Tyvek(R) is just a DuPont trademark for a whole range of materials based on flashspun high-density polyethylene fibers. There are many different varieties of Tyvek, ranging from the fabrics designed for weatherproofing timber framed buildings and roofs, through the familiar white coveralls worn by spray painters and forensics teams to films designed for airline packaging, envelopes and pharmaceutical products.
Tyvek fabrics are non woven, they are created by heat bonding the finely spun fibres together.

Most uses are based on the fundamental properties of Tyvek which are a resistance to tearing and liquid water penetration but permeability to air and water vapour but vary highly in their actual specific properties.

Saying "I am buying some Tyvek to make a groundsheet" is like saying "I am buying some nylon or I am buying some wood to make a box.

http://www.dupont.co.uk/products-and-services/fabrics-fibers-nonwovens/protective-fabrics/brands/tyvek.html

There are on the cheap DIYers that have done so but, like the early white/transparent Cuben fiber garments, one looks a bit like a hazmat suit with a rucksack on.

dont expect to make many new friends. ; )

Most of the permeable membrane products used in waterproof clothing work in pretty much the same way, a bunch of microscopic fibres fused together to create a fabric which has microscopic permeability to vapour but not liquids. Gore-tex is a fluoropolymer fabric. Fluoropolymers (think Teflon)are also highly hydrophilic, i.e. they also actively repel water. Gore-tex has a mechanically induced porosity created by stretching the polymers while they are warm in order to increase the number of pores but still keeping them way below the size of a water droplet.

Many of the other breathable fabrics are made of bonded polymers including HDPE, just like Tyvek. Sympatex works in a slightly different way in that it doesn't contain the microporous structure of most of the other breathable membranes.

To answer your question, you could wear a Tyvek coverall on the hill and it would make a pretty tough wind and water resistant, breathable suit, but it wouldn't have the performance of a modern multilayer product which normally includes a strong resilient lightweight outer layer coated in a hydrophilic product designed to shed water, a thin core of microporous membrane and an inner layer of wicking fabric designed to pull moisture away from the users skin. Essentially, most Tyvek fabrics are a water resistant, breathable, tough paper. Great for covering a house or making a tough windproof shipping label or a disposable suit for a spray painter but not ideal for outdoor clothing.

As someone who spent his early years tromping around the hills wearing a heavy, bright orange, knee length, PU coated 'cagoule' which always seemed wetter on the inside than on the outside, I never stop being amazed at the performance of modern outdoor clothing which can be bought very cheaply these days.

My goodness, Brian, I am now wondering, with your obvious delight in materials research, what exactly is your outerwear of choice for challenge conditions? Having just re-proofed my 6 year old Montane event jacket (which failed me spectacularly by Dalwhinnie in 2016) and my horribly ripped/tenaciously taped over trousers, i might need to 'up my game'?

My head hurts. I am not worthy.

Agreed, HMP3, tomorrow is another day, go to bed.

Hi

Feeling sorry i asked......can i be arsed to wash it, screw it up several times, tumble dry with a wet towel on cold setting et al ?

.....but i did ask... so thanks for responding.

WUW

Julie,
I'm not going to fall into that trap, everyone has got their opinions.
I would suggest that vapour permeable membranes are a pretty mature technology these days and there isn't a great deal of difference between different brands. Some work better in colder conditions or with different humidity conditions inside and outside. You are probably going to benefit more by thinking about the practicalities like fit, hood design, number of pockets etc. They are the sorts of things that are going to bug you the most if you get them wrong.

What I would suggest though is, don't forget, if you are doing hard work you are going to sweat (even ladies do, I know). We all sweat liquid not vapour, sweat cools us by being warmed up and evaporating. The discomfort is caused by failing to get that evaporation going and we get that familiar rivers down the back between the shoulder blades feeling. That is why it is more comfortable working in the desert at 40degC than it is working in a humid rain forest at 30degC.

For trying to maintain comfort when you are working hard and the outside of your shell layer is dripping wet with rain is to concentrate on what is touching your skin. I would suggest that you would be far better off concentrating on your base layer, you want something that will wick that liquid sweat away from you and deposit it as water vapour on the inside of your shell layer where it stands a chance of being driven through the membrane.

You need a temperature difference between your skin and the outside world and a way of getting the liquid sweat away off you skin and turned into vapour.
You would probably get more bang for your buck spending a few quid more on a good base layer and mid layer than spending hundreds more on a top of the range outer shell.

You can, or could, buy Tyvek groundsheets from Bob at Backpacking Light. I have two of different sizes. They are excellent as a footprint if you want one. They did not need washing or scrunching up to make them useable. They do get softer and more pliable with use. But they are NOT completely waterproof and I would not, therefore, rely on Tyvek as a groundsheet in Scotland in May.

Thanks David,i got one when i got my scarp 1 in 2009/10 ish but never used it.It's been hiding in my garage forgotten about ever since and it never got used.
I have just purchased a duomid and was toying with the idea of trying the tyvek out, just wanted some views on it.

Cheers.

Yes, I've used Tyvek up until now.

Used a sheet direct from the builder's yard and it's tough stuff. Not noisy and easy to clean and waterproof.

Also bought a sheet from Backpacking light, bit crinkly, but you can peg it out and is water resistant enough.

Now bought a tub from Oookworks.