a project.
Tools from Residential Energy Dynamics and Heyoka Solutions can help strengthen the “V” in HVAC. They have been designed from the ground up to be essential for any tradesman who requires a ventilation strategy that meets either ASHRAE standard with a few simple clicks. They provide the needed CFM and can assist in selecting equipment and compatible controls to meet your ventilation requirements. Finally, with additional features such as duct sizing and report generation compliant with all efficiency programs, they can quickly become an instrument to use daily.