By the breeze when I open the doors and windows. But seriously, it's not an enclosed attic like a house, so at this point it's open to the rest of the space so no extra ventilation needed. That's what I am worried about by adding insulation then you seal in the moisture and would need some kind of ventilation.
I had a choice of spray foam or rolled fiberglass. I choose fiberglass with paper back .. wired to the ceiling. The cost is lower with the fiberglass
Our roof was higher than yours, But I put up a dropped ceiling sorta. Ran 2x4's and laid 3/4" 4x8 foam sheets across it. Once in a while I have an issue with wind lifting them, but for the most part not.
Having an effective moisture barrier between the roof and interior space is important to the life of your roof. The roof on a building some friends and I bought rotted out along the purlins after about 30 years due to moisture buildup under the roof. The original insulation was vinyl faced fiberglas rolls. Basically, the seams between the insulation were not sealed and moisture worked its way in and condensed on the underside of the metal roof. Also, birds got into the building and destroyed areas of insulation under the roof when they nested. The moisture attacked imperfections in the metal coating, and around the nail holes. It was amazing how the roof just rusted out in big straight lines under the purlins, while the spaces in between were largely intact. For the replacement roof, the installer put down accordion panels of thin vinyl faced foam, taped the seams, then installed the new roof. Hopefully this will keep the moisture away from the metal and extend the life of the new material. Our building is taller than yours, about 14' at the eaves, but I would think the moisture issue would be the same if you don't prevent it from reaching the metal.
i did a drop ceiling with foam panels. the tape i used for seams for silver backed foam is henkel ul181b-fx - no sign of movement or loosening up for last 5 years. sticks and installs easier than you would think.
You're very welcome - and thank YOU for not commenting on my embarrassing mess. I taped the corners (wall to wall and wall to ceiling) with TekFoil Joining tape: http://www.teksupply.com/contractor...stry-ts1_greenhouse_polycarbs_2;pgdh8004.html $12 for 150 feet of 2.5" wide tape. I've seen similar foil tape locally, but the TekFoil stuff is really sticky.
I would just use some R19-R30 insulating batts with paper facing and staple the facing to the bottoms of the Joists. If your bays are too wide for 24" batts then you can use thin galvanized wire strung accross the joists about every 16-24" using roofing nailson each joist and wrap the wire around each nail. That creates a wire tray basically for your insulation to lay on. In walls you can do the same technique to hold the insulation back into the stub bays. This technique works great if you want to use thicker insulation that your studs or joists are....R13 is 3-1/2" thick and R30 is 10"....you could put R30 in a 2x4 joist or stud bay using the wire to retain it without over compressing it.
Or Andy Warhol's Silver Factory: But it is a lot brighter with the same amount of electric light, and that's good. Warmer in the winter, cooler in the summer, brighter all year 'round? Keep yer boring shit-rock! (Hmm.. If I make some room, I could get a couch in there)
Consider 2" of styrofoam on the roof joists. It will allow the hot summer air to go up in the chase you have created. Easy stuff to use, cut it with a carpenters saw, use caulk/roof nails with washers to install it. No mold or vector problem like fiber glass. If you want to go with fiber glass go with foil faced, it will reflect light/heat. Doesn't have the flame spread problem like paper faced fiber glass does. If you are working with scissor or regular trusses, etc You might want to consider putting chicken wire across the joists with a staple gun. Start stapling a couple courses of 24" chicken wire with the bonded edges. Then you can start a roll of insulation or bats between the joists, gives it a nice clean look.
What about this stuff? Insulfoam R-Tech 1V. 2" thick 4x8 panels are about $20 at Home Depot. So I could do the ceiling for about $900. http://www.insulfoam.com/images/stories/docs/6081_RT_IV.pdf
you got a pic of this somewhere? i understand the concept - just wanted to see how this looks in real life...
I got the Monitor 30 vented kero heater going today in "The Silver Factory", after < 2 hours the thermostat turned off the burner: Top temp is inside the TekFoil insulated 20x24 portion of the garage. Bottom temp is the other 20x30 portion of garage. I was working on the bike in shirtsleeves - and snowmobile boots (the floor is cold on the feet). This stuff works! Mel Gibson, Andy Warhol, Dr Evil & Mini Me would all be comfy, too.
Plain YES! Even if you put in drop ceiling or anything else, highest R-value for the roof. Saves money big time.