On 2/25/2011 9:50 AM, Home Guy wrote:
Bert Hyman wrote:

What "killed" our shingles was time.

Convection moves air from the soffit vents to the roof vents.

Dream on.

Convection will not move enough air during the dog days of summer to
keep your attic cool.

I have properly ventillated soffits, several passive vents AND a powered
roof vent that I manually control. When I forget to turn the fan on
until noon on some summer days, it's not uncommon for my $15
battery-powered temperature sensor to read a temperature of 140 F in the
attic.

15 minutes after I turn the fan on, the sensor will be reading 120 f and
still dropping.

This is for a roof section that is about 35 feet by 30 feet with a low
pitch. I'm in the same climate zone you are - I'm about 120 miles more
south than you, and a few hundred miles to the east.

Wind-powered roof turbines are a crock of ****. Maybe you have some
sort of romantic or nostalgic attachment to them, but they will not do
squat to keep your attic cooler as compared to just having a hole in the
roof. And during the dog-days of summer when there is no wind, the
turbine blades will actually HINDER convective air flow because of the
resistance to air flow they cause vs just having an open hole.

Just curious as to what type of vents you have. I have ridge vents
running the entire length of all my roof sections. I have heel trusses
with lots of room for insulation above the outside walls plus a good 5
inches of opening to allow air to enter the attic through the soffits.
I have been up in the attic when the sun has been shinning all day
and the outside temp are in the high 90's. It's warm up there but not
hot. I would estimate the temp up there to be about 5 deg above outside.

My neighbor has the regular square vents on his roof. According to him
he has the required amount of vents per code. He does have well
ventilated soffits but his attic is hot.

You can work in my attic with little discomfort. I wouldn't even go up
into his.

LdB