Insulated pants

I can't answer your all your questions, but I made a pair of insulated pants with primaloft sport. I just used scraps that I had from another project so I sewed them on in panels.

Others might have more knowledgable information, but if I were to make a pair for serious, I would cut the insulation in the pattern shapes and then sew it around the edges onto the ripstop or whatever you're using.

I adapted a Controlled Exposure fleece pants pattern and found it easy to do the two layers with insulation between, and I've heard the thru-hiker pattern is fairly easily adapted to insulated pants too.

I made some insulated pants

Probably pre-Apex Climashield or Polarguard. About 3 oz/yd2.

I used a pattern I made myself from a pair of pants. 2.5 Apex is 0.6 inch loft. Multiply by 2 pi – make the pants 4 inches bigger around to allow room for the insulation.

I butted the insulation together at the inseam and put in hand stitches to the inseam of the pants liner to stabilize the insulation. Then there's no sewn through thin places. And sewed around the waist and legs.

I've fooled around with vapor barrier and never found it to be useful, but that's just my experience. I think it's better if you're in very cold conditions for extended periods – like an arctic expedition.

I made some with 3 oz Polarguard 3D, using a pattern i Already had developed for shell pants. I found I had to add substantial extra girth to the outside shell pieces to allow for the insulation to loft – so if you are working from a shell pants pattern, you'll end up doing the same.
As to splitting the insulation, from my experience you'd have a heck of a time getting it to split evenly or anything close to evenly – meaning you'd end up with a large variation in thickness. I'd look for some insulation closer to the thickness you are after.
On my pants – and a jacket I made at the same time – I sewed the insulation to one layer of the fabric, around the edges, then sewed the pieces together into pants, and then sewed the other layer of fabric to that, so the insulation is stabilized at the edges only, and not entirely sewn thru at the crotch seams or leg seams.
I found that pinning the insulation to the fabric helped a lot – without the pins I could not keep the insulation lined up with the fabric and got into trouble quickly. Hte other issue was the insulation getting caught on the presser foot. The only fix I found for that was constant vigilance. If I could have a large, bowl-shaped presser foot that would be great but I haven't seen one.

"Hte other issue was the insulation getting caught on the presser foot. "

Same here. You have to constantly press the insulation down and feed it under the presser foot. The presser foot keeps catching on loops of the insulation.

Somebody put a strip of fabric on top to avoid this.

Or sometimes I just put hand stitches through the insulation and the seam allowance of the inseam. Maybe one or two stitches per inch. You don't need a lot to keep the insulation stabil.

I read somewhere on the internet that if you tape your presser foot with smooth tape the insulation doesn't get caught. I tried it and with me it worked very well. The 'hole' between the two feet was covered, the smooth side being towards you. Hope this helps.
Kind regards and a happy New Year,
Marianne

I am finishing up some pretty simple 3.0 primaloft pants that I made without a pattern. Its a pretty simple process. I kept the insulation on the bottom instead of against the presser foot. It never really jammed or hooked. I'll post some pictures when I finish it. I just have to add a drawcord channel.

All good advice! It makes sense that the insulation needs room to loft so some extra material will be needed…also pins are a seamsters best friend!
It looks like thru hiker has some primaloft sport that may be better suited for this particular project…so i may just do that…the pattern and insulation looks like it will run about…65-75 bucks or so…which is much cheaper than most other insulated ants out there…plus i have a strange body (long torso with shorter legs) and being able to get my size of 32×30 can be a pain…
Mr Duke-Ill be looking out for those pics!!! and ill be sure to post some of mine when im done….
Happy new year everyone!

One thing a bit tricky with pants patterns is to get the butt shaped correctly. Not too tight or loose. Hard to know how to alter it if it's shaped incorrectly.

LOL!!!! Well i have no butt…so ill assume that i can make the seat of the pattern a bit smaller….but yeah good point!!!