About to insulate the shop.

[atgcpaul]

I just moved back to the East Coast after being in San Diego for nearly 6 years.
My coldest winter since has been a Christmas in the south of France. These
past few weekends have been brutal. Nearly 40 degrees outside! I didn't
realize how cold/hot sensitive I had gotten until I moved back. Wimp.

Anyway, I'm going to insulate my unattached garage's walls and close off
the ceiling, too. There are no vents at the eaves and there is no roof vent.
The main questions I have are: The roof has a steep pitch, but to do it
properly, I would need to add vents at the eaves, those stiff foam air channels
to prevent ice dams, and a roof vent, right? Do I even need those air channels
if the roof angle is say 30-45 degrees. One more question. Can you add
a roof vent from just the top of the roof or do I need access from under the
roof?

Thanks, Paul

[crokett]

I have no idea on the question ,but also post this over on Woodnet. There are several guys in the Home Improvement forum there who can help.

[Russianwolf]

If you are going to keep the attic as "cold" space, then why not just a couple gable vents (one at each end)? That would keep the attic at outdoor temp and provide ample airflow with minimal effort.

The idea with the ridgid foam channels is if you are planning to insulate the roof itself. You need space between the insulation and the roof skin so the inside and outside of the roof are equal temps.

[THyman]

The main questions I have are: The roof has a steep pitch, but to do it
properly, I would need to add vents at the eaves, those stiff foam air channels
to prevent ice dams, and a roof vent, right? Do I even need those air channels
if the roof angle is say 30-45 degrees. One more question. Can you add
a roof vent from just the top of the roof or do I need access from under the
roof?

Thanks, Paul

You may or may not have to add the stiff foam air channels depending on what type of insulation you install. (Blown-in=yes, batts=yes for only the first 3-4 ft)

Regarding the ridge vent, you can add one from the top by cutting a 3-4 inch hole the length of the roof and then install the ridge vent according to the instructions. You will have to pry-up the top most set of shingles so that the ridge vent installs underneath the vent cap. Then you will have to install shingles on top of the ridge vent. HD and Lowes carries the ridge vents so you may want to take avisit and see what the instructions look like.

[LarryG]

The baffles, whether foam or cardboard or whatever, do help prevent ice dams but only as a side effect of their real function, which is to maintain a clear air space for ventilation from the eave vents to the uninsulated attic space.

Gable vents alone won't work. Proper ventilation of an attic requires vents down low, typically at the eave line, to allow the air to enter; and vents up high, either at the ridge or at the gable ends, to allow the air to escape. (This is called "gravity venting," even though it works in the direction opposite to gravity). Of the two upper vent types, continuous, properly-installed ridge vents are superior to gable vents.

All the above assumes a cold roof. You can also install the insulation directly under the roof sheathing, which technically makes the attic a conditioned space. If you do this, you must use great care to ensure that the insulation entends up the wall, up and over the roof, and down the wall on the other side without interruption (except for the usual framing members, of course), with NO gaps between the tops of the batts and the underside of the roof sheathing above it.

[JR]

These
past few weekends have been brutal. Nearly 40 degrees outside!

Whoah, Dude. I don't know about all that insulation stuff, but do people really live in that kind of weather? Do you have to wear special flip-flops and stuff?

Hey, I know, you could wear a wet suit all the time!

JR

[Hellrazor]

You can have 3 setups.

1. Gable vents and only Gable vents

2. Soffit and ridge vents

3. Soffit and Can vents

[atgcpaul]

Thanks for the responses everyone. The roof is basically a 4 sided pyramid
with no gable ends. There's only 3ft of ridge at the top. It seems like soffit
vents and can vents it is.

Paul

[JSCOOK]

LarryG is right on the money here with his post ... with cold attics above a warm space, you definitely need to create air movement to deal with moisture that may try to collect ... it will also help keep the workspace a little cooler in the summer time too.



See the following link for some really good information on Roof ventillation:

www.Roofhelp.com

The baffles, whether foam or cardboard or whatever, do help prevent ice dams but only as a side effect of their real function, which is to maintain a clear air space for ventilation from the eave vents to the uninsulated attic space.

Gable vents alone won't work. Proper ventilation of an attic requires vents down low, typically at the eave line, to allow the air to enter; and vents up high, either at the ridge or at the gable ends, to allow the air to escape. (This is called "gravity venting," even though it works in the direction opposite to gravity). Of the two upper vent types, continuous, properly-installed ridge vents are superior to gable vents.

All the above assumes a cold roof. You can also install the insulation directly under the roof sheathing, which technically makes the attic a conditioned space. If you do this, you must use great care to ensure that the insulation entends up the wall, up and over the roof, and down the wall on the other side without interruption (except for the usual framing members, of course), with NO gaps between the tops of the batts and the underside of the roof sheathing above it.

[jhart]

Geez, at 40 degrees, we still have people running around in shorts and t-shirts here, sort of our extended summer. It doesn't really get cold until it gets below 0.

Actually, we're going to have a heat wave the next few days, into the mid and upper 50's. I can see people heading for the lakes to cool off!!

Actually, those temp's will be about 20 degrees above normal for this time of year

[atgcpaul]

www.Roofhelp.com

Thanks for that link! My next question would have been how many vents do I
need and this link answered them.

Paul