Humidity problem in our storage area

Looking for any ideas - similar experiences -and/or advice on stopping 
surface mold

Our primary storage facility - heated and cooled by a ground source heat 
pump system has developed a problem - first occured late summer/early 
fall last year - our HVAC contractor made some adjustments that appeared 
to fix the problem - but it was end of cooling season so it went away on 
its own anyway - now it has reoccurred only worse

HVAC system is cooling - will cool to pretty much any temp we set it at 
but it is not controlling humidity
this am it was 71 degrees and 78% RH
I and our contractor cannot find anything that has changed since mid 
summer last year - it was controlling it to 72 degrees with RH 45-50 
consistently then late summer RH began reading in the 60s

Our fix for the moment is to crank the temp down 65 (or less) to get the 
RH down - has anyone experienced an HVAC system (or more specifically a 
ground source heat pump system) suddenly changing like this?  Our 
contractor is consulting the system manufacturer and has already gone 
over the system from top to bottom and found nothing out of specs - I 
can find no change in conditions around the facility - no water 
intrusion  or changes that would increase the RH.

Immediate problem - while most of the collection are in boxes and 
buffered from this RH problem (above 70% today but was at 60-62% 
Thursday when cooling setback was done) we have a collection of county 
land records that are stored in roller shelves so the top book and edges 
are open to the interior air - we have a beginning outbreak of surface mold.

 From various sources the recommendation seems to be first to wipe off 
any mold on the surface - any other corrective measures for the 
immediate? These items were stored in a county basement vault for years 
and were cleaned on all surfaces and stored isolated for 6 months prior 
to moving them to the current storage. They have been here for 4 years 
with no signs of any mold until now (spot checked at least once a month 
because of their history prior to arriving with us).

Thanks for any suggestions or advice  - FYI there are about 300 of these 
over sized land and tax records.

Chris Taylor
Executive Director
Atchison County Historical Society
P.O. Box 201
200 S. 10th Street, Santa Fe Depot
Atchison, KS 66002
913-367-6238
[log in to unmask]
www.atchisonhistory.org


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