Cotton vs Polyester vs PVC

[Yurts_latvia]

Hey everyone,


I've been grateful for the feedback from Jafo and Bob Rowlands about yurt cover materials - yet it's such an important topic for yurts with constant innovations, so let us discuss this in more detail!



From what I understand:


Felt is a wonderful, warm, breathable and traditional cover in Central Asia, but less suitable for most of the west due more rainfall and birds taking the wool for nesting!



Weather-proofed cotton seems like the ideal option in the short-run - it's natural, breathable and almost fully waterproof with a tight weave and right treatment... And yet even the best Sunforger brand will only last a few years of constant exposure to Sun before degrading severely. Cotton also shrinks so this is an extra consideration when making a cover.


Polyester fabrics tend to be slightly less breathable than cotton, but are naturally more water-repellent and durable.



Cotton-polyester mixes incorporate the best of both...



Some more expensive mixes seem to include an acrylic coating and even hemp to increase the durability of polyester further.



(actually Hemp canvas sounds amazing from reports I've heard of the old army tents lasting a decade or more, but I've heard nothing about it being tried on yurts. I imagine it is rather heavy?)



In general though, these breathable,woven fabrics will tend to expire after 5 years or so at most if the yurt is up all the time.


That's why so many people have opted for PVC on permanent yurts, which is king in terms of waterproofing (100%) and durability (10 years or even more) but has the downside of being totally unbreathable, and off-gassing toxic vapours.



Jafo kindly explained in a related post that PVC gassing is normally reduced by inner layers preventing the gassing penetrating inside much... any further feedback on this issue, anyone?



Breathability could also likely be improved incorporating cotton or polyester walls - where 100% waterproofing is less critical.




Am I on the right track here, are my conclusions valid, from your experiences, dear fellows of the yurt?


Your sharing would likely help many more here



Thanks,


Charlie

[HawaiiYurts]

Great summary of the the subject matter! I'd love to hear more about why people think breathability is such a major factor in coverings for modern, North American styled yurts.

In my experience, even yurts with a poly-vinyl cover 'breathe' to some extent because there are venting points at the bottom and top where the structure is not air tight.

Is the concern mold/mildew? If so, I have seen this completely remedied/prevented using vapor barrier material between the cover and lattice/rafters, such as reflective

insulation

with a simple poly-cotton liner to the inside. I've used the method on hundreds of yurts in Hawaii, a very humid climate, with near 100% success rate over the last 17 years.

Off gassing is minimized with the same technique, as Jafo mentioned, coupled with a

dome

that can remain open (but we are in a temperate climate - this is not part of the options available to those who need to keep the

dome

closed to retain heat).

Interesting subject, I look forward to hearing people's thoughts.

[Bob Rowlands]

My experience is 100% cotton canvas with a sunforger type finish, in 17 oz. weight, is a fantastic yurt cover for one year. Extremely pleasant atmosphere in the yurt.

The second year is good but not AS good as the first, and the third year is noticeably poorer than the first two. After three years there is a RAPID decline in water shedding and overall performance, and structural integrity. The 'feel' inside the yurt just wasn't as nice.

IMO that is >incredibly good< for a natural cotton fabric. Imagine leaving a pair of blue jeans out in the sun for three years straight. That will give you an idea.

50/50 poly cotton blend untreated 12 oz. painters tarps from Depot were my yurt wall. They lasted longer, but they were wall cover not roof cover. The material and weave was more porous. Definitely pleasant to sit next to on a hot day. Lots of breathability.

I know zilch about other yurt cover materials from experience.

[TSRalex]

Originally Posted by HawaiiYurts

Great summary of the the subject matter!

Agree - thanks @Yurts_latvia

Originally Posted by HawaiiYurts

Is the concern mold/mildew? If so, I have seen this completely remedied/prevented using vapor barrier material between the cover and lattice/rafters, such as reflective

insulation

with a simple poly-cotton liner to the inside. I've used the method on hundreds of yurts in Hawaii, a very humid climate, with near 100% success rate over the last 17 years.

I would opt for an fire retardand hemp liner as inner layer, because of the advantages over cotton:

Hemp fiber is over 4 m long, cotton fiber is only 2 cm long, the hemp fiber is 8 x stronger and about 4 x more durable than cotton fiber.

Fabrics made of hemp have a natural sheen and they behave similarly to silk - in summer they have a cooling effect and in winter they have a warming effect.

Hemp fabrics are very durable.

Another advantage is intensive

moisture

absorption and fast release, because materials made of hemp fiber are absorbent and dry very quickly.

The oxygen content in hemp fibers prevents the formation of bacteria, and because hemp fiber does not contain protein, there is no need for treatment against moths and beetles.

And the antimicrobial properties of hemp fiber are effective protection against mold growth.

Originally Posted by HawaiiYurts

I look forward to hearing people's thoughts.

You got mine above.

What is your opinion about to have an additional 3D-Mesh-Layer between reflective insulation layer and the outer shell (PVC layer)?

[Yurts_latvia]

Nice feedback guys!



So Bob sounds like your poly-cotton painters tarps for walls weren't treated at all - did rain ever come through? Or did they ever go moldy?


TS, thanks a lot for your insights on hemp. Great to understand a bit more about its virtues.


Do you think if was waterproofed it would also hold up well as an outer cover for several years?


My current thinking of my ideal would be to have a single breathable cover like that for the summer (I just love the simplicity, breathability and light penetration of single layer) whilst perhaps the reflective insulation and pvc would be a good bet for the colder months.



I think having a pvc cover backup is a nice touch also if there's ever a problem with a more delicate material - you can be sure that stuff is pretty bomb-proof!


+ I wonder about woven materials under snow? Sheeting off drops of rain is one thing but being impermeable to a slowly melting foot of snow - that seems like a tall order!



Thanks all of you

[Jafo]

Don't dismiss reflective materials for summer.. They reflect heat AWAY too. Yurts heat up very quick in the sun.

[Bob Rowlands]

poly cotton painters tarps are untreated, and as cheap as a tarp can get. But, for wall covering on a rustic camping yurt, ok. If my yurt was a primary residence, and not a camping yurt, no way.

Yes it molded but not as bad as the 100% cotton cover. The cotton roof cover had no mold until the waterproofing started to fail in a couple years. Hope this helps.

Thanks for info on hemp material. Doobie doobie do. haha

[TSRalex]

Originally Posted by Yurts_latvia

TS, thanks a lot for your insights on hemp. Great to understand a bit more about its virtues.

Do you think if was waterproofed it would also hold up well as an outer cover for several years?

On fact, that I haven´t the experience with hemp as outer shell I need to ask my crystal sphere and got the answer: "YES, maybe better than cotton".

During my evaluations for the right outer wall cover I found in an high-strength polyester fabric, with high UV resistance and a soft-PVC coating on both sides.
Thanks to the special surface sealing, durability and best dirt-repellence are ensured.
Properties:
Weight: 690 g/m²
Max. tensile strength: 3000/3000 N/5cm
Tear strength: 300/300 N
Surface: high gloss, lacquered - many colors
Membrane: flame retardant according to EN 13501-1 and fungicide finish


BTW: An alternative possibility to the - in my previous post mentioned - inner liner with hemp, would be an mold resistant and dirt repellent cotton/polyester mixed fabric, which I found too during my search.

Properties:
Weight: 430 g/m²
Max. tensile strength: 2200/1700 N/5cm
Tear strength: 75/60 N
Surface: only in light sand color available
Membrane: fungicide finish

[TSRalex]

Originally Posted by Yurts_latvia

Do you think if was waterproofed it would also hold up well as an outer cover for several years?

Your question was somehow an incentive for me to look up again briefly regarding the robustness of hemp fabrics and I want to share one interesting link:

Is Hemp Really Stronger Than Steel? How?

[Bob Rowlands]

Resurrecting this old thread.

The poly tarp I covered my yurt with about one year ago is done. I made the yurts roof cover from a heavy duty white poly tarp, that I had previously used for about a half year to cover my wall tent frame.

So, after 1.5 years of continuous exposure here in sunny CO it's leaking. We just had our first big snow of the year. I thump the roof cover with my fist from inside the yurt to get the snow to slide off. I tore it in multiple places. Loss of strength from exposure to the elements.

Just thought I'd let you guys know what my experience was with a heavy duty white poly tarp. IME canvas lasts 3X as long. Anyway there you go.