RH problem

[Farrell]

Not trying to be argumentative, but a vapor barrier will not solve this 
problem. The condensation is from water vapor in the air inside the room. If 
the room is at 40% RH and 72 degrees, it has a certain amount of water vapor 
in the air - whether more vapor is coming into the room and being removed by 
a dehumidifier or whether the room is vapor-sealed and at 40% RH with no 
humidifier or dehumidifier operating. When air under those conditions is 
chilled to 46 degrees, condensation form - no need for additional vapor to 
enter the room. Presumably it is insulation you need - not a vapor barrier.

However, a vapor barrier is likely always a good thing to have - will help 
keep your room conditions constant and minimize the work a climate-control 
system has to do with humidity - but the specific problem here is 
insulation.

Or a warmer climate. Just wait a few years. Unless of course the Gulf Stream 
stops.......

Terry Farrell

----- Original Message ----- 
> Thanks Chistopher, Terry... and Don.
>
> I wonder if you could expound a bit on exactly what a vapor barrier is... 
> is that like a space of dead air in between double panes of window glass ?
>
> Terry... about the Farhenheit bit.... I was speaking Amerilish for youz 
> guys's benifit you see... :)
>
> Cheers and thanks.
> RicB
>
> Responding as an architect, I asked a senior technical architect in our
> office for his thoughts. He agrees with Mr. Farrell. The building
> envelop needs a vapor barrier. If it is a hot humid climate, the barrier
> should go to the outside. If it is a cold dry climate, like here, it
> should go towards the inside.
> ------------------------------
>
> My best guess is that the ceiling and upper walls are poorly insulated.
> These are outside walls? The dew point for 40% RH and 72 degrees F is 46
> degrees. So if it was 36 degrees F outside and the walls were around 40
> degrees F or so, condensation will occur on the walls.
>
> I thought Europeans used the Celsius scale for temperature.
>
> Terry Farrell
>