WBRR - Which Pad

[BillyBob58]

I'll try quick and dirty, lol. You and I tend to get tangled up.

Remember- all insulation is simply trapped air. The smaller the air pockets and the more air pockets... the better.

Down filled mat- basically an UQ really. That downmat 9 is 3.5" of down... suspended from compression inside the pad. In some ways it's BETTER than an UQ because you can't install it wrong, get a draft, or have any leaks.
3.5" of down is about -10* of down. Most zero degree UQ's sold by vendors here are 3" or more of down.

Synthetic filled mat- next best thing... however they are not filled to the brim like down mats are. In the case of the Hyperlight series by exped... the end chamber has zero insulation. But that isn't across the board.

Closed Cell foams- are basically the smallest air bubbles you can trap, millions of them, and they cannot move or shift.
Think of it like sealed glass windows... but with lots of panes. Other than the fact that it packs poorly and it requires a decent amount of it... it's probably ideal insulation to lay on (compress) because you can't compress it.

Open Cell foams- same idea... but the foam is air permeable. That's why it compresses better. Fine when suspended inside a pad that stops it from compressing... but not so good to just toss in and lay on as you will compress it.

A purely air pad- dead air is insulation. Much like the sealed pane window mentioned. In fact the difference between the neoair xlite and the xtherm is that one is a double pane (one air chamber) and the other is a triple pane (two pockets of air). That said; there is a reason that glass windows are not much more than 1/2" or so of dead air. The bigger the pocket of dead air the more micro currents form.

STILL AIR is a great insulator. MOVING AIR is convection and increases heat transfer. So a 3" thick sealed pane window would actually develop air movement within the chamber itself and reduce it's insulating value.
When the wind is blowing across the bottom of an Air pad, it increases the air movement within the pad itself and causes the pad to loose R value.

So that answers one of your questions... partially deflating an AIR pad... doesn't hurt and may even help.
However partially deflating a down mat much past 2/3 would reduce loft and potentially create a cold spot.

Because Closed Cell Foam is closed... it is not very vulnerable to convection loss and does make a decent barrier under an air pad. The issue is this gets a bit clunky... but it a very commonly used trick from the ground that also works in the air. On the ground you're fighting conduction. CCF does an effective job at 'breaking' that flow of heat loss in both scenarios.

On a pad like the Exped synthetic... the pad isn't filled like a downmat. The synthetic that's in there acts in a similar manner to a CCF layer. It breaks up the air movement within the mostly air filled chamber so you never develop a micro current of movement within the baffles. It keeps the air still by providing a thin layer of undisturbed or insulated air. It's a bit like closing a storm door over the regular door. The storm door has little if any R-value but it has enough to let the door itself do it's job. Again... that's why even half inflated these do well. So long as you don't bottom out to less than a half inch you have the same layers of still air working.

Besides simple convection losses from wind moving across the surface of your UQ... when it's really blowing it will magnify any minor leaks you may have.
As many here say... hammocks are pretty easy until it gets cold... then any little wisp of failure or weak point in your UQ fit is magnified.
Most of us have had that 'finger of frost' slip in some wrinkle of fabric or pucker of quilt.

Heat rises... so with an UQ you need to make sure you are trapping enough heat up top for it to warm the UQ itself too. In a gathered end you get a decent seal with the wrap up the sides and your UQ to complete the cocoon.
So long as your fit is good you're not leaking that small pillow of super warm air directly under the body fabric and before the UQ.
Cold air sinks... so when you do have a leak you have that pillow of air trying to rise out... and the cold outside air falling to take it's place if possible.

That's the issue with a bridge, especially mine. Since the profile is more like a floating cot... wherever your top quilt isn't overlapping the UQ you are providing an uninsulated spot for the warm air your UQ has trapped to escape.
In that sense.. a pad can do better in deeper cold as it covers the surface more fully. Even a small 1/4" air gap of hot air trapped between the underside of the bridge and the UQ has plenty of opportunity to work away from where the top quilt seals it to a portion of the bridge body that is uncovered and rise away. By the same token... any open area of bridge body provides an opening for cold air to sink into that pool of air.

I find that a bigger open quilt or even a down blanket occasionally serves me better in my bridges than a top quilt as it can insulate the full surface more fully. The problem with that is it's easier to 'spill' the blanket as I move around.
A fully sealed pod system would do the job... but greatly reduce the benefit of bridges... which is ease of motion and multiple sleep positions. It's not an impossible problem... but to me around 20* it gets to be a problem I'd rather not try to solve as there are lighter, easier, better options readily available IMO.

Thank you for your thorough explanation and review. I share in your experience regarding the ease of losing heat by way of leaks/drafts/gaps with various hammock/TQ/UQ combos.

I find that a bigger open quilt or even a down blanket occasionally serves me better in my bridges than a top quilt as it can insulate the full surface more fully. The problem with that is it's easier to 'spill' the blanket as I move around.

Now that is very interesting, as I have thought about trying my TQ with the foot box opened and in blanket mode. I have not yet done that, as it did seem like it would be easy to kick something open in my sleep.

A fully sealed pod system would do the job... but greatly reduce the benefit of bridges... which is ease of motion and multiple sleep positions. It's not an impossible problem... but to me around 20* it gets to be a problem I'd rather not try to solve as there are lighter, easier, better options readily available IMO.

Ah yes, my personal all time over all fav for gathered hammocks, a Speer Pea Pod. Nothing beat it for ease of use and consistency, never failed me, never any struggles to get it to work as expected. ( The MWs on my JRB matched it on the bottom, but still had the potential TQ related draft issues on top, though seemingly less so than with my GE hammocks. ) and for me, used with a GE of course, it was the ultimate in freedom of movement. No matter how I moved around in the hammock, there was no worry about developing a draft or gap, because the pod stayed put top and bottom. And, like my HHSS, very easy to augment if needed. I wish I had not sold it. And it really did not weigh any more than 1 full length TQ + UQ. It's one draw back: while easier to match or exceed it's 20*F rating on the bottom, it was much trickier on top due to the hammocks edges lifting the TQ portion, causing a gap on top that lowered the temp rating. Easy to fill with a summer TQ, but that of course added weigh and bulk. However, once this was done, it was now actually a lot warmer than 20F, as you now had the loft of the added TQ plus the original 2.5" top loft of the pod. Most of the time, I simply used the clothing I had with me layered on top of me to solve that issue, which would get me into the 20s just fine. But I digress, none of that is about pads.