Wearing Jacket to Bed to Boost Bag Rating

That is exactly what you should do! Works Great…I would say that is what many of the members here do.

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Go for it! I use my Montbell Thermawrap jacket and pants, as needed to increase the warmth of my North Face Beeline. Works great, and I can wear the jacket and pants without the bag.

I purchased the Montbell Down Inner Parka and Pants for this same purpose. Do you think these will provide the same additional warmth as the Thermaloft series? I am still using my 3 lb 20 deg Blue Kazoo but hopefully I will come up with enough guts to try a 30-35 deg bag (25-27oz).

Any idea how much using the parka will reduce my sleeping bag temp rating?

In other words – bag is 35 – would it then probably be a 25 or 15 bag? (I know it is hard to say but best guess is appreciated).

I don't have any accurate measurements, just anecdotal evidence. I believe the Thermawrap jacket and pants, including a North Face windblocker beenie and Smartwool hiking socks, keeps me warm down to the low 20's. That's in an Evolution 2P, double wall tent. I've used this combination in my Integral Designs Unishelter EXP bivy also. In both shelters I used a Thermarest Prolite 3.

Duh: All of the above in my North Face Beeline 30° down bag.

"I purchased the Montbell Down Inner Parka and Pants for this same purpose. Do you think these will provide the same additional warmth as the Thermaloft series?"

Do you mean the Thermawrap series by Montbell? I personally have found the Down Inner Parka keeps me a little warmer than the Thermawrap Parka.

I did mean the Montbell Thermawrap jacket and pants. They wont last as long as down but, since they don't breathe, they'll handle the moisture better.

Denis,

I was actually commenting on Laurence's post where he asked about "Thermaloft".

I agree with you that the Thermawrap would probably handle moisture better than the Down Inner, I just find the Down Inner a little warmer feeling. I feel I need to wear a heavier base layer with the Thermawrap to get the same warmth as I can with a lighter baselayer and the Down Inner.

An extended wet/cold weather trip might prove a different story.

Thanks Pamela and Denis,

I was referring to the Montbell Thermawrap jacket/pants as you surmised. You answered my question perfectly. I guess I have no excuse to avoid the light weight 35deg F sleeping bag now :)

My Beeline is 20 ounces for 30°. The new models even have a zipper.

How much singly layer loft does your jacket and sleeping bag have?

Add both. Now see the table here to find out till what temp you will be comfortable:
http://www.backpackinglight.com/cgi-bin/backpackinglight/bpl_sleeping_bag_position_statement.html

If you are trying to figure out the warmth adding effects of a synthetic jacket, consider the weight of the insulation. My Thermawrap parka has 80g/m insulation which I think is about 2.6 oz/yd. The exceloft insulation probably has about .65 clo/oz, so about 1.7 clo. I use thru-hiker.com's clo/temp ratings guide because it works with my metabolism accurately. My parka would add about 15* when coupled w/ similar pants. Your metabolism may be different though, so you should adjust for that.

I personally don't take loft measures into account when using synthetics. It has been long discussed and proven to hold little water. When using down, I think knowing the ounces of down in a garment or bag is more accurate than measuring the loft. If going that route, consider adding the amount of down in both the top and bottom garment to the amount of down in the bag. Find a bag from the same company with a similar amount of down as the bag+clothes, and that should be where you base your temp rating, adjusted for the companies ratings vs. your experience with your other bag.

"If going that route, consider adding the amount of down in both the top and bottom garment to the amount of down in the bag. Find a bag from the same company with a similar amount of down as the bag+clothes, and that should be where you base your temp rating, adjusted for the companies ratings vs. your experience with your other bag."

OK… using WM bags as example, the ultralite (20F) has 7oz more fill than the summerlite (32F). A montbell inner and pants has only got about 4oz of fill in total though, so from that reasoning you wouldn't expect the pants/jacket combo to be enough to lower the summerlite bag rating to the same as the ultralite. In fact it seems like it would be closer to 25F.

But plenty of folks on the forums seem to reckon that a 10F gain in bag rating is a reasonable expectation from wearing inner pants/jacket.

I don't know what the correct answer is, but just thought I'd point it out and see whether someone else can make sense of it!

Actually according to WM's site it is a 6oz differential in fill. Also I would think the fill used in the full down collar in Ultralite is included in the fill weight. And that collar would affect the overall rating of bag in that specific placement of that amount of down.

We are talking about too many variables. Humidity, wind, shelter, metabolism, weight, body mass, gender, height, hat, socks, genetics, hygiene, dinner, timing, length of sleep, mood, health….comfort is always subjective. I think a reasonable range is the best anyone should offer.

> Actually according to WM's site it is a 6oz differential in fill.

I think maybe you were comparing the 6' summerlite with the 5'6" ultralite. WM site shows the 6' summerlite to be 9oz fill and the 6' ultralite to be 16oz.

But as you say, very subjective. But I would expect a gain of 7F in bag rating to be at the lower end of the range.

>I think maybe you were comparing the 6' summerlite with the 5'6" ultralite. WM site shows the 6' summerlite to be 9oz fill and the 6' ultralite to be 16oz.

No I was referencing the main page for the Summerlite that specs it at 10oz. I see that the standard specification chart specs the 6' at 9oz and the 6'6" at 10oz. But if you look at the metric spec chart you will note a 175g difference in fill which puts the bags at 9.7oz(6' Summerlite) and 15.9oz(6' Ultralite).

What I do if I get cold is drape my down jacket over my torso then zip up my bag. This way my jacket isn't getting squashed under my torso – and my pad keeps my back nicely warm. The jacket retains its loft and has air space that warms up.

I get warm fast that way!

David,
Where is that table in thruhiker? i couldnt find it under articles…?

Mike

i'm thinking of getting a pair

I have a size medium that fits welland my waist is 31" and my inseam is 31.5", so I would say that their sizing is right on. They are roomy in the legs, though.

I wear a large Mountain Hardwear pack pant and I have the inner pants in a xl. I could wear a large inner pant, but I'm glad I got the xl. I can wear the down pants over my pack pants with long underwear underneath.

I highly recommend the MB down inner pants. If you don't have a pair, get them you'll love them.

They're like a really light, really warm pair of sweat pants.