[time-nuts] frying pan antenna

Chuck Harris cfharris at erols.com
Tue Mar 16 18:44:49 UTC 2010


Joseph M Gwinn wrote:
> The tar paper is there primarily to reduce air infiltration when the wind 
> blows.  Now days this purpose is served by the white housewrap, the 
> original brand being Tyvek. 

That doesn't follow.  Most houses in the US have attics below the shingles
that are open to free air by way of soffit vents.

Even in the case of cathedral ceilings, the space below the roof sheathing
is open to the outside air... to not do so will seriously compromise the
shingle life due to excess heating.

Tyvek is never used on roofs.  It is always too slippery for walking on.

> Water that blows past the shingles is stopped by the tarpaper or 
> housewrap, keeping the sheathing and insulation dry.

Nope.

There are two layers of shingles over any given part of the roof.  Modern
asphalt shingles have an asphalt glue down strip that ties the shingle
tabs to the course below.  There isn't going to be any air infiltration
of significance.

Builders and roofers are of a mixed mind over tarpaper.  Many leave it
off because it is a hazard to the roofers.  The stuff is very slippery
if it gets even the slightest bit wet.

The roof stays dry either way.

-Chuck Harris



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