Wetsuit Warmth

Your body gets cold as it loses heat to the surrounding environment through “thermal conductivity”. Thermal conductivity is the heat transfer from your body to your surrounding environment. An environment with a ‘low thermal conductivity’ means heat transfers away from the heat source (your body) at a relatively slow rate. Air has low thermal conductivity. An environment with ‘high thermal conductivity’ means you lose heat faster, and thus get cold faster. Water has ‘high thermal conductivity’. The nerdy engineering term for thermal conductivity is called the “R-value”. For air, its about 0.024 W/ (m*k). This is basically your energy (heat) lost per degree of difference for a given surface area (your body’s surface area).

Some important R-values are:
Air: 0.024
Neoprene: 0.054
Water: 0.58

Umm, so what does this mean? You lose heat over 20 times faster in water than air (R-water is 20 times larger than R-air). This should make sense when you think about how quickly you get cold in board shorts in 65-degree water versus 65-degree air. Now, if your wetsuit absorbed ZERO water, it would be about 11 times warmer than wearing trunks based on these R-values. Of course this is dependent on wetsuit thickness, a 4/3 would is about 33% warmer than a 3/2. But if your wetsuit absorbs 20% water, which is typical for lower-end wetsuits, then you get an effective insulation only about 4 times better than trunks. (20% xR-water + 80% x R-neoprene is 4 times lower than R-water) Does your suit weigh 3lbs more wet than it does dry? It probably fits in this category then.

Japanese Yamamoto rubber is 98% water impermeable. Actually the rubber itself only absorbs 0.3%, but the jersey material on either side also absorbs some water. This means you get insulation close to 10 times higher than with trunks.

How about those fuzzy liners? Yes, they typically have thermal conductivities very close to neoprene; wool and polypropylene are both around 0.05. But, using polypropylene as an example, it still absorbs up to 30% water. This results in additional insulation for sure, but it also makes them a heavier, less efficient alternative to water-impermeable neoprene. You are better off adding 0.1mm of neoprene than 0.5mm of a typical fuzzy liner.

This analysis is obviously simplified and ignores flushing and leakage. Still, it shows that Yamamoto Japanese neoprene can have up to twice the insulation of lower end rubber, and the reason we chose to use it despite its high cost. It's also the reason some manufacturers say you can wear a Yamamoto suit 1mm thinner than you are used to. We don’t want to make this claim, but we do know it’s substantially warmer.


#39 Yamamoto neoprene at 5X magnification

FERAL jersey material at 5X magnification

First Black Friday / Week o' Cyber Hell Deal in Years!

*Tops Sold Out, Promotion Has Ended* In partnership with our favorite (and only) East Coast retailer, Saturdays NYC, we are giving away a FREE SNYC x FERAL 1.5mm Top ($115 value) with every fullsuit purchase. The offer went live at 9am PST, Wednesday, Nov 22nd, and will end when we run out (supplies are limited).

How to score the deal: Add a fullsuit of your choice to your cart, then add your size of the men's or women's SNYC x FERAL 1.5mm Top to your cart, and the discount will automatically be applied. The tops will not be eligible for returns or exchanges so choose wisely.*

The SNYC x FERAL 1.5mm Top is the same suit as our super minimal #39 Yamamoto 1.5mm Top, but with Saturdays All Terrain Activewear branding. Our suits are available to try on and purchase at the Saturdays NYC Crosby Street location for all our New York FERAL friends. They'll be fully stocked this winter for all your blizzard barrel needs!

*Only fullsuits (long legs, long arms) are eligible for the promotion. All sales final, no size exchanges on the SNYCxFERAL 1.5mm Top. If you want to return your unused fullsuit for a full refund please include the unused top in the package—if the top is not included Alex & Buzz will deduct $115 from your refund and have a private pizza party, just the two of them. Offer only available at feralsurfing.com, and won't be applicable at any FERAL retailers. Offer cannot be applied to existing orders, or orders placed before Wednesday November 22, 2023. No other product(s) can be substituted for the SNYCxFERAL 1.5mm Top. Limited to available sizes while supplies last. Once we're sold out, the promotion is finished. The offer may be terminated at any time by FERAL without notice.