Warming up a pad

Posted by: veloz

Warming up a pad - 04/17/16 08:47 PM

Hi there
I backpack often in the spring and fall where the nights can be 30-40 degrees. I'm a cold sleeper and have tried insulated pads, the current one being Big Agnes Double Stuffed Double Z pad, supposed rated at R5.9. (Have also used a variety of Therma Rest ultralight/insulated pads). None of them are warm enough.

I use a Katabatic Quilt to cover me (pure love!) but the weak link continues to be the pad. Seems like to matter what I do, I'm aware all night that the side of my body on the pad is chilly and I'm always flip flopping to avoid the chill.

So the basic question is: how to get a warmer sleeping surface? The pad with the next highest R rating I can see is one that has a rating of 11, but weighs 4 lbs - totally out of the question.

Today I was thinking maybe the trick would be to wrap the pad in a microfleece blanket (with hook and loop on the back so I don't have to cover the back with blanket).

Any ideas out there on whether sleeping on top of a blanket would substantially warm a guy up?

I have an extra ultralight down quilt, but I'm thinking that sleeping on top of that would just compress it and render it useless - I think any blanket you would sleep on top of has to have a bit of density to keep your body off the chilly pad.

Any/all thoughts are welcome!
Michael
Posted by: JustWalking

Re: Warming up a pad - 04/17/16 08:58 PM

Get a thin closed cell foam pad, and then put that on top of your insulated pad. Minimal extra weight but just might be the trick to keep you warm.
Posted by: veloz

Re: Warming up a pad - 04/17/16 09:21 PM

Interesting idea. I wonder what that would do to the comfort factor?
Michael
Posted by: bluefish

Re: Warming up a pad - 04/17/16 09:30 PM

We use a piece of Reflectix (available at Home Depot and Lowes) insulation cut to fit the pad and held on by straps to immediately radiate heat back to you for winter camping. I use a bag, but use it as a quilt thrown over us 90% of the time. When set up on snow and ice we also use a SOL e-blanket as a tent floor. I think the Reflectix would solve your problem very easily.
Posted by: veloz

Re: Warming up a pad - 04/17/16 09:32 PM

Do you put the Reflectix between the pad and ground or between you and the pad?

Michael
Posted by: wgiles

Re: Warming up a pad - 04/17/16 09:37 PM

I use a short pad made from a foam called Low-E insulation. It's a polyethylene foam with an aluminum coating on each side and It's under 1/4" thick. I've got a pole barn that's insulated with this stuff and had some left over pieces. I cut a 26" X 48" piece and made a fanfold pad with duct tape hinges. When folded, it provides padding in my pack. I use it under my inflating pad. I use a Z-Seat pad under my feet. The Aluminized Z-Rest pad may work, but I don't have one and can't say. I have a cheap Chinese EVA pad that is Aluminized on one side, but I've only used it to make cozies. I've used this setup down to freezing with my quilt and been quite warm. I'm not certain how sleeping pad R-value is measured and I wonder if it is reduced by compression, just like the bottoms of sleeping bags. A reflective layer might be better in this case.
Posted by: Franco

Re: Warming up a pad - 04/17/16 10:02 PM

Unfortunately there isn't a uniform standard for mats so R5 from one manufacturer could be R7 or R4 from another.

One mat that seems to get mostly positive comments about the given rating is the Exped DM7, now available in a UL versiopn at about 23 oz inc pump.
(it's a down mat)
Another one that many have compared to the Exped is the Therm A Rest X Therm,15 oz, rated at R5.7.
(the warmest of the Neo Air family)
Posted by: bluefish

Re: Warming up a pad - 04/17/16 10:55 PM

Originally Posted By veloz
Do you put the Reflectix between the pad and ground or between you and the pad?

Michael


On top of the pad, as I don't have it against bare skin. I've used a piece that was 4'x5' underneath both our pads, basically under our torso portion of the pad, and placed the individual pieces on top. We use thermarest neo-airs that are rated between R3 and R4. This took us below zero. The greatest gain to be had in r-value is to use the dead air space inherent in the pad sandwiched between the 2 layers of Reflectix. One layer will reflect back well, though. I've been using Reflectix commercially since it came on the market in the late 90's. I've used it for various insulating projects, but especially for radiant residential heating purposes. You can read many arguments on its effectiveness, I just know what it can and can't do from years of using it on the job and for myself in winter backpacking.
Posted by: BZH

Re: Warming up a pad - 04/18/16 10:58 AM

Originally Posted By veloz
Do you put the Reflectix between the pad and ground or between you and the pad?

Michael


I don't do this but I have heard enough testimony that I am convinced putting the foam insulation on top (between you and the air pad) is warmer. The engineer in me scoffed at this initially, but I believe it has to do with the air pad being full of cold air at the beginning of the night. When you lay directly on the pad, you have to warm that air up. Separating yourself from that cold air is to your advantage.
Posted by: wgiles

Re: Warming up a pad - 04/18/16 12:16 PM

If radiant heat is the main reason for body heat loss, then having the reflective layer next to the body makes sense. Less heat is transmitted to the air pad and less is lost by convection. I simply do not know how effective the reflective barriers are. Would a space blanket or an aluminized Mylar sheet provide as much reduction in heat loss? I think that a lot of people would decide not to use a Mylar sheet because they don't like sleeping on a plastic sheet. Reflectix is probably the first choice for a reflective blanket because it is so widely available. If I get around to it, I might try a space emergency blanket under a piece of Tyvek to see how it performs.
Posted by: BZH

Re: Warming up a pad - 04/18/16 05:30 PM

Originally Posted By wgiles
If radiant heat is the main reason for body heat loss, then having the reflective layer next to the body makes sense. Less heat is transmitted to the air pad and less is lost by convection. I simply do not know how effective the reflective barriers are. Would a space blanket or an aluminized Mylar sheet provide as much reduction in heat loss? I think that a lot of people would decide not to use a Mylar sheet because they don't like sleeping on a plastic sheet. Reflectix is probably the first choice for a reflective blanket because it is so widely available. If I get around to it, I might try a space emergency blanket under a piece of Tyvek to see how it performs.


Once you make physical contact, conduction dominates radiation. Radiation is important within the air pad, but an aluminized surface touching you or the ground is not going to help much.
Posted by: wgiles

Re: Warming up a pad - 04/18/16 07:21 PM

I would agree with you that conduction would dominate, but why do many of the supposed insulating pads have Aluminized coatings. I have never used a space blanket for anything other than a reflector, since I figured that, once I came into contact with it, it wouldn't do much to stop heat loss. If the reflective coating isn't that important, bubble plastic ought to be as effective as Reflectix. I don't know where to go for real world testing.
Posted by: BZH

Re: Warming up a pad - 04/18/16 11:43 PM

If you create an air gap reflective coating is quite effective at reflecting incidental radiation. You can often create airgaps. It is quite beneficial on top of a you. Often times reflective coating is added for marketing purposes and has no real benefit.
Posted by: Gershon

Re: Warming up a pad - 04/19/16 08:23 AM

I never use a pad, so I can't comment about how well they work. I do have some other ideas you might try.

Where you set up your tent can have an impact on how cold it will get at night. Cold air goes downhill, so it will be coldest near water or in a low spot. Even a few feet of elevation change can make a big difference.

The ground will be different temperatures based on the moisture content and the sun exposure. I've had the best success with bare dirt that gets the sun early in the morning.

The battle for warmth takes place quite close to your skin. It doesn't matter how good the sleeping bag is (within limits), if you wear a synthetic shirt near your skin, it's going to be cold. I generally wear a thermal top at night. With a great sleeping bag, it's best not to wear anything. Experiment with different clothing combinations.

You mentioned feeling the cold coming through from the ground. I lay my fleece under my sleeping bag which helps some. As long as I'm otherwise warm, that little bit of coolness is refreshing.

What you eat makes a difference. There is no mechanism in the human body to turn carbohydrates into fat. If a person eats excess carbohydrates, all the body can do is turn it into energy or heat. I burn about 70 calories/hour while I'm sleeping. If I want to sleep eight hours, eating about 500 calories of mostly carbohydrates just before retiring has a big effect on how warm I'll sleep.

Many people say eating fat has more effect. Rather than getting into that discussion, experiment to see what works well for you.

The coldest part of the day is the half hour after sunrise. We always get up before well before first light. My son starts the fire, and I make the coffee. We get on the trail quickly after coffee and eat breakfast after it warms up.

Note: My opinions are based on past experience and haven't changed much during the last 50 years. However, I reserve the right to change my opinions without notice. smile
Posted by: balzaccom

Re: Warming up a pad - 04/19/16 10:40 AM

Originally Posted By Gershon
I never use a pad, so I can't comment about how well they work. I do have some other ideas you might try.

Where you set up your tent can have an impact on how cold it will get at night. Cold air goes downhill, so it will be coldest near water or in a low spot. Even a few feet of elevation change can make a big difference.

The ground will be different temperatures based on the moisture content and the sun exposure. I've had the best success with bare dirt that gets the sun early in the morning.

The battle for warmth takes place quite close to your skin. It doesn't matter how good the sleeping bag is (within limits), if you wear a synthetic shirt near your skin, it's going to be cold. I generally wear a thermal top at night. With a great sleeping bag, it's best not to wear anything. Experiment with different clothing combinations.

You mentioned feeling the cold coming through from the ground. I lay my fleece under my sleeping bag which helps some. As long as I'm otherwise warm, that little bit of coolness is refreshing.

What you eat makes a difference. There is no mechanism in the human body to turn carbohydrates into fat. If a person eats excess carbohydrates, all the body can do is turn it into energy or heat. I burn about 70 calories/hour while I'm sleeping. If I want to sleep eight hours, eating about 500 calories of mostly carbohydrates just before retiring has a big effect on how warm I'll sleep.

Many people say eating fat has more effect. Rather than getting into that discussion, experiment to see what works well for you.

The coldest part of the day is the half hour after sunrise. We always get up before well before first light. My son starts the fire, and I make the coffee. We get on the trail quickly after coffee and eat breakfast after it warms up.

Note: My opinions are based on past experience and haven't changed much during the last 50 years. However, I reserve the right to change my opinions without notice. smile



This is a great post--particularly about the practical applications of how to sleep warm: stay out of cold depressions, make sure you are well fed, set your camp in a site that gets early morning sun, etc. I would also add that rinsing off, to get the salt off your skin, also helps keep you warmer.

I have only one disagreement to register, along with my wholehearted approval of the approach. Sleeping naked, no matter how good the bag, is not actually warmer than sleeping clothed. True, the nature of the clothing will have some effect, but R-values of clothing do add warmth to your experience. If you are slightly cold sleeping naked in a down bag, a layer of light wool clothing will make you warmer, not colder. Unless, of course, the clothing is so bulky that it compresses the down of the bag. Then all bets are off.
Posted by: bluefish

Re: Warming up a pad - 04/19/16 11:03 AM

I'd also add, I like the fact that warm clothing for sleeping purposes and sedentary activities when not on the trail readily applies to dual purpose/lightweight backpacking principles.
Posted by: Rick_D

Re: Warming up a pad - 04/19/16 11:12 AM

I'm persnickety about not sleeping in my hiking clothes, and carry featherweight boxers and tshirt for that. Also allows me to rinse out my salty hiking shirt, nightly. I only add sleeping clothes when temps drop below what my bag/quilt handles.
Posted by: wandering_daisy

Re: Warming up a pad - 04/21/16 01:53 PM

I cannot imagine sleeping directly on top of any insulating pad. With a sleeping bag, you do not do this. With a blanket, you do. I suspect that the cold is due to moisture. The pad is waterproof-airproof, so your body moisture will collect on it. Moisture/humidity creates on your skin acts like air conditioning.

Possibly you could sew (or tape together) a pad cover- space blanket on bottom and 100-wt fleece on top. Sew or tape three sides and slip your sleeping pad in the open end.