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  1. #14
    Join Date
    Aug 2004
    Location
    S.E. Pa
    Posts
    6,175

    building science

    I suggest you first read Joe Lstiburek's book for your climate available at http://www.buildingscience.com

    Read on the Top 10 Stupid Things Builders Do in the South. See the part about vinyl wallpaper? You have a vapor barrier trapping moisture inside your home. Your bathroom is a terrarium! Remove that wallpaper.

    -Install proper powered ventilation that exhausts to the outdoors
    -Balance the house including makeup air for the "fart fan". Follow ASHRAE 62.2-2004
    -Do NOT install a return in the bathroom. That is polluted air you want exhausted--not shared with the house
    -Monitor your indoor Rh% and control as needed
    -Get the water away from your house. I install gutters with the leads run well away from the house even if you feel that sandy soil can handle it. If crawl space, install a vapor barrier. Seal off vents to crawl space
    -Take cooler showers for shorter periods. Take Navy showers (rinse,stop water, lather, rinse, done)
    -Install functional exhaust fans over stove and other bathrooms.

    The last thing you want to do is to share that funky bathroom moisture with your ducts, even if metal lined. You'll grow goobers in there and soon your house will smell like gym socks.

    HTH,

  2. #15
    Join Date
    Aug 2003
    Location
    Fort Worth, TX
    Posts
    11,326
    hearthman,

    Take cooler showers for shorter periods. Take Navy showers (rinse,stop water, lather, rinse, done)
    -Install functional exhaust fans over stove and other bathrooms.
    Navy showers?? Nope, ain't happenin'. I spent three years on a cruiser enduring an anemic mist from a push-button shower head, water temperature that could go from blast furnace to sub zero in a heartbeat, and shower shoes. Oh yeah, and water hours, where you couldn't shower at all (dang leaky Main Control, couldn't run a tight plant if their life depended on it...which it DID!)
    Nope, it's nothin' but Hollywood showers for this old snipe.

    P. Student,

    A rhetorical question... is it really superior to keep that humidity inside the bathroom or shower space? Will that increase or decrease the likelihood of problems vs. homogenizing the air through the whole house?
    You don't want to keep the elevated humidity trapped in the bathroom if at all possible. The only good way to "homogenize" the air is to remove the more humid air in the bath and replace it will less humid air from the HVAC system and the house, doing so in a way that minimizes "stink creep" and does not introduce unnecessary humidity further into the house.

    The 12 x 12 hole into the next bathroom is merely allowing air to be drawn from that bathroom into the one where the exhaust fan is running. Air from the house is replacing the air in that bathroom, then flowing into the other bath.

    The air cycler device you refer to doesn't sound all that different from the VisionPro "circ" feature. Either one can be potentially troublesome in a humid climate with a wet coil. My personal experience is that it's better to cycle the fan with the compressor and leave it off when the compressor is off. At my own building that I manage, we began experiencing odor problems in systems where the blowers ran continuously. The air handlers were wired from a previous energy management system to run continuously. I have since gone in and wired each air handler to cycle with the compressor, and the odor problems have gone away. This happened late in the year; I'm awaiting the return of humid weather to note improvements in interior humidity levels.

    • Electricity makes refrigeration happen.
    • Refrigeration makes the HVAC psychrometric process happen.
    • HVAC pyschrometrics is what makes indoor human comfort happen...IF the ducts AND the building envelope cooperate.


    A building is NOT beautiful unless it is also comfortable.

  3. #16
    Join Date
    Jul 2004
    Location
    West TN
    Posts
    983
    Was doing a search for a Humidity Controlled Bathroom Exhaust and found this interesting web site.... didn't read it all so take it for what its worth hehe....

    http://biorealis.com/ventsystem/coldcomfort.pdf


    Those Fantech fans look really nice.
    You could get one of those and parrallel a humidistat with the light switch.
    Humidity gets too high and it will close the switch to bring the fan on, or turn the fan on manually (for those times when ya just gotta read something).

    If it were mine, I'd put in some makeup air.
    Run a pipe from outside to the return. Be sure the air is filtered. If you really want to get geeky, put in a zone damper that opens only when the bathroom vent, range vent a hood, or clothes dryer is running.
    THere are controls that can actually monitor outdoor humidity and temperature and modulate the damper.
    Some commercial systems use stuff like that, they use it not only to bring in fresh air but also to bring in cooler air if its winter time and they are needing Air Cond.

    Extend to others the grace that God has given you.

  4. #17
    Join Date
    Jan 2005
    Location
    North Las Vegas
    Posts
    783

    [/quote]

    Navy showers?? Nope, ain't happenin'. I spent three years on a cruiser enduring an anemic mist from a push-button shower head, water temperature that could go from blast furnace to sub zero in a heartbeat, and shower shoes. Oh yeah, and water hours, where you couldn't shower at all (dang leaky Main Control, couldn't run a tight plant if their life depended on it...which it DID!)
    Nope, it's nothin' but Hollywood showers for this old snipe

    [/B][/QUOTE]

    Lol well would not have had to worry about water hours if those darn deck apes would learn to shut off the water, but then too those guys in main control most likely had showers built in like we did lol no water hours for us and clean laundry too lol
    Far better it is to dare mighty things, to win glorious triumphs even though checkered by failure, than to rank with those poor spirits who neither enjoy nor suffer much because they live in the gray twilight that knows neither victory nor defeat. (President Theodore Roosevelt)

  5. #18
    Join Date
    Jun 2004
    Location
    4H: Hot, Humid Houston H.O.
    Posts
    3,304

    Just some clarifications

    >>The 12 x 12 hole into the next bathroom is merely allowing air to be drawn from that bathroom into the one where the exhaust fan is running. Air from the house is replacing the air in that bathroom, then flowing into the other bath.

    I probably did not explain it sufficiently. The exhaust fan has nothing to do with it. That 12*12 vent is the main return air path for 375 CFM when the master bathroom door is closed and the air handler is on. The master bedroom added 260 CFM when its door was closed. Otherwise, it is entirely under-the-door.

    The old situation resulted in pressurization well beyond what Lstiburek or Florida building code would approve. Using an old Dwyer micro-manometer I measured 7.5 pascals (.03 inch w.c.). With this return path open, I measure 3.0 pascals. Caveat: with me operating it, that Dwyer is precise to maybe 0.5 pascals.

    The 5-10% average reduction in relative humidity (RH) in the bathroom was an unexpected surprise. I guess I expected a small reduction but this seems to tell me that air mixing has more potential to even out humidity, than I originally expected. It is my opinion that intermittent exhaust fans are good for removing stink but the humidity situation will not respond to that. Mixing with main house air gives the AC a greater opportunity to dehumidify which is our goal all along.

    Currently I am measuring 5-10% greater RH in the bathrooms compared to the rest of the house. Mold growth is supposed to be a hazard at 70%, I am averaging 55-65%. Haven't found any experts to advise me, so I am in guesswork territory. But it pleases me to minimize that RH knowing that air feels better, smells better, and makes mold growth less likely.


    >>The air cycler device you refer to doesn't sound all that different from the VisionPro "circ" feature.

    Almost exactly right. The main functional differences I know of are...
    1) AirCycler is at heart a Lstiburek product. It begins its "off-time" counter upon the end of an AC call, so the coil gets its drying time. VisionPro runs only at random so some of the time it is adding house humidity via the coil.

    2) AirCycler allows your choice of duty cycle anywhere between 5% to 95%. VisionPro is set to 35% only.

    3) AirCycler FR-V model controls a fresh-air intake plan. It counts the minutes of air handler on-time and when the quota is met for fresh air intake, closes a motorized damper. VisionPro does nothing of the sort (but it looks terrific!).
    http://www.aircycler.com/AirCyclerFR-V.html
    http://hem.dis.anl.gov/eehem/01/010511.html


    I know I had not communicated my statements clearly enough. Hope this clarifies things.

    Best wishes -- P.Student

    P.S. Remember this is in a hot-humid climate where outside humid air infiltration is the larger threat. Positive pressurization is not harmful here in itself, the problem lies in the rest of the house which must be depressurized (unless there is a fresh air intake). In a cold climate it would be a fine idea to run a bathroom exhaust continuously, in a hot-humid climate we must not.

    P.P.S. Regarding JFS's original post, I think a good big exhaust fan would help his problem a lot. With a timer so it can really work the room during/after a shower. It is the most obvious choice in keeping with conventional wisdom.

    [Edited by perpetual_student on 03-30-2005 at 10:07 AM]

  6. #19
    Join Date
    Apr 2004
    Posts
    7,680
    I would just use the YMCA bathroom to S,S&S. I cant use the little flower shaped soap or use the towels hanging on the rack... I guess those are just for show.

    Get a big exhaust fan, not a home depot price fighter unit and then have it installed properly as has been mentioned.

  7. #20
    wow, what a great discussion! Thanks everybody!

    I wasn't really thinking of a return air duct in the bathroom, as that really wouldn't do anything unless your showers always coincided with the AC running, and in the winter time running the heat would probably over humidify the rest of the house...

    I'm about to start the process of putting in one of those hot water starter pumps? I forget the name, but they connect under the sink and basically pump the hot water down the cold water pipe until they actually get some hot water up to the tap. Though the hot water tank is directly above this bathroom, the pipe seems to go somewhere else first and you waste quite a bit of water before you can actually get into the shower without it being a "navy" shower Since the action of turning that on is a pushbutton that the computer will be able to monitor as well, I'll know when someone is taking a bath or a shower. Since there are communicating thermostats on the AC unit in question I'll also know if the AC is actually running while you're taking that shower. in that case I'd open the damper that connected the vent with the return air duct directly above it in the attic. It would not replace the regular stink fan in the little toilet room, so I don't expect recirculating other odors from the bathroom would be a problem. This is strictly to remove shower and bath humidity.

    The outside humidity can be as bad as the bathroom in the worst of the summer. And sometimes the outdoor smells are worse than the bathroom ones believe it or not. There is a salt marsh a mile away or so, and at low tide with the wind blowing in the right direction the lovely scent of dead and decaying aquatic creatures can be enough that we keep the windows closed... (or at least I do, my wife having grown up around here just thinks it smells like the beach... no beach I've ever been to!) Pulling that in with a regular big exhaust system would not add to the livability of the house.

    The fantech stuff is exactly like what I was planning for the outside exhaust portion of it. I hadn't really thought about growing goobers in the ducts due to all the humidity. I'd be connecting to the main return duct not 10 feet from the coil in question, so it might not be too bad.

    What I'll probably end up doing short term is installing either a fantech, or something similar and keep my options open for more complicated ducting and automation in the future while I keep thinking about the implications that you guys brought up.

    Thanks!
    James

  8. #21
    Join Date
    Aug 2002
    Location
    Office and warehouse in both Crystal River & New Port Richey ,FL
    Posts
    18,836
    Here's one more,buy an ERV(Energy Recovery Ventilator),and install it as the bath exhaust for your home.

    Bathroom air out,fresh air "conditioned and filtered",blown back into the central return duct.

  9. #22
    Join Date
    Dec 2002
    Location
    in a house, Appomattox, Va.
    Posts
    3,293
    I've got my fan directly over the shower, glass doors, tiled surround and the top is that white fiberglass combosite you see in commercial bathrooms sometimes.
    Never had any mold since the steam is contained in the shower while the fan is running.
    Never had a steamed up mirror, either.

    Cold vs blast furnace Navy shower. I wish, almost always too cold. And a hint of fuel oil in there, too. How about those salt water showers?
    At least the water hose always had potable in the pit. Was always thirsty.
    Col 3:23


    questions asked, answers received, ignorance abated

  10. #23
    Join Date
    Jun 2004
    Location
    4H: Hot, Humid Houston H.O.
    Posts
    3,304

    Remedial question

    JFS said:

    >>The outside humidity can be as bad as the bathroom in the worst of the summer.
    >>...at low tide with the wind blowing in the right direction...
    >>...can be enough that we keep the windows closed...

    Like you I am not in love with the smells of many beaches. But the more important question I feel the need to ask is... how much of the time do you open the windows? Is it more realistic to consider this a non-air-conditioned house?

    That might change a lot of thinking (mine at least!) regarding humidity issues. Everything I have said has been with the assumption that the house is air conditioned all summer long. Honestly I forgot it might be to some peoples liking to open windows, with a few exceptions for mild (and DRY) spring and fall days.

    Best wishes -- P.Student

  11. #24
    Join Date
    Aug 2003
    Location
    Fort Worth, TX
    Posts
    11,326
    Cold vs blast furnace Navy shower. I wish, almost always too cold. And a hint of fuel oil in there, too. How about those salt water showers?
    At least the water hose always had potable in the pit. Was always thirsty.
    DFM in the drinking water. Mmmmm...healthy.



    BTC mentioned a washer and dryer in the pit. Yeah, in One Fireroom on our ship, and you had to know someone from that pit to use it. As for us, I came up with a steam powered washing machine when we could no longer buy wiping rags for our engine room. It consisted of a trash can tilted into the angle irons, 50 pound steam, a tin can from the mess decks, wire, and water. The steam would heat the water, thereby loosening the oil from the rags, which would float to the top of the can and skim off into the bilges. After most of the oil turned loose I'd lower the water level a tad, toss in some detergent, and open up the steam valve. The rags would swish around quickly and turn loose of the remaining oil. After rinsing, we'd hang the rags out to dry around the main engine steam turbine and reduction gear.

    Ah...memories!

    P. Student -

    ) AirCycler is at heart a Lstiburek product. It begins its "off-time" counter upon the end of an AC call, so the coil gets its drying time. VisionPro runs only at random so some of the time it is adding house humidity via the coil.
    I have to wonder how quickly a coil will dry after a cooling call when sitting in an enclosed cabinet with no air circulation. You might get a little air movement from natural convection as the ductwork, air handler, coil, etc begin warming up at their different rates, but I've seen coils hold onto their moisture for some time when there's no air moving past them and the air surrounding the coil is saturated with moisture.

    • Electricity makes refrigeration happen.
    • Refrigeration makes the HVAC psychrometric process happen.
    • HVAC pyschrometrics is what makes indoor human comfort happen...IF the ducts AND the building envelope cooperate.


    A building is NOT beautiful unless it is also comfortable.

  12. #25
    Join Date
    Jun 2004
    Location
    4H: Hot, Humid Houston H.O.
    Posts
    3,304

    AirCycler, what it does and does not do

    I had stated:

    >>AirCycler is at heart a Lstiburek product. It begins its "off-time" counter
    >>upon the end of an AC call, so the coil gets its drying time.
    >>VisionPro runs only at random so some of the time it is adding house humidity via the coil.

    Shophound replied:

    >>I have to wonder how quickly a coil will dry after a cooling call when sitting in an
    >>enclosed cabinet with no air circulation. You might get a little air movement from
    >>natural convection as the ductwork, air handler, coil, etc begin warming up at their
    >>different rates, but I've seen coils hold onto their moisture for some time when
    >>there's no air moving past them and the air surrounding the coil is saturated with moisture.

    Good observation on the dynamics of moisture on a coil, I too wonder what is the answer. Let me emphasize that the AirCycler ensures its function is dormant for a time period following a cooling call. It does not inhibit the rest of the system from doing what it is designed to do.

    In the case of Trane/A-S and its "Comfort-R" function, it is my understanding there is a period of reduced airflow following a cooling call. I don't claim to understand it all but trust that Trane engineers know what they are doing. Per my understanding, VisionPro could interfere if its random on-time happened to occur then, preventing the Comfort-R algorithm from being completed as Trane designed. AirCycler is designed so it would not interfere.

    If any of this is erroneous, I would appreciate a correction. However it sounds as if you are knocking AirCycler on the basis of this, when if anything deserves a knock it is VisionPro.

    Regards -- P.Student


    [Edited by perpetual_student on 03-31-2005 at 10:19 AM]

  13. #26
    Join Date
    Aug 2003
    Location
    Fort Worth, TX
    Posts
    11,326
    If any of this is erroneous, I would appreciate a correction. However it sounds as if you are knocking AirCycler on the basis of this, when if anything deserves a knock it is VisionPro.
    Actually, if I'm "knocking" anything, it's the idea that the indoor blower should run for any duration longer than the usual 90 seconds or so after a cooling call in a humid climate. For the first 90 seconds after the compressor stops, it can be argued that there's a residual refrigeration effect from both a cold coil and refrigerant still moving through the evaporator as the system equalizes. This would continue both a cooling and dehumidification effect to a steadily diminishing degree as the system equalizes. Afterward, there's no such effect and if the blower continues running, any moisture remaining on the coil will blow off into the air vs. being condensed into the condensate pan, and tend to raise the relative humidity in the home until the coil is dry.

    If one were to insist on a VisionPro but balk at the possibility of the "circ" feature beginning immediately after the compressor stops, a simple "delay on make" relay for the blower motor would eliminate that problem. It would not allow the fan to re-energize for a set time after the "G" call ceases.
    But I don't think it's worth the effort. Leave the fan "OFF" when the compressor is "OFF" in a humid climate. If you need whole house filtration, I think there's other ways to do it in addition to the HVAC system in humid climates.
    • Electricity makes refrigeration happen.
    • Refrigeration makes the HVAC psychrometric process happen.
    • HVAC pyschrometrics is what makes indoor human comfort happen...IF the ducts AND the building envelope cooperate.


    A building is NOT beautiful unless it is also comfortable.

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