Insulation R values

bigone5500

Well-Known Member
I have some 1/2" insulation board which has an R value of 3. If I use 3 layers of this material it should have an R value of 9 right? I have tried to find information on this and what I have found really doesn't tell me for sure. I may have to go with some roll insulation but want to use this stuff I have already. If the R value is only 9 then I will probably not use it. I have been rebuilding a storage shed and have insulated the walls with R13 fiberglass rolls. It may be best to continue to use that in the ceiling.
 

Tony

Staff member
Yup, what Steve said. The rolls will work better than the sheets though, and the spray in will work better than the rolls. And yes, this stuff is espensive but down there in La you shouldn't have much problem with freezing temps but if you are trying to keep it cool, then yes, go with the rolls and use a moisture barrier.
 

bigone5500

Well-Known Member
I got the insulation done. I used 3 1/2" thick R13 rolls. I went with Johns Manville encapsulated fiberglass and did the whole building in it. The walls and ceiling are covered with 1/8 thick tempered hardboard. I'll be installing either a 5000 or 8000 btu window unit to keep it cool. I didn't use a moisture barrier so I may have to get some desiccant and hang it in there. At this moment, I still have to build the door and frame then trim it out. It's overkill but fun.
 

Tony

Staff member
Another thing you could have done is put a layer of the R3 behind the R13. If it is only 1" thick, you would not lose that much space for the 13 and it should still work just as it should.

But as usual, I came late to the party and you are already done lol. Thank you work for taking me away from teh site for too long hahahahaha.

and the only reason I mentioned the moisture barrier is because you are pretty close to the gulf. It's not manditory, and that AC unit will do a great job of taking the moisture and dripping it outside (that is the water you see coming from an AC unit. As the Evaporator inside gets cold and runs air through it, it will produce condensation since cold air can't hold as much moisture as warm air, and thus you get water in a tray and it just drips out the back of the unit. ). So no need for any drying agents inside as long as you have that AC running. And in the dead of winter when it is 50 down there (lmao), the air will not have as much moisture so no worries.

Post up some pics!!!! We must see the man shed lmao.
 

bigone5500

Well-Known Member
Another thing you could have done is put a layer of the R3 behind the R13. If it is only 1" thick, you would not lose that much space for the 13 and it should still work just as it should.

But as usual, I came late to the party and you are already done lol. Thank you work for taking me away from teh site for too long hahahahaha.

and the only reason I mentioned the moisture barrier is because you are pretty close to the gulf. It's not manditory, and that AC unit will do a great job of taking the moisture and dripping it outside (that is the water you see coming from an AC unit. As the Evaporator inside gets cold and runs air through it, it will produce condensation since cold air can't hold as much moisture as warm air, and thus you get water in a tray and it just drips out the back of the unit. ). So no need for any drying agents inside as long as you have that AC running. And in the dead of winter when it is 50 down there (lmao), the air will not have as much moisture so no worries.

Post up some pics!!!! We must see the man shed lmao.
The pics are not good. I'm not very good at carpentry. This thing was a learning experience for me. I learned not to use hardboard on the walls. It soaks moisture like a sponge and will buckle on you. My corners are not square but I can say that this entire building is not square. That's what has given me so much trouble. I tried to get things back to square as possible when I had it torn apart but that didn't happen. I think it turned out pretty good though given what I had to work with. I'll post some photos later.
 

Tony

Staff member
As long as it keeps the rain and heat out, that is what counts. My OCD will not allow me to have a non square building, but that is not everyone lmao. Can't wait to see it.
 
Top Bottom