Two Questions to Ask Your HVAC Contractor If You Want Cleaner Indoor Air

Many of today’s air-cleaning furnace filters put undue stress on your HVAC system, causing it to wear prematurely, according to Eric Weiss, a technical trainer for Trane Residential. If you’re replacing or installing a furnace and clean air is a priority, there are two key questions to ask your furnace contractor that can accomplish your clean-air goals and head off costly HVAC repairs.

Don’t need a new furnace? You may be able to modify your existing one instead.

The Problem With Air-Cleaning Furnace Filters

The filter you regularly install between your return duct work and the furnace protects the blower unit, straining out debris that can damage the fan or cause it to wear prematurely. That’s a good thing. However, as homes become tighter and more energy-efficient, they also prevent indoor air from turning over, causing indoor air quality to suffer. Enter air-cleaning furnace filters, specially designed to catch dust and minute particles, essentially turning your HVAC system into a massive air purifier.

The “good, better, best” marketing of these filters describes their varying ability to filter out the tiniest of particles — the lower the MERV value, the less efficient the filter. But it doesn’t at all reflect their ability to protect the blower, which is their original and primary job.

What’s more, your HVAC system is tuned to specific pressure levels based on the low resistance of the basic filter specified by the manufacturer. A more restrictive air-cleaning furnace filter causes the blower to work harder to move the same amount of air. That in turn generates more heat, which the filter also helps to retain, sapping life from the system’s moving parts.

The good news, Weiss says, is that you can make these air-cleaning filters work seamlessly with your blower.

Installation Asks

The best and most cost-effective solution lies in making adjustments during a new installation or replacement. Weiss says that as long as the space around the furnace allows the modifications, they should only cost a few hundred dollars extra. For comparison, a new blower might run you in the $500 to $700 range, on top of the headache of it failing at an inopportune time. (Reminder: They’re always inopportune times.)

Your contractor can help determine if either or both of these adaptations provides enough airflow to keep your furnace blower humming along happily while the filter pulls double-duty, protecting your investment and cleaning your home’s air.

Question 1: Can You Increase the Filter Area?

Weiss’ first solution involves increasing the filtration area by creating space for a second air-cleaning filter, which allows more air to reach the blower. Accomplish this in one of two ways:

• Add ductwork that can accommodate a second filter adjacent to, but apart from, the furnace.
• Cut space for a second filter on a side of the housing adjacent to the first, or even below the blower housing.

Question 2: Is There Room for a Thicker Filter?

Weiss recommends ensuring there’s enough space for a high-quality five-inch pleated air-cleaning filter, which is comparable to having 10 of the cheap, flat filters working simultaneously. This may involve slightly modifying the ductwork and installing a frame that can accommodate the thicker filter.

Existing Furnace Solutions

While it’s much easier to make the above modifications during installation, you can also see if either or both can be made to your existing furnace.

If you’re lucky, you have a horizontal furnace installation, common in crawl spaces and attics. These usually have more room surrounding the housing, and the orientation allows the modifications without major adjustments and additional parts. You could get the helpful filter-area adjustments made for as little as a few hundred dollars.

If you have an upflow furnace installation, common in basements and closets, there may be less space. Then the modifications may require cutting lines and recovering the refrigerant, likely costing more than $1,000 in parts and labor.

At the least, always choose the thickest pleated furnace filter that your existing filter slot will accommodate.