water dropplets on bathroom ceiling


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Old 04-20-11, 04:15 AM
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water dropplets on bathroom ceiling

we have a fan we run , but when it gets 85 degrees or hotter in the summer , the water droplets appear toward the middle of the afternoon when its the hottest . Is there too much insulation above it . there is a attic above it . we had a new roof and siding put on a month pior to this happening. thanks
 
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Old 04-20-11, 04:41 AM
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Is there any relationship between the time the shower is used and the drops of water?
Is the new roof darker? has the attic ventilation changed any?
 
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Old 04-20-11, 08:26 AM
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I would say about 8 hrs difference from 6 am to 2 -3 pm when the droplets show up . also roof same color and exhaust is going thru the roof
 

Last edited by razzle51; 04-20-11 at 08:28 AM. Reason: cahnge time
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Old 04-20-11, 04:06 PM
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it's got to be condensation due to the dew point meeting the ceiling temperature. If the A/C was running it could also be leaky ductwork making the ceiling cold. So this didn't happen before the roof work was done? You could check to see if your bath fan exhaust was done properly. They might have dropped it into the roof accidentally or something.
 
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Old 04-20-11, 05:31 PM
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I agree with x does the fan have a damper? How long after showering is the fan being run
 
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Old 04-22-11, 06:02 AM
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Is there an air movement /vapor barrier under the attic insulation? Also, when the new roof was installed was there any changes made to your attic ventilation air flow vents? Air above the insulation should always be the same temperature as the outside air. Most insulation is not a thermal break, but only a barrier and excessive attic heat can penetrate through to the drywall creating a very large difference between the inside air temperature and the wall board. There is naturally higher humidity in the bathroom air regardless of ceiling fans and this cooler moist air can condense on super heated wall board. I would first check and make sure that when they installed the new roof they didn't change the attic venting also by covering some up for instance, or moving them to poor locations that could affect the air flow. .
 
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Old 04-22-11, 07:00 AM
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equinox, you said: "this cooler moist air can condense on super heated wall board." That doesn't seem to be correct. Warm moist air will condense on a cooler surface, but a warmer surface will not lower the dew point which is what is needed for condensation. The transition from moist air to water droplets requires a significant amount of heat adsorption and a surface that is already warmer can't do that. If the bathroom is filled with hot steam from one of my daughters showers, then even a warm ceiling might still be cool enough to form water. But that doesn't match the timing of this problem.

raz, I would check where the exhaust that goes through the roof connects to the fan. Since they were working on the roof, that connection may have been disturbed. That could leave morning showers being vented into a cool attic forming condensation that takes awhile to work its way through the drywall. However, I would expect some discoloration and possible sagging to be apparent as well. Check out that vent to be sure the exhaust air is going out as you expect. If it is working fine, then try leaving the fan on for 30 minutes after each shower. They actually make switches with a delayed off just for that purpose.

Any ac ducts in that area as x said should also be checked. If any, they should be sealed and very well insulated.

Bud
 
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Old 04-23-11, 01:17 PM
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I would still check that the attic ventilation is adequate and whether any were blocked or removed during the roof installation as it seems the problems started just after the new roof and siding were installed. What kind of attic ventilation is used? Are there soffit vents involved to help with a good air convection and were they changed also when the siding was done?
 
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Old 05-17-11, 06:42 AM
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well the fan isa just vented in the attic , so will have to get someone out to vent it outside . thanks for all your help
 
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Old 05-18-11, 10:24 AM
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Dew Point Calculation Chart (Fahrenheit)

% AMBIENT AIR TEMPERATURE IN FAHRENHEIT
20 30 40 50 60(70)80 90 100 110 120
90 18 28 37 47 57 67 77 87 97 107 117
85 17 26 36 45 55 65 75 84 95 104 113
80 16 25 34 44 54 63 73 82 93 102 110
75 15 24 33 42 52 62 71 80 91 100 108
70 13 22 31 40 50 60 68 78 88 96 105
65 12 20 29 38 47(57)66 76 85 93 103
60 11 19 27 36 45 55 64 73 83 92 101
55 9 17 25 34 43 53 61 70 80 89 98
50 6 15 23 31 40 50 59 67 77 86 94
45 4 13 21 29 37 47 56 64 73 82 91
40 1 11 18 26 35 43 52 61 69 78 87

An example at 70f and 65%RH the "Dew Point"
is 57f thats when condensation starts to form.

The above may come in useful?
It shows the temperature and the relevant humidity when condensation will occur.

I have selected a temperature of 70f and a relevent humidity of 65% as an example. When this temperature and this relative humidity meet a window, ceiling, whatever that is below 57f then condensation forms.

I would suggest that you buy a hygrometer to check the relative humidity and an infrared temperature gun, with these you can check the temperature of any surface and see if condensation is forming. Note: With wood, plaster, drywall and some other things the condensation forms inside and is not visible on the surface.
 
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Old 05-22-11, 01:51 PM
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Fan is now vented to the outside and what a difference . thanks to everyone on this board for all the good advice . Roz
 
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Old 05-22-11, 02:15 PM
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Glad you got it worked out
 
 

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