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  1. #1
    Join Date
    Jan 2007
    Location
    Whitehorse, Yukon
    Posts
    20

    Both HRV and Bathrrom Fans?

    I have read conflicting thoughts on having both HRV and bathroom fans. Some say just use the HRV, some say use the bathroom fan for demand uses (like showering etc.)

    We will be running a Lifebreath 200 on 20/40 intermitent. I was planning on installing digital timers in the bathrooms for demand use to engage the HRV into high for a timed 20 minute session. Although the HRV is more efficient as conserving warm air, we are in a cold climate and these HRVs seem to run in the defrost cycle more than half the time in the winter. This would be even moreso if I was pushing hot humid shower air over the exchanger with -30F air coming in. Defrost cycle will happen immeditaley.

    Also the HRV will removing air from all around the house when on high not just the required area.

    My ventilation advisor said I should install bathroom fans on 5/10/15/30 mintue electronic timers and just exhaust it during demand and leave the HRV on 20/40 intermittent.

    Any thoughts, arguments or experience on this?

  2. #2
    Join Date
    Dec 2006
    Location
    Northern VA
    Posts
    389
    An HRV won't expel as much humidity that an exhaust fan will. Stick with a good exhaust fan and only run it when you need to.

  3. #3
    Join Date
    Jan 2007
    Location
    Whitehorse, Yukon
    Posts
    20

    Bathroom Fans

    Well that is the way I am leaning. Placed an order for 4 panasonic whisper quiet fans based on the rave reviews here in the forum.

    Thanks for your input.

  4. #4
    Join Date
    Dec 2006
    Location
    Northern VA
    Posts
    389
    If you are concerned about noise you may consider the remote mounted fans if they are exhausting through the attic. The motor mounts up in the rafters and you won't even hear a humm in the bathroom. If they are between floors then what you have ordered will work well.

  5. #5
    Join Date
    Feb 2006
    Posts
    91
    We built a new airtight house and, of course, included a HRV system. We were recommended not to put fans in the bathrooms but to put in switches that switch the HRV into max for 20 minutes. The bathrooms are all quite large and, even when it's -10F outside, there are no problems with condensation. If anything, we use the HRV boosters less in winter since the extra humidity is actually a bonus. The money saved on installing bathroom fans was pretty much equivalent to the HRV unit itself!

    Paul in Montreal

  6. #6
    Join Date
    Jun 2004
    Location
    4H: Hot, Humid Houston H.O.
    Posts
    3,304
    >>We were recommended not to put fans in the bathrooms but to put in switches that switch the HRV into max for 20 minutes.

    Are the HRV returns located in the bathrooms? I am a Texas guy to whom this is fairly novel.

    Thank you -- Pstu

  7. #7
    Join Date
    Feb 2006
    Posts
    91
    Quote Originally Posted by pstu View Post
    >>We were recommended not to put fans in the bathrooms but to put in switches that switch the HRV into max for 20 minutes.

    Are the HRV returns located in the bathrooms? I am a Texas guy to whom this is fairly novel.

    Thank you -- Pstu
    The HRV exhausts are in the bathrooms, the supply side of the HRV (post heat exchanger) is connected to the return air of the main HVAC system so the regular HVAC ducts provide the source for the HRV. The only place there isn't an HRV exhaust is the kitchen as you don't want grease etc. ending up in the system.

    I'm not sure how well HRVs work in a hot and humid climate. I'd imagine that you'd want the air conditioner after the HRV to remove any humidity. Of course, in winter, it would be different and the air conditioner wouldn't be running anyway.

    Paul.

  8. #8
    Join Date
    Jan 2004
    Posts
    108
    I have a setup just like Pyropaul. HRV exhausts from the bathrooms, HRV supply to the return side of the airhandler. We have pushbuttons to put the HRV on high for 20 minutes. Those pushbuttons are rarely used. The HRV moves about 35 CFM on low and slightly over 100 CFM on high. The system has works well at minus 30 F in winter and 102 F with 70 F dewpoint in summer. We have four people in the house.

    Jim in Ashland, WI.

  9. #9
    Join Date
    Jan 2007
    Location
    Whitehorse, Yukon
    Posts
    20

    HRV Control

    Well based on the replies here it would seem silly to go with the bathroom fans. My last was was the same as the ones described (HRV Only) and we hardly ever had fog on the mirrors during showers and we never pressed the buttons. This could be due to the fan-coil system running on low continuously so bathrooms were suplied with incoming air all the time, even when the HRV was off.

    The company I orderd the fans from just email with my shipping quote so I have the opportunity to save myself over 700 US be dropping the fans from the system. I'll have to think about this a bit more.

    Pyropaul and Engineerguy.... I made another post about the HRV control, but did not get any feedback yet. Are you running any fancy controls (prgramming) for the HRV or using the stock ones (on/off or 20/40 intermittent)? I would like more control than the stock ones. Any ideas if this can be done?

  10. #10
    Join Date
    Apr 2002
    Posts
    11,808
    Sometimes having that bathroom fan for quick removal of odours is a good feature to have. Especially after two for one burritos, and specials on corona.
    The way we build has a greater impact on our comfort, energy consumption and IAQ than any HVAC system we install.

    http://www.ductstrap.com/

  11. #11
    Join Date
    Nov 2007
    Posts
    6
    I have a LifeBreath 200 Max going into new construction. I have six locations that I was going to have it draw from. Three full baths, a powder room, laundry, and kitchen. All locations that the LifeBreath install manual recommends.
    Being split up that much I don't feel I would get enough draw from the full baths to remove moisture. I thought of using motorized dampers to regulate the flow to a couple of rooms as needed. That started to sound too complicated.
    My HVAC installer recommended the bathrooms have regular bath vent fans feed the HRV with a relay turning on the HRV when the bathroom vent was turned on.
    With just bath fans and no HRV in a tight house where else would the supply for 200cfm of bath fans come from?
    Any thoughts if this will work? He claims to have done it before with good results.

  12. #12
    Join Date
    Aug 2007
    Location
    MN
    Posts
    2,677
    I believe Lifebreath has a control that will ramp it up for different conditions/contaminants in the air, installs next to your Tstat we used one in a dental office, pretty sure that was a lifebreath system.
    You can't fix stupid

  13. #13
    Join Date
    Nov 2007
    Posts
    6
    The problem with just the HRV is that the bathrooms should need 80 - 100 cfm each. The HRV is only 200 cfm total. Split that to six locations would be 33 cfm each if they were perfectly balanced.
    Using the bath fans would force feed the HRV and the backdraft dampers in most bath fans should make the HRV get all the air from the bath fan that is on. Or will it??

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