I have been playing with the idea of using my ski gear for summer time camping and leaving the my sleeping bag at home. Do any of you just wear down pants and jacket in a bivy and leave the sleeping bag at home?

No. A down jacket and pants will likely not be as warm as as a sleeping bag (extremities are not as well insulated), and they will not be as light as a summer bag. Since I don't generally need that warm of clothing on a summer trip, it would be weight inefficient to use that system.

> Do any of you just wear down pants and jacket in a bivy

Nope. First my sleep systems are lighter than the clothing I would use to be comfortable in the same conditions. Assuming the same materials in clothing/bag, the bag will be lighter: (1) it has a better ratio of shell -vs- insulation (2) bag has less surface area to insulate.

In cooler conditions I will combine clothing with a quilt... but never just clothing. Clothing that is warm enough to sleep in is at least 2x as warm as what I would want for any other purpose.

--Mark

I've used it sort of but only in weird situations most are unlikely to encounter.

If you're doing a race or event with wide temp variations...say roughly 85F to 25F...a synthetic top and bottom will allow you to keep moving through almost all weather and still get some sleep inside a bivy. It's not really lighter than a bag, just might keep you moving more.

I take a bag and synth vest for almost all trips instead but once and a while the pants/jacket combo might be better.

I had a bear steal my pack one night and slept out in my friend's warm clothes. It sucked.