Houston is hard on allergy sufferers. The growing season never really stops, so there's pollen all year, and our humidity keeps mold going. We also keep the windows shut and the AC running about 9 months a year. Whatever is in the indoor air just goes around and around.
Most of what moves indoor allergen levels is in the HVAC system. Below, ranked, is what works and what gets sold to allergy sufferers without doing much.
The four indoor allergens that matter most in Houston
- Dust mites. Microscopic critters that live in soft furnishings and feed on shed skin. They thrive at 70 to 80 degrees and 60 to 80 percent humidity. The allergen is their droppings, more than the mites themselves.
- Mold spores. They come from colonies in HVAC systems and bathrooms. They also grow inside walls after a leak, and in attics or on any damp surface. In Houston they're around all year.
- Pet dander. Tiny, sticky particles of skin and saliva. It works into carpet and fabric and recirculates through the HVAC.
- Pollen. It rides in on shoes and clothes and pets, then settles on the furniture. The Houston "season" runs pretty much year-round: cedar in winter, oak in spring, grass in summer and ragweed in fall.
Lever 1: Humidity, between 40 and 50 percent
Dust mites can't survive long below 50 percent relative humidity, and mold grows poorly under 60. At 45 percent, your house is hostile to two of the four big allergens.
Outdoors, Houston humidity runs 70 to 90 percent. Your AC pulls moisture out only while it is cooling, which leads to three situations.
- A correctly sized AC running long cycles keeps indoor humidity in the 45 to 55 percent range on its own. That's the goal.
- An oversized AC that short-cycles can leave a cool house sitting at 60 to 70 percent. That's the "cold and clammy" feeling.
- If a good AC still can't get you under 60 percent, you may need a whole-home dehumidifier ducted to the return.
Start with a $30 hygrometer in the living room. Check it at different times of day for a week. If it regularly reads over 55 percent, you have a humidity problem, and we can fix it.
Lever 2: Filtration that matches your ductwork
For pet dander and pollen, filtration does the heavy lifting. An allergy household should have:
- A 4-inch or 5-inch media filter (lots of surface area, low pressure drop)
- MERV 11 to 13 rating
- A properly sealed cabinet so air can't slip around the filter
- A change every 6 to 12 months
Set up that way, the filter catches most of the dander and pollen going through the air handler. Run the fan in circulation mode about 30 percent of the time and you're filtering the house continuously.
One warning. Don't jam a 1-inch MERV 13 filter into a system built for fiberglass. It chokes airflow, can ice the coil in summer and wears on the blower over time. Either retrofit a 4-inch cabinet or stay at MERV 8 to 11 in the slot you have.
Lever 3: Address the duct system
Leaky return ducts in the attic pull dusty, sometimes moldy attic air into your filtered, conditioned house. Return-side leakage is common in the systems we test, and every leak is a bypass around your filtration.
Get a duct leakage test. If leakage is high, aerosealing closes it up and cuts the dust and spores coming in through the duct path, along with pollen and dander.
Lever 4: Source control at the worst rooms
Bedrooms and basements (where there are any) usually make the most difference.
You spend 8 hours a night in the bedroom breathing the same recirculated air, so start there:
- Allergy-rated zip-up mattress and pillow encasements. $50 to $200, and they work.
- Wash bedding weekly in hot water. 130 degrees or more kills dust mites.
- Hard floors over carpet where you can. Carpet holds dust.
- A HEPA-bag vacuum, at least weekly.
- No pets on the bed if dander is a trigger.
In bathrooms and the laundry room, humidity drives mold:
- Run the bath fan during showers and for 15 minutes after.
- Replace exhaust fans that no longer move air. Lots of them are clogged with lint.
- Recaulk anywhere the caulk has gone soft or shows mold around a tub or sink.
Lever 5: HVAC system biological control
When the evaporator coil or drain pan has growth on it, every cooling cycle blows spores into the house. Growth in the ductwork does the same.
- Annual coil cleaning at the tune-up. We pull and clean it if it's accessible.
- Drain line treatment every 3 months, with vinegar or pan tablets.
- A UV-C lamp at the coil for high-risk households. It won't sterilize the air, but it keeps biofilm off the coil and pan.
- Replace flex duct that shows visible contamination. Cleaning contaminated flex rarely holds.
Lever 6: Whole-home air purification (when it makes sense)
For severe allergies or asthma, or chemical sensitivities, going past filtration helps:
- An electronic air cleaner such as Trane CleanEffects. It charges particles and collects them on cells, down to 0.3 microns, pollen and smoke included. The cells need cleaning monthly.
- A HEPA bypass cleaner, for true HEPA filtration on the whole system.
- A whole-home dehumidifier, if the house won't stay under 55 percent with a working AC. It is ducted in and runs on its own humidistat, and installed it runs $2,400 to $3,200 and up.
What doesn't help much
- Standalone ionizers. Most make ozone and do little for particulate. Some can make asthma worse.
- "Air purifying" houseplants. Not at the scale of a whole house.
- Salt lamps and Himalayan rocks. Decorative.
- Ozone generators. Don't run them in occupied spaces. Ozone is an irritant itself, and the EPA does not recommend them.
- Duct cleaning by itself. We do duct cleaning, and it helps when the ducts are dirty. If the humidity, the leaks and the coil growth aren't fixed too, the contamination comes back within months.
Working with your doctor
If you think someone in the house has an indoor allergy, get tested. An allergist can pin down dust mite, mold, dander and pollen sensitivities with skin or blood tests, and knowing exactly what you react to tells you which fixes to do first.
Bring us what the allergist tells you to avoid, and we'll work on reducing it in the house.
Cost-ranked fix list
- Hygrometer, mattress encasements and hot-wash bedding. $100 to $250. Always do these first.
- MERV 11 filter and 30 percent fan circulation. About $50 a year plus a thermostat setting.
- Annual HVAC tune-up with coil cleaning. $99, or $79 with our website coupon.
- HEPA-bag vacuum. $200 to $500 once.
- 4-inch MERV-13 media cabinet. $600 to $1,200 installed.
- Duct leakage test and aeroseal.
- UV-C lamp at the coil.
- Whole-home electronic air cleaner.
- Whole-home dehumidifier. $2,400 to $3,200 and up.
For most allergy households, the big improvement comes around step 5 or 6.
Your allergist handles the prescriptions. We handle the house. We'll check humidity, filtration and ductwork in one visit. Call 281-992-7866 or book online.