HVAC and Filtration Best Practices for Healthy Home

This blog expands on an earlier post about the 25 Principles of Building Biology and the Healthy Home Standard Checklist. Here we’ll dive deeper into the Indoor Air Quality Checklist, and focus on best practices for Heating, Cooling and Ventilating a healthy building. “HVAC and Filtration Best Practices for Healthy Home” is part 2 of 3 from the IAQ Checklist.

Moving beyond a solid foundation, let’s dive into what Building Biologists thought were the most important IAQ elements of a healthy HVAC system.

Heating, Cooling and Ventilating a Healthy Home

• For heating use radiant heat, such as radiators, baseboards, or in-floor/walls systems.
• If there is forced air system with AC, the AC system is properly sized for the space based on calculations. Any good HVAC designer or contractor should be able to provide specifications and calculations to claim credit. (GreenPoint Rated has good credit requirements for this.)

Manual J and D – HVAC Load Calcs and Duct Sizing

• The forced air unit (FAU), ducting, and ventilation system are not located in the crawl space.

Ducts in Crawlspace – Bad IAQ. We find this more than you’d like to imagine…

• If there is ductwork installed, ductwork is not located in exterior walls or in or under a concrete slab.
• If there is mechanical HVAC, use metal boxes. Duct seams, end caps, round duct starting collars, plenum to FAU interfaces are sealed with low-VOC mastic.
• If there is forced air do not use unlined wall cavities as return air plenums or for supply air.

Wall Cavity for Duct – Bad Practice for Several Reasons.

• If there is ducting there should be no fiberglass exposed to the air stream in the air handling unit (AHU) or ductwork.
• FAU fan compartment doors have a gasket (taping is not desirable as it will likely be removed and not reinstalled as the years pass.)
• If there is a heating or air-conditioning or ventilation system is in the attic, the FAU and ductwork have been inspected with a thermal imaging camera for leaks, hot spots and improper seals and repairs to leaks have been made.
• If ductwork is installed for heating or cooling or ventilation system, a duct blaster inspection was performed to pressure check the ductwork before closing up wall and ceiling cavities.   Leaks were repaired as identified.
• If new construction, the HVAC or the ventilation system delivery and return openings were sealed with plastic during construction and the system was not used for heating or cooling during construction.
• If new construction, all air filters were changed out upon the completion building and before occupancy.

Best Practices for Ventilation and Filtration

• An HRV/ERV outdoor air exchange system is installed for ventilation per ASHARE 62.  In humid climates the humidity should be taken out of the air as it enters using an energy recovery ventilator (ERV).  In very cold climates and/or drier climates, use a heat recovery ventilator (HRV)

Heat Recovery Ventilator – HRV

• A low-sone Kitchen range hood is exhausted to outside. (LEED for Homes requires a minimum of 100 cfm fan. For defining “low sone,” I’d defer to Energy Star Guidelines for Sone Ratings:

Energy Star Low Sone Guidelines

• HRV/ERV is designed for adequate make-up air to prevent negative pressure and the potential for back drafting of gas appliance.
• Use a air filter with a minimum of MERV 10 filtration rating in the air handler and or the HRV/ERV. (LEED-H requires a minimum of MERV 8, and gives one point for MERV 10 and three points for MERV 13 or above.)

HVAC and Filtration Best Practices for Healthy Home

This blog covers a handful of HVAC and Filtration Best Practices for Healthy Home, but I’d recommend reviewing GreenPoint Rated and LEED for Homes (LEED-H) for additional ideas. In general the Healthy Home Standard incorporates common “green building” measures, AND then adds additional layers of protection for occupant health. But don’t take my word for it – dig in yourself!

It takes time to research and familiarize yourself with best practices. But we’ve already done the homework… so I suppose that’s why we’ve got good job security and a growing business!