School me on Gable Vents

[spotco2]

I have a 30x30 pole barn with 10' walls and a 4/12 roof pitch with 12" overhang. There is no ridge vent and no soffit vents. The building was wrapped with bubble insulation and the interior walls are framed out with 2x6, bat insulation and OSB. The building has traditional trusses spaced 5' OC. There is no ceiling inside.

It's hot in there! I shoulda put vents in when I built it but was not sure what I was going to actually do with the building. I still don't know but I know it's hot in there with no circulation and all of the heat building up in the top of the building.

I think a gable vent on each end would help get the heat out. I can always cover them in the winter if I need to.

I've been looking at vents but have a question about size. Is bigger always better? Can they be to big? What size do I need?

I don't want powered vents.

Any info is appreciated.

 

[pattenp]

You say the walls are insulated with batt insulation; how is the roof insulated? Usually gable vent are used with enclosed attics and soffit vents are needed.

 

[yeldogt]

So the roof is insulated ?

Is the building heated? AC


Whenever outside air is introduced in a humid climate .....care must be taken

 

[spotco2]

Roof only has bubble insulation under the metal.

I do have a heater mounted in one corner. I might add air at some point after a ceiling of some sort.

My budget is blown at this point and I am only working on it as extra money is available. Don't have the funds to install an insulated ceiling right now or AC.

 

[Cyberbear]

If money is a problem right now you might want to check with Home Depot and see what vents are available. In your situation, I don't think too large will be a problem, better too big than too small, as you can always block off what you don't want. All metal vents are great and they are low maintenance.

 

[MagKarl]

I would put in an attic fan in one of the gables. I did this at my old house and it made a huge difference. Bought a fan and gravity louvers at HD or Lowes, can't remember, was not too spendy. Set the fan to come on at whatever temp you decide. You will have to add vents for fresh air to come in, soffits or other end gable.

 

[ScottsGT]

I would put in an attic fan in one of the gables. I did this at my old house and it made a huge difference. Bought a fan and gravity louvers at HD or Lowes, can't remember, was not too spendy. Set the fan to come on at whatever temp you decide. You will have to add vents for fresh air to come in, soffits or other end gable.

This is what I would do. Draw cooler air across the top of the building to draw out the hotter air that stays higher.

 

[Ray-CA]

I have 3 of these on our 28x30 shop along with 2 dormer vents, a pair of gable vents and soffit vents. Two of the turbines are duct-ed directly to the shop and the remaining vents handle the attic space only. Shop heat vents fine.

Ray

 

[kbs2244]

Gable vents are better than nothing.
They will let some of the hot air out.
And you do not have to get up on the roof.
But the turbines will work better and are with out any power need.

 

[spotco2]

Honestly, I don't like turbine vents. I don't like the look of them and think that the easiest way to create somewhere for your roof to leak is to cut some big, round holes in it. I know they normally work well but I just don't like them and would rather do gable vents.

I was thinking a vent in each end and possibly a fan in one to help draw across, up and out. Would soffit vents help, hinder or be indifferent? They are boxed in but would be easy to put some in but don't want to if it is going to cause issues with air flow of the gable vents drawing the heat out.

 

[Crfdell]

soffit vents are indifferent until you finish the ceiling soffit vents work with roof vents and gable vents on a stack principal. Hot air rises and cooler air is brought in through the soffit but with what you described two gable vents one electric on a thermostat would be ideal . When you finish the ceiling the system will still work fine . I always recommend highest up on the gable as possible.

good luck let us know what you decide to do and how it works out .

 

[spotco2]

So I would not need soffit vents if I go with 2 gable vents, correct?

I have a gable vent fan that I was going to install but use with a manual switch instead of a thermostat since I go weeks without ever going into the building for anything, but sometimes have to spend hours in there.

 

[Chuck]

Roof only has bubble insulation under the metal.

I do have a heater mounted in one corner. I might add air at some point after a ceiling of some sort.

My budget is blown at this point and I am only working on it as extra money is available. Don't have the funds to install an insulated ceiling right now or AC.

That's actually the main source of your trouble. Sadly, my understanding is that bubble insulation has basically zero insulation value when tested by any independent lab that isn't a bubble insulation manufacturer. I haven't seen any independent evidence myself that it functions as anything other than a vapor barrier.

Right now, the bigger the vent, the better. Your best bet at this point is to try as hard as you can to get it to behave as a completely open, uninsulated building. I have a similar issue with one outbuilding, and am actually considering a power ventilator at one end on a timer, in an effort to get a handle on the moisture problems that come with this sort of trouble.

So I would not need soffit vents if I go with 2 gable vents, correct?

I have a gable vent fan that I was going to install but use with a manual switch instead of a thermostat since I go weeks without ever going into the building for anything, but sometimes have to spend hours in there.

That actually depends a lot on how you plan to finish your roof system, and where you want your insulation. If you do your insulation on top of the roof deck, with no batts, and do a good job of sealing everything else, you won't end up needing venting under the roof space at all. If you plan to put in a ceiling with insulation at the ceiling level, you'll need either soffit + gable or soffit + ridge venting to get enough air flow to keep moisture down.

 

[spotco2]

That's actually the main source of your trouble. Sadly, my understanding is that bubble insulation has basically zero insulation value when tested by any independent lab that isn't a bubble insulation manufacturer. I haven't seen any independent evidence myself that it functions as anything other than a vapor barrier.

I think the name is misleading. It's not really an insulator but more of an isolator. I do know that it works very well as a radiant barrier.

The metal panels would be well over 180° after sitting in the sun all day and the bottom side of a bare panel is untouchable without burning your hand. With the bubble wrap under the metal you can lay your hand against the bottom of the bubble wrap and it is only slightly warm to the touch. There is supposed to be an air gap between the bubble wrap and the surface that it is blocking the radiant heat but many times people do not do that.

You can do basically the same thing with regular bubble wrap. This stuff just has a shiny side but the clear works almost as well.

 

[Ray-CA]

If you are set on gable vents and a single fan, here is a solar powered one: http://shop.solatube.com/solar-star-attic-fans/interior-mount-attic-fan-im-1200.html

Ray

 

[over40pirate]

2 gable vents mounted as high as possible is my choice. 1 with an exhaust fan. Larger would be better.
If unable to but a ceiling in with insulation above, I would staple a visqueen sheet or poly tarp on the bottom chord of the trusses.