No exhaust fans, moisture drawn out through HVAC into air exchange?

5 years ago

A house that I'm currently working on purchasing does not have exhaust fans in the bathrooms. Two are on the second floor and are along exterior walls, and one is in the middle of the basement. According to the inspector, each bathroom has a small vent on the wall near the ceiling that is somehow connected to the HVAC system. He said that you flip some switch, which does something that ultimately draws the moisture out of the bathroom and ultimately into the air exchange system. This was, apparently, code for a brief period of time in the early 2000s.

Is this something to be concerned about? Should I proceed with purchasing the home? Am I going to want to install traditional exhaust fans to vent steam directly outside, and if so, 1) what might this cost, and 2) should I negotiate the installation of such or perhaps a reduced price into the purchase agreement?

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Comments (6)

mike_home
5 years ago
Did the inspector say if the bathroom vents are supply or return vents? In either case they are allowed by code. I am not confident this inspector has given you a correct explanation of what he has found. If you are concerned you should hire an HVAC contractor to do an assessment.

When I installed exhaust ceiling fans when I renovated my bathrooms 10 years ago. Neither had exhausts vents since each bathroom has a window. It is difficult to estimate how much it will cost. In my case each vent went installed up through the attic and roof deck.
Brad Smith
5 years ago
Our recently-demised house had an HRV system, as will the new build. In our area, it's commonly set up with the intake vents in each bathroom and one in or near the kitchen and/or laundry room (ours was the latter).

The intent was to draw the moist air from those rooms and vent to outdoors, but in a way that recovered the heat and heated (or cooled) the incoming fresh air to the system, which itself was then sent into the HVAC, directly or indirectly depending on your precise install.

What you describe sounds similar. Some models, like our old one, just runs constantly. Others run at low speed, or off, and then can be switched or use a humidistat to ramp up the fans. The switch would typically activate a timer.

It's unfortunate your inspector wasn't a bit clearer, because in addition to you knowing the ducts are there, it'd be nice to know they're actually connected to some active device.
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Can you run the exhaust duct vertical up into the attic, then horizontally out the side gable wall? With a long run, you can install a remote inline fan in the attic itself. The bathroom will simply have the ventilation grate in the ceiling. Check out Fantech fans. Do not vent the fan directly into the attic space, even if the attic is open to free air. Bad, bad, bad. As far as the HVAC portion, it can depend. Plumbing is rigid and waste pipes have to be set to a specific pitch for drainage. I'm not a big fan of flex HVAC, but there are times when its use makes sense. So prioritize. 'Larger" and "more rigid" and things that need to be set at a proper pitch (waste pipes, for example) get to be set first. "Smaller" and "more flexible" get set last. Sometimes the depth or width of your joist bays will allow them to coexist in the same space. I think you know what has to be done and you're simply asking for confirmation. You're on the right path. Draw out your floor framing with joists and joist bay spaces. Superimpose the location of your plumbing fixtures over that. Then draw in your rigid waste lines which have to be pitched for drainage. Then your HVAC as needed if it's rigid duct. You have more flexibility with flexible duct (sorry). Plumbing supply is small diameter and can normally be routed around things. Copper is rigid, PEX can waffle here and there but needs more support. Soft electrical can go anywhere and gets what space is left over.
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Much has been written on your very problem and it can get quite complex. I'll just be general on the topic but I think you'll get the idea.....At minimum, a building should have 4 complete air exchanges per day to be healthy. Public buildings are required to have air exchange systems installed in my area. This of course means you will also have to condition that air which is counter-productive to high efficiency equipment. Older homes that leaked air didn't have the poor air quality that newer leak tight homes have. Think about it, just about every material now days is either from oil based products or, covered with them. Oil evaporates. When you clean the inside of the windshield on your car, that brown stuff that everyone calls nicotine is actually an oil film from the plastics in the car, evaporating. That's why dash boards in an older car eventually have cracks in them, the seats also. They are dried out i.e. the oil has evaporated from them. In your home, the carpeting, the sealant on hardwood floors, stain on furniture and so on, all these things add up to a poor air quality. Then there is dust (mostly dead skin cells) and no matter what you do, there is a certain amount of mold in the air. So everyone is breathing that stuff. Some are allergic to some of these things or at minimum, irritated. Also, when the heat comes on and dries the air, it also dries the mucous in the nasal cavities. This mucous is the body's first line defense mechanism to capture airborne germs and irritants. So in an air tight environment where the air gets stale, people just keep passing airborne germs and bacteria around, generally new ones they bring home from school or, you bring home from work. These things appear to be contributing to higher instances of asthma reactions also. So from the monetary side, you save money on utilities in air tight homes with efficient equipment but if you are sensitive to the stale air, you lose that money savings in medical expenses, even if only cough syrup, aspirin, Kleenex or prescriptions and doctor visits. You can minimize some of the problems by exchanging with fresh air, proper filters, proper relative humidity and of course hygiene.
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I agree, talk to a good HVAC contractor. Finding the good ones is the key point. I'd question if what you are asking for makes sense for your house (how new and how tightly, or not. is your home sealed). Do you want unheated/unconditioned air coming directly into your kitchen, do you want to stand under that supply of air when it is 32 degrees outside? Qualifier: I'm not familiar with Fantech products. What is used in newer, well sealed homes are devices knows as HRV or ERV (Heat Recovery Ventilators or Energy Recovery Ventilators). What these devices do is get any heat from air being exhausted from the structure (cooking, bathroom exhaust, clothes dryer exhausts, etc.), and exchange the heat to add it to air coming into the structure (some do exchange of moisture along with heat). In some areas, northern and colder climates and Canada, these devices are required by code. If your structure is older and enough makeup air comes in through door and windows seals, mail slots, screen doors, garage entrances, dryer and bathroom exhausts when not in use, etc., etc. then you don't want this arrangement. A good HVAC contractor will have someone on staff who understands all this stuff and can tell you what options make sense for your house.
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You are right ray but maintenance is only the half of it . In the author's furnace configuration it's a worse case scenario for problems. If the CO poisoning doesn't get them the starchybotrys mold will if a humidifier is is not installed perfect and with a better control than the cheap humidistat which comes with most humdifiers . Running a pipe down to the return is a direct pathway for condensation to drip down into the wood under the furnace and a breeding ground for black mold. I'm just assuming it's only wood underneath (I'd put money on it) and any humidifier configuration could destroy their house. Two much humidity, short heating cycles, and leaks will allow condensation to migrate to that wood box. Even the condensation from the A/C if the evaporator coil catch tray was leaking could get down there causing mold (and rot). After calling in a professional to verify combustion air intake is available and no chance of backdraft have a professional pan the return box to contain any unwanted condensation. Only then would I install a humidifier so I can over humidify and destroy my wood floors and furniture, and also grow mold in the rest of the house. If you're reading this dazhou, the point is even a simple thing like putting in a humidifier can have huge consequences by overlooking minor problems you're not familiar with. Another thing, is the plenum (#1) sheet metal or fiber duct board under the insulation? Good luck hanging a humidifier on duct board.
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Elmer J Fudd
5 years ago
last modified: 5 years ago
Yes, I agree with Mike. There's not enough information to know if the setup is reasonable or Mickey Mouse.

The air from bathroom exhaust fans needs to run to the outside, whether or not through an HRV/ERV. Not into an HVAC duct. The incoming outside make-up air can be put into an HVAC duct, again whether or not through an HRV/ERV. I don't live in an area where these are used but I have to wonder if "small vents" in three bathrooms have enough draw to do the job. Remember that there's more than bathing humidity that needs to be drawn out of bathrooms.

Bathroom exhaust fans can also be wall mounted, which is sometimes easier and less potentially problematic than making a hole in the ceiling and roof.
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Austin Air Companie
5 years ago
Is this something to be concerned about?

Depends on how much of a fan you are of smelling methane gas every time someone takes a number 2 in the bathroom.

The main reason those vent fans exist --- so you don't smell el craperino through out the house when someone takes a dump.

Oh, well we are high level society here. We don't go number 2. ROFLMAO.
wdccruise
5 years ago
I've seen vents like this in hotel room bathrooms. No guest-operated fans, just the wall vents.
opaone
5 years ago
If this is an exhaust vent running to an HRV/ERV then I'd say you're in good shape. This is a much better setup than what many HVAC folks do today which is to pull the HRV/ERV exhaust from a return duct.

No exhaust fans, moisture drawn out through HVAC into air exchange?

Comments (6)

mike_home

Brad Smith

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