Originally Posted by
neilfein
Hmm... would it help if I replaced my groundcloth with something a little thicker, or am I better off spending that weight on a heavier groundcloth?
The groundcloth is irrelevant; regardless of the thickness, it provides no meaningful insulating value. The sleeping bag and pad are by far the most important factors in whether you stay warm or not. I've slept in open-sided shelters with wind and snow blowing around and have been perfectly warm and comfortable.
Take all sleeping bag ratings with a grain of salt. My rule of thumb is that if you want to be comfortable, the bag must be rated around 15 degrees lower than the outside temperature. So if it's freezing out, you want at least a 15 degree bag.
BUT - and this is also why the ground cloth makes no difference - you MUST have adequate insulation under you. When you lay down in the bag, you compress all the fill underneath you, and its insulating value rapidly approaches zero. At that point, you rapidly lose heat through conduction - and I can guarantee that the ground under you will have no problem absorbing all the heat you can generate. For 30+ temps, any common air mattress will be fine. Under that, and you should start to seriously consider a closed-cell pad. They're bulky and heavy, but hey, you want to be warm, right?
A decent cold-weather bag will run $200-$250 retail, minimum, and can climb rapidly from there. I prefer down bags for their compressability and weight, but synthetics work just as well and have lower price points.
Hooded mummy bags are great if you sleep on your back or stomach and want to stay warm. They're not so great for side-sleepers ( like me ). But I prefer fidgeting to get comfortable to not sleeping because I'm freezing. :-)