UKH

I was looking at the RAB Ascent 1100 as it seems suitable for my needs and noticed that RAB also do Andes 1000. Both appear almost identical on paper but the Ascent is £310 and the Andes is £680. This makes me wonder if the Ascent is a good sleeping bag. If it's not would ypu recommend other model or brand in the -18/-30 range? 

The Ascent 1100:

https://rab.equipment/uk/ascent-1100

The Andes 1000:

https://rab.equipment/uk/andes-1000

The Andes is a top of the range bag using finest quality goose down and top end fabrics. It's aimed  at serious mountain expeditions. 

The ascent is a more budget bag using average quality duck down and heavier fabrics. It's aimed at the more amateur level. 

They’re both warm bags but the Ascent has lower quality down (650fp) which means it will weigh more to provide similar warmth.  It also weighs in at 1750g. The Andes has less down but of higher quality (800fp) which results in a warmer bag (-27c vs -25c for the Ascent.  The better quality materials also mean it is 145g lighter and also probably packs down smaller.

I’d recommend looking at the Cumulus range of sleeping bags.  This one is is the equivalent to what you’re looking at: http://sleepingbags-cumulus.eu/uk/categories/sleeping-bags/excuistic-1000?g...

I have two of their bags, the most recent of which that I bought, the panyam, has truly excellent warmth to weight.  The down is of very high quality and they use pertex fabrics like all the major manufacturers.

I have the Ascent 1100 as a winter bag and it’s kept me warm down to minus 14 degrees Celsius.  I sleep cold.

But I only camp at campsites, so only have to carry it short distances.  if weight and bulk aren’t a factor then it’s a great value bag.

Bought this exact model of sleeping bag a couple of years ago.

First impressions are brilliant, excellent value for the money, but after extensive use, especially whilst using for a bivi, the exterior fabric really wets out.

So for the second time in my life whilst purchasing sleeping bags, I'm wishing Id spent the extra money & bought a PHD or a mountain equipment sleeping bag.

Classic case of buying twice to eventually get what I should have originally bought.

That’s interesting.  I would point out that the shell used on the cumulus model (pertex quantum pro) is used by various manufacturers (eg Rab Alpine pro and Neutrino range).   To save weight some use pertex quantum which is less waterproof (eg Rab Mythic).  If your Cumulus bag is a couple of years old it might be made with either, I’d be curious to know which.  Certainly PHD bags and some ME bags have the option of a drilite shell which may or may not be more water resistant than quantum pro.  I have experience bivvying using a bag with PHDs hypershell and didn’t experience any wetting out but it was generally cold and I used an bivvy bag with it.

Edit:  it’s worth noting for the OP that of the two Rab bags the Ascent 1100 uses pertex quantum for its outer shell while the Andes 1000 uses Quantum Pro which is more waterproof.

Edit 2: After a little more searching I found that Pertex Quantum Pro has a hydrostatic head (waterproof rating) of 1000mm and Drilite Loft has a head of 1500mm, so could be worth going for a drilite bag if you’re going to be doing damp bivvys.  PHDs hypershell also has a hydrostatic head of 1000mm.