[time-nuts] frying pan antenna
d.seiter at comcast.net
d.seiter at comcast.net
Tue Mar 16 19:25:38 UTC 2010
I think tar paper basically has two functions these days- it's a cheap backup in case the roofers don't install correctly, and the lines on the paper are used as a guide to install the shingles.
Dave
----- Original Message -----
From: "Chuck Harris" <cfharris at erols.com>
To: "Discussion of precise time and frequency measurement" <time-nuts at febo.com>
Sent: Tuesday, March 16, 2010 11:44:49 AM GMT -08:00 US/Canada Pacific
Subject: Re: [time-nuts] frying pan antenna
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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