Ceiling in MN

[Ramper]

Here is my "plan" from bottom to top:

• Metal roofing screwed to joists
• Prodex stapled to joist
• Air space (width of 2x4 joists)
• Two layers of 4" eps foam fitted on top of joists
• Cannned Spray foam in all cracks

My terminology might not be right. I have a 30x40 metal shop with six "rafters". There are two "joists" perpendicular to these "rafters". I added more to support the foam.

So it is metal and prodex (double bubble) below the 2x4's and 8" of EPS above them.

I would like to maybe blow-in some additional insulation (I put it the covers at the vents (only one side had them)).

How does this sound for a MN Winter?

 

[mygarageone]

Here is my "plan" from bottom to top:

• Metal roofing screwed to joists
• Prodex stapled to joist
• Air space (width of 2x4 joists)
• Two layers of 4" eps foam fitted on top of joists
• Cannned Spray foam in all cracks

My terminology might not be right. I have a 30x40 metal shop with six "rafters". There are two "joists" perpendicular to these "rafters". I added more to support the foam.

So it is metal and prodex (double bubble) below the 2x4's and 8" of EPS above them.

I would like to maybe blow-in some additional insulation (I put it the covers at the vents (only one side had them)).

How does this sound for a MN Winter?

The only thing I would add is roof sheating under the steel. Yea I know X tra money but it will help keep the noise down when I rains and the roof steel is. Pretty flimsy with. Out it.

 

[Ramper]

This is going from the bottom UP. There will be lots of air, foam insulation, dead air, Prodex and steel roofing between the actually roof of the shed and the ceiling of the shop.

 

[mygarageone]

This is going from the bottom UP. There will be lots of air, foam insulation, dead air, Prodex and steel roofing between the actually roof of the shed and the ceiling of the shop.

Sorry , I just realized what I read. I did the same thing in my garage

 

[Ramper]

Would you add blown-in OVER the top of the 8" of EPS foam? If so how much?

 

[mygarageone]

Would you add blown-in OVER the top of the 8" of EPS foam? If so how much?

I blew in about another 15" and it really makes a difference.
But according to some insulation sites. There is a limit as to when there is little effect.

 

[jimgerken]

What is the heat source? How high above the floor is the ceiling? What temp do you plan to heat to? Are you planning on turning heat up and down daily or weekly, or leaving up all the time (continuous occupation, or weekend type occupation)?

I am having trouble with the air space. Is this going to lead to condensation collection? I realize this is probably a workshop, not a house so not as humid, but still, I think the air space encourages water to condense there. Maybe I am wrong.
Another thing -- I love foam, but everything has its place. blown in fiberglass or celluose can conform to the space so well, is such a common practice (and so cheaper), can be added to as you wish for more depth if your shop useage changes, etc. It just seems to be better to do:
(from bottom to top)
Ceiling steel (which can be what is known as "liner", less money than steel "siding" product)
vapor barrier stapled onto bottom of trusses
Celluose blown in, your choice on depth, recommend 15 inches for ~R40 after settling

Fewer steps, known technique, no condensation space. My 2 cents worth anyway. I just built similar near Rochester MN, btw.

 

[jvitez]

Sorry, I'm not following your layout. It sounds too complicated.

Can you give us a photo or drawing?

Foam board whether EPS or XPS is far more expensive than blown-in insulation. You're in MN so you'll need a warm-in-winter vapour barrier. Forget the double-bubble stuff, unless you want some chewing gum......

The easiest and cheapest way would be to install a 6 mil vapour barrier to the underside of the ceiling framing members, use red sheathing tape and acoustical sealant to make an air tight seal. Make sure the attic space you just created is ventilated, ie gable or roof vents with soffit vents. Install your metal ceiling screwing through the vapour barrier. Then blow in lots of insulation over the whole ceiling space, min R40 but better would be R50 in your climate.

EDIT: Geeze, I just about copied jimgerken's post as I started writing and got distracted so didn't see his post. Curiously enough wer're both in a similar climate and give the same advice.

 

[Ramper]

Fewer steps, known technique, no condensation space. My 2 cents worth anyway. I just built similar near Rochester MN, btw.[/QUOTE]

I live just south of Rochester (near Stewartville)

 

[Ramper]

One issue is that I have the materials to do my "plan". I bought the Prodex and the foam (CL) and the metal roofing (CL). I could sell some if it and just blown in 100 bags of cellulose. It does seem easier to do it that way.

 

[mygarageone]

One issue is that I have the materials to do my "plan". I bought the Prodex and the foam (CL) and the metal roofing (CL). I could sell some if it and just blown in 100 bags of cellulose. It does seem easier to do it that way.

Use the. Prodex as your vapor barrier on the bottom of the rafters , if you have an inch of air space both sides . I believe you get an r15 out of that stuff.

 

[pantera1]

My 12' ceiling is steel, vapor barrier, then 15"+ of cellulose. I would skip the foam board in the ceiling also.

 

[rburke65]

I did metal ceiling, plastic sheeting for a vapor barrier, I cut and fitted 2 1/2" EPS between the truss bottom cords, then blown Fiberglas....R-30 or so. I have OSB under the metal roofing.