Start with the cause, not a gadget
The EPA’s guide to air cleaners puts it simply: “The most effective ways to improve your indoor air are to reduce or remove the sources of pollutants,” and filtration “does not replace the need to control pollutants and ventilate.” So before we price any add-on, we look at what’s feeding the problem: a filter that doesn’t fit its slot, a return duct pulling air out of the attic, a wet drain pan, or an AC that never runs long enough to dry the house out. Fixing one of those often does more than any device. The EPA also says plainly that air cleaners and HVAC filters can’t solve a mold problem; that takes fixing the moisture.
Whole-house media filters and MERV ratings
A whole-house filter only cleans air while the blower is running, but in a Houston summer that’s a lot of hours. The EPA recommends a filter rated “at least MERV 13 or as high as your system will accommodate,” and says most systems can take a MERV 13 filter if it’s changed often. The catch is airflow. EPA’s technical summary notes that a pleated filter has more resistance than a flat one of the same thickness, while deeper filters, 4 inches and up, spread the air over more media and limit that resistance. It also says any higher-efficiency filter has to be matched to the system it’s going into.
That’s why we don’t just jam a dense 1-inch filter into a return grille. Where the system needs it, we install a media filter cabinet (we’ve put in Honeywell and Carrier cabinets) that holds a thicker filter, such as a 20x25x4, and we check the airflow after. Your technician will tell you which rating your blower and return can handle.
UV lights for the AC coil
We’ve installed UV lights in air handlers for years. Here’s what they do well, per the EPA’s technical summary: UV aimed at the indoor coil and drain pan can keep mold and bacteria from growing on those wet surfaces, because the light hits them for hours on end. A cleaner coil also moves heat better. What the same report says about germs in moving air is far more modest: UV added to a system that already has a MERV 13 or better filter gives “only minimal infection control benefits” over the filter alone.
So we sell a coil UV light as a way to keep the coil and pan clean in a humid attic, not as a germ killer for the whole house. It doesn’t replace keeping the drain line clear, which is part of AC and heating maintenance. The EPA also notes that uncoated UV lamps can make ozone, so ask your technician which lamp goes in and when the maker says to replace it.
REME HALO in-duct air purifier
REME HALO, made by RGF, mounts in the ductwork. RGF says it “combines UVC light with an advanced catalyst” to put low levels of hydrogen peroxide and charged ions into the air, and that the current model is “CARB certified” and verified zero-ozone to the UL 2998 standard. We’re quoting the manufacturer there; RGF also makes health claims about germs and allergens that we don’t repeat.
What CARB certification means: California tests electronic air cleaners, including in-duct units since October 2020, for electrical safety and an ozone limit of 0.050 parts per million. It doesn’t rate how well a device cleans the air. The EPA says to avoid air cleaners that intentionally produce ozone, a lung irritant, and we don’t install ozone generators. RGF’s spec lists a replacement cell on a roughly two-year timer, so plan for that.
Houston humidity: keep the house under 60%
The EPA’s mold guide says to keep indoor humidity below 60%, ideally between 30% and 50%, and ENERGY STAR adds that anything above 50% may promote mold growth. Your AC is your main dehumidifier: it pulls water out of the air on the cold coil and sends it down the drain line, but only while the compressor runs.
An oversized system cools the house fast and shuts off before it has dried the air, so the thermostat reads 74°F and the house still feels sticky. Sizing is covered on our AC installation page. Two smaller things we check first: a fan left on “On” instead of “Auto,” which keeps air blowing over a wet coil after the compressor stops, and a thermostat that can’t control humidity at all (see thermostat repair and installation).
Whole-house dehumidifiers
When the AC is sized right and the house still sits above 60% in the shoulder seasons or on cool, rainy days, a whole-house dehumidifier is the next step. ENERGY STAR describes these as units “installed to use your home’s air ducts,” with the drain routed to a floor drain or condensate pump by an HVAC professional. We’ve installed them, including a 155-pint Clean Comfort unit. A dehumidifier is sized to the house, so your technician will look at the home and the existing system before recommending one.
Dust, odors and the ducts
Heavy dust that comes back days after you clean is often a duct problem, not a filter problem: a leaky return in the attic pulls in insulation dust and hot, wet air, and no filter downstream of that leak can stop it. If the ducts are the source, our air duct cleaning page explains when cleaning helps and when it doesn’t, and duct repair covers sealing and new runs. A musty smell at startup usually means moisture at the coil, drain pan or duct insulation; that’s an AC repair first.
What we don’t do
We don’t do mold remediation, and we don’t promise that a filter or purifier will cure allergies or asthma. The EPA says portable cleaners and HVAC filters “possibly” help allergy and asthma symptoms, and that the studies don’t always show major improvements. If a family member has a health condition, talk to their doctor; we’ll handle the equipment side.
Sources: EPA, Guide to Air Cleaners in the Home (2018) · EPA, Residential Air Cleaners: A Technical Summary, 3rd ed. · EPA, a brief guide to mold, moisture and your home · ENERGY STAR, dehumidifiers · California Air Resources Board, air cleaner information for consumers · RGF, REME HALO Zero product page. Checked November 2026.
