Insulating My Metal Building
Thirteen years ago, when we were building our house and shop I was here (Breaktime) almost every day. But once the buildings were up my interest moved on to building hot rods.
I live in Northeast Arkansas (Jonesboro) with a climate that is hot and humid in the summer and moderate to cold in the winter. I’m closing in on 70 and working in my shop has become increasinly difficult to work in. The problem is heat in the summer, cold in the winter, and mosquitoes in between.
My only hope is a heat pump.
My problem is insulation. Here are the details.
I have a metal clad building.
The building has metal posts and trusses and wood purlins. A 1″ layer of “Ag Board” is sandwiched between the metal skin and the purlins. The Ag Board has a reflective aluminum foil on the outside and a white pebbled aluminum foil on the inside that clad a 1″ thick, R3 fiberglass panel. All seams were sealed with tape. In essence I have two inpermeatable external layers on the outside of my building. The interior picture shows the hybred metal/wood structure (and the frame for the storage loft that I am building).
Obviously, R3 is not enough insulation and I need an upgrade. My plan is to have open cell foam sprayed in the ceiling and unfaced fiberglass batts in the walls.
The ceiling will be covered with 29 guage steel siding running horizontally. Internal vents will be left open at the wall edges and the peak.
The walls will be finished with painted 7/16″ OSB.
All of this background is for a simple question. With an impermeatable exterior do I need aditional moisture beariers under my planned vented interior metal ceiling and OSB walls?
More pictures here: http://www.flickr.com/photos/ratpoison/
Replies
So, are on the outs with your wife so you'll have to be living in there? Taking showers? Cooking?
For the summer you want the moisture barrier on the outside (which you have). In the winter, even if it got cold enough to worry about condensation (which is doesn't in Arkansas), condensation is not a problem unless there's a major source of moisture in the structure. Since you're only using this for a shop, there is no significant moisture source.
What you've got is fine. Use whatever insulation you like.
First off, Bib, I'm just an houror so away from you, so I know exactly the climate you're facing. Let's back up a bit, first, and look at the building itself.
First off, buildings of this type have three advantages: they go up quick, they're cheap, and you have a pretty good span between the posts.
The problem is that they are terrible by every other measure. They're difficult to heat, cool, and ventilate; the acoustics are terrible; and they're hard to change. Let's look at how you can improve those things.
The first is: ventilation. Especially in the summer, you need a way to vent the hot air from the top of the ceiling. I'd start with a pair of fans placed near the peak, one at either end. Don't forget to add intakes for the replacement air.
Now, for the comfort level ....
First, I'd construct a double entrance, where you need to pass through two doors to get in. Screen doors are a plus. The idea is to keep unconditioned air (and mosquitoes) out, and conditioned air in.
Reduce solar gain. Covering your entire windows - and not just the part that opens - with screen material will greatly reduce the amount of solar heating. Adding a 'cold roof' (essentially a second roof spaced above the existing roof, with a free-flowing air space between) will make a huge difference. Properly placed cypress trees can also throw shade on theplace when it's most needed. Simply painting the place white will make a big difference.
Don't forget the floor. Simply laying foam panels on the floor, then topping with plywood or OSB, will make a huge difference in how you feel.
I'd forget about making any moisture barriers. With your constant high humidity, I think you're better served by making sure there's plenty of ventilation.
Finally, don't forget ceiling fans to keep the air moving.
DanH, Amish Electrician, thanks for responding.
I'm going to stick with my basic plan and hopefully make incrimental imrovements in insulation and wall/ceiling covering over the next couple of years. It would cirtainly be nice to go back to square one and start over. At 69 I don't have the time and being retired, I don't have the money. It is also important for me to keep my focus on what I like to do in my shop, build traditional hot rods, and not let marginal improvements to the facility sap away my time and resources. Hopefully I will have the electric finished over the weekend and the ductwork sometime next week. Then I can really start making tracks!