Sleeping bag/quilt temp rating question

Is there a general rule of thumb about adding layers to a bag or quilt to suppliment the temp rating? I know temp ratings are subjective to begin with...

The reason I ask is I am considering a Enlightened Equipment quilt and would like to go with the 40degree quilt and hope it could be my 3 season option. What I am thinking is on any trip where temps drop well below 40 I could wear a base layer, I typically sleep in underwear only. I am also a hot sleeper.

Or...for about $20 and 3oz heavier I can go with the 30 degree quilt. Probably the smarter option....suggestions?

BTW I have camped twice in the last year at or below freezing, but I do have a 20 degree down bag that I "could" use, although I think I would still be tempted to try and use a 30 or 40 degree quilt in the spirit of weight savings.

Generally, I rely on clothing layers only as a safety margin for the sleeping bag when conditions get colder than forecast.

I pick the bag to meet the lowest temperatures I expect to encounter. If my trip projects lows in the mid-40's, I take my 40-degree bag; if lows are forecast between 20 and 40, I take my 20-degree bag; lower than 20, I generally stay home.

This strategy worked very well for me one fine January evening, when the lows (predicted to be 20) ended up being zero. Fortunately, my bags are rated about 5 degrees conservative side, which got me to 15. Midweight longjohns, down pants, down jacket, down vest, down mittens, and down booties) kept me comfortably warm to zero. Of course, two other critical factors were an adequate mattress (Thermarest with an R-value around 4) and the fact that my bag was cut wide enough that I could wear all that clothing inside it without compressing the down in the bag or the clothing.

While many others may not agree with me, I don't see "Take a warmer bag and rely on my clothes to make up the difference" as a valid lightweight strategy. The risk seems disproportionately high relative to the 3-ounce reward of the lighter load.

I can't fault you if you come to a different conclusion - provided you're aware of the issues. I'd maybe suggest that, if you do go the route of relying on your spare clothing, it might be best to do a test run camped at (or a short walk away from) your car, in case it doesn't work as well as you hope.

I agree with Glenn. I've been in too many situations in which the nights were a lot colder than expected. Like Glenn, I consider insulating clothing worn inside the sleeping bag to be a hedge against colder than expected temperatures, rather than a means of making an insufficient sleeping bag/quilt do for "normal" temperatures. I tried that once, and had a couple of sleepless nights as a result!

In any case, it's lighter to carry the extra insulation in your sleeping bag rather than in your clothing!

Yeah I know the smart thing to do is err on the side of caution, but what's the fun in that

I have not spent enough nights out in differnet conditions yet to know for sure how to gage my comfort level sleeping in different temperatures. I do know my Kelty 20F bag is fine in the lower 30's. I also know the Kelty bag is perfectly comfortable in a very leaky tent in a monsoon at around 60F, although the situation was somewhat disconcerting!

Also I have never been far enough out or put in a situation where my equipment choices could comprimise safety, but your point about situations changing is a good one.

I think the smart thing to do is go for the 30 degree quilt, it should be more versatile than the 40 degree, and worst case layer up make the best of it!

^^^yeah what that guy said^^^^^

Where do you go? I never leave without my JRB 3 season quilt. It is reliable to 25f before i have to start adding clothing. The Sierra Nevada can throw you snow in August... My rule of thumb is to plan for ten degrees below forecasted temps, and with the addition of clothing, to be able to survive 20 below forecast.

I have ended a trip early when a ranger informed us the forecast would be for a full thirty degrees below what the forecast Had been when we started hiking. My companion finished our hike to the car while wearing every stitch of clothing she Had - the day temp Had dropped that much.

You can always throw one of these in your sleeping bag.

http://www.amazon.com/HeatMax-Hand-Body-Warmer-Count/dp/B0007ZF4Q8

I only carry them in the winter months.