Should I insulate my sweating supply plenum?

[richmod]

With the one zone only being 1/2 open and the other full opened. movement is more then ok.
When both zones are full open. The bypass opening is indication of duct problems.

I'll guess I'll see what the bypass does after they fix the damper. I don't want to be a PIA to the tech unnecessarily, so for clarity - with both zones fully open, absolutely no movement of the bypass damper is the only acceptable scenario?

[beenthere]

There are many zone systems that the damper moves. when both zones are open.
It shouldn't.

[teddy bear]

Wow - quick replies - thanks!

Also, any recommendations for a decent, inexpensive dehumidifier for about 1700 square feet, average 2 feet high crawl space? I've seen the Sante Fe models for almost $1000 - wondering if there's anything around $500 or so.

The other spot to check for mold in above your insulation aroung the cold air supplies. The moisture condenses above the insultation on the underside of the subfloor. Closing the crawl after putting a good vapor barrier on all of the earth, and maintaining 55% RH will fix all of that.
Considering that you going to get a dehumidifier anyway conside ther following. If you are able to maintain 50%RH in your home during cool wet weather, you are not getting enough fresh air in your home to purge indoor pollutants and renew oxygen. If you get a Santa Fe, you will have enough capacity to bring in a small amount of fresh air into your home to assure indoor air quality. Check my data logging on my home regarding fresh air. It's worth investigating. It will improve the comfort level in your home. The cost to operate the Santa Fe keeping your crawlspace dry and providing fresh dry air to your home will be less than a cheap resid. dehu dealing with the crawlspace. The Santa Fe is also more durable. I will come back with the thread with the data on ventialtion and energy useage. Regards TB