Thoughts on Overstuffing and Understuffing down insulation

[MedicineMan]

put on a wool jacket today and wondered if felting of wool related to slightly compressed down.

[XTrekker]

Hmmmm...
Lets just apply this same concept to how our walls are insulated in our homes. If this was true then I should still be able to have the same insulation rating with less insulation in my walls. But, this is contradictory to what is the norm for insulating our homes.
The better we trap the air pockets the better the R rating; and having insulation in the walls much like down in a quilt, traps the air. The more down the better job it does trapping the air in place. Personally I would think having less down would allow more air flow in a quilt and lessen the R rating of the quilt. I understand that Down and Fiberglass insulation are not the same but the concept is still the same.

Ill place my bets on over-stuffing quilts. Im no expert but it seems like more insulation is the better option. Especially on something that will be exposed directly to the elements and will be moved and shifted around when in use.

[turnerminator]

put on a wool jacket today and wondered if felting of wool related to slightly compressed down.

Felted wool is indeed warmer than non-felted.

As the wool felts, it forms permanent bonds between the fibres and you get that shrinking we all hate in our favourite wool clothes.

As the wool felts, its must effectively contort the fibres and reduce the size of the air pockets, whilst increasing their density. The similarities with compressed down are there.

[FLRider]

A question that might be pertinent: are you talking about top quilts or underquilts (or both), Risk?

The reason I ask is that, the more "drapability" (for lack of a better term; the more that it conforms to your body shape, eliminating dead air spaces underneath it) a top quilt has, the warmer it generally feels (assuming comparable amounts of insulation). Slightly understuffing a top quilt may lead to it conforming better to one's body, leading to it feeling warmer (since one's body won't have to heat those dead air spaces where the quilt is not touching).

The understuffed quilt wouldn't be any actually warmer than a standard-stuffed quilt unless serious drafts were involved, but it would feel warmer faster due to more skin (or clothing) contact.

Just a thought.

[Hotdogman]

The overstuffing keeps the down in place better. If you understuff a baffle it will work fine laying flat but if you move it around or its not flat the down will migrate to the lowest point, creating cold spots. The proper amount of down or a little extra keep it all in place.

[jordo_99]

I understand your theory but you're overlooking the convection currents that will be present in the "bonus air" space and the pumping of the air mass with every movement.

If this worked, we could just suspend our UQ's in a manner that would form a perimeter seal but leave a gap under our torso's to take advantage of the bonus insulation. In reality, this has been shown to result in CBS.

As to the idea of minimal down amounts, this will create fewer, larger air spaces within the down vs. over stuffing (within reason) which will increase the number of smaller air spaces providing better control of convection currents/air movement. The effect would be similar to comparing an open cell foam with large holes to a micro cell foam.

First off, sorry for the novel that's following this...I got running with an idea and I just kind of kept going.

Secondly, I'm not familiar with the CBS acronym. What does it stand for?

Convection currents (referring to them as "CC" from now on) are a very interesting point to make and you could definitely be right that it would make this unusable...I'm just playing devil's advocate but here are a few counterpoints to bounce at you and keep the gears spinning so to speak:

I guess I should have elaborated better in my first post but I tried to keep it simple...I shouldn't have suggested that understuffing an UQ would result in 2 separate layers...it would lead to the "air" layer being less "down dense" than the bottom (down) portion and it would be a gradual change...this would mean that the area close to your body is more susceptible to CC and drafts than the outside...which is the area where CC would have the least affect.

Continuing on what I was saying before (but adding convection currents), this would mean that the warmer side of the quilt could be susceptible to "CC" but the colder side would have more down insulation and inhibit “CC”…so you’re left with the warm and cool air mixing but the cold air near the outer shell remaining unmixed. I made a diagram for this…if “CC” was applying to the “air portion” that would mean the 60F mixing with 35F but since down inhibits “CC” the coldest part of the quilt shouldn’t be affected.

By all means, understuffing is less efficient for warmth (seems obvious that would be true) compared to a normal or overstuffed UQ…but from a weight/cost-to-warmth perspective it might be worth looking into.

Another thing that I’m concerned about is whether or not convection currents would really be that prevalent within a 20-50F range. I mean, that's a big temperature range for our bodies, but usually when people refer to convection currents they're talking about applications which involve much warmer temperatures such as those involving fire being applied to a pot...in those situations the temperature is much hotter, and thus the elements/air are vibrating and moving much faster which would seem to make this less likely to have as much of an impact.

Another counterpoint to this could be that a down bag is still overwhelmingly filled with air, whether it is understuffed or overstuffed it’s still mostly air. If you have, say 16oz of down in a quilt and compress it as much as possible...that is very close to the amount of volume the down actually takes up in the quilt (which isn't much). Just compare the size of your quilt when packed to unpacked and that’s what I’m talking about.

All of that said, I'm just playing devil's advocate here and I see where you're coming from and I would say that reducing “CC” is likely the biggest factor in creating a warm quilt.


The important part--that I think actually could be a good idea.
I think that for a understuffed UQ to be viable it would need to have the baffles done in a way that shifting isn’t possible. If the down shifts at all and creates a cold spot then entire “air pocket” would be cooled. Using double wall baffles could possibly work (only filling one of the walls, and leaving the other empty) but at that point you’re negating some of the weight saving to accomplish it (adding a mid-shell of noseeum).

Now that I’m thinking about it, a double wall baffle might be very interesting for an UQ since you could carry a single UQ and use it for variable temps (hang it down-wall up on warmer nights, or air-wall up on colder nights). Again, this is under this assumption that CC wouldn’t completely ruin this idea…you’d also need to have a perimeter of down as well to create/insulate the pocket. This wouldn't be applicable at all for a TQ since the "air wall" would just compress regardless of which side is up. I'm going to draw this up in sketchup and create a new thread to see what people think.

[gmcttr]

CBS = cold butt syndrome.

[OneThing]

I use a very simple equation when it comes to Overstuffing.

Price per oz = $8
Money in Wallet = $20

Amount of overfill = 2 ozs. (Plus Double Cheeseburger, Fries, an a Coke)

Works every time.

[ringtail-THFKAfood]

I have a 20 degree Nunatak quilt. It was accurately rated, but early in the morning when I watered the bushes I needed to shake the quilt to get the down back on top. I sent it back and had it overstuffed. No more shaking the down to the middle at 3:00 am.

The overstuffing keeps the down in place better. If you understuff a baffle it will work fine laying flat but if you move it around or its not flat the down will migrate to the lowest point, creating cold spots. The proper amount of down or a little extra keep it all in place.

[Rolloff]

Shug talks a piece in one of his vids about "manipulating" the charge of down in his UQ baffles, to suit the temps and his needs.

Seemed like he was doing this on set up and not worrying so much about overnight migration. To further regulate at night, he would center or vent the UQ as needed

Not sure what % of over stuffing would negate the ability to do so. Probably a sweet spot to be found much like our lays and SRL tension.

To go lighter and cheaper from here, also demands higher set-up skill factors to make it work. Less bomb and idiot proof. Less margin for error in actual backwoods application. Still minimalist is minimalist, and those are usually the sacrifices demanded to get there, in most circumstances.

One thing that does strikes me in application.

We pack for our fears.

An understuffed quilt, would certainly dry out better in the field, under suitable drying conditions, than would one overstuffed. Conversely, under poor field drying conditions, loss of loft could get critical at a much faster rate. It all depends on conditions, skill, and application.

That said, if you're worried about less down making you too cold, then adding 10-20% overfill doesn't probably require the same amount of skill set, that it might require to make the understuffed insulation work for you. Depends on where you like to confront your fears