shop insulation

[mshel]

I'm getting ready to insulate my shop and have a question for which I need an accurate answer. I want to insulate under the roof so I can leave my ceiling rafters open for storage. What do I need to do to prevent condensation on the underside of the roof sheating? I saw a thing called a roof baffle but I believe they are used at the bottom of the roof where the roof meets the sidewall. I am wondering if I could just continue them all the way up to the top and then apply the insulation over that. This would create an airspace which should prevent any condensation from collecting. Pros, Cons, am I way off base, better suggestions? Don't think I can afford spray foam insulation so that isn't an option.

Thanks,
Mike

 

[Marlin]

You can use the baffles all the way up. Just start them at the top so if any leaks happen the water drains down and not into the insulation.

After that then install the insulation as normal.
I did this at my BiLs house. We also put some aluminum foil on first then the baffle but not sure how much that will help. After that just stapled in some R-13 and that was all.

 

[gator]

Mike -

I need to do the same with my shop. I have been looking at polyiso foil faced on both sides. Foil on the outside to reflect the sun in the summer and foil on the inside to reflect the room heat back in in the winter. Being rigid, you can screw it directly to the bottom of rafters and then tape the seams with aluminum duct tape. This leaves you the air space under the roof sheathing and in my case (I have a roof vent) leaves space for the air to flow from soffit to roof vent. This way you leave the ceiling open for storage.

Here is a website that tells a little about polyiso

http://www.greenbuildingadvisor.com/green-basics/rigid-foam-insulation

George

 

[mshel]

Mike -

I need to do the same with my shop. I have been looking at polyiso foil faced on both sides. Foil on the outside to reflect the sun in the summer and foil on the inside to reflect the room heat back in in the winter. Being rigid, you can screw it directly to the bottom of rafters and then tape the seams with aluminum duct tape. This leaves you the air space under the roof sheathing and in my case (I have a roof vent) leaves space for the air to flow from soffit to roof vent. This way you leave the ceiling open for storage.

Here is a website that tells a little about polyiso

http://www.greenbuildingadvisor.com/green-basics/rigid-foam-insulation

George

George,

Where is this stuff sold and how does it compare in cost to regular type insulation?

MIke

 

[gator]

George,

Where is this stuff sold and how does it compare in cost to regular type insulation?

MIke

I don't really know. I have just been researching material on the web and this stuff caught my eye. I also have been considering bubble insulation (foil both sides). Comes in a roll and can be stapled to the rafters in the same manner. Just not as great as an R-value.

As far as cost comparison, I am looking as ease of installation as well as base cost. With baffles and fiberglass batts, you buy the baffles and batts and then have to install the baffles between each set of rafters and then install the batts and then install some way of holding the batts up. With the foam, you just use screws (and maybe wide plastic washers) and fasten the foam sheets (which come 4 x 8) to the rafters (no baffles needed) and then tape the seams. With the bubbles, same basic idea, just staple it to the rafters and tape seams. With the bubble, you overlap so any condensation or leaks go over the top and down to the walls and not into the shop.

George

 

[bobby g]

Mike,

It's fine, and desireable, to use the baffles all the way up. Be sure to have path for the rising hot air to escape... like at the ridge if you have a continuous ridge vent.

bobby g