Air quality work that does something measurable

Filtration

The 1-inch fiberglass filter in most systems exists to protect the blower, not your lungs. Upgrading matters — but so does airflow. A MERV 13 filter jammed into a 1-inch slot chokes the system and can cost you more in efficiency and blower life than it gains in filtration.

Our usual recommendation is a 4- or 5-inch media cabinet at the return, MERV 11 to 13. Big surface area means low pressure drop, and you change it twice a year instead of monthly. Installed cost is typically $650 to $950 including the sheet metal work, and filters run about $45 each.

• Pets, allergies, or a wood stove nearby: media cabinet at MERV 13
• Someone in the house with asthma or COPD: media cabinet plus a dedicated room HEPA unit
• Recent remodel or drywall dust: temporary filter changes every two weeks

Humidity, both directions

Winter here runs 20 to 28% indoor relative humidity in a heated house, which is desert dry. That's the static shocks, the split hardwood, the cracked trim, and the sinus headaches. A bypass or steam humidifier plumbed into the supply and controlled by a humidistat holds you at 35 to 40%. Bypass units run $650 to $900 installed; steam units, for larger or tighter houses, run $1,400 to $2,200.

Summer is the opposite problem. If your house is cold but clammy, the AC is oversized and short cycling. The fix is usually correct sizing at replacement or a variable-speed blower — not a dehumidifier bolted on to cover the mistake. In a damp basement, a dedicated whole-basement dehumidifier draining to the sump is the right call, around $1,600 to $2,400 installed.

Duct cleaning — when it's worth it

We'll clean ducts, and we'll also tell you when not to bother. It's worth doing after a renovation, after a rodent infestation, if there was water damage or visible mold growth, or if the system ran for years with no filter at all. It is not worth doing every three years as routine, and any company that shows up with a shop vac and a $99 coupon is selling you a photo of a dirty vent, not a service.

A proper cleaning means negative-pressure vacuum on the trunk, agitation of each branch, blower and coil cleaned, and before/after photos of the same registers. Typical house runs $650 to $1,100 depending on the number of runs.

What we won't sell you

We don't install ozone generators — ozone is a lung irritant. We're skeptical of most "active" plasma and hydroxyl products; the field data doesn't support the marketing, and some produce byproducts. If you want UV, we'll install a coil-mounted lamp to keep the evaporator clean, which is a legitimate use, and we'll tell you it isn't going to sanitize your house.

Ventilation for tight houses

If your home was built after 2010 or you've had spray foam and new windows, it may be too tight to dilute indoor pollutants on its own. An ERV brings in measured fresh air and recovers most of the heat. That's a $2,200 to $3,800 install and the single biggest air quality improvement available in a tight house.