On May 27, 2011, at 10:40 AM, Chris S wrote:

> Got pics?
> 
> Since it holds water, are there issues with vapor breathability?
> 
> I heard of hikers using tyvek to insulate their tents in the winter. 

Tyvek is a breathable house wrap used to allow any vapor migration from the warm side, usually the inside, to the outside. I think it should be a very good/inexpensive material for a car cover, unlike a plastic tarp or Visquene.  A vapor barrier like foil or plastic is placed on the inside to keep vapor from traveling into the insulation where the dew point usually occurs & condensing in the insulation/wall. The house wrap allows moisture to pass out but not in because of the warm to cold path that vapor takes.
Now if it is warmer outside than inside, the path would be reversed, but at that point, I don't think the dew point occurs in the insulation so no condensation? Someone help moi here?

YMMV,

Mr. BZ-on outside of tent only?

> 
> Chris.
> 
> Wysłane z iPhone'a
> 
> Dnia May 27, 2011 o godz. 11:23 Jim Felder <jim.felder@GMAIL.COM> napisał(a):
> 
>> Recently I made a westy cover out of $1/yard tyvek. I love it. Here are some
>> thoughts:
>> 
>> 1. It will roll into a small ball and stash under the seat or in a closet,
>> which is great.
>> 
>> 2. It takes exactly 40 yards of 40 inch material (look on ebay). You will
>> have only a few square feet left over.
>> 
>> 3. You almost can't tear it.
>> 
>> 4. You CAN burn it. Ask me how I know. Turn off the light on your sewing
>> machine and use some other light source.
>> 
>> 5. Amazingly, it holds water like you wouldn't believe (it has a very soft
>> feel, seems like water would pour right through). You have to leave an
>> opening in the "luggage rack" to drain it or you might not get the cover off
>> the car for a long time after a rain.
>> 
>> Jim