[pbhjpbhj]

Is that right? As a beardy guy, I find beard is cooler in Summer and warmer in Winter. I'd speculate that hair allows more heat transfer to sweat. Hair also send to keep a local air layer near the skin which helps Summer-cooling and Winter-heating.

[caymanjim]

Keeping a "local air layer" near your skin is not going to help at all with summer cooling. You need constant sweat evaporation to cool off. I don't think a beard is going to have much effect either way, since it's small, and our cheeks and chins are not designed to radiate heat or even sweat much compared to most of the body.

[pbhjpbhj]

Surely if the evaporation can cool the skin surface, then a local insulation layer would prevent ambient air from heating the skin. Just as a locally warmed layer prevents ambient air from cooling the skin during Winter.

It's certainly a hypothesis I've long held but never had chance to test.

Citations for support/contradiction welcome, thanks.

[caymanjim]

Unless it's above body temperature, the local ambient air isn't heating your skin up, and if it's that hot you need to sweat profusely to avoid hyperthermia.

[SuoDuanDao]

I think the beard is cooler in summer because you lose so much moisture from exhaling, it would go to waste not evaporating from your beard. In the winter, it solidifies and adds an extra layer of insulation. But if we were pushing that much moisture out everywhere, we'd probably dehydrate much too quickly.

[dmoy]

How hot and/or humid is your summer?

[pbhjpbhj]

I don't know really, UK, so not hottest, a bit humid on occasions.

[dmoy]

Ok I think you might have issues with actual cooling needs up above 32/35+.

But, I don't think it matters much. It doesn't help, but it's a small surface area.