Pamela Silvestri wrote:
> Where I have placed a hygrothermograph is in a room where I have a
> large fan and a dehumidifier...so I do suspect the measurement would
> be higher (probably close to 100%).
Put the fan opposite the dehumidifier. The fan will help move air past
the dehumidifier from another part of the room. The dehumidifier seems
to be doing it job (75% locally) so moving air from all parts of the
room by it is desirable. I'm assuming it in the 30x60 room.
> The HVAC system was installed 5 years ago -heat only. Vents are only
> in our larger room...which is @ 30'x250'. The other room is 30'x60'
> and there is a large doorway between Perhaps I should turn it on just
> to get some air circulation?
Circulation yes, heat no. Most system will allow for circulation only.
Following all codes and precautions with the supervision of the building
manager, turning off the supply of fuel to the heating units will
prevent heat form being generated. Warmer air will be able to hold
more moisture, but that just means the condensing surfaces don't need to
be as cool (relative) to condense out moisture, a bad thing.
> Don't know if the budget can handle the use of xtra propane, but if
> it's only for these wettest days...shouldn't be a burden. Vents are
> only in our larger room...which is @ 30'x250'. The other room is
> 30'x60' and there is a large doorway between these rooms.
>
I'd put any available budget into dehumidifiers and fans.
> Like Dave mentioned - it would be a good idea for me to cover the
> doorway and this should help with the one room. Incidentally - none of
> the windows open . I have a ventilation fan at the end of the larger
> room - and I can open the door (which I keep closed to try to stave
> off the humidity for as long as possible).
If the outside air has less humidity (moisture content or lower dew
point) than the air in the dead-air locations, then flushing with the
outside air is desirable. Your call.
Do you have a sling psychrometer? The chart and/or slide rule will help
to show the lack of suppression of the wet bulb under "low dew point"
and "high moisture content" conditions, e.g., wet and dry bulb readings
are similar. This is all in Thomsons' "Museum Environment."
> I do open the door when the weather is nice -but only to dry out. No
> screen door (I did request one last Fall) so when I do this -barn
> swallows have flown in and all the flying insects. How they find
>
> Pretty much, I've found that during the summer, indoor conditions are
> worse than that present outdoors - for the most obvious reasons here.
> I do not use a dehumidifier in the larger room because there are
> enough spaces open to the outside and otherwise with no insulation I'd
> just be drawing moisture in.
"Spaces" open to the outside, when you are trying to lower humidity with
dehumidifiers, is a problem. Lack of insulation isn't. Insulation
keeps heat in, or out, depending on conditions; it is largely an
economic (fuel) issue. If you can seal the room (plastic over those
"spaces") and run multiple dehumidifiers with fans to circulate the air
past the dehumidifiers from dead areas, you will be ahead of where you
are now.
>
> The industrial fan that I just got for the smaller room - well what I
> really needed was an exhaust fan installed but we weren't able to do
> this. I can move air around but I really can't achieve good ventilation.
Assuming the dehumidifier is in the small room, moving air past it (room
sealed from the outside air) with an indication (RH/Temp monitoring)
that the general RH is going down, would be a good solution. It will
take a while to get all that water out of everything. One or two more
dehumidifiers in the small room would speed the process. Emptying all
that water has to be kept up, with unless the dehumidifiers are
continually drained via a hose hookup.
>
> Just an example of the many challenges here - there are several
> footlockers...all containing wool uniforms and cotton clothing. I've
> struggled with deciding whether or not to place these in textile
> storage boxes. With the humid conditions...the footlockers stay drier
> than boxes would. And I would need to have all the items properly
> cleaned/conserved before doing this anyway.
Textiles do not need to be cleaned and conserved to be stored in
containers that will do no additional harm. Good storage is the start
of the preservation process. The foot lockers may be drier, if the
present "high humidity" condition are transient, if the high RH
conditions are normal, the moisture content inside will come into
equilibrium with the outside air, based on leaks and permeability.
Almost nothing is sealed to water vapor (and oxygen). OK, wax is a very
good barrier, the thicker the better.
> I can't take objects from an unstable environment and place them in
> yet another.
>
> One solution I did find though is that I could hang these in the dry
> storage closet. I did buy padding for hangers and archival plastic covers.
How did you get a "dry" storage cabinet in this wet space? Can this be
replicated?
>
> As always, whenever I post these issues I get useful information and
> often these responses get the wheels turning in my head.
>
> Oh one last question - just by chance there were no visitors to the
> museum today. If it's much the same dampness tomorrow or on others
> days...should I consider not having the museum open?
If you are sealing and dehumidifying, the opening of doors to let a
modest number folks in and out should not be a problem. If you going to
have the doors opened to circulation, the more the merrier. I think
someone needs to be in the space observing condition, emptying
dehumidifiers and responding to events.
Tim Vitale
510-594-8277
>
> Thanks,
> Pam
>
>
>
> In a message dated 6/29/2006 9:18:20 P.M. Eastern Daylight Time,
> [log in to unmask] writes:
>
> Your humidity is higher than 70-75%, based on how you describe the
> feel
> of things. Items in the room probably are getting cool at night, and
> then, the even more humid night air (cooler air holds less water)
> condenses as water on the cooler surfaces. This liquid water creates
> even higher humidity as it evaporates back into the air, as water
> vapor,
> as the dew point increases. Your air may have been as measured,
> 70-75%
> RH, at some point midday, but if you feel wetness at that
> humidity, this
> is telling you a different story.
>
> You can live with 70-75% RH for a good long time.
>
> Fabrics that feel damp in 70-75% air, are far wetter than fabric at
> equilibrium with that moisture content should feel. They are
> probably
> wetter, and are evaporating off that "gained" moisture as the "dew
> point" of their local room air allows. Use a recording
> hygrothermograph
> if you can find one, you can even use old charts if you can use a
> different color of ink; the digital version would be ideal. These
> will
> tell you the real story at night, in the morning and midday.
>
> The most unstable materials are those that have already had
> contact with
> mold in the past. [Big help, right?] Spores are dormant for a long
> time waiting for the right pH, RH and lack-of-air-movement
> conditions.
> Any of the materials you mentioned could be the first to go, based on
> the degree of mold present in/on them. Closed books are slow to
> follow
> moisture changes, even on the way back down again.
>
> The solution is to put "devices" in "the room" that will condense
> water
> from the air before it can condense on cool surfaces. When water
> condenses on a surface, it is depositing moisture in the room more
> permanently, rather than just being in the air, which can be
> transient.
> These "devices" are dehumidifiers or window air conditioners.
> Install
> as many as you an manage, with the windows closed. OK, if you're
> in the
> area of the floods then you have problems. The next less effective
> solution is to keep the air moving, with the windows open. If you
> are
> getting condensation, then keep the air "moving" all night as well.
> This means you will need active guards watching everything.
>
> No good answers, sorry. You have a difficult situation, at a
> difficult
> time. Its best to be vigilant, you'll smell mold before you can
> see it.
>
>
> Tim Vitale
> Paper, Photographs &
> Electronic Media Conservator
> Film Migration to Digital Format
> Digital Imaging & Facsimiles
> Preservation & Imaging Consulting
> Preservation Associates
> 1500 Park Avenue
> Suite 132
> Emeryville, CA 94608
>
> 510-594-8277
> 510-594-8799 fax
>
>
> Pamela Silvestri, Seasonal Interpretive Guide
> Northeast States Civilian Conservation Corps Museum
> Connecticut State Department of Environmental Protection
> State Parks Division
> Shenipsit State Forest Headquarters
> 166 Chestnut Hill Road
> Stafford Springs, Connecticut 06076
> Telephone: (860) 684-3430
> e-mail: [log in to unmask] or
> [log in to unmask]
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