Making a sleeping bag warmer?

[domonic]

I have a goose down sleeping bag but it's sewn through. It's a chinese made AEGIUSMAX lightweight goose down sleeping bag. Very light and fluffs up well but the problem is the baffles are sewn through. I bought this just to experiment making some lightweight kit.

Because the baffles are sewn through. naturally wind will make it through the bag sewing holes which will be a problem for warmth.
I have a polyester/spaceplanket hybrid sack I could put it into. It could act as a shell to stop the wind from getting into the bag and through the holes. It breathes rather well thankfully as it's covered with numerous octagons of a foil like substance with gaps of polyester in between.

I was wondering whether putting that around the outside of the bag would help at all? I haven't had the chance to test it in the cold yet so I thought I would ask some of you what you thought about this idea.

I naturally want my kit to be as light as possible.

Thanks

[ChrisJHC]

You can unpick some of the stitches so that the baffles are further apart. Just make sure that you even the down out when you’re ready to use the bag.

[eggs]

I have a light weight setup with a good quality sleeping bag but not negative rated - and I slip it into a breathable bivvy bag if I need more warmth.
That setup can go into sub zero temperatures.

[domonic]

I have a light weight setup with a good quality sleeping bag but not negative rated - and I slip it into a breathable bivvy bag if I need more warmth.
That setup can go into sub zero temperatures.

Thats exatly what i mean. So I gather from your answer, this works well?

[Al M]

Combining a bag shell, even a light weight one that won’t be cheap and still weigh about 300-400g plus the sleep bag 600g = 1kg so not that light weight really. A cheap shell will likely weigh a lot more so maybe better to lookout for used 800-1000g full down proper sleeping bag for around $100-200 in Gumtree.

Have you tried sleeping with the bag using an internal silk liner to see it doesn’t work or are you assuming it won’t?

[Orion]

I have a breathable bivy I sometimes use in conjunction with my quilt. I think it adds at least 5°C to the overall rating. It weighs 140g.

But a better solution is to have a sleeping bag that is warmer. Sewn through construction doesn't save weight, just money. You could line your bag with $5 notes for extra insulation.

[Hiking Noob]

Could you use a flexible seam sealer on the seams?

[Aardvark]

Making the bag warmer? Has the bag complained about the cold? It could move to a warmer climate.
Maybe buy the bag a heater or just sit it on the chair in front of a fire. Better still, set it on fire.

Think about the physics behind what you are proposing. The lack of a baffle, hence the stitching passing through the bag means HEAT LOSS through the stitching more than it means accessibility to wind. Unless you're talking about the wind inside the bag.
Making the bag warmer, for you inside, is best achieved by coupling it with another layer. ie a silk sheet, another liner bag or a shell such as bivvy bag etc.
Taking up unoccupied space inside the bag with fabric items may also help but it starts to compromise your movement. Wearing extra layers will often only end up trapping a certain amount of water vapour from you within the clothing. (turns to sweat). A human body may produce a litre of water vapour overnight.

[Moondog55]

How much warmer do you want the bag to be?
How much warmer does it need to be?
Is it big enough internally to wear a down parka or jacket? If it isn't at least 150mm bigger around the chest than you are there probably won't be enough room to wear a downie
Aarvarks litre of water is a quantity I have used myself but latest best guess is that most of this is in the form of vapour from of lungs.
A windproof layer on the outside will put a layer of dead/still air above those stitched through lines so you might get up to a 10C boost in comfort.
You can add loops to the outside of the sleeping bag and sew some matching buttons to the parka and button the parka to the sleeping bag gaining several centimeters of insulation, my big -40 C rated sleeping bag actually came from the factory with this system of loops sewn in already, although this assumes you are not going to move and wriggle during the night.
An overbag can add a lot of warmth, up to the point where it starts to collapse the down in the liner bag and I know my own APEX and Robic overbag from Nunatak adds a good 10 to 15C when I use it as designed but being conservative I rate it at +8C when working out my comfort levels.
Also please remember that your insulation underneath has to be or should be rated warmer than your sleeping systems rating above you, R3.5 minimum for winter and add a bit more [ or a lot more] for sleeping on snow
Also remember that comfort and a good nights sleep is essential for our health and well being so use the bags comfort ratings and not the survival ratings which can be up to 20 degrees lower

[ChrisJHC]

Also please remember that your insulation underneath has to be or should be rated warmer than your sleeping systems rating above you, R3.5 minimum for winter and add a bit more [ or a lot more] for sleeping on snow

I fully agree that the bottom insulation is very important. Remember that down provides effectively no insulation when compressed so the bottom half of your sleeping bag is just dead weight. Some people carry a warm pad and a quilt only and find it very comfortable.
I also have a bivvy that I used to use when cowboy camping (no tent or tarp) and while it definitely adds warmth it is also heavy.

[Moondog55]

Out of interest which sleeping bag did you purchase?
They list several sewn though bags on AliExpress

[Aardvark]

Aarvarks litre of water is a quantity I have used myself but latest best guess is that most of this is in the form of vapour from of lungs.

yeah but you'd have to agree it doesn't sound as convincing when you say 'the body may pass 100-200ml of vapour in a night'