[time-nuts] Water Proof Vent

[Jim Lux]

On 5/15/12 9:05 AM, Brooke Clarke wrote:
> Hi:
>
> You might consider using a piece Tyvek material. You can get it free
> from the USPS in the form of a priority mailing envelope or at a
> construction site where it's used to warp the outside of houses.
> Passes water vapor and air but not water.
>

I don't know that all things labeled as Tyvek have that semi-porous 
property.    There are hazmat suits made of Tyvek, and I doubt they're 
porous.


According to Dupont, Tyvek (r) is a whole family of spun bonded olefin 
stuff (polyethylene fibers that are matted and melted).

It can be made in a variety of forms, some porous, some not.


http://www2.dupont.com/Tyvek/en_US/products/structure_types.html

type 16 is used in disposable garments and is perforated with tiny holes 
(much like GoreTex is).  130-510 microns, which is pretty big, compared 
to GoreTex (around 1 micron holes)