Sleeping Bag Fill - For HIGH Humidity 80% - 95%

Down vs Synthetic

Technology has come a long way with treated down and new DWR bag fabrics. I'm not concerned about becoming rain soaked, which I can guard against.

I live in the Tropics and typical daytime temps are around 85-90F with 75-95% humidity. The mountains here go up to around 9,000 feet and the temps drop about 5 degrees centigrade per 1,000 meters increase in elevation in high humidity. Typical temps at altitude are around 32F on the low side to the more typical 40 - 60 degrees. BUT the humidity is always high and with weather changes is is possible to have freezing to just below freezing temps.

I am leaning towards a synthetic bag, but hate the weight and size penalty. A Big Agnes System bag would eliminate some of that

What are your sleeping bag choices for high humidity conditions?

You might want to consider a synthetic quilt. Ray Jardine offers a range of quilt kits for different conditions, some of them fairly light. He has a website, just google RayWay and look around.

I haven't camped in those conditions, but I've camped in a lot of rain and I tend to believe the water sensitivity of down is overblown. Every time I've tried to wash a down bag, it is a pain to get the down wet so I can wash it.

With high humidity, I guess you are worried about the down slowly absorbing moisture from the air. I would still prefer a down bag and be sure to dry it thoroughly between trips. You could also get a bit warmer of a bag than you otherwise would to account for some degradation during the trip.

If you make the decision that only synthetic will work because of the constant humidity, look into a quilt as was mentioned above. If you don't want to make your own Ray-way quilt, I've been quite happy with my Enlightened Equipment down quilt. They also make synthetic quilts. Though you might be able to get a local seamstress in the Philippines to sew a Ray-way quilt for less out the door than an EE quilt.

I don't have the altitude to deal with, but I do hike and camp in the Ohio River valley, where daytime conditions in the summer are temperatures in the 80s and 90s, and humidity in the 80s and 90s. In the winter, about the worst I'll go out in would be lows in the low 30s and humidity around 60 or 70 percent.

As someone else said, I think down's susceptibility to moisture is overrated. I've used down quilts in those conditions for years with no problems at all.

You might consider a system like this:

A down quilt rated to the mid-30s (I use a Thermarest Vesper 32, which has a comfort rating of 40 degrees.) As important as the quilt is the pad under it: I'd go with a r-4 rating or higher. (My choice: Thermarest XTherm regular, r-5+) I'd choose a quilt because they aren't as bulky as a sleeping bag (a synthetic quilt will be less bulky than a synthetic bag, too.) Also, they're easier to use: if you're camped lower and warmer, it's easy to reposition the quilt or stick your arms and legs out to adjust the warmth. I use my 40-degree quilt on 80 degree nights without any issues.

A down-filled balaclava, which becomes a hood to use with the quilt if you need one. Montbell has a really nice one in its Superior Down collection that I use.

Down-filled jacket (hooded or unhooded, your preference), down-filled pants, and down booties. You can wear these around camp before you go to bed, then wear them under your quilt to get another 10-15 degrees of warmth while you sleep. (How much depends on the loft of the garments. I've stayed toasty at 25 degrees in Smartwool long johns under Montbell Superior Down hooded jacket, pants and booties, using my 40-degree quilt.)

Another advantage to this "system" is that you can leave the jacket, pants, booties, and balaclava at home when you don't expect temperatures to drop close to or below the quilt's rating.

I can't swear this will give you the flexibility to meet the wider range of temperatures you encounter versus what I deal with, but it might nudge you in the right direction.

I'd buy a quality 25*F down bag with a waterproof breathable cover.

I imagine you already know this, but just in case...
The trick to getting the bag wet is to put it in the stuff sack and then feed it directly from the stuff sack into the water before it has a chance to expand. This assumes you're washing it by hand in the bathtub, of course.