Waterproof and Breathable – The Inside Scoop

What does 'waterproof and breathable' really mean to cyclists?

There's a lot of hype about 'waterproof and breathable' fabrics when it comes to cycling, but getting a handle on what the term actually means for real-world riding is a little more complicated than the simple phrase suggests.

Castelli works with the biggest names in the industry, developing advanced fabrics to make your cycling as enjoyable as possible, whatever the weather. But there isn't one magic fool-proof solution for waterproof and breathable performance in all conditions.

Here's the lowdown on what we mean when we talk about a Castelli product being 'waterproof and breathable' and some advice on choosing kit for the right conditions.

For more on this, don't forget to check out our guide to Castelli temperature ranges.

The science of waterproofing

Waterproof and breathable fabrics are designed to resist liquid but allow vapour to pass through. It's the ability to block rain and snow while allowing sweat vapour to evaporate that's so attractive for cyclists.

Standard laboratory testing protocols define the performance of waterproof and breathable fabrics. Water resistance is measured by the amount of water, in mm, which can be suspended above the fabric before water seeps through. Breathability – or moisture vapour transmission rate – is measured by the rate at which water vapour passes through, in grams of water vapour per square meter of fabric per 24-hour period (g/m2/d), often abbreviated to just 'g'. Phew.

Typical mid-range fabrics tend to have values of 5,000mm of water resistance and 5,000g of breathability. The very best materials have stats around 20,000-plus for each.

What 'waterproof' means in real life

When a fabric is described as 'waterproof' that usually means it's able to withstand over 1,000mm millimetres of water without leaking and also needs to have waterproof construction such as a waterproof zip, taped seams or covered vents.

In short, 'waterproof' fabrics don't guarantee to keep the rain out forever – performance will depend on how much it's raining. Compounding the issue is that no matter how good the fabrics and construction, if rain can get in down the neck or up sleeves, you're going to get wet!

What 'breathable' actually means

When it comes to breathability, it's a similar story. Performance is greatly affected by humidity levels, temperature and airflow while riding.

Airflow is probably the biggest issue. We've all been there: sweat soaked on a turbo with a puddle on the floor because there's no breeze to evaporate sweat and cool you down. It's the same situation if you wrap yourself in a waterproof jacket, leggings, gloves, overshoes and a head thingy. Rain won't get in, but sweat can't get out. Just that it's happening inside your kit. Yuck.

It's exactly this situation that we get the most waterproofing feedback about. People expect a waterproof jacket to keep them dry and think theirs is leaking if they're wet after a ride. It's almost always just sweat through lack of airflow that's causing the perceived problem.

So, I'm better off without a jacket then?

Not really. If you forego the waterproof, your skin will breathe better, but you'll quickly get soaked and the cooling effects of wind chill as you speed along will conduct heat away from your body. You'll rapidly become numb with cold and performance will suffer. Wet and cold is much, much worse than warm and wet – and hypothermia is a real pain. There is an alternative.

Enter the Gabba

The middle ground was innovated by Castelli and launched in 2010. It's called the Gabba, the game-changing jersey that proved protection and performance could go hand in hand.

Soft-shell technology has been widely in use in the outdoor world for some time, but Castelli's genius was in applying it to the world of cycling to address the needs of racing in poor conditions.

The Gabba and its sister Perfetto range offer wind protection and a high degree of water repellency in a garment that fits snug and is highly breathable. It won't keep you bone dry – and it's not designed to – but it will offer you the best of both worlds, shedding most of the rain and all the wind. This means you don't chill rapidly while your skin can breathe to cool you.

So, the Gabba is the death of the rain jacket, then?

Although the Gabba is perfectly suited to high activity levels in normal to wet conditions, at lower intensities, where you won't be generating lots of heat or sweat, or in very, very bad conditions, you still need a shell garment.

In fact, watch any race in bad conditions and you'll see a peloton full of examples showing a variety of kit is required.

Heavy-rain roll-out: all the riders wearing shells as they pedal dispassionately out of an anonymous industrial Belgium town.

The race hots up, but it's still lashing: the riders strip off their shells (more realistically sails and are down to wearing their Gabbas, which provide a balance of warmth protection and an aero fit great for chasing breaks.

The last 20km: riders strip down to a race jersey, got to keep the sponsors happy and every ounce matters during the sprint to the line.

So actually, I need a Gabba and a rain jacket?

If you're committed to riding in the rain, part of the mental toughness required is accepting you will get at least partly damp – remove any thoughts about staying dry and work on staying comfortable and warm.

Sometimes, this means grabbing your Gabba and riding hard. Other days it might be a traditional rain jacket for those long winter rides where the rain is heavy and the pace is slower. Oh, and if you happen to be riding in a rainforest you might be best off in just a climbers jersey!

Castelli functional waterproofing

Castelli is growing its line-up of functional waterproofing garments, which, like the Gabba and Perfetto, are designed to keep the worst rain off you without you melting into a sweaty puddle.

The Nano Flex range has been improved and now includes a selection of warmers as well as bibs and tights. We also have the new RoS – Rain or Shine – family of products, garments designed for training in cooler conditions than the Gabba is suited for and which offer more breathability and adaptability, but aren't designed with a sleek racing cut.

Lastly, keep an eye out for the LW tight, which combines thermal protection on the upper leg and a spray-resistant lower leg – perfect for spring or autumn.