Feedback For The Week: 08/19/2002

IAQ Begins With Builders

I am a home inspector who does not install or service HVAC systems, but I look at them every day. Being in North Carolina, 99.9% of the homes here have forced-air systems, and probably better than half of them are in crawl spaces. I look at older systems that are extremely leaky, dirty, and quite moldy. I also look at a lot of newly installed systems.

Most of the new systems today are well sealed. However, many of the systems are still quite leaky on the return side of the systems, allowing dirt, mold, and moisture to be drawn into the system.

I feel little fault lies with the HVAC mechanics who install the systems, but the greater source of system contamination lies with the builders. The builders allow all kinds of drywall dust, sawdust, and paint debris to be drawn through the system during construction because they use the systems prior to occupancy to keep their workers warm or cool during winter and summer months.

If it were possible to seal off the returns, registers, and air-handling equipment until the home was completed and cleaned for move-in condition, there could be no blame on heating contractors or builders for contamination of the environmental air within the home. After that, it is the homeowner’s responsibility to maintain proper filtering, using quality higher-efficiency filters and having their systems serviced as per the heating contractor’s recommendations.

Jim Hussey said it best — “The single biggest contributor to the forced-air/mold problem is inadequate filtration and inferior return-air systems. Forced-air systems that have leaking return systems or bare wood return plenums, introduce negative pressure into wall cavities that subsequently draw exterior moisture/ humidity through failed vapor barriers.”

Many installers down here supply systems with moisture by allowing auxiliary condensate drip trays to remain plugged and not installing the auxiliary drains to drain the tray should the main drains become obstructed. Instead, the condensate water overspills the tray within the cabinet, wetting the insulation and leaking out wherever the water can find a hole.

I feel Mr. May is not trying to tell everyone to remove their forced-air systems, but to be aware of how easily they can contribute to spreading bioaeresols throughout the home if not well sealed, cleaned, properly filtered, and maintained by a professional heating contractor on a regular basis, which too few homeowners do.

Ed Gerhardt, Surelock Homes, Inc., Home Inspections, Chapel Hill, NC

Numerous Variables

I started my career in HVAC air filtration in 1984 and got actively involved in the IAQ field in 1988. I am a National Air Filtration Association (NAFA) Certified Air Filter Specialist (CAFS) and certified by the National Balancing Institute (NBI) for testing, adjusting, and balancing (TAB) HVAC systems for residential and commercial applications up to 40 tons.

Regarding comments made by the individuals for forced-air systems and contaminants, several issues must also be addressed:

1. Total cubic feet per minute (CFM) of supply air;

2. Air changes per hour (ACH);

3. Air filtration efficiency;

4. Ventilation effectiveness;

5. Temperature and relative humidity;

6. Construction materials used in the home; and

7. What contaminants are being generated in the home, etc.

There are so many variables in determining what is acceptable HVAC. Each application requires various attention to details. It is very hard to support blanket statements that are being made about these issues. We have standards and guidelines. However, each application should be considered on an “as per” basis. One must also consider taking into account the occupants and their sensitivities as well.

Stephen W. Nicholas, CAFS, President, Air Industries, Inc., North Andover, MA

Publication date: 08/19/2002