Arkansas HVACR NewsMagazine March 2024

HVACR NewsMagazine March 2024

Tech News

Tying Fresh Air Ducts Directly into the Return Simply stated, tying fresh air ducts directly into the return requires special considerations at best and is a recipe for disaster at worst. It's not a good idea at all in Climate Zone 1 (think Miami, FL) due to the very high temperature and humidity. In other climates, especially the Midwestern United States, exceptionally humid shoulder seasons and cold winters pose a unique challenge. The moist outside air will come into contact with the cool surface of the duct and reach the dew point, which causes condensation on the ducts. Condensation on the inside or outside of the duct can lead to indoor air quality issues, and it can happen on ducts of any material. The number-one thing to consider about ventilation strategies is that there is not a one size-fits-all solution. There are specific climate and lifestyle factors that will affect the need for ventilation. One of those is, as mentioned earlier, the need for more advanced filtration — at least MERV 16 — when the outdoor air is laden with pollutants, such as during wildfires. Those situations are not always predictable, but systems designed with the capability to mitigate those risks will bring in higher quality air. The same applies to when we need to go into "airborne virus mode," which is when the ventilation system may need to ramp up the air changes per hour (or "air cleanings per hour") to dilute and filter out viral pollutants in the air when there are more occupants present. For that reason, it's usually advantageous to have a little bit of variability in the ventilation strategy. (And some ERVs may not have much variability, so be sure to Other Things to Consider

than you'd have with dedicated ductwork for the ERV. The downside of installing an ERV with a dedicated duct system is an increase in the cost of installation. This is especially true in retrofit applications. Exhaust-only ventilation is usually better than none at all, but it comes with a unique set of risks. If the structure is under a lot of negative pressure, then it's possible that additional exhaust ventilation could create conditions that resemble that of a blower door test. Gas fired appliances, including fireplaces, may backdraft as a result. Things like makeup air (MUA) systems can help bring in fresh air to replace exhaust air, especially in kitchens with gas-fired appliances. Kitchens are often the largest source of harmful indoor pollutants, so the need for ventilation is usually critical. Exhaust Only Ventilation

Exhaust paths also need to go one way out of the home. Recirculating things like natural gas pollutants or combustion products from a range can negatively impact the occupants' health.