Bag liner/foam pad/tyvek liner question?

[Bazookas]

Hey all, looking for some feedback on an upcoming early September elk hunt. I have a 25* REI Zephyr bag and an REI Helix pad (R4.9). I've been told to plan to a range of 0-40 degrees at night. Not sure the 25* bag is going to cut it. Question from me is rather than getting a new bag altogether ($$$), is it possible to make the following options work as effectively?

Bag liner - Sea to Summit Reactor liner (14oz) - states up to 25* improvement (likely closer to half)

Tyvek footprint - will this add to the R value from below?

Extra foam pad - possible to have additional R-value with a lightweight foam pad

Ultralight bivy - do these work to increase heat retention?

 

[TL406]

You’ll be fine with your current set up. A 25-deg bag with the 4.9-R pad will do fine. Wear your puffy jacket and a beanie hat inside your bag if it gets real cold, which it shouldn’t in early September.

 

[Geewhiz]

I use a 15* bag with an uninsulated big agnes pad in montana in sept and and am more often too warm than not warm enough.

 

[BBob]

Bag liner - Sea to Summit Reactor liner (14oz) - states up to 25* improvement (likely closer to half) IMO they aren’t worth the weight penalty. Use your jacket, extra clothes for unexpected temp drops.

Tyvek footprint - will this add to the R value from below? No

Extra foam pad - possible to have additional R-value with a lightweight foam pad Yes you could but what you have is fine for Sept

Ultralight bivy - do these work to increase heat retention? Mby a bit but wouldn’t count on it to add too much. Would probably help with wind under a tarp. I’m talking something like a Borah or MLD super light.

I use an El Coyote 30° quilt, Thermarest Xtherm in an MLD DCF superlight bivy under a tarp for CO Sept elk. If it gets cold enough (not often) I’ll put on clothes and use my puffy over my shoulders/body under the quilt. I don’t like wearing the puffy in the bag, it feels too constricted to me.

 

[87TT]

Early September, I sometimes end up on top of the bag.

 

[t_carlson]

I think your hunting partner is lying to you about 0 degree temps.

Legit 0 degrees is very cold. I've lived in Montana for 38 years and have never seen 0 degree temps before mid to late October.

Certainly NEVER in September.

 

[Bazookas]

Thanks all. Sounds like I’m in good shape with the current setup.

 

[AZ_Hunter_2000]

Look at the specs for this specific bag:

Technical Specs
Tested Lower Limit 25 degrees (F) - ISO
Tested Comfort 38 degrees (F) - ISO
Temperature Rating (F) 25 degrees (F)

No experience with the liner but I'd tend to do a pass on it as "magic bullets" tend to be more myth than reality.

Only the OP can determine to what temperature he/she/whatever can comfortably take the proposed system.

 

[Wapiti Hunter]

I bought a very lightweight Big Agnes down liner that was made to fit my 15 degree BA bag. I used it in an unusual cold snap of single digit temps during a winter hog/javelina hunt in the mountains of deep west Texas and it worked very well. Added less than a pound of weight and compressed down very small. I will use it again rather than buying an additional bag should the need arise.

Mike