side/belly quilt sleepers: stopping the chimney effect?

Maybe sew an insulted flap above the neckline of your quilt? I remember a Roger Caffin post about how he always puts a "hood" on his quilts accompanied by a pic of how it covered the head of a stomach sleeper. I have a long quilt that allows me to pull it over my head (it's synthetic so condensation is less of a concern), and that somewhat accomplishes the same thing, but I get in my mummy bag when it's super cold.

When sleeping on my left side, I rock forward a little and then reach my right arm under my neck and pull the quilt under my left shoulder. Then I rock back onto my side, anchoring the one quilt securely in place under my shoulder. Then grab other side of the quilt in front of my and pull it tight around my neck as I pull my arm/hand up near my chin to sleep.

If you sleep with your hand out of your quilt (ie. under your pillow) then you will need some other system. Most quilts have a snap or velcro closure, plus a cinchcord around the top hem to cinch it around your neck. I prefer rolling up in it though.

Agree with Dan: "Most quilts have a snap or velcro closure, plus a cinchcord around the top hem to cinch it around your neck". I find this also reduces side air infiltration. I'll wear a beanie or down hood (like JRB's) or hat (like Black Rock) or hooded puffy jacket inside the quilt as well in cold weather.

I've got a Big Agnes bag (insulated on the top only with a sleeve for a sleeping pad), that has a down-filled collar at neck height which hangs down from the top half of the bag. It reminds me of a the carrying yoke on a canoe – narrow (maybe 2" wide) in the middle and wider (4-5") on each side so you neck fits into the narrow part, so your neck and shoulders are all sealed to the bag to prevent a bulk flow of warm air.

I was surprised how effective it is and, per ounce, it has to be one of the most effective feature of the sleeping bag.

I greatly preferred it to the draw-string collars on other bags – it didn't constrain me, I could roll over just as easily, and it would settle back into my neck whether I was on my side (usually) or front or back.

It would be a pretty easy retrofit – buy a down jacket from a thrift store, use the down from it and the inner nylon taffeta as a fabric. One long seam might already be sewed for you and it doesn't take much force at all, so any old stitching job would hold it in place.

Easier to use synthetic for collar rather than down.

Also, water from your breath can get that piece wet, so maybe synthetic is better

I have a MYOG top bag with zipper down the middle top. On each side a flap that's about 12 inches at the middle tapering down to 2 inches at the edges. Something like that would maybe work.

I only use a quilt sometimes, and then only down to around 40F. Whatever jacket or coat I've brought for around camp use works well to keep my exposed neck, shoulders, and arms warm when worn under the quilt or mummy bag. I even did this with a 0F mummy bag down to 9F this winter.

A good quilt will have a draft collar and a way to synch down the top around your neck to seal out the cold (typically a snap and or draw cord). The best example is what you see with the Katabatic Gear quilts.

My wife and I always share a two-person quilt, so the draft problem around the top is worse than with a one-person quilt, especially since we usually sleep under tarps.

As it gets colder we first start putting on additional clothes (we do NOT sleep in our wet/dirty/smelly hiking clothes). First we replace a t-shirt with a long-sleeved shirt, then put on a hat, then a pullover and/or warmer hat. When it's really cold we will have puffy jackets or vests with us so we use them to close off the openings and for extra warmth around the neck. This worked well down to 15 degF in a tent, the coldest we've been in since we started using quilts.