Arkansas HVACR NewsMagazine March 2024

HVACR NewsMagazine March 2024

Tech News

know the equipment you're installing.) MERV 16 or better filtration is also important for removing contaminants from the airstream. However, that brings us to the conversation of simple vs. complex. The verdict is that it really depends on the customer. Some contractors know that they will need to install as simple of a system as possible — like an outdoor duct with a damper instead of a full-blown ERV — because customers may not be willing to maintain units like ERVs. You will need to discuss the maintenance needs with your client to see where they stand. That conversation will help you determine if a simple or more complex solution will be better for their specific needs. When we're thinking about ventilation in a structure, we'll need to consider the use of space to install the equipment properly. Is there room for an ERV? Will we get a relatively straight run of ductwork? If you were to put in a ventilating dehumidifier, how would you route that drain? Can you run it in such a way that it drains out to a safe location while following local codes? Many of these design-specific considerations will be easier to address in new constructions. They can be quite a challenge if you want to apply a ventilation strategy to an existing home that wasn't designed with ventilation equipment in mind. In some existing homes, it may be easiest to approach the need for ventilation by running the bath fans and assessing the needs from there. Air circulation is also an important design factor, especially in high-performance homes (especially those with mini-splits and in cases where the air handler or furnace doesn't run at night). Bedrooms with closed doors will have naturally high CO2 levels in cases where Design-Specific Considerations

the HVAC doesn't run and circulate the air, which isn't ideal for occupant health. You can also identify the problem you aim to solve using the "four Ps" of building science; you have an IAQ problem when you have p eople, p ollutants, p athways, and p ressure. The interesting part about the four Ps is that you can solve most problems by taking away just one of those "P" components. (Neil Comparetto wrote a great tech tip about these four Ps HERE.) Corbett approaches ventilation system design with the 4-3-2-1 method: four elements, three improvements, two systems, and one goal. Infiltration, or air that enters a space uncontrolled, is another aspect of ventilation that we ought to think about. We should be aware of infiltration and monitor it (to the best of our abilities) before making decisions to address it. That said, we can take credit for it in single family homes. (ASHRAE Standard 62.2 allows you to do so if you perform a blower door test. You can't take credit for infiltration by doing a blower door test in multi-family homes.) But just because we can doesn't necessarily mean it's the best decision. Moreover, the credit may not amount to very much if there's already an operable ventilation system in use. There is no perfect ventilation strategy for every situation, though some degree of modulation and flexibility will always be advantageous, regardless of the device you use to bring in or exhaust air (bath fans, ERVs, etc.). Ventilation also heavily depends on air pressures when we're not relying on powered fans to move the air. We ought to be especially careful of home pressures when it comes to Taking Credit for Infiltration Conclusion