While insulation is very important, it is a vapor barrier that will enable you to maintain the proper RH. Without it, the brave mini split will be overwhelmed by the general climate outside. 

One of the things I've learned about climate control for historic buildings is that some types of construction count on vapor transfer to maintain the integrity of materials composing the walls. If a vapor barrier is added to walls requiring vapor transfer, you risk harming the wall in the long run. 

I would seek a qualified HVAC Engineer (not a local contractor) with significant experience with museums to evaluate the facility and devise a plan for better control of the environment. With the engineer's analysis and drawings in hand, any local contractor should be able to bid on the work. The key to success is hiring an qualified engineer with significant museum experience, and in your case one also experienced with the Secretary of the Interior's Standards for the Treatment of Historic Properties (or that consults with a historical architect on SOI Standards).

Hope this helps,
David


On Jul 9, 2017, at 3:52 PM, Douglas Nishimura <[log in to unmask]> wrote:

Mr. Hosley, I would suggest https://www.imagepermanenceinstitute.org/resources/videos/effect-humidity-rare-book for example, to see why HVAC is a good thing to have for the protection of collection materials.

 

Last year I had an institution in a Gulf coast state call and mention that they had experienced HVAC failure during January a year or so earlier and they had books “jumping” off of shelves. Given that they didn’t stuff books tightly on the shelves and the shrinking covers trying to open, jumping would indeed be the result as RH dropped. Tightly packed, the covers, likely at the spine, would’ve have failed.

 

In addition, we have learned that with regard to chemical deterioration of materials in the dark, periods of bad storage conditions count for more than the periods of great storage. If you have an object stored at some condition that would give it 10 years of life before reaching some agreed upon endpoint for half its life and another condition that would give it 1000 years of life before reaching some agreed upon endpoint for the other half of its life, you would find that the maximum life that you would get out of the object would be 19.8 years to reach the agreed upon endpoint.

 

Mr. Harvey is correct and the first 20 years or so of my career were spent studying the effects of storage environment on mainly archival materials. That taught me that storage conditions are critical to the survival of materials in collections.  More than ten years farther down the road, we’re satisfied that there are no substitutes for a good storage environment and now we’re trying to figure out how to achieve it at minimal cost.

 

Respectfully,

 

-Doug

Douglas Nishimura

Image Permanence Institute

Rochester Institute of Technology

70 Lomb Memorial Drive

Rochester, NY 14623-5604

1+(585)-475-5727

1+(585)-475-7230 (fax)

1+(585)-475-5199 (general)

[log in to unmask]

www.imagepermanenceinstitute.org

 

 

From: Museum discussion list [mailto:[log in to unmask]] On Behalf Of William Hosley
Sent: Saturday, July 08, 2017 7:10 PM
To: [log in to unmask]
Subject: Re: [MUSEUM-L] ductless HVAC unit in historic house attic

 

HVAC is a hugely unnecessary expense

 

Bill Hosley

Sent from my iPhone



 



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