Blog
Fresh air intake duct and whole system air purifier – GreenBuildingAdvisor
Above is a picture of my current attic with my furnace as well as a basic diagram of my plan for visualization.
House details:
-
Two-story house, approximately 2,500 sq ft, built in 2007. Definitely not air tight.
-
Existing (basically brand new, installed less than 2 years ago) Lennox 5-ton furnace/air handler located in the attic.
Project goals:
-
Introduce a controlled fresh air intake to reduce indoor CO₂ levels and improve air freshness without opening windows.
-
Install a whole-home Lennox PureAir purification system to filter and purify all incoming and recirculated air.
Fresh air intake requirements:
-
Install a dedicated fresh-air duct (approx. 6″ diameter), pulling outdoor air into the return plenum of my attic furnace.
-
Include a motorized damper (e.g., Honeywell ARD series) to control the intake airflow.
-
Add an inline filter box (MERV 11–13) on the fresh-air duct to pre-filter outdoor air before it enters the system.
Purification system requirements:
-
Install a Lennox PureAir system (e.g., PCO3-20-16) at the furnace return to handle both recirculated and fresh intake air.
-
Integrate the fresh-air intake so that all air is filtered through the PureAir system before supply distribution.
Automation:
-
Connect the motorized damper to a smart relay (e.g., Shelly Plus 1) to allow future automation (such as controlling the damper based on CO₂ levels or schedules).
I can use my existing kitchen hood (1100 CFM) manually for big, quick flushes (like heavy cooking or after gatherings). Also I plan to upgrade bathroom and laundry fans to smart switches, then automate them to help exhaust air out.
In mild SoCal weather, a fresh-air intake duct with Lennox PureAir seems more practical than a dedicated ERV/HRV because there’s 1) no need for heat or moisture exchange, 2) much simpler to install and maintain, 3) less costly up front and long term, 4) seems like current plan will work perfectly with my existing HVAC system while still achieves goal of lower CO₂ and better air quality.
Wanted to get the input from the experts here and get feedback on my plan. Is this practical and possible for my situation? Any critique or suggestions?
Thanks and much appreciated!