UKH

Off to the bugs in August. Likely to bivvy on some big routes. 

In the alps I've bivvied at -10/-15c in my rab 400gr down bag plus various other layers (crux down jacket, all my other clothes and and survival zone bivvy bag). Usually been warm enough. 

In Patagonia (Avellano, "Patagonia-lite") I did similar but with my synthetic bag. Warm enough, was around 0c and windy. 

However, I'm not expecting super cold night time temps, and I expect I'll have a down jacket with me anyway, so I'm wondering about getting belay/puffer troos (pants), thick socks and a bivvy bag. Anyone tried this combo? (no sleeping bag) 

Get a blizzard bag! Worked for me on my long routes in the Alps. Very light quite bulky warm enough. Cheap too.

Interesting. Just in your normal day clothes? Ideal for those routes where you hope not to but are quite likely to bivvy. 

Normal day clothes plus a light down jacket. Works well.

I've found a blizzard bag to be too sweaty in summer temps. On  the American Direct a few years ago I ended up wearing my waterproofs in it to try to stay dry... grim.

That's unlikely to work because membranes like gore-tex need a humidity gradient to work. If you're inside a humid non-breathable bag your freshly made humidity isn't going to pass through the membrane. Paramo might do the trick though...

I get sweaty in a sleeping bag in a tent, so I'll do a bit more research before buying anything. 

Indeed! Not that pleasant at all...

I was there in July 2019, we weren't bivying but camping I had a 500g down bag in a tent and was never cold. I think your 400g bag will be warm enough for bivying, maybe a thin synthetic to boost to make you a bit more comfortable camping? 

Can't beat it on price for sure! but Blizzard bag is 385g compared to for example: Rab Alpine Bivi bag 440g so the size/weight benefit of Blizzard is negligible.

In cold and dry conditions the Rab one will trap much less moisture meaning your clothes will be drier when you wake up and so drier at the start of your day

I don't bivvy much, but climbed a lot in the Selkirks and Purcells.  I think the weather in August will be pretty warm, even at night.  You could easily have a cold front and it could be snowing, in which case you'd not be climbing or if you were, you'd be bailing out.

Not tried it myself but could a pied d'elephant/half bag be an option?

The blizzard bag is also insulated so you don't need a sleeping bag. 

Fair enough... I suppose being impermeable will also reduce evaporative heat loss too. As a single night with a pile jacket (does anyone discuss fibre pile these days, or am I the only dinosaur 🦖) it sounds an option, but it sounds a bit grim especially for multi night

In the great tradition of UKC, I have not actually used any of the SOL range of bivi bags.

However. Apparently they are breathable light and repairable. Could be worth a punt (and test night before your trip) for the possible overnighters you might be enduring.

I have the lightest bag still in it stuffsac as an emergency option cost about £15. The thermal one around £48 and 156g  might be the best option to get some extra warmth for your legs.

Edit SOL Escape Lite Bivi

Cheers Rick, I'll do some digging but that sounds like a promising option. 

I have tried this in UK autumn and it was... Not good. The troos don't pack down much smaller or save much weight versus a light sleeping bag anyway, so I've never repeated it.