Comments on: Do Airtight Houses Need Makeup Air?

By: Cindi Anderson

Cindi Anderson — Wed, 26 Apr 2023 17:43:07 +0000

In reply to Brian Cornwell. Most people say anything but the smallest house can handle the 120'ish cfm of a dryer without make-up air. I guess I will know soon when I move into mine with ACH<1.

By: Brian Cornwell

Brian Cornwell — Mon, 24 Apr 2023 21:10:00 +0000

Ditch the dryer vents and go with ventless. Makeup air is now only needed for the oven hood. I love a high CFM hood that has a varied speed. No smoke, no odors after cooking. It’s a dream. Less energy efficient, but comfort comes first.

By: Cindi

Cindi — Sat, 22 Apr 2023 21:05:59 +0000

In reply to John. I can't directly answer your question (although yes, you need to seal that into your thermal envelope). But I would be very concerned about an attic that smells. You need to figure out what is causing that because it is likely something unhealthy.

By: John

John — Fri, 21 Apr 2023 14:09:06 +0000

They do it out here in the Mountain West as well. Every home I’ve had in the last decade or more has had this type of constant exhaust fan. Never really gave it a second thought until getting this mini-split installed and having attic air leaking in. I already have an air intake for the furnace, so I wonder if I could split that and pull air in into the AC system with something like the unit you mentioned. So far it seems like just cracking a window upstairs solves the issue, providing the nose, but once our temps are 100*F, that’s going to be a less desirable solution.

By: Jacob

Jacob — Fri, 21 Apr 2023 09:20:00 +0000

In Florida open cell sprayfoam insulation is getting a lot more popular, especially in these air tight houses that custom builders like to show off to homeowners. A company I worked for always brought in make-up air (outdoor air) to make sure the sprayfoam off-gassing didn’t erode the evap coil. Was a real lifesaver.

By: Thomas Dugan

Thomas Dugan — Tue, 18 Apr 2023 20:08:32 +0000

I have read about the constant exhaust fan code for New England states. It is about the dumbest thing possible to do. Making a house go negative on purpose opens up a can of worms for air infiltration. Your house is desperately looking for a “nose” to breathe in. I design the “nose” into every house I build using a QFAMD unit from AirKing. It pulls in outdoor air at a selected CFM with programmable limitations for temperature and humidity levels outside. It uses a 6″ duct cut into a grill in the soffit or wall. My attics are all unvented so I simply bring fresh air into that space. With a vented attic, you would need to bring it into the HVAC trunking or into some part of the living space.

By: John

John — Tue, 18 Apr 2023 18:49:54 +0000

While researching an issue that I have, I stumbled upon this site, which more or less covers what I think is going on. I have a fairly new house with a constant exhaust fan. The HVAC system that was installed by the builder is whatever the minimum requirements were for it to be an HVAC system. They didn’t even add a return air vent on the second floor. All the houses in my development are like this, and this builder actually said it isn’t required because there are so many supply vents. This meant the master bedroom (upstairs) was always a good 8-10 degrees warmer. I didn’t want to run my AC at 65 at night so the first floor can be an ice box and the second floor can be a sweat box. I considered a portable AC, but felt they were too inefficient and the HOA would likely not like the window kit. I had a contractor install a Mitsubishi Mini-Split. It was a ceiling mount unit, so no unit hanging on the wall. This was supposed to be the cleanest look possible. Their install was less than satisfactory. The next day the smells from the attic permeated my bedroom. They assured me it was contained and sealed, but I could remove a panel and blown-in insulation would fall out and I could stick my hand into the attic. They came out and “sealed” it (duct tape), which did nothing. Eventually they stopped returning my calls. I went up there and used loctite and foam panels to build an air tight box around it. It obviously isn’t that air tight because I can still detect the attic smell, just not as strong. If I crack a window upstairs the smell is gone. I think the constant exhaust fan is creating negative pressure which is sucking the attic smell through whatever gaps still exist in my enclosure. Any suggestions on how I might address this? Once the temps start pushing 100 outside, I’m reluctant to leave a window open, even just a crack. Perhaps adding a fan to exhaust the box the mini-split resides in?

By: M Rokicki

M Rokicki — Thu, 13 Apr 2023 15:14:35 +0000

In reply to Cindi.

Hi, Cindi – you are of course right, as LeeH noted below. I’ll just call it a BS Urban Legend – lots of those about! The reason I love these conversations is when assumptions are challenged and corrected.

By: Cindi

Cindi — Wed, 12 Apr 2023 23:28:20 +0000

In reply to Robert Bean. Unfortunately the cheapest system with a damper, pre-heater and air filter is several thousand dollars. It's kind of insane since we already spent $30k on an ERV system. Why it can't just adjust it's other flow for the few minutes the hood is on is beyond me.

By: Cindi

Cindi — Wed, 12 Apr 2023 23:25:18 +0000

In reply to Scott Spahr. Where is your makeup air coming from?