[CAUT] Hygrometers

[Fred Sturm]

On 11/15/07 7:13 PM, "Greg Newell" <gnewell at ameritech.net> wrote:

> Paul,
> 
>                 40-45% at what temperature? At 50 degrees, for instance, that
> would be quite wet.
> 
>  
> 
> Greg Newell

Hi Greg,
    Actually, 40-45% RH at 50 degrees F is a fairly low ³absolute wetness²
level for the air. If you don¹t change anything except temp, and raise the
temp to 70, the RH will drop to something like 30%. (The hotter air could
hold a good bit more moisture. RH is a measure of how much it holds compared
to how much it CAN hold).
    RH is a fairly useful measure for how much water will move how fast
between the air and wood that is not acclimated to that RH (has a higher or
lower moisture content than would be a stable state in that RH environment).
If you vary the temperature, but keep the RH constant, the wood will stay
pretty constant (maintain the same moisture content), at least within normal
interior temperature ranges. But that means adding moisture when heating, or
subtracting moisture when cooling.
Regards,
Fred Sturm
University of New Mexico


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