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TimboTractor
Member
Eddie, how thick should the insulation be under the metal roof? Also considering putting attic exhaust fans in the gable peaks to pull out hot humid air.
Gable and side wall overhang....necessary or not?
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TimboTractor
Member
Can an eave still ventilate the attic space without an overhang and soffit?
BuilderML
Gold Member
Yes you would have to cut back the plywood at the eave and install a vented drip edge. I don't recommend.
BuilderML
Gold Member
You do not install both "systems" in the same application.
You do soffit and ridge vent or gable vents. Pick one but not both.
I am a fan of this type of ridge vent not the rolled SOS pad.
Bing187
Bronze Member
I have seen, on many occasions, rot that was a direct result of not having an overhang. It does protect the walls from rain water running down to a certain extent, unless the wind is blowing.... It also keeps window casing and door casing out of the dripline... Granted, these need to be flashed correctly to begin with, but keeping water from running straight down the wall does help. Gutters also help, but a 12" overhang does keep it away from the building somewhat without gutters. It also provides a convenient spot, as others have pointed out, for lights and soffit ventilation.
As far as attic venting goes, I am partial to gable vents with a gable mounted power venter. It has a thermostat, and will draw air through the soffit vent and blow hot, humid air out.
Aside from all that, my own opinion is that gable overhangs and a 12" overhang just plain look better. YMMV
Mike
As far as attic venting goes, I am partial to gable vents with a gable mounted power venter. It has a thermostat, and will draw air through the soffit vent and blow hot, humid air out.
Aside from all that, my own opinion is that gable overhangs and a 12" overhang just plain look better. YMMV
Mike
EddieWalker
Epic Contributor
The idea that you can pull out the hot humid air or that a fan will "cool" an attic space is just a myth. It's a sales gimmick just like the latest diet pill or paint with primer. People buy it because it sounds good and they want it to work.
Attic space is supposed to be hot. Heat rises, and when it enters the roof at the soffit, it travels up to the ridge vent or gable vent or whatever you might have. The higher it is the better. Moving hot air faster with an electric fan doesn't change anything, it just uses more electricity.
As for insulation, you don't need a lot to significantly reduce the amount of condensation that's form. The rolls of insulation that are sold for metal roofs work great. an inch of Styrofoam will work. It just needs to be tight up against the metal to create that barrier of the inside air from the outside. If you are planning on heating or running air conditioning, then you will need a lot more. R60 in attics is the goal for houses. What you want to spend and put into it really depends on how much you want to put into heating and cooling it.
Eddie
paulharvey
Veteran Member
I guess we all think different things when you say pole barn. To me it means a roof with poles, and generally no walls, just gable walls, or maybe a 3 walled barn; I didn't think we where dealing with a fully enclosed pole-framed building. If it's like 95% of barn/sheds you'll have plenty of ventilation.
jwstewar
Elite Member
We just built a 36x54 pole barn for our goats. Completely enclosed with a 10x12 slider in the front, 4x8 slider on one side, and a 4x8 slider at the rear. The smaller sliders are for animal access. We were torn between adding an overhang or not. Wife said no, I said yes. She didn't want to spend the $1500 for the overhang, she didn't care about looks since it is a true animal barn, but she also didn't understand the benefits of it. In the end, we got 12" overhangs (one of the few debates that I win) all the way around. We put soffit vents on the sides and ridge vent the length. We also did the "bubble wrap" insulation under the metal roof. After having it "completed" for almost 8 months, we have yet to have it rain inside. We also had 2' of clear polycarbonate installed the length of the sides walls for daytime lighting.
As part of the "finishing" process, we are putting 1" foam insulation on the walls between the wall purlins and then OSB attached to the purlins between the 4x6 support posts. We are doing the walls first to try to get the heat away from the red metal away from the goats and also to keep the goats from beating the metal up from their playing. Eventually we want to put an actual ceiling of some type and some type of insulation....all with due time.
As part of the "finishing" process, we are putting 1" foam insulation on the walls between the wall purlins and then OSB attached to the purlins between the 4x6 support posts. We are doing the walls first to try to get the heat away from the red metal away from the goats and also to keep the goats from beating the metal up from their playing. Eventually we want to put an actual ceiling of some type and some type of insulation....all with due time.
300UGUY
Super Member
I have 2ft overhang on the sides, 1 ft on the front and back. I noticed that the siding looks better on the sides than it does on the other 2 sides, it doesn't get as much water on it, and less sun. If I built a new barn, it would have at least 2 ft on all sides.
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TimboTractor
Member
I completely agree that overhangs/soffits look much better, but I'm still not sold as to their value. More work and cost for sure for the soffit.