Vapor barrier liner @ 35 degrees to extend 40 degree bag usefulness?

[wisenber]

A VBL becomes useful in subfreezing temperatures as its benefit is to reduce insensible perspiration. 35 degrees is too warm for that feature to be of benefit. In warmer temperatures, you'll just be clammy. If you want to stay warmer without a weight penalty, wear your jacket in your bag.

[wisenber]

+1 on VB clothing versus liner. You can still wear other clothing over VB clothing to stay warmer whereas a VB liner requires that you be wearing nothing or next to nothing to work.

[bkrgi]

Just seems so much simpler, warmer, safer to bring the 20 bag and know your good for a warm nights sleep
I just would not be experimenting out in the field and have it not work right.
Test test and test some more the whole VB concept first and see if it works for you before diving in on a road trip

[Helium33]

I'm planning a trip during which the night time temperatures might dip to 35 degrees or so. I would like to bring my ultralight zapacks down bag, which is rated for 40 degrees, rather than bring my much heavier/bulkier 20 degree bag. Think I can get away sleeping in a merino top, and use my ultra-light cuben fiber vapor barrier liner inside the bag, to extend the range of the 40 degree bag? Or should I bite the bullet and bring my heavier/warmer bag?

I've never been a top/under-quilt guy. Always a bag sleeper in the hammock. If I'm carrying my double-layer, I put a thin ccf pad between the layers, and I'm happy. With my single layer, I sometimes use a Klymit X-Lite inflatable pad inside my down bag. Both work fine. I will probably use the CCF on this trip (CCF can't leak, and works better in a go-to-ground emergency if the ground has sharp stuff on it). An advantage to my winter down bag is a zipper in the footbox that allows my to pull the bag around my hammock (works with my tiny GT Nano 7, but not with my BIAS hammock, due to larger hammock size).

This is a 400-mile bicycle tour, and I am a weight weenie, so I would prefer to take my zpacks 40 degree bag for both weight and bulk reasons.

I know, I know, this is very subjective and everybody sleeps differently. Just wondering, though, if using my vbl makes any sense at 35 degrees. I've used it only in the 0 to 20 degree range before when doing winter camping.

Use the barrier and 40 bag.

[dakotaross]

Some folks know that I tend to poo-poo reflectix, but actually, one of the ways reflectix intrigues me is to use it with a Klymit pad. You would put the reflectix in the hammock layers and then use the Klymit pad on top of it. The reflectix pad is probably as good as your regular "thin" pad and you'll get some benefit from radiated heat given the distance between your body and the holes in the Klymit pad. I actually have a pad on order that I'm hoping to try out soon in that exact configuration.

On a personal note, the pad inside the bag thing used in the hammock sounds like forced ground-dweller theory use in the hammock. The idea of negotiating a bag, as well as a pad inside the bag sounds like nails on a chalkboard to me. Try unzipping the darn thing and using as a quilt. Surprise yourself. And yes, even when cold. But make the pad or reflectix 24" wide or more.