house air cleaner.... le sigh

[Ryan Brucks]

I've been upgrading my shop DC capabilities, and now my shop air is more often cleaner than my house air. Wife and daughter have random respiritory issues so I have been thinking of what I can do to improve the indoor air quality.

Had a HVAC guy over this morning for a quote on installing some sort of whole house air cleaner. I honestly don't know much about the options here, so just wanted to talk to someone to get the ball rolling. Wanted to bounce what he said off here, since the guy seemed pretty.... shall we say "derp"?

First thing he says, is my floor vents are sucking up crawlspace dust via venturi effect, and I should get all my ducts sealed... $800. OK... crawlspace is pretty dusty I know (I have to change water filter down there)... thinking maybe at this point...


Then we stalked about whole house filtration. I was curious about the kind where you modify the house's ducting to adding an Active intake that puts the house under constant positive pressure with all intake going through HEPA filter. He said this option would be north of $5k.

Then he said he usually installs Honeywell inline HEPAs. I have two HVAC systems, he quoted me ~1800 for one installed, 3k for both systems.

Now here's the "derp" part.

I started asking specifics about what level of filtration was required here, and he said:

"Air molecules are around 3 microns so if you go any finer than that you get no airflow"

OK, obviously this guy doesn't know what he's talking about. The honeywell units he is describing are indeed HEPA so I'm not worried about that... but I am a bit worried about getting anything installed by someone with such a basic lack of understanding of the mechanical sizes involved..


Am I being over critical, or would this be a non-starter for you?
And what do you guys think on those prices? He made sure to remind me how much work sealing all the ducts would be... never care for the hard sell myself.

[paul cottingham]

I don't know if you have already done this, but I would read user reviews of the hepa systems. I have a heat pump, and the company I bought it from recommended against the hepa system, as they have had too many complaints about it. Apparently other installers in this area feel the same way.
As for the installer, if you were talking to a woodworker with that kind of knowledge gap about something that basic, how would you feel?
Its a tough call.

[Don Jarvie]

You can have an electric air cleaner installed right before the return meets the furnace. It will zap the dust particles so you don't need to keep changing a filter. If your game enough you can seal all your vent pipes yourself.

If you want to see how bad the Venturi effect is get a HEPA furnace filter and put it over the floor vent. You'll get to see what's coming though the vents.

[Steve Meliza]

About a year ago we had a guy out to clean our heating ducts and he pointed out the gaps around the floor vents that would allow air to be pulled into the house from the crawl space. I believe that he would have charged $100 for our 6 floor vents, but told my wife (I was at work) that I could easily get a tube a caulk and do it myself so that is what I did. $800 sounds right if you've got about 50 floor vents in the first floor of your house. I think a second estimate is in order.

[Ryan Brucks]

Thanks. I have someone else meeting me tonight. Interestingly, I asked the 1st guy if it was just caulk and he said no it was something special... but didn't tell me what it was?! That combined with his 3 micron air molecule seem to say move on....

Also I am now learning that in NC, in order to put the house under constant positive pressure, an ERV is basically mandatory or you get high humidity inside. Based on the research I have done, putting the house under positive pressure is more effective than the filtration itself, especially since I have 5 dogs and 30 chickens which make a hell of a dust cloud on our back porch all the time.