And now, a word (or acronym) from your friendly filter

I’ve come to understand newspaper editors don’t like acronyms. But when writing a column about ventilation and air filtration, they save a lot of space and it’s hard to avoid them. At the top of the list is ASHRAE, which stands for the American Society of Heating, Refrigerating and Air-Conditioning Engineers. Around since 1894, they are the original building scientists. Their word is gold.

Last week’s column offered a cheap alternative for air filtration in homes in which ASHRAE has no business, as those dwellings get heated by tubes of hot water embedded in concrete slabs. They’re installed by plumbers, not heating, ventilation and air conditioning technicians. HVAC people follow ASHRAE rules.

ASHRAE is so respected it’s referenced by the U.S. Centers for Disease Control and Prevention. The CDC recently issued guidelines for ventilation and suggested a MERV 13 filter can capture most of the airborne particles that viruses cling to as they float around. MERV stands for minimum efficiency reporting value. The bigger the number, the better.

While in-floor radiant heat has strong market penetration in Santa Fe, the vast majority of homes, including every manufactured home ever built, have forcedair heating. Some even have forced-air cooling, but those are rare in Santa Fe. What all have in common is an air filter.

What also is common is virtually none have MERV 13 filters in place, yet all could. Before rushing out to buy one, a few words of caution. First thing: Find the filter in your furnace. Or maybe even find the furnace. Changing a filter is the simplest and most ignored DIY (do-it-yourself ) home improvement task one can do.

If you are a renter, it’s not your landlord’s job. Find the filter and figure out how to remove it and which way the air flows in the furnace. If the dimensions are not completely covered by dust and furballs, write them down for future reference. Also note how deep the space is where the filter slides.

The reason there’s not much point in rushing out to buy a new MERV 13 is you’ll wind up standing in line outside a big-box store only to get in and find they don’t have your size in stock. There will be plenty of the kind you just removed, which is undoubtedly

the cheapest and least effective filter available, the same kind everybody buys.

An HVAC professional will correctly note that a MERV 13 filter or higher reduces airflow, puts more strain on furnace motors and diminishes the volume of air coming out room registers. All true — but a small price to pay for cleaner air. Plus, the cheapo filter just removed with an inch of dusty pet hair was probably more restrictive than a fresh new MERV 13. Your furnace may thank you.

One way to mitigate the strain is to order a deeper MERV 13 filter, like 2 inches deep instead of the standard one-inch variety. Online ordering is the only way to get the right size and the right depth, but that’s part of the pandemic protocol these days. Most retailers offer bundles, which is cost-effective and will allow you to change the filter more frequently.

It’s counterintuitive that a deeper filter creates less strain, but there’s twice the surface area for the air to flow through, which means half the strain. That’s why noting the depth of the filter tray in the furnace is important. Fourinch deep MERV 13s can be found, but they might not fit.

Turns out Santa Fe building snobs sneering at forced-air heating for decades now might be wishing improving their indoor air quality was as simple as changing a furnace filter.