How to use a vapor barrier with cycling shoes for cold weather riding?

Question

I've heard many people like to use plastic newspaper bags or grocery bags as a vapor barrier when cold weather cycling. I'm already wearing winter cycling boots which prevent outside water infiltration, but I've been considering this for really cold days or longer rides below freezing since my insoles eventually get soaked with sweat eventually and become very good at transferring the cold from the bottoms of my shoe to my feet.

What is the most effective way to use vapor barriers inside shoes to keep warm? Should I wear the vapor barrier over my socks, under my socks, or between two layers? What is the theory behind it?

Answer 1

I rode a couple winters as a bike messenger in the northeastern US, and this is a classic messenger trick for the worst cold wet days. While your feet may still become somewhat wet, at least they will be warm and wet. I liked wearing a thin sock on the inside, the plastic bag, another pair of socks, then shoes.

This is not really a dry-day technique. Then, as @hillsons said, you will just have wet feet for no reason. When it's dry and really cold, put flat pedals on your bike and wear normal civilian winter footwear. Hiking boots, for example. But when it's 35 degrees and raining and you are silly enough to be on your bike, the plastic bags trick is the way to go.

One place to search advice on vapor barriers is in the camping/backpacking world, there's been plenty of experimentation with them since at least the 60s in that community.

Answer 2

I have used this technique in emergencies while hiking, but never thought of deliberately using it day-to-day.

When the weather unexpectedly turns foul (and this is before I had the money to buy quality waterproof hiking shoes), my feet would soak. So I would takeout a thick plastic bag from the backpack.

• Put dry socks on.
• Put the plastic bag over them, but leave a lot of space in front of the toes. Otherwise when putting on the shoe, and when walking, the toes tear the plastic bag.
• Put the wet sock over. This will prevent the plastic bag of sliding against the shoe and tearing.
• Put the shoe on.

So this works for several hours (with increasing levels of discomfort) and keeps the feet dry-ish in an emergency. However, the feel is slippery (with every step the socks slip a bit). Really not my idea of "fun".

Answer 3

For maximum effectiveness, a vapor barrier should be worn as close to the skin as possible. A vapor barrier works to keep your warm two main ways. The first is that is stops your sweat from carrying heat away from your body (stops evaporative cooling). The second is that because your sweat doesn't move away from you, your insulation stays dry and is more effective. Many people dislike the slick, wet clammy feel of a vapor barrier against their skin, which is why many people recommend putting it on after a liner style garment, however, this technically isn't the most effective method of using one. RBH Designs, which manufactures a variety of vapor barrier clothing bonds a cloth layer to the inside of their barriers to reduce that "sandwich bag" feel. Their site has some good data on vapor barrier reasoning and use.

Answer 4

A rehash of a previously posted answer, but I wear socks with SPD sandals in the wintertime. I can pile up as many layers of wool socks as I need for the day's temperature conditions, and just adjust the straps on the sandals to make room for the extra bulk. The plastic grocery bag I put between the outermost and next inner layer of sock. I've done this, had my feet soaking wet yet still toasty warm in temperatures as low as -20F.

They key though is that you need to select your footwear to target about 20-30 degrees warmer than the ambient air, so that you are not sweating when biking. If you are standing around doing nothing, your feet should be cold.

Answer 5

It's not actually that cold, so a decent pair of old-fashioned non-breathable leather boots or hiking shoes with 2 pairs of socks should be enough, 3 pairs at the very lowest temperatures you mention.

Hiking trainers + 1 pair of warm socks is fine down to -6C (21F) for me in the dry, so long as I keep the wind off my ankles.

If you do go for a vapour barrier, you need enough packing (in the form of socks) in there that your feet don't move around - another reason for boots over shoes, even if just ankle boots.

A grippier option may be replacement latex socks for a drysuit - with only thin socks underneath and thick on top if needed, plus they're generally quite long.

Answer 6

I've been experimenting with the whole cold/sweat/wool/plastic bag dilemma and I think that I may have found another way to go about it.

Yesterday, I put one of those toe warmers that you stick to the toe part of your insole. I put on a pair of medium weight wool socks. My feet sweat like crazy like always but they were pretty warm, even when I'd stop. I would recommend wearing a thick wool sock however: one of my feet started to get too hot because of the sweat combining with the insert.