You would need to check your local code.. some local codes do not require an exhaust vent if there is an opening window in the bathroom.

The vents in my house just vent to the attic where an exhust hose takes to to the eaves, no additional holes through the roof.

Have you ever NOT had a bathroom fan?

I ask, because if you have always had one, it is difficult to overstate how much you do need one. Our current (tiny) bathroom does not have one nor a window, so every time one of us showers, every surface is beyond damp. I killed my (non-waterproof) watch by leaving it laying on the counter while I showered over the course of the last year. The toilet paper will get noticably moist if it isn't covered and needs to be set aside until it is dried out. Even the fresh towel on the back of the door is not actually dry when you are ready to use it. Every. Single. Surface.

So even if code says you don't need one, I vote that you really do. Unless you have a window, you really do.

Oops, just read the posted date of this discussion. Sorry.

I just installed a new Broan exhaust fan with "sens aire". It has a humidity sensor that turns the fan on and a minimum run timer that keeps it on after the humidity level drops back down. The whole thing can be over ridden by the wall switch. It works great, a little noisy - but great. I dont have to remind the Mrs. to turn the fan on when showering.
...

Our code allows us to not have a fan if we have either a window or forced air vent from a central air/heater.

I live in San Antonio where our weather is influenced heavily by the Gulf of Mexico. We're not nearly as humid in the summer as Corpus or Houston, but we have our share of mold and mildew. We just remodeled one bathroom and are finishing with another pretty soon (not soon enough). The first one was enlarged to just about double its size. I installed a Panasonic fan such that it blows dry air INTO the room rather than exhausting it out. The moist air must escape into the house, although I now realize it is also going up into the air conditioning vent (oops! Didn't think of that). But anyway, we take 18 showers per week in that room and have yet to fog the mirror. I should point out that the fan was not installed for several weeks after we started using the shower and still the mirrors do not fog. Not only do the mirrors not fog, the room is not steamy even with my wife's hot showers. Of course the room is humid, but I'm surprised it is not more of a problem. Fully one half of the walls and floors are lined with porcelain tile, so it is my thinking that the thermal mass of the tile is absorbing the heat and keeping the steam down. Our next bathroom has significantly less percentage of tile, so it will be interesting to see how it works. The Panasonic fan in there sucks air out and blows it into the hallway rather than up through the attic.

For the past 20 years I have run five Vornado fans in strategic locations throughout my houses. They all run 24/365. I especially run one outside each bathroom door, set on the floor, and set to blow cooler floor level air up toward the ceiling inside the bathroom. That was my only means of clearing the steam from my bathrooms prior to the fan installation in this remodel. They work great to clear a bathroom, so if you're having trouble and can't install a fan, you might check into that. I know Vornados are expensive, but they are the only fan I tried that lasted longer than a few weeks running 24 hours a day. And 20 years is a long time for any appliance to run nonstop.

What a novel idea!!!!! Now, whenever you have guests over for a formal sit-down supper, they will all be treated to the stench of methane gas generated by any unfortunate guest that takes a huge stinky dump in your bathroom. LOL

Who gave you that idea... Borat?

DC Hall, even if there's no law saying you have to have an exhaust fan in the bathroom, I'm sure you're violating some law (even just the laws of common sense) by your arrangement. I won't go as far as castoff but he/she is right.

Moist, stinky air needs to be drawn OUT of the bathroom - there should be a slight negative pressure in such rooms (not so great as to cause drawback from any combusting appliances, though) - You need to change this.

You are right, you're going to mess up your a/c and run the risk of causing mould problems throughout your house.

Not sure about these fans of which you speak but it sounds like a lot of electricity consumption, I can't see how they'd be better than just running your furnace fan 100% of the time - I bet that'd be cheaper, too.

Frankrizzo,

I think I need one or more of those Broan fans, are you in Canada? That brand seems to be the standard here. I'm from Australia and hadn't seen the nice interchangeable motor/base with the plug, it made renewing the downstairs fan (which sounded like an aircraft engine in the upstairs bedroom) very easy.

So where is the sensing apparatus? Is it in the fan, or the switch, or elsewhere? I'd like to be able to change over to such a system, one bathroom has the fan on a separate switch, the other's integrated with the light. There are good and bad with both.

pjb999,
I am 100% male. LOL Just for the record.

As for Broan, they have been a popular brand of fan here in Canada for many years. However, they were bought by Nutone, a company that I think puts out mostly crap. Broan was Nutone's major competitor. I hate it when that happens.

Black and Decker USED to be a great name in the power tool business and then the morons ran it into the ground. Now their name is so ruined, they had to be the well-respected DeWalt name in order to get back into tools that contractors would even consider. Even so, the DeWalt line isn't up to the standards enjoyed by the company prior to being bought by B&D.

Emglo was the premier compressor manufacturer and of course, Dewalt bought them up.

Every message board needs a few people willing to experiment AND thick skinned enough to report the findings, even if they might be considered negative. So anyone else have some observations besides the obvious which might not have been thought out before the installation? All except the venting out the AC duct were considered and accepted as more important than the negatives of running wet air through a fan and ductwork.

What is your argument for pulling a vacuum on the room versus pressurizing it to remove the moist air?

PJB999:
Here is the link to the whole ses aire line of fans:
http://www.airshack.com/Merchant2/merchant.mvc?Screen=CTGY&Store_Code=FCFAA&Category_Code=BX-SenSaire

90CFM, but 2.5 sones. The sensor is built into the fan housing and it's adjustable. It trips almost immediately after starting the shower, and we have it set to run about 5 or 10 minutes after the humidity level drops below the setpoint to clear the room. I installed the wall switch upside down and you can toggle the fan on by flipping the light switch off and on again quickly.
I have to say it works really well

Here is a link that might be useful: Broan exhaust fans

First off, your method would never be passed by an building inspector in my neck of the woods.

Millions upon millions of bathroom fans pull warm moist air from the room and push it outside of the building envelope.

Hot air rises and most exhaust fans are mounted either ine ceiling or at the top of the wall. Pressurizing the room does little to remove the air because with the door closed, the only gap is under the door at floor level. The rest of the room is a sealed box.

You obviously have no understanding about "static pressure" and how a fan's efficiency is altered by it. You cannot choose a fan for a conventional installation based upon CFM alone. You must take into consideration the number of bends and the length of the entire exhaust ductwork.

Long runs and many elbows can render some fans useless. I suspect that your installation is also relatively useless from many aspects. You are welcome to experiment all you wish. It's your house. I just pity the poor SOB that buys it from you down the road.

There's a difference between experimenting and pissing in thw wind. My dad taught me the difference many years ago.

DC Hall,

Your reasoning is flawed, I'm sorry. Your bathroom may not steam up, but that's because the moist air is rapidly being distributed throughout the house. It's not an acceptable form of humidifying. I am all in favour of experimenting and I come up with far more than my share of harebrained schemes, but any measure of logic dictates what you're doing is wrong. I don't know about "static pressure" per se but you're not really 'pressurising' a room if it's part of the building envelope, extracting fans do create a negative pressure since they exhaust the air outside.

I moved to Canada from Australia, where they tend to be a little optomistic or even naive about moisture control which is ironic since many parts are very humid. I'm not sure about the current building codes but no fan was required in bathrooms back in the day, mind you, leaving a window open is not out of the question most of the year, unlike in colder climes.

Most clothes dryers sold there are not vented outside, which blows my mind somewhat, but it's true. The result is frequent mould problems.

Apart from anything else, you jeopardise future sale of your house, by doing something so, quite frankly (no offense intended) weird and illogical. Like I said, just run your central furnace/ac fan 100% of the time instead of a bunch of what- portable fans strewn round the place? I'd have thought ceiling fans would be better, at the very least.

Okay, back to this.

You obviously have no understanding about "static pressure" and how a fan's efficiency is altered by it.

If I had a perfectly sealed room, then static pressure might be important. And, not to be snotty back at you, but I was a certified rocket scientist for 28 years with the last 10 years being in jet engine logistics (double checking the designers, so to speak). I'm pretty up to speed on the way fans work. If my use of fans throughout the house seems unconventional, it is based on the "logic" of aerodynamics and significant experience with the application thereof. I can't help it if millions of fan installations were done backwards - y'all should have asked me (just kidding).

If you need real numbers to help me understand where I'm going wrong on this, the fan is a 110 cfm, connected to 4-inch pipe, 4-feet long, with two L turns. My door crack is 28 inches wide and 1/2 inch high. The AC duct leading to my bathroom is 6-inch diameter and is 6 feet long before opening up to 2-foot square box duct.

Your reasoning is flawed, I'm sorry.

I sincerely appreciate your criticism and suggestions; however, if my reasoning is flawed, I haven't seen anything posted here that was not already considered in making the decision. The only weakness in my installation is the humidity stays indoors. We'll see how that works in the summer when the humidity rises.

Hot air rises and most exhaust fans are mounted either ine ceiling or at the top of the wall. Pressurizing the room does little to remove the air because with the door closed, the only gap is under the door at floor level. The rest of the room is a sealed box.

So with the door closed, in a vacuum type system, doesn't the air still have to come from under the door?

Like I said, just run your central furnace/ac fan 100% of the time instead of a bunch of what- portable fans strewn round the place? I'd have thought ceiling fans would be better, at the very least.

My central air unit uses over 7,000 watts (if I'm converting 9.6 horsepower correctly). My five fans use 150 watt each and put exactly the desired amount of air where I want it. I can't aim my ceiling fan on me in the summer. And in the winter I can't just have a ceiling fan gently lifting the cold air from the floor in the corner to mix it in the room. You might like the look of ceiling fans, but I look at them and see the dusty, noisy, wobbly contraptions of old movies. Sorry, I know Hunter makes a good fan, but try to minimize them in my house.

Regarding blowing the humidity up into the AC registers and creating mold: The ductwork is designed to handle air saturated at 100% humidity. In fact the ducts do carry saturated air all summer long. When cooled air leaves the A-coil in the attic (or wherever) it is saturated. Then it travels through the ducts until it exhausts into every room. If you see a difference between the moist air coming from the bathroom and the moist air coming from the coil, I'm willing to discuss it.

I don't know about "static pressure" per se but you're not really 'pressurising' a room if it's part of the building envelope, extracting fans do create a negative pressure since they exhaust the air outside.

When I blow up a balloon in my house, it really is higher pressure inside the balloon that holds the balloon's rubber skin out. Just because it's in my house, does not make the inside and outside the same pressure.

My bathroom fan does exactly what yours does in one respect. It replaces the moist air inside the bathroom with drier air from somewhere else. 100% of the exhaust fans bring the air in from the crack under the door and from any other leaks into the room (e.g. AC duct, windows, unsealed electrical sockets, etc.). My "exhaust fan" exhausts dry air from an adjacent bedroom and forces it into the bathroom and out the door cracks, etc., as mentioned. Hmmm, much like a forced air AC unit. Coincidence? Not really. There are millions of installations of those units, too.

I am not trying to be defiant of your remarks, but just trying to defend the logic of the decisions. I thought about this for years before we could afford to remodel. If this thing doesn't work when challenged by our summer humidity, I'll let you know. Or write to me to remind me.

Crikey.

Indeed, the air does draw under the bathroom door in the 'vacuum' setup (ie the normal, legal, accepted version of bathrooms everywhere) - because the pressure in the bathroom is lower.

The beauty of this is it keeps the moisture from diffusing through the house; furthermore, it keeps odours from reaching the rest of the house. It also promotes the exchange of air (bringing fresh air from outside) provided the rest of the hvac system is correctly configured, and that's important - with our super well-sealed homes, I guess it's conceivable we could reach a stage where people could suffocate.

The bathroom moisture and condensation DOES dissipate by this method for two reasons: firstly, because moist air is being drawn out of the room. That encourages more condensation to evaporate, since it replenishes the air's capacity to hold moisture. Also, with "lower" air pressure, water evaporates more easily.

Your bizarre method and logic may make the condensation evaporate more rapidly (or so you may think) because you are encouraging it to evaporate I guess into a larger area, however, that capacity would diminish over time, since the overall humidity will increase to the point of what is it - equilibrium? Where the air will hold no more moisture, and condensation begins to reform. This is where the structural damage sets in, mould forms and it becomes an unhealthy environment.

OOps, the rocket just crashed. Re-read my last reply carefully. I am not suggesting you run your HEATING OR AC constantly, it would of course be very wasteful and would over-heat or over-cool the place. I was suggesting running FAN ONLY which is usually an option on thermostats with more than two wires, or most furnaces etc with a switch for this purpose. The FAN will run, whether any heating or cooling is going on at the moment. On a modern furnace, the blower/fan may not use any more than just ONE of your fans, and you are running 750watts of fans, as I understand it, not including your bathroom odour and moisture distributing reverse fan.

Do you see what I mean? The fan/blower in your furnace air handler thing will use less power, and you will get OVERALL air circulation (plus the bonus of increased air filtration) throughout your house. You will save money on electricity which you can put towards rectifying your bathroom fan error before you sell the house, or when a building inspector tells you to. Hopefully your insurance company doesn't find out, because they might well refuse certain claims (like dampness damage) since there's non-compliance. You may even have created a fire hazard with the reverse bathroom fan (the other advantage of the normal bathroom fan is it allows a pressure release valve, so outside doors and windows operate correctly (the damper in the bathroom fan which prevents the ingress of cold air, will allow the pressure created by a door closing or opening to escape through the damper)

Ceiling fans may have their drawbacks and I don't love cleaning them either, but I think I'd prefer them to a bunch of fans sitting around on the floors or furniture....having said that, I have nothing against air filters/cleaners if one has the need for them (we have a shedding dog so probably will purchase a couple in the future)

If you're not trying to be 'defiant' of our reasoning, you're certainly trying to convert us to your way of thinking, and I don't think it's going to happen.

Firstly, I'm not going to contradict a building code, especially when there's no discernible logic (ok you disagree but fail to impart what actual advantage your system offers) or advantage to it.

You mentioned your area does have mould issues....(as do all areas I guess) - your system is particularly unwise due to that. You are creating an unnecessary hazard.

It's rather like 'vacuuming' or should I say reverse vacuuming, a room by blowing it all out with compressed air. There may be something about that system you like, but you're just taking the dust from one room (read humidity and bathroom smells) and spreading it throughout the rest of the house.

If you go into a bathroom, close the door and take a long hot shower, the humidity begins to condense on the upper part of the walls first because the hot air rises to the ceiling level immediately. The more time spent in the shower, the further down the walls the condensation takes place.

Putting an exhaust fan in the ceiling where this warm, moist air is sitting and sucking it out of that space is in tune with the known science of how nature works. Cooler air rushes in to the room by way of the space between the floor and the bottom of the entrance door/s to replace the air being evacuated.

That cooler air then pushes the warmer air in an upward direction to the exhaust fan so that the balance of the unwanted moisture is expelled to the exterior of the residence.

The same can be said about the methane that is released during defecation and otherwise. This gas is lighter than air and therefore rises naturally toward conventionally placed exhaust fans.

If you agree that warm air and methane rises, then your proposed method works against these principles. There is no question that you can pressurize the room and that by doing so, you will force existing air to exit beneath the entry door or into a vent leading to an air handling system. The question is one of efficiency and effectiveness.

Under your proposal, warm moist air isn't actually being expelled from the room in it's current state. All you are doing is diluting it with cooler, drier air being injected into the room. That diluted air is then being forced from the room and into the rest of the building envelope. Whatever negative elements were present in the bathroom air are now being dispersed into a larger space.

Here's my analogy. If your dog defecates on your front porch and you get a shovel to pick it up and put it into the garbage pail, then the feces is gone from your property 100 percent come the end of garbage day.

However, if you get out the hose and blast the feces apart while washing down the porch, the feces is still present on your property....... just in smaller pieces.

Whatever harm the feces might cause is certainly leesened but it isn't eliminated.

If you're not trying to be 'defiant' of our reasoning, you're certainly trying to convert us to your way of thinking, and I don't think it's going to happen.

Clearly you are not open to this idea, but others may at least consider it. So far the inspectors have not said anything. I consulted with two of them, the city engineer, my contractor, and fan suppliers before doing it.

Firstly, I'm not going to contradict a building code, especially when there's no discernible logic (ok you disagree but fail to impart what actual advantage your system offers) or advantage to it.

I'm not going to run to the library immediately to check the code, but I do get there reasonably often and will check. Again, the inspectors who are familiar with the code are okay with my installation. It could be that a fan is not required simply because I have ventilation into the room via the AC ducting and/or a window, so whether I have a fan in the room is my call.

You mentioned your area does have mould issues....(as do all areas I guess) - your system is particularly unwise due to that. You are creating an unnecessary hazard.

There seems to be no mold issues in the southwestern deserts or the Rocky Mountains. Our weather is heavily influenced by the Gulf of Mexico so we have humidity in the summer. I don't think it is going to be a problem but is certainly is an issue. Definitely not a hazard.

You may even have created a fire hazard

You're being alarmist. Explain to me how my house catches fire because the bathroom doesn't vent to the outside.

There are a couple advantages to my system. First the fan draws only dry air into it. This keeps the wet dust from collecting on the fan blades and reducing the fan efficiency to near zero in a few months. Second, the fan is mounted 24 inches above the floor in the bedroom. If I need to clean it, which I doubt I will anytime soon, its right there at knee level instead of overhead on the ladder. Third, the air at 24 inches is blown up to the ceiling in the adjacent bathroom 9 inches down from the 9-foot ceiling. As you pointed out, warm air rises. My system blows relatively cool and dry air in a the ceiling height to thoroughly mix the warm/moist air with cool/dry air to get a more uniform air temp and moisture throughout the room. Fourth, air sucked into a fan is only sucked extremely locally. Without a few classes in aero I can't really get into how that works, but you'll notice the exhaust of a jet engine, or even an electric fan for that matter, can be felt much farther away from the blades than the intake air induction can be felt. You have to hold your hand directly to the back of a fan to feel any air intake at all. My system, even with a diffuser at the opening into the bathroom, blows the air into the room hard enough that I can feel it against the far wall, thus ensuring thorough air stirring and mixing. Fifthly (?), in the winter humidity is not a problem here. In the summer it can be if your AC is not properly designed. Mine seems to be but this room has not endured an entire summer. Actually spring is slightly worse for humidity because the humidity is up but the temps are not warm enough to trigger the thermostat. In the summer the AC runs day and night as the outside temps sometimes don't come down into the 80s for several days at a time.

It's rather like 'vacuuming' or should I say reverse vacuuming, a room by blowing it all out with compressed air. There may be something about that system you like, but you're just taking the dust from one room (read humidity and bathroom smells) and spreading it throughout the rest of the house.

And your vacuum system sucks dust in from outdoors and blows it all over the house. Which is better - the dust you already have indoors or the new dust your vacuum system is sucking in?

I knew which fan you were talking about, but I was way off on my house fan power specs. Apologies. I'm not sure what model of blower I was looking at but mine is 3/4 horsepower - more like under 500 watts versus the 750 watts used by my directed fans. If one of my little fans wears out, I have backup. If my furnace fan wears out, it's a service call and a $12,000 AC system (mine is ready to be updated).

Your bizarre method and logic may make the condensation evaporate more rapidly (or so you may think) because you are encouraging it to evaporate I guess into a larger area, however, that capacity would diminish over time, since the overall humidity will increase to the point of what is it - equilibrium? Where the air will hold no more moisture, and condensation begins to reform. This is where the structural damage sets in, mould forms and it becomes an unhealthy environment.

From a heat transfer point of view, you need to watch your terms better to make that make sense but I think I know what you were trying to say. Still, the last sentence is the important one. The humidity increase from a shower is unlikely to saturate the 18,000 cubic feet of air in the house. However, this is exactly what I'll be looking for in the summer. These bathrooms are at the far end of the house. The concern is getting that air moved out of the confines of the bedrooms and out to the AC air intake in the living/dining rooms. I don't think it will be a problem in the summer with the AC on all the time, but we'll see. I'm more afraid of freezing my butt off in the shower with all that dry air coming in on me.

I may have mentioned that I do not get any condensation in my bathroom now and I do not get any even when the fan is off. The reason for that is not clear. I'm working on the theory of massive tile heat sink where the moisture is actually condensing on the cooler tile but there is so much tile that I'm not noticing it. But there is never any fog in the bathroom and no condensation on the mirrors.

Ceiling fans may have their drawbacks and I don't love cleaning them either, but I think I'd prefer them to a bunch of fans sitting around on the floors

Clearly I'm not going to change your mind on that either but I have convinced several friends to use floor fans, especially in the winter, to mix the hot air at the ceiling with the cold air on the floor. Suddenly my short friends can get warm and my tall friends don't have cold feet. If the thermostat is at 5 feet off the floor and you're 5 feet tall, you live in a world where all the heat is above your head no matter what you set your thermostat to. But if you're six feet tall or taller, your face is always hot and your feet are always cold. With the little fan on the floor pointed at the ceiling behind the sofa, the air mixes in the entire room and everyone is comfortable. Everyone I demonstrate this effect to is amazed. A ceiling fan can be reversed and pointed at the ceiling, but you get into the problem again of the air intake being at 8 feet off the ground blowing air up to the 9-foot level. You really have to have the fan honking to blow that air to the walls and down. Then people seem to complain about the wind in the room. My little fans simply punch a localized hole in the thermal layers and mix them up.

I keep ignoring the indelicate subject of bathroom odor, because that does not seem to be a problem in my household. It must be all the lard in the tamales down here ;-) Actually my wife pumps the veggies and fruit into us - I'm not a dietitian.

Sorry I'm getting so wordy. Maybe this will stop now that we realize we're not going to change each other's minds.

I don't know why code would require them, other than that the electricians are union and WANT the government to require them. Our bathroom is somewhat big. As a result, the fan--because they cannot be directly over the water source (i.e., IN the shower)--is outside the shower. It does absolutely no good. The only thing that works is opening a window or using my blow dryer on the mirrors before using it on my hair. If the fans could be directly over the steam source, then they might be useful. Otherwise, they are only there for looks.

I'm glad mmkrzus31 cleared up this 10 year old post. Now I'll sleep better.

You're welcome.

roof35-

Don't exaggerate...it's only a 9-1/2 year old post!

Bumping this post: I'm moving into a place where both bathrooms do not have an exhaust fan. If I buy a ceiling light/exhaust fan combo, will that work? And is it as simple as installing a new ceiling light, but just running it with the one light switch?

First, seriously, just start a new post. Second, it's not as simple as just installing a new ceiling light because a fan/light combo requires ductwork to move the moist air out of the house. As to the switch, you can purchase a fan/light switch that will operate each separately, or one that will turn on the fan every time the light is turned on and leave the fan running for a set period of time after the switch is turned off (these are my preference because the fan is always on when it should be and nobody has to remember to turn it off).

Lots of confusion here, mmkrzus you can put the bath fan/light over the shower, it just needs GFCI protection. Easy to do if you run a line from the load of one of the bath GFCI outlets to the fan/light switch(es). Wiring light and bath fan separately is useful. Use a 3 way wire for this, the neutral can be shared and the hots can be separate. Same can be done for ceiling fan/lights throughout the house.

It is a good idea to have a bath fan, and has nothing to do with electric unions.... or other conspiracy theories. If you manage humidity in your house (which you should) you would notice that if you take a shower in a bathroom without an exhaust fan the humidity gets up to 80% or 90%. Easy to monitor with one of those clocks with built in humidity reading. That is when your mirrors steam up. You want it around 60% with the fan running, hard to get it lower than that during/after a shower. Your bath fan could probably be located better but there may be a ductwork problem or some other problem. Your mirror should not fog up with the bath fan on. Perhaps it is just an old fan that barely moves any air.