[maxwellput]

I live in middle Tennesse, hot and humid summers, somewhat cold and wet winters. I have a Tuff shed (16'x12') I want to convert to a conditioned space. I already have the walls insulated, but the roof poses some uncertainties. It doesn't have a ridge or soffit vents, although I could drill some soffits if necessary. It also has a gable vent in what will soon be the conditioned space.



I have a window vented ac unit and electric heater that are both rated well for the cubic space, but can't keep temp without an insulated roof.



The rafters are 2x4s. I'm planning on using 3" r13 faced batted, with radiant foil between that and the conditioned space.



Should i drill soffits and install ventilation baffles before putting in the r13? Is it necessary to vent the roof if it doesn't get too cold and I'm using a dry heat source? Is a radiant barrier worth it? and will venting the roof space increase Rvalue, or help the insulation work better in any way?



Every contractor says something different, each with eyes to sell.



Appreciate any neutral advice that might come my way


many thanks mighty internet.

 

[Nealtw]

Can you add a ceiling or is that to low?

 

[maxwellput]

not really room to drop a ceiling, I'd like to put osb direct up against insulation, with the "A" style cross beams exposed, if possible, to save height

 

[Nealtw]

not really room to drop a ceiling, I'd like to put osb direct up against insulation, with the "A" style cross beams exposed, if possible, to save height

Perhaps you could make it a vaulted ceiling??

 

[maxwellput]

that would be cool - unfortunately the gable vent is on the wall below where the ceiling would be, should i create one. the only ways i could vent the roof is to rip a strip down the ridge and put in a ridge vent (which realistically i'm probably not going to do) and drill soffit holes on each eaves and hope that is enough w/o a ridge.


OR not vent it at all b/c i'm not generating a ton of moisture in the winter it usually doesn't go below 20 degrees in nashville

 

[Nealtw]

that would be cool - unfortunately the gable vent is on the wall below where the ceiling would be, should i create one. the only ways i could vent the roof is to rip a strip down the ridge and put in a ridge vent (which realistically i'm probably not going to do) and drill soffit holes on each eaves and hope that is enough w/o a ridge.


OR not vent it at all b/c i'm not generating a ton of moisture in the winter it usually doesn't go below 20 degrees in nashville

People make humidity in a closed space, heat makes it rise, so absolutely sealing the ceiling is important. With out venting the roof can not cool itself in the summer so the roofing gets baked and the heat radiates down into the space below. R value of insulation is like a measurement of time. How long will it take for heat or cold to get to the other side.

 

[Porsche986S]

What is your sun exposure ? Are you mostly in the shade or fully exposed to sun ? Being 90 degrees out and humid but in the shade is MUCH different than 90 degrees out and humid and the roof/sidewalls baking in the sun for 10 hours . What is the exterior roof material ( metal/shingles ) and what color ? A light color like white or silver is much better than black or dark brown in full sun exposure .

When I lived in Orlando I wanted to add more insulation in the attic due to blistering sun exposure/heat . One foam contractor said they would shoot the entire roof structure INCLUDING the ridge vent basically making a 100 % sealed space . Their theory was if you can keep the heat out the living structure will be so much cooler . I did not go with them but I have always remembered what he said .

In a small structure like you are talking and because of your venting issues maybe .......... I repeat maybe closed cell foam is the way to go but I'm no expert . If I were to do it I would fill the entire 3 1/2 " cavity AND finish the ceiling with foam panels every bit of R value will help . I would think but have no proof that if you ran the AC all the time ( once warm enough to warrant ) that it would pull enough moisture out of the space . Run it as low speed as possible when you are not in there and crank it up when you are working in there . Keep us informed on what direction you go and the results .