How does goretex breathe with a PU lining?

no, the permeability of the PU is higher than the gore tex, otherwise you wouldnt need the gore tex.. the breathability is more often determined by how wet the face fabric or the inside of the fabric is and humidity and temperature

'GORE-TEX Paclite: Pacite is ideal for exactly what the name suggests, packing light. This fabric is a 2.5 layer construction and whilst it’s waterproof ratings are solid, it’s more suited to travel and urban wet-weather gear than strenuous rough outdoor activities.' That's not what they intended when they made it. Sure. It was to be able to pack light but it was not to be used by travellers only. That would be the point of view from someone who thinks longevity is more important than simply having the item best suited to do the job. These companies make cutting edge gear for adventurers. They want gear that is intended to do the job. The cost is not the primary concern. If it was, then they are trying to do extreme things by compromising. That costs lives. Bringing the item back isn't as important as having it when it counts. I used the first paclite jacket by Gore in 2000. It was given to me to try out. I was doing a TMC on the Tasman glacier. It was a mountaineering cut on the jacket. I had to return the jacket. I understand that a tramper is nearly always going to put cost of an item higher on the list of priorities. Understandably so. They take less risk. They are notoriously stingy. It took some education before i too realised that walking outdoors isn't necessarily meant to be FREE.

paclite is terrible for breathability. gore tex isnt the best, various other technologies are comparable or better for breathability gore just put massive sum into marketing themselves as cutting edge, their material is above average only. some of the membranes have far worse breathability though and get overloaded by anything more than a stroll along on flat ground i have a neoshell, that is far more breathable and so is eVent.. but they still get overloaded with sweat in ideal conditions... physical vents are far more effective in keeping sweat buildup down.. take anything the manufacturers or vendors tell you about the technology with a grain of salt. raincoats are wet suits. breathable ones may be a bit less of a sweat box than non breathables. some brands want to maximise profit, so they put a few bells and whistles into their garments and market them heavily and they put a big premium on them non breathable or the low breathable ones are cheap, theres not mch profit in them rainshells are plastic... normally plastic is cheap, you're buying a few hundred grams of plastic. how much does that cost before its manufacturered into a rainshell. a few cents? and you can pay hundreds for a rain shell because you believe its worth paying that. various outdoor chains also market the expensive clothing as much as possible for the bigger profit they offer. once a apon a time trampers wore non breathable PVC or oilskins that were little better. when gore tex came in, it cost a fortune and it was still poor quality. few could afford it. but now breathable fabrics have permeated outdoors people. i read blogs that tell people not to use non breathable rainwear because its dangerous because of the sweat buildup... when once apon a time it was considered totally acceptable to use non breathable PVC or membranes. we live in a modern world where people think all sots of things are essential to their lives that arent, the marketers have succeeded in convincing th vendors and the customers that breathable rainwear is essential.. ed hillary got to th top of everest which no outdoors person would use today because it would be considered inadequate. you dont complete your trips primarily because of wearing modern technology, it helps but not having the latest technology is not going to affect your trip that much gore tex at one stage would refuse to supply any clothing company that wanted to make clothing out of their rivals eVent membrane. they have a policy if you manufacture with their products you must only make your premier storm shells from their membranes and relegate rival products for lower end products.. that is anti competitive behaviour, they are holding the outdoor clothing companies to ransom based on their reputation, if you stop selling gore tex then you stand to loose clients who recognise and want gore tex, plus gore tex do the marketing for their material. the clothing companies don't have to... its free publicity. some people want the best and thats fair enough, marketing is a game where the manufacturers try and convince you their product is the best and its as much about familiarity through massive constant marketing as it is anything else.. i've read studies that i've had to purchase that show gore tex isnt that much better, fabric thread denier or weight, ie the fatter the thread the heavier it is, can affect breathability more than the membrane itself beause it determines how many threads there are, more threads in the fabric then more gaps for moisture to move through... fatter threads reduce breathability beause thers more of a physical barrier reducing that breathability... but you believe its as breathable as the membrane... https://sectionhiker.com/hiking-rain-jacket-like-wet-suit/ https://andrewskurka.com/2015/why-im-hard-on-gore-tex-the-king-of-hype-tm/ "Gore-Tex might be a cash cow for gear manufacturers, but you wouldn’t have heard a lot of gratitude by surveying last summer’s OR crowd. I asked dozens of industry veterans and designers about the unprecedented marketing attacks from Columbia and Polartec, and the first thing I noticed was the fear. Hardly anyone was willing to speak about Gore-Tex on the record. When I asked one manufacturer why people were being so coy, he told me, “Everybody hates Gore, everybody needs Gore, so everybody’s afraid of Gore. They can make or break you.” He was referring to an open secret among industry insiders: that Gore’s licensees are afraid to work with non-Gore technologies, lest the market leader terminate their contracts. " https://www.outsideonline.com/1898541/insane-membrane

I can see why Earth Sea Sky wouldn't be held to ransom and chose Milair (Reflex-type of breathable membrane).