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Adding overfill to a Summerlite
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Andrew F
(andrew.f) - F - M

Locale: San Francisco Bay Area
Adding overfill to a Summerlite on 03/12/2011 00:40:17 MST Print View

I have a WM Summerlite that I love, but I find that a 32F bag is not quite warm enough for a lot of the trips that I go on. I am considering trading the Summerlite for an Ultralite, but that is a change in EN lower limit rating from 35F to 15F. I want a sleep system that is good to 25F and don't expect going any lower than this, so the Ultralite seems like it would be overkill.

One other option is having Down Works add 4oz of overfill to the Summerlite. This would make it very similar to the Feathered Friends Hummingbird - both narrow bags, neither have draft collars, and both have 13 oz of down fill. The Hummingbird is rated by FF to 20F. Adding the down would put my Summerlite at 24 oz, 5 ounces lighter than an Ultralite and 3 ounces lighter than the Hummingbird.

What do you think - do you think adding 4 oz of down to the Summerlite would make it good down to 25F?

Here is my current sleep system. I am a cold sleeper, and have found the limit for this to be around 35F, even after eating a big meal, moving down to the top, etc. At 35F, I was nice and warm up against the NeoAir, but my legs and feet were feeling the cold thru the top of my bag. I know I will probably have to add a thinlight or z-lite to hit 25F, but the weakest link right now is definitely insulation on top.
Mid-weight wool socks
Patagonia Capilene 4 long underwear
150 g/m2 wool t-shirt
Patagonia R1 hoody
Montbell UL Down parka
NeoAir (I always blow it up all the way, this is most comfortable for me and also the warmest)


Mike M
(mtwarden) - MLife

Locale: Montana
summerlite on 03/12/2011 08:22:53 MST Print View

it's been awhile since I've had mine (great bag, but was too small for me), but it seemed the summerlite was filled pretty decently- if that is the case then it won't benefit nearly as much from an overfill as a bag that is more loosely filled. I know someone inquired of WM about overfilling a summerlite and they wouldn't do it (they didn't elaborate why)

curious, if feasible, what's the cost? do they use comparable fill?

might be easier (cheaper?) to sell your summerlite and go to a warmer bag- my comments on your gear list were for a warm sleeper (me :))- appears your at the other end of the scale


Mat Tallman
(wehtaM) - F

Locale: Midwest
Re: Adding overfill to a Summerlite on 03/12/2011 08:56:48 MST Print View

Seems the easiest, cheapest, though perhaps not always lightest option would be to add some insulation under you. 25 Degrees is stretching the R-value of that Neo-Air pad in my mind (also a colder sleeper).

Perhaps adding a one of the thinner evazote pads on top of the Neo could bump things up enough to maintain comfort? Wouldn't cost too much to try at least. With all of the other insulation you have listed, the pad jumps out at me as the definite weak point.

Eric Blumensaadt
(Danepacker) - MLife

Locale: Mojave Desert
Sell it... on 03/12/2011 14:13:07 MST Print View

Sell your summerlite and buy an overfilled WM Megalite, which has the room for overfill AND extra insulated clothing if you need it.

Edited by Danepacker on 07/12/2013 13:56:22 MDT.

Mike M
(mtwarden) - MLife

Locale: Montana
last two points on 03/12/2011 14:53:26 MST Print View

^^ I'd have to agree w/ both- I'm a warm sleeper and right about freezing is about it for the neoair for me (I know it's higher than that for other folks)- a simple 1/8" GG ccf pad is all I need for temps into the 20's

point two- the megalite can be over-filled w/o question and more room for additional layers

Andrew F
(andrew.f) - F - M

Locale: San Francisco Bay Area
Re: comments on 03/12/2011 16:22:44 MST Print View

Thanks guys. I think I am going to pick up an Ultralite instead of trying to create a Frankenstein sleeping bag :)

I will also try adding some more insulation under the NeoAir. I have a 3/4 length z-lite that I'll bring along next trip to try.


Sean Passanisi
(passanis) - MLife
Bringing back an old thread on 07/12/2013 10:30:58 MDT Print View

I found a couple of threads discussing overfilling the Summerlite but has anyone actually done it? I spoke with WM this morning and they said they could add 1 oz or so, which they said would allow me to pick up a few degrees of warmth.

FYI, I also own a Versalite. I'm interested in seeing how far I can push the Summerlite before using the heavier bag.

Stephen M
(stephenm) - MLife

Locale: Mind your own business
Re: Bringing back an old thread on 07/12/2013 11:17:24 MDT Print View

1oz is not really a lot, when I asked them about my Alpine lite they said 3oz would add 5f so I did not bother.

Harald Hope

Locale: East Bay
overfill it, not 32 on 07/12/2013 11:35:01 MDT Print View

Andrew F, I have a summerlite too, and and someone here in a bag discussion thread a while ago corrected me when I said that western mountaineering accurately rate their bags, this was and is false, they do not. If you can find the actual EN rating for the summerlite, which that guy did, I think it was eric chan but not positive, you will see that it is comfort rated to 40, which is exactly what my body tells me it is good for, and what its loft suggests it's good for, and its name (summer...), just as the hilite is a 50 degree bag, with sewn through baffles.

Don't get me wrong, I like the summerlite bag a lot, it's great and feels very good, but I do wish that western mountaineering would post the true, full range, EN ratings on their website, not just the lower comfort level, which is what they post. My experience is that the upper comfort rating of bags is the only rating that matters when comparing them, so if I want a 32 bag, then an overfilled summerlite would be a great bag in my opinion. The 20 degree bags are pretty thick.

I much prefer how gear sellers have to rate their gear in Europe, you know all the actual data when you buy stuff from euro makers because they have to test it and post the results.

I'm not clear why a great company with a great history like western mountaineering doesn't post true full en ratings, I had assumed they used the actual comfort rating because they are such a good company, but they don't.

Also, for under insulation, check out lawson foam pads, that's very high R factor for the thickness, a 1/8" is rated at r .0.75,

Edited by hhope on 07/12/2013 11:37:50 MDT.

Brian Lewis
(brianle) - F

Locale: Pacific NW
I've done it on 07/12/2013 11:40:49 MDT Print View

I had both my summerlite and ultralite models overfilled, by WM. Took a while, but as I recall they alerted me to the delay in advance and that might have just been the particular time that I sent mine in.

When I first got my Summerlite, it weighed 20.4 oz, and that included the black stuff sack that came with it (difficult to weigh when not in a stuff sack ...).

In early 2010 I bought a cuben stuff sack; at that point it was 20.1 oz in that. Might have lost a few feathers since I bought it, however; I had maybe 1500 miles of backpacking on that bag by then.

After overstuffing, it was 24.0 oz in the cuben sack. So indeed, looks like I got close to 4 oz over the standard amount. I didn't specify how much overstuffing, just left it to their discretion.

I had definitely lost some feathers by the time I overstuffed, so certainly it was MORE than 4 oz that they put in. It was looking thinner in places, no matter how much I fluffed it up. But I had over 3000 miles of backpacking with that bag by that time, so I'm not complaining. WM bags are excellent.

I don't have enough data to suggest how much warmer it is since overstuffing. Each trip is a little unique so there's not much in the way of objective comparative data. It's certainly warmer since sending it in, but that's a false baseline to compare to, so ... my best guess is that they're accurate in saying that it will be a few degrees warmer.

Stephen M
(stephenm) - MLife

Locale: Mind your own business
En rating on 07/12/2013 11:48:14 MDT Print View


I have a Wm alpinelite and Puma and tge en rating is what Wm use.

Harald Hope

Locale: East Bay
they use en on 07/12/2013 11:58:54 MDT Print View

I didn't say they don't use EN rating, to be clear, I said that they do not post the full en rating, what they post is I believe the lower comfort rating, ie, the next bar down the en rating chart. So the summerlite is en rated at 40F comfort, 32 F lower comfort, but wm should simply show the full En rating, see? summerlite. Notice the table does not show the actual full en rating rage, just says: rating?

I learned this first on my highlite, which I sold after one night when I realized it was most certainly not a 40 degree bag, it was a 50 degree bag, and it was only after I think Eric convinced after digging up the true en ratings charts for wm bags, which you can find somewhere but not on the wm site, that he convinced me that I was in fact wrong.

My experience with lower comfort rating is that they are most certainly lower comfort, comfort is the actual comfort level, unless you sleep very warm, then you are fine in a lower comfort rated bag for that temp range.

I really wish wm would fix this, it's kind of not cool in my opinion, they have their bags rated, they know what the full en comfort rating is, so it's not like they don't have the data. I was tricked by this by northface too a while ago, though those bags did show the full range, they just promoted the lower comfort in big numbers, but wm should not do that.

Stephen M
(stephenm) - MLife

Locale: Mind your own business
Re: they use en on 07/12/2013 13:31:50 MDT Print View

I often read on here that Wm ratings are fairly on the money.

I sleep cold though so always add 10f on to a bags rating, I find the Wm rating
Much similar to bags I have used in Europe.

Edited by stephenm on 07/12/2013 14:01:48 MDT.

Eric Blumensaadt
(Danepacker) - MLife

Locale: Mojave Desert
My WM Megalite & comfort on 07/12/2013 14:07:10 MDT Print View

My original WM Megalite (30 F. rated by WM) kept me warm at 24 F. with ALL of my day clothes on at 8,300 ft. in a high valley on the PCT.

After that experience I sent it to WM for an overfill. By my digital scales they added 2 oz. of down. The bag now looks like the Michelin Man and I can no longer shake down from the top to the bottom, as before.

BUT... I can still wear my E.B. down sweater and Thermolite pants inside without feeling cramped at all. I'll use it like that in October at around 8,000 ft. in the Ruby Mountains of northern Nevada for deer hunting. Did it before at 11,000+ ft. in Colorado at 15 F. and was cozy. This BEFORE having it overstuffed.

Harald Hope

Locale: East Bay
chuckle on 07/12/2013 16:16:37 MDT Print View

Stephen M I can't put this any more clearly without posting an actual wm en chart. I'm not talking about opinions here, not subjective sensations of warmth, which is precisely what en ratings are designed to bypass when rating sleeping bag temperatures, the fact is that wm posts their lower en comfort rating as the rating, not the true comfort rating, which is the top number. I was resistant, like you, to hearing these words, but I was set straight by a link to the actual full en ratings of the bags, well, the best eric could find. Lower en comfort rating is an actual measurements, it's not a subjective statement that says it's lower comfort, though that also applies since the measurement measures the bag's ability to keep you warm. Top en comfort rating is the rating that I believe most users will be comfortable, no problem.

The only area this is a slight criticism on wm is the fact they do not show the actual en ratings linear gradient on their web pages, but chose to show the lower comfort rating, which they really should not do as a high end bag maker, they have these ratings available but chose not to show them on their website for some absolutely inexplicable reason. This is not a subjective opinion, the fact is, they do not show the en ratings of the bags on their website, only one rating, this is not correct and they should remedy the problem, I'm unclear why they still have not done so.

These are great bags, I own two, but I own them knowing that if it's going to be getting down to the 30 or so point I'm bringing the 20 degree bag, not the summerlite, ie, in california 'winters' at altitude. As I noted, the highlite was called a 40 degree bag but that's nonsense, it has sewn through seams, I felt those cold spots at well over 50, which of course you have to feel, there is only a layer of very thin nylon between you and the cold.

If you show the full en bar of temp, a purchaser can judge the comfort of the bag by noting that they need upper comfort for that temp range, or if they are a very warm sleeper, the lower comfort, but if you only show the lower comfort then there is a suggestion that is in fact the true upper comfort rating of that bag, which is not the case here.

Just to avoid this to returning to making the same exact mistake I made in this bpl rating thread here's the summerlite rating.

Summerlite Temperature Rating. EN 13537 tested:
T comf: +6ºC (42F)
T lim: +2ºC (35.6F)
T ext: -14ºC (well, you didn't die, maybe....)

Amazingly, my memory did work, and it was eric chan, tip of the hat to him for not allowing my mistaken belief that wm ratings on their site were accurate to be left unchallenged, and for finding an actual rough ratings chart for it, though I am unable to find the actual graphic version. I'll carry on the tradition of bpl gear geekdom here by passing on the link, and the link to the thread where he corrected me, even though it's a bit painful to read since it makes me look fairly foolish there, but what the heck, why not?

While some people sleep warm enough, or pack enough extra clothing to pad out the bag's lower rating, I personally have found the upper comfort rating to be quite accurate, since I sleep reasonably cold, that is, I will be fine in a summerlite 40 degree bag at 40 degrees, upper comfort rating, that's the actual top number. All bags should list these numbers in this way because that way all users of bags can judge fairly accurately based on how warm or cold they sleep if the bag works in that range, ie, a cold sleeper will be cold in a summerlite at 32.

With 3.5 to 4oz overfill, a summerlite should be a true 32 degree bag, that's what I'd use if I were to get mine again.

Edited by hhope on 07/12/2013 16:37:15 MDT.

Stephen M
(stephenm) - MLife

Locale: Mind your own business
Re: chuckle on 07/12/2013 16:34:39 MDT Print View

Thanks Harald for pointing that out, I am not in one both restiant to what you are saying, I was just a bit surprised.

As mentioned earlier I always add 10f for a bags rating, My 3 season bag is 20f and winter bag is -25f I know these are good to 30f and -15f for me and then I need to start adding either an overquilt or down clothing.

Coming from Europe I am used to seeing the En ratings on bags.

Harald Hope

Locale: East Bay
me too. on 07/12/2013 16:41:25 MDT Print View

stephen, I was surprised too, believe me, I really did not expect wm to do that, but that is why I read bpl, to learn stuff, even if I have to look somewhat foolish at times in the process, heh. I'm actually grateful to eric to pointing out that I was wrong because that lets me use these bags without disappointment, ie, I know the summerlite without overstuffing is a 40 degree bag, and it's a really great 40 degree bag. Just as the Ultralight is a very good 25 degree bag or so. I really wish wm would correct this issue because in my opinion it can lead to disappointed cold sleeper who are mystified why they are shivering all night at 32 f in a summerlite, when they would have bought the right bag if they had been properly informed, to me this is in wm best interest, and I honestly do not understand why they do not correct this oversight.

The en ratings was supposed to, and actually does, correct having to add 10f, as you can see, the wm summerlite in fact is precisely 10f colder than it's listed temp, the ultralight is about 8f colder.

Ultralight Temperature Rating. EN 13537 tested:
T comf: -2ºC
T lim: -9ºC
T ext: -27ºC

as you can see, the '20f' ultralight is actually about 28.5 f or so. What I realized is that you can compare using en ratings bags if and only if all list the full range, then you can compare the top comfort number that corresponds roughly to your method of adding 10f to the bag's lower number to get the true number. Ideally all bag makers would list the real en stuff that way you could actually compare say a zpacks bag to a wm bag to a ff bag to various european bags and have the comparison be meaningful.

Edited by hhope on 07/12/2013 16:46:55 MDT.

Stephen M
(stephenm) - MLife

Locale: Mind your own business
Re: me too. on 07/12/2013 16:52:26 MDT Print View

Hi Harald,

I owned a Summerlite for a while and found it bit lacking but always put it down to the lack of a down filled collar, my 3 season bag is now an Alpinelite and love it, I really like the extra space in it even though its a couple of ounces heavier than the Ultralite.

One thing to note is that the temp rating Wm give are much the same as what Feathereed friends give for the same specs.

I myself know that I need a certain amount of down to get me to a specific temperature and that's what ai look ad and not the ratings.

Dave Heiss

Locale: Pacific Northwest
Good info on 07/12/2013 17:24:33 MDT Print View

This is a fascinating discussion, and explains a lot - like why a WM Caribou I used to own, marketed as a 35F bag, would not keep me warm if nights dropped to the low 40's...

rOg w
(rOg_w) - F

Locale: rogwilmers.wordpress
deleted on 07/12/2013 17:39:41 MDT Print View


Edited by rOg_w on 09/08/2013 16:24:23 MDT.