Damn is it dusty in here
April 10, 2016 5:40 PM   Subscribe

No, that's not a euphemism for crying. It really is very dusty in my house. Is running the HVAC fan 24 x 7 a smart way to reduce dust?

While cleaning today we noticed that it is really damn dusty in our house (2 story colonial built in 2002). In fact, after dusting the 22 ft walls in our 2-story family room the dust was so thick I could literally see it in the air. I had an idea that turning on the HVAC fan would recycle the air in the house and catch all that dust in the filter before it settled onto the carpet and floors. It worked surprisingly well, so now I'm wondering if running the HVAC fan all the time might not help keep the house less dusty. If so, what are the pros and cons?
posted by COD to Home & Garden (15 answers total) 4 users marked this as a favorite
Your HVAC blower motors are probably not rated for long duty cycles. They will need frequent maintenance checks much more often than "normal" use.

You'll also have to clean/change your filter every 30 days or so. But the blower duty cycle wear and tear is what'll get you.

Experience: wife suffers from MS and we live in a SoCal valley, which basically means cooling has to be on from June through November. Every year something fails during August, no matter what we do.
posted by infinitewindow at 5:45 PM on April 10, 2016 [1 favorite]

Sure, it works. I'd take a good look at the power consumption of the fan. Some use a lot more power than others and it can really add up when you run it 24/7. If yours isn't an ECM fan, replace it with one. The lower quality, less efficient fan is also more likely to burn out sooner.

You'll want to look at the filter too. Is it capturing dust down to small particle sizes effectively? Does it clog up really fast? I know that some people who design systems for this use prefer the bag-style filters as they have less resistance to airflow, are very effective, and last a long time without clogging.
posted by ssg at 5:46 PM on April 10, 2016

It makes a huge difference for the level of dust in our house whether we're using regular filters, or the "allergy" ones. They don't have to be the highest-rated ones (and in fact, the higher the rating, the more frequently they have to be switched and the more they cut down on your air flow). The lowest rating ones that catch dust mites is what I buy.
posted by BrashTech at 5:55 PM on April 10, 2016 [1 favorite]

The blower motor will die a lot faster if it's running constantly, but in my experience setting the system to "auto" with the temperature set to whatever it is outside should cause the thing to turn on and off frequently enough to keep the dust levels down, and the motor lasts as long as anyone says they're supposed to.

I also have to switch my filters out every thirty days, but I have asthma and my symptoms are aggravated way before the system starts functioning badly.
posted by SMPA at 6:02 PM on April 10, 2016

It would probably be cheaper in the long run to invest in an air purifier.
posted by cecic at 6:09 PM on April 10, 2016 [1 favorite]

My HVAC maintenance guy advised against using the heavy HEPA-like filters in the furnace unit. The blower motor works too hard to pull air through it and will wear out quicker. He says the cheap blue fiberglass filter works best.

If you want to clean the air, then either invest in a whole-house air cleaning system attached to the HVAC (like an electrostatic air cleaner), or use some tabletop HEPA units in various strategic places in your home.
posted by JoeZydeco at 7:31 PM on April 10, 2016

JoeZydeco: " He says the cheap blue fiberglass filter works best. "

The cheap blue filters work best at protecting the HVAC equipment (or at least they are sufficient to prevent evaporator coils from clogging); they are going to be the worst at cleaning the air of particulates.

COD: "I'm wondering if running the HVAC fan all the time might not help keep the house less dusty. If so, what are the pros and cons?"

If you had a decent filter then the HVAC system will be effective at reducing the dust in your house. The big con from my way of thinking is the power draw of the motor. Even though your blower motor is a fractional horsepower motor it's still drawing power when running. EG: A 1/4 horse fan motor is going to draw maybe 200-250W depending on efficiency. Or a Kilowatt/hour every 4-5 hours. Depending on your electrical rates you could be looking at 5-10 dollars a day to run the motor. In the summer if you have A/C you would also be adding those watts to the heat load that has to be dumped by your condenser incurring additional cost.

It could be a lot less though. Many modern furnaces have variable speed motors that draw much less power at their lower settings. Said lower settings would probably be sufficient for air cleaning.
posted by Mitheral at 8:39 PM on April 10, 2016

A 200-250 watt motor definitely does not use $5-$10 of electricity per day. That should be $0.50-$1, I assume.
posted by ssg at 9:35 PM on April 10, 2016 [1 favorite]

Ugh, your right I slipped a decimal some place (damn it, I even double checked because I always have trouble anytime kilowatthours are involved)

For the record: State electrical prices last year varied from an average of 8.13 cents per kilowatthour in Washington to 33.08 cents per kilowatthour in Hawaii. A motor consuming 250 watts and running 24 hours a day in Hawaii would cost .3308 X 6 kilowatthours per day or merely $1.98 per day. In Washington it would be 49 cents per day. US Average was 12.01 cents per kilowatthour. I think that's sans tax.

TL; DR: Down side only 1/10 as down as originally stated.

PS: Dang Americans generally have expensive power.
posted by Mitheral at 9:56 PM on April 10, 2016

I've heard/read people rave about attaching a filter to a box fan. Apparently the cost effectiveness is high. But I haven't tested this myself.

I've also researched air filters, and the following have been recommended highly:

- RabbitAir MinusA2
- IQAir HealthPro Plus
- Blueair Air Purifiers

I happen to own one of each. The RabbitAir is the best overall and is the sleekest. The IQAir seems to have the most purifying power (at the cost of a ton of noise on higher settings, and requires a lot of space).

If you're optimizing on air purity I'd recommend the IQAir HealthPro Plus, leave it on its max setting while you're out of the house.
posted by reeddavid at 11:30 PM on April 10, 2016 [1 favorite]

This might be self-evident but just in case- do you dust with a wet or dry cloth? Dusting with a dry cloth or any kind of fluffer just raises the dust right back into the air, where it'll make you sneeze and then land on your stuff all over again. To actually get rid of it, dust needs to be wet, so use a damp cloth to dust, which you can then discard or rinse.
posted by pseudostrabismus at 11:33 PM on April 10, 2016 [2 favorites]

Our three year old furnace has a variable speed blower and I've been told to let it do its variable speed thing 24/7 with a decent allergy filter. I think it helps a lot and it uses a lot less energy than the 20 year old furnace it replaced. That furnace is set on auto fan so it did power cycle the fan.
posted by advicepig at 6:39 AM on April 11, 2016

Our thermostats are fancy schmancy and allow for programming a custom cycle. We run the blower for about 20 mins/hour to circulate the air. We also invested in a high quality BAGGED vacuum and I use the hose attachment to dust everything and then follow the vacuum dusting with a microfiber cloth.

Another thing to look at is if your walls are sealed down to the floor. When your a/c runs it creates a draw from the house. If the walls are not sealed to the floor then you're going to draw air from inside the walls which are open to the attic space. This will cause a lot of dust and particulates to enter into the house. My house was also built during the boom of 2002, so it wasn't, um, the best construction. When we moved in I used expanding foam to close the gap between the floor and the baseboard (once the carpet was pulled out) and then used quarter trim to seal it up. Then laid the new carpet. Just a thought.
posted by PorcineWithMe at 7:14 AM on April 11, 2016

For REASONS, I got rid of all books, magazines and upholstered furniture. An unintended and unexpected consequence was that dust went way down.

You don't have to go that extreme to see a benefit. You might try staying more on top of junk mail, cleaning out closets and donating/selling stuff, etc.

In addition to upgrading the filters, which does help, you can try cleaning the ducting more frequently. My mother was a serious hausfrau and she was hell on wheels about this stuff. Cleaning the duct work and so forth helps a bunch.
posted by Michele in California at 10:59 AM on April 11, 2016

Maybe you can open some windows before you begin dusting, and leave them open until the dust settles (30-60 minutes?). It sounds like the HVAC blower isn't meant to be left on all the time and might wear out. Maybe a combo of open windows and HVAC blower while dusting for extra help.
posted by serenity_now at 2:00 PM on April 12, 2016

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