Sorry, thought you were pulling my leg about the breathable cuben. Maybe you are without knowing it, as I am not a big fan of big sky. Fool me once, shame on you; fool me twice ...
Guess there is no reason why the mylar in cuben could not be replaced with something else that is microporous. Somehow, I doubt that whatever it is will be available to me to use this winter. Looks more and more like cuben and net, with a different top vent design.
So could you tell me what grade of cuben you are using? I understand the CT1K.08 is 0.51 oz. per sq. yd. If you have had such good results with that, will probably use that with bonded reinforcements at the seams and stress points. Otherwise, am thinking of of the 2K.
I obtained a MH Bunker once, intending, I'm embarrassed to admit, to replace the floor with a deeper silnylon version and the poles with carbon. No, that's not even the dumbest thing I've tried. Anyway, was not very happy with the quality of construction, and immediately sent it back.
Design-wise, it has an elbow at the top of the short pole axis, but none on the long. I have put an elbow on the long also, not just to relax the pole stress, but also to minimize the loosening of the canopy tension above the door when the door is opened. Found that there is still a big increase in headroom over a cone shape, even when the long axis pole is only slightly bent. Found from models that the door can be opened up to 9" from the apex (41" height at that point) without such loosening, but after that there is a bit. Am going to let the door open up to 5" from the Apex anyway, for ease of entry/exit when it's not raining, and d**n (expletive blocked by BPL) the looseness. Can remember to not open the door all the way up in storms-not so hard. Note: have been saying door, singular, but plan to have zips on both sides of the front pole so as to have 2 doors. That's one great thing about MYOG. It's a lot of work, but you can have it the way you want it.
The air is pretty fresh on my back deck where the fabrics are being rain-tested for almost two months now. Not sure where oil could come from. Oh, just realized, maybe from my own fingers when feeling to see if it is dry on the inside after a storm.
But there are always fine particles of whatever in the air here on the national forest border. Anyway, will definitely try the wash before giving up on the Epic. One problem: it's going to stop raining and start snowing pretty soon here, and am not going to wait till spring to get started on the tent.
Agree with Franco about the stack effect. What's not clear, is whether the slight increase in apex height to 46"
will be enough. But don't see how it can hurt to have good venting at the very top, together with lots of venting below. I heated solely with a wood stove for several years, and occasionally had days where the air just seemed so heavy it would not move. Also learned that too large a pipe could lower the draft. There will be zip closures on the inside of the vents, so can play with it and see. As you say, there will be condensation regardless, and that's why the canopy will either be breathable or have a net inner in the back.
Appreciate all of your thoughts very much.