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  1. #1

    Humidity and Closed Cell Foam Insulation in Bathroom

    We are adding a 220 sq. ft. bathroom off of our Bedroom. We will have a pass through doorway. I am adding a 12,000 BTU LG 26 seer mini-split ductless system over the doorway between the bath and the bedroom. I was considering using closed cell foam under floors, in walls and on vaulted roof. I woke up this morning wandering if that would create a humidity problem in the Bathroom or if the ductless system would act as an air exchanger, eliminating humidity concerns. We have lots of windows in the bathroom but prefer not to open them in the winter time for obvious reasons. We have a conventional heat pump AC in the rest of the house. We live in Georgia where it can be hot with lots of humidity. I appreciate your thoughts and ideas....

  2. #2
    Join Date
    Feb 2004
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    677
    Install a bath fan with a humidity sensor. It will run the fan whenever excess humidity is present.
    I am the "Wally". All others are meer imitations of the original.

  3. #3
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    Jan 2009
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    +1 on bath fan. I think it's code to have forced ventilation for bathrooms now even if there is a operable window. To me it's common sense. You may want to consider heated floors. It might get a little chilly in there at times. The small electric useage might be worth it.

    FYI - Georgia is very humid, but only moderately hot as hot goes. Texas is hot and humid. Believe it or not Iowa nd much of the center of the country has the same desing temperature and only slightly less humidity. When siazing equipment yu have to be careful not to correlate the number and frequency of hot days with a peak load. The pacific northwest has probably more cooling degree days than Minnesota, but it's a temperate climate so design temp is relatively high. Its' easy to oversize there, which will kill you in terms of removing humidity. Less of a concern with minisplits. But still an issue. You want long, long run times to control humidity and for equipment effciency. Spray foam insulated spaces heat up and cool off a lot slower and have less air leaks.

    Something to keep in mind.

  4. #4
    Join Date
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    Northern VA 38 degrees N by 76 degrees W
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    Quote Originally Posted by motoguy128 View Post
    +1 on bath fan. I think it's code to have forced ventilation for bathrooms now even if there is a operable window. To me it's common sense. You may want to consider heated floors. It might get a little chilly in there at times. The small electric useage might be worth it.

    FYI - Georgia is very humid, but only moderately hot as hot goes. Texas is hot and humid. Believe it or not Iowa nd much of the center of the country has the same desing temperature and only slightly less humidity. When siazing equipment yu have to be careful not to correlate the number and frequency of hot days with a peak load. The pacific northwest has probably more cooling degree days than Minnesota, but it's a temperate climate so design temp is relatively high. Its' easy to oversize there, which will kill you in terms of removing humidity. Less of a concern with minisplits. But still an issue. You want long, long run times to control humidity and for equipment effciency. Spray foam insulated spaces heat up and cool off a lot slower and have less air leaks.

    Something to keep in mind.
    IRC 303.3 mechanical ventilation not required, but is an option to the ventilation requirements for bathrooms

  5. #5
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    Jan 2009
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    Quote Originally Posted by second opinion View Post
    IRC 303.3 mechanical ventilation not required, but is an option to the ventilation requirements for bathrooms

    Thanks. I find that rediculous. I bet fewer than 5% of homeowners would open a window to vent the humidity in a bathroom. I bet that mold and mildew are major problems in at least 1/4 of all bathrooms in the US as a result. I know our home when we bought it didn't have mechanical ventilation and the paint on the ceiling was peeling and the mildew in the shower was terrible. The AC system were also oversized. All are of course corrected now . Adding a bath fan was one of the first projects we addressed when moving in.

  6. #6
    Join Date
    Feb 2004
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    The code says that fans are required only in toilet rooms not shower rooms. The code addresses smells only, not humidity. I think its stupid to worry about smell and not humidity. I can tolerate Aunt Fridas poo but cant tolerate mold and mildew. Most any inspector I've talked to feels the same too.Panasonic makes a nice quiet fan that will auto handle the humidity. Not cheap but a nice fan non the less.
    I am the "Wally". All others are meer imitations of the original.

  7. #7
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    Those panasonic units can also provide continous ventilation as well at soemthing like 8-10 watts power consumption. Although it would make the space slightly negative.

    If the whole house is tight, the best strategy is an HRV with inlets in all the bathrooms and if possible the kitchen, then using wall switch to trigger hi speed and have it run on low continously.

  8. #8
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    michigan
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    Quote Originally Posted by motoguy128 View Post
    Those panasonic units can also provide continous ventilation as well at soemthing like 8-10 watts power consumption. Although it would make the space slightly negative.

    If the whole house is tight, the best strategy is an HRV with inlets in all the bathrooms and if possible the kitchen, then using wall switch to trigger hi speed and have it run on low continously.

    The HRV is an excellent idea. I thought I read that he was only remodeling the bath tho. Seems to be a major undertaking if hes not doing a whole house remodel. Unless its a ranch home and he can assure that if he puts the HRV in the attic it wont freeze. I didnt notice if he lives north or south.
    I am the "Wally". All others are meer imitations of the original.

  9. #9
    Join Date
    Oct 2006
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    So. NH
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    The Panasonic fans are what I usually recommend, quiet, efficient and actually move air. Coupled with a humidistat and properly sized it should do the job.

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