Stacking TQs?

[tjm]

I have used two UQs [JRB ORM & JRB HR] along with nesting a down mummy rated for 15 deg F inside a synthetic semi-mummy bag also rated for 15 deg F as TQs.

This got me down to -7 deg F wearing with mid-weight wool base layers, a balaclava, and down booties.

So it was a ton of gear for a sleep system & I typically need to use a pulk but I don't have to buy more gear.

[wisenber]

Replace "send bag reating" in the article with second bag rating and it will make more sense

I think Pan was either sampling some fine bourbon or suffering from early stages of hypothermia when he wrote that.
Still, it is pretty handy.
Another bit to consider when doubling bags is where the dew point will be in your insulation. If you're off on that one, you may find one of your bags is frozen in the morning and you might be too.

[wisenber]

I have used two UQs [JRB ORM & JRB HR] along with nesting a down mummy rated for 15 deg F inside a synthetic semi-mummy bag also rated for 15 deg F as TQs.

This got me down to -7 deg F wearing with mid-weight wool base layers, a balaclava, and down booties.

So it was a ton of gear for a sleep system & I typically need to use a pulk but I don't have to buy more gear.

That's where I went wrong! I tried a baklava, but found that a Greek dessert did little to keep my ears warm.

[catalyst]

I think Pan was either sampling some fine bourbon or suffering from early stages of hypothermia when he wrote that.
Still, it is pretty handy.
Another bit to consider when doubling bags is where the dew point will be in your insulation. If you're off on that one, you may find one of your bags is frozen in the morning and you might be too.

How do you determine where the dew point will be?

[wisenber]

How do you determine where the dew point will be?

That is more art than science. The dew point is science, but figuring out where in your insulation that temperature will hit is where the art comes in.
The more important temperature would be the frost point which will be warmer than the dew point in below freezing temperatures. The frost point also determines where either your perspiration or the atmosphere's condensation freezes. If that magic temperature happens to be found somewhere between your body and the outer most layer of your insulation, that trapped moisture will freeze whether it be encased in down, synthetic, wool or a finely knitted chihuahua blanket.

This is also a good reason to consider vapor barrier clothing when staying out in temps well below freezing as it will eliminate the insensible perspiration from factoring in to the equation.