Thoughts on Overstuffing and Understuffing down insulation

[BillyBob58]

This subject has come up oft before, and I don't know if I was ever convinced one way or another. And now Risk makes the argument for understuffing maybe = more warmth per uniy weight, if I understand his point.

But 1st of all, please define overstuffing.

800 ci/oz Fp down, if poured into a container, will puff up and fill a container of 800 ci, is that right? And if the length and width or diameter of that container are the right specs, then the hight ( loft ) of the filler area will be, say, 3". So put a lid on the container ( or a nylon cover when baffles make up the container ) that will just barely be touching the down, and now it is niether over stuffed or understuffed ( is that an actual condition? ), but simply "stuffed". It id simply filling the 800 ci of space that it's specs call for, correct?

Now, what happens if we overstuff that container? We put some more down in it. Does the height (loft) of the container remain the same, due to the "lid"? If so, does the warmth supplied by that same 3" of loft now increase? Or does it remain the same or possibly even decrease, due to less trapped air which has been replaced by down? The only thing I know for sure right now is it will be heavier.

Buy what if the lid is movable, not fixed? Or, the nylon "lid" is loose and allows the added down to rise up higher than the container walls(baffles). Is that what is meant by overstuffing? Well, now it is both heavier and has more loft, so I am pretty sure it will be warmer. Though maybe not quite as warm as adding more down AND increasing the baffle height so that the down just rises exactly to the top edge of the baffle? Because the loft will be more uniform and not peaking just in the center of the baffle?

But, if you increase the baffle height(container size ) to accommodate the added down, it is no longer overstuffed, correct? It is simply the new height ( loft ) that the increased amount of down and container size allow. So which is warmer? Enough down to just barely fill a 3" high container being allowed to do just that, or that same amount forced into a 2.5" container? The latter would definitely be more "stuffed" than the former. And denser, one of the reasons, I suppose, of overstuffing. But would it even be as warm, much less warmer?

So I 1st need o know exactly what is meant when someone says overstuff. And if that results in more loft, then I am sure it will mean more warmth. If it does not, then I am not so sure it will. But I don't know!

I can greatly increase warmth in certain areas in my PeaPod, a seriously "understuffed" quilt I suppose, as well as one of the warmest I have used, by shifting the down where I want it. But, there is so much space in those chambers, this does not so much overstuff the areas where I push the down, as it does increase the loft. I can have the rated 2.5" of loft along the 9 ft length, or I can have 4+" of loft is a smaller area.

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.

OK ( just rambling aimlessly ), if you fill those walls up with just enough insulation to fill the space, you have all of this trapped, dead ( can't move much like when there is no insulation) air providing insulation. And many folks always say it is actually the dead air that insulates, that's what they say anyway!

So let's say we overstuff these walls by a factor of 2 or 4 or 10. At some point, we will have compressed all of the dead air, and the only thing providing any insulation will be the insulation fiber itself, not any dead air. And I suspect it won't be near as much R factor as a lot of trapped dead air.

So, back up some. Let's say we add 20% more insulation than the exact amount needed to fill up the wall space with still uncompressed insulation. We have to stuff it in there just a little bit. We now have more insulation but maybe less air. Will this be warmer? As warm? I have no idea, but I'm sure there is some insulation expert that does know!

[OneThing]

One thing that does strikes me in application.

We pack for our fears.

Depends on where you like to confront your fears

That about says it all.

[MarshLaw303]

Something that hasnt been addressed is baffle size. Larger baffles need a higher percentage of overstuff to limit down migration. Thin baffles can limit migration with the "stuffed" amount and potentially thinner ones with the "understuffed" amount. The volume of each baffles plays into the needed overstuff percent to maintain constant loft without migration. KARO baffles, large 8" baffles, and heavily differential baffles need 20%-30% overstuff to limit migration where as thin 5" baffles can perform fine with less/no overstuff.

Baffle height should also be considered. I would never plan to stuff a 3" baffled quilt to 3", too much space inside and potential for migration. But 5" wide baffles that are 2.5" high lofted to 3" can be done without adding overstuff, or additional overstuff depending on your definitions.

For my quilts i had .5" to the baffles then an additional 20%. This is for KARO baffles which do require a high amount of overstuff. That overstuff controls down migration while at the same time increasing warmth. It allows my quilts to have a very conservative rating while also having reduced down shift.

That said, i hope to release a non overstuffed 5" vertical baffled top quilt in the future as this can be much lighter and still work very well.

[ringtail-THFKAfood]

Safety and comfort are very different.

I feel safe doing an emergency overnighter with about 2 pounds of gear in my day pack - not clean, not comfortable, but plenty safe.

I feel safe doing a planned overnighter with an 8 pound base weight. But I sacrifice convenience and clean.

I generally hike with a 12 pound base weight because I like to sleep in a hammock and have a change of clothes so I can rinse my hiking clothes fairly often. I carry less than a pound of first aid and emergency gear - including a saw.

The "what if" can add weight, but carry the gear needed to create the experience you seek.

One thing that does strikes me in application.

We pack for our fears.

Depends on where you like to confront your fears

[Risk]

I filled the underquilt I built yesterday with about 9-10 oz of cheap down from a pillow rated as 600. When I shake the underquilt vertically, the down shifts into the tubes and fills about half the tube, from looking at it with a bright light on the other side.

I slept very nicely for a couple hours last night, but it was warmish outside. I'll have to see how this does with time.

BTW, I am not convinced that this cheap down is worth the trouble. I dearly love the THru-Hiker top quilt that I made from their kit several years ago with their 900 rated down. 12 oz of down. This stuff is VERY warm and it has stood the test of time. I could probably replace the 10 oz of cheap down in my UQ with 6 oz of great down and have more loft. I could also buy lighter cloth than the 1.1 oz nylon.

It might be worthwhile to buy the present top quilt kit for ~$150 and use it to build a winter and a summer underquilt.

[XTrekker]

This subject has come up oft before, and I don't know if I was ever convinced one way or another. And now Risk makes the argument for understuffing maybe = more warmth per uniy weight, if I understand his point.

But 1st of all, please define overstuffing.

800 ci/oz Fp down, if poured into a container, will puff up and fill a container of 800 ci, is that right? And if the length and width or diameter of that container are the right specs, then the hight ( loft ) of the filler area will be, say, 3". So put a lid on the container ( or a nylon cover when baffles make up the container ) that will just barely be touching the down, and now it is niether over stuffed or understuffed ( is that an actual condition? ), but simply "stuffed". It id simply filling the 800 ci of space that it's specs call for, correct?

Now, what happens if we overstuff that container? We put some more down in it. Does the height (loft) of the container remain the same, due to the "lid"? If so, does the warmth supplied by that same 3" of loft now increase? Or does it remain the same or possibly even decrease, due to less trapped air which has been replaced by down? The only thing I know for sure right now is it will be heavier.

Buy what if the lid is movable, not fixed? Or, the nylon "lid" is loose and allows the added down to rise up higher than the container walls(baffles). Is that what is meant by overstuffing? Well, now it is both heavier and has more loft, so I am pretty sure it will be warmer. Though maybe not quite as warm as adding more down AND increasing the baffle height so that the down just rises exactly to the top edge of the baffle? Because the loft will be more uniform and not peaking just in the center of the baffle?

But, if you increase the baffle height(container size ) to accommodate the added down, it is no longer overstuffed, correct? It is simply the new height ( loft ) that the increased amount of down and container size allow. So which is warmer? Enough down to just barely fill a 3" high container being allowed to do just that, or that same amount forced into a 2.5" container? The latter would definitely be more "stuffed" than the former. And denser, one of the reasons, I suppose, of overstuffing. But would it even be as warm, much less warmer?

So I 1st need o know exactly what is meant when someone says overstuff. And if that results in more loft, then I am sure it will mean more warmth. If it does not, then I am not so sure it will. But I don't know!

I can greatly increase warmth in certain areas in my PeaPod, a seriously "understuffed" quilt I suppose, as well as one of the warmest I have used, by shifting the down where I want it. But, there is so much space in those chambers, this does not so much overstuff the areas where I push the down, as it does increase the loft. I can have the rated 2.5" of loft along the 9 ft length, or I can have 4+" of loft is a smaller area.





OK ( just rambling aimlessly ), if you fill those walls up with just enough insulation to fill the space, you have all of this trapped, dead ( can't move much like when there is no insulation) air providing insulation. And many folks always say it is actually the dead air that insulates, that's what they say anyway!

So let's say we overstuff these walls by a factor of 2 or 4 or 10. At some point, we will have compressed all of the dead air, and the only thing providing any insulation will be the insulation fiber itself, not any dead air. And I suspect it won't be near as much R factor as a lot of trapped dead air.

So, back up some. Let's say we add 20% more insulation than the exact amount needed to fill up the wall space with still uncompressed insulation. We have to stuff it in there just a little bit. We now have more insulation but maybe less air. Will this be warmer? As warm? I have no idea, but I'm sure there is some insulation expert that does know!

The insulation IS what traps the air. The wall cavity does a poor job of this. Thus the need for insulation. Here is another factor to toss in the equation. Spray foam insulation is alot more dense and very little is needed to achieve the same R value of regular Fiberglass insulation. It only traps tiny air bubbles and yet does a much more effective job a insulating. I think the main key here is just in how effective you trap air movement for insulation. And an under-stuffed quilt, IMO, will not do that as effectively as an overstuffed quilt. But to each his own..HYOH.

[MedicineMan]

BB58 said 'At some point, we will have compressed all of the dead air, and the only thing providing any insulation will be the insulation fiber itself, not any dead air.'
Now on the fiber level consider the polar bears hair....when your down to that you still have insulation because I think each individual hair is hollow, isn't this correct? Can't say about down; but if it also has spaces/hollows on a fiber level then even when all external (to the fiber) spaces are removed from compression you would still have insulation.

[BillyBob58]

The insulation IS what traps the air. The wall cavity does a poor job of this. Thus the need for insulation. Here is another factor to toss in the equation. Spray foam insulation is alot more dense and very little is needed to achieve the same R value of regular Fiberglass insulation. It only traps tiny air bubbles and yet does a much more effective job a insulating. I think the main key here is just in how effective you trap air movement for insulation. And an under-stuffed quilt, IMO, will not do that as effectively as an overstuffed quilt. But to each his own..HYOH.

Exactly. I'm sure there is some happy medium, I'm just not sure what that is. Too little down to fill a given space ( or other insulation to fill a wall cavity) will not hack it. OTOH, if " the main key here is just in how effective you trap air movement for insulation.", and if it is the trapped air that is actually doing the insulation, at some point by adding insulation to a given space, you have less air and more insulation, or even almost no air. Where is the happy medium? Do we know?

BB58 said 'At some point, we will have compressed all of the dead air, and the only thing providing any insulation will be the insulation fiber itself, not any dead air.'
Now on the fiber level consider the polar bears hair....when your down to that you still have insulation because I think each individual hair is hollow, isn't this correct? Can't say about down; but if it also has spaces/hollows on a fiber level then even when all external (to the fiber) spaces are removed from compression you would still have insulation.

Then there is that: air trapped inside various insulation material, yet another variable.

[WV]

When I think too hard my brain cells compress and my head gets hot. Approaching that point now.

[te-wa]

800 ci/oz Fp down, if poured into a container, will puff up and fill a container of 800 ci, is that right? -BillyBob, down is tested in a cylinder with a 1oz* weight applied. 800 fill down would consistantly loft to 800 c.i. under this weight.
without a weight, it will "loft" to much larger area.

*iirc