Attic venting in a shop

[Blazinzuk]

I'm getting ready to finish my shop up. That includes sheetrock and attic insulation. It is a pole barn and has almost no roof over hang. No soffits to speak of at all. It does have conventional trusses though

I'm guessing I need to vent it. What's the proper way to do this. Will a couple large gable vents work? Do I need to do roof vents?

I plan on blowing in 20" worth of attic cat insulation.

 

[Falcon67]

Gable better than nothing. They work, tons of older houses used them for years. Or old house had both gable and roof vents, open overhangs with no eve venting - never had any problems with that.

 

[blair683]

Gable vent at each end. With a ridge vent. If no ridge vent I would get a power vent from on of the big box stores. They have a thermostat on them. My house is older and has no soffit vents. I have a gable vent at each end, a ridge vent, and a power vent. I keep the thermostat set on 100 degrees. On real hot days in the summer time if you are real quiet you can here it running. I have black dimensional shingles and they still look fine. They also make them wind powered metal vents. Although I have no expierence with them.

 

[Blazinzuk]

The roof was done when I moved in. So no ridge vent. I don't think the shop was ever meant to be finished. It's a metal roof

Another question. The gable vents need to be as low as possible when combined with a couple roof vents, correct?

More info also. I live in Wyoming. So -25 in the winter and summertime highs of 90 at most. More likely highs in the high 70s. I plan on heating the space 24/7, no cooling necessary in summetime

 

[jetnow1]

Ridge vent with gables is a bad idea., air goes in at end then up through first/second bay ridge vent, center gats no air flow. If using gable vents make sure they are large enough,
I think it must be at least 1/300 of the total area being vented but I am going by memory,
don't quote me. I think the ridge vent/eve vent is great if the bottom of the rafters are covered, but I have real concerns about how well it functions in an open attic space.

 

[matt_i]

I would do a couple of gable vents up near the top, some are sort of a modified triangle shape, but the rectangles could be easier to fit into the metal. Screened to keep out pests. I would think with 2 of them you'd be all set. As far as the size I am not sure.

Having multiple venting systems is not ideal in my thinking as they "steal" airflow from each other, since they are automatically the path of least resistance for makeup air. On a shingled roof, I like the soffit + ridge & keep the rest closed up tight.

I did put rectangular gable vents on my shop but they are pure non-functional. Just for looks to break up what would be a massive span of vinyl up there.

 

[ct03911]

If you have vented eves and a ridge vent you don’t want to have gabled vents.
Conflicting airflow.
I wanted my garage to look like a traditional barn with a cupola so I did not want a ridge vent. Old barns had a “clean” roof line.
So, I just did two gabled vents.
Yeah, it gets warm up there in the summer and cold in the winter but they seem to move the air a bit.
The space above my garage is just storage 26’x14’ so I don’t put anything up there that is temperature sensitive like storing summer tires etc.

 

[BFGMT33]

Like others have said, you can do gable or you can do ridge but not both.

Have you thought abut spray foaming it? It would cost a lot but then you would not have insulation on the floor and could walk around up there and store stuff. You could also just put in a fan on gable and blowing out and the other just an intake for the air to come in. Attic fans having gotten controversial as they can put negative pressure on the building and **** air up into the attic - especially when heating.

Is there room to walk around up there? How big is the bottom cord on the rafters? beefy enough to store stuff?

 

[Blazinzuk]

I would do a couple of gable vents up near the top, some are sort of a modified triangle shape, but the rectangles could be easier to fit into the metal. Screened to keep out pests. I would think with 2 of them you'd be all set. As far as the size I am not sure.

Having multiple venting systems is not ideal in my thinking as they "steal" airflow from each other, since they are automatically the path of least resistance for makeup air. On a shingled roof, I like the soffit + ridge & keep the rest closed up tight.

I did put rectangular gable vents on my shop but they are pure non-functional. Just for looks to break up what would be a massive span of vinyl up there.

This seems to be the most common answer I am getting a couple of gable vents and it should be fine.

If you have vented eves and a ridge vent you don’t want to have gabled vents.
Conflicting airflow.
I wanted my garage to look like a traditional barn with a cupola so I did not want a ridge vent. Old barns had a “clean” roof line.
So, I just did two gabled vents.
Yeah, it gets warm up there in the summer and cold in the winter but they seem to move the air a bit.
The space above my garage is just storage 26’x14’ so I don’t put anything up there that is temperature sensitive like storing summer tires etc.

I really didn't want to mess with the roof as its already there. I also don't have vented eaves as there aren't really any eves on the building.

Like others have said, you can do gable or you can do ridge but not both.

Have you thought abut spray foaming it? It would cost a lot but then you would not have insulation on the floor and could walk around up there and store stuff. You could also just put in a fan on gable and blowing out and the other just an intake for the air to come in. Attic fans having gotten controversial as they can put negative pressure on the building and **** air up into the attic - especially when heating.

Is there room to walk around up there? How big is the bottom cord on the rafters? beefy enough to store stuff?

Spray foaming oh yes I have thought many many times about this. Schemed and budgeted different ways but it is just not a reality for me. I do plan on using great stuff to seal up all the cracks. Goal is to have no daylight in there that I can see at all.

My trusses are all 2x4 construction. Spanning 40 feet I'm not even comfortable walking on them. Their construction does not lend itself to very easy movement. I thought about storage up there but its just not a very good place. Plus 13.5' off the ground makes only light stuff up there and I can build a couple wall shelves up high for all that stuff.

Not the best pic of the trusses but you get the idea

 

[lakeroadster]

Relative humidity is pretty low in Wyoming. A gable vent in each end is plenty.

In reality, you may not even need those but since it has OSB sheathing under the steel roofing the gable vents would be wise.

 

[Blazinzuk]

Relative humidity is pretty low in Wyoming. A gable vent in each end is plenty.

In reality, you may not even need those but since it has OSB sheathing under the steel roofing the gable vents would be wise.

It's a pretty simple thing to do and fairly easy to do now. It's also not much money. So pretty easy to do it right.

 

[lakeroadster]

It's a pretty simple thing to do and fairly easy to do now. It's also not much money. So pretty easy to do it right.

"Right" is the question, but what is the answer?

The housing codes have strict rules for attic venting, but the issue is that housing code is universal from Maine to Phoenix. And the actual environmental issues are no where the same in every location.

And you're talking about a barn, not a house. Kind of not an apples to apples comparison.

Case In Point

Here where we live in Central Colorado our attic has (1) small roof vent... and that directs the bathroom vent out the roof. I was alarmed when we looked at the home as prospective buyers.

Once I and the home inspector spent some time in the attic we noticed everything looked great... and the house was built in 1978! He said that was not uncommon, no attic vents. I thought he was nuts.

Then I started looking at other homes. And the no attic venting was a common thing.

Low relative humidity, in a climate with moderate temperatures in the summer... means the heat won't get excessive to the point of damaging anything in the summer. And in the winter that attic will stay warmer without the venting, which is great.

Also, in areas prone to forest fires, not having a positive attic flow means fire embers won't get sucked into the attic.

So what's "right" in locations of the country that are vastly different than you very likely have zero bearing on what you should do.

But when you ask the question folks will naturally default to what is done where they live.. which may be great advice... or may not be worth anything.

 

[Blazinzuk]

"Right" is the question, but what is the answer?

The housing codes have strict rules for attic venting, but the issue is that housing code is universal from Maine to Phoenix. And the actual environmental issues are no where the same in every location.

And you're talking about a barn, not a house. Kind of not an apples to apples comparison.

Case In Point

Here where we live in Central Colorado our attic has (1) small roof vent... and that directs the bathroom vent out the roof. I was alarmed when we looked at the home as prospective buyers.

Once I and the home inspector spent some time in the attic we noticed everything looked great... and the house was built in 1978! He said that was not uncommon, no attic vents. I thought he was nuts.

Then I started looking at other homes. And the no attic venting was a common thing.

Low relative humidity, in a climate with moderate temperatures in the summer... means the heat won't get excessive to the point of damaging anything in the summer. And in the winter that attic will stay warmer without the venting, which is great.

Also, in areas prone to forest fires, not having a positive attic flow means fire embers won't get sucked into the attic.

So what's "right" in locations of the country that are vastly different than you very likely have zero bearing on what you should do.

But when you ask the question folks will naturally default to what is done where they live.. which may be great advice... or may not be worth anything.

Yep I started looking at roof vents up here when I realized wait a minute I need attic vents for the shop. My house has 2. Several friends houses have none. Even some newer homes that are way larger than my house only have a couple on them.

I really do think I will be fine with the some gable vents. You in Colorado might be really close to what I am. I actually live in one of the more humid places in Wyoming. But humid in Wyoming is dry as bone in Florida.

Just trying to do the best I can and not make any huge mistakes. We are getting to the age where if we move it will be for an awesome pay raise, but that is not likely to happen. So hoping to be working in this shop for the next 40 years if I'm lucky