another garage insulation thread

[mwmx54]

I am new to the forum, we just moved so that I could have a garage, but now it needs some work, its freezing damn cold right now. I live in Utah, hot summers, and freezing winters, I am a diy type guy, single handedly finished the basement in my last home using spray foam, which I love, but its just not cost effective in this situation, I will be spending a lot of time in the garage, its is 100% of the reason we moved after all. so the ceiling is regular non-attic type 2x4 trusses(2x6's along the roof), soffit vents, and 2 1x1 roof vents, which I believe is adequate for my 20x20 garage. what are my options for insulating the ceiling, I would love to leave the trusses open to store lite things, IE molding, if at all possible. I have searched for days here, and in general google, which is where I came across this wonderful forum that has been consuming days of my life. is the best option non faced FG with vapor barrier facing garage and fire code rock? is there any option for insulating directly along the roof using those styrofoam air gap things? if I rock the ceiling can I just blow cellulose in, I hear thats a vapor barrier/retarder in itself... what about foam board? is there something non flammable that would be easy to just through up, and later down the road if i can't stand not having the storage along the bottom of the trusses, easily tear down? again, I know there are many articles on this, but most are based on having a ridge vent, and I have scared myself with the problems that can occur if not done right. thank you for any input.

 

[hagfan72]

I too would like to hear other's opinions

 

[mwmx54]

Well, I can no longer wait, gotta get this finished before I have a new baby in my lap, I have decided to put up 5/8 rock, and blow in cellulose with no vapor barrier. I don't like the idea of a vapor barrier trapping moisture between it and the Sheetrock, or between the insulation and the vapor barrier for that matter. The drywall will be finished and painted, so that should help contain moisture as well. So, if anyone, anyone at all! Can chime in with som input on this plan, speak now or forever hold your peace! I am way to excited and anxious to get this thing done so i can get started on my workbench shelving plan.

 

[cybrdyke]

I'm not experienced either, but I have a similar set up as you. I can only tell you what I was told. My 24x24 has soffit vents and 2 roof vents, no ridge vent. Without a ridge vent, you cannot use those "styrofoam air gap" things. You shouldn't spray or insulate right under the roof either because the roof and shingles will get too hot and will fail quicker than they should. The correct method is to insulate across the ceiling joists with faced FG facing down. The "attic" , then, would be an unheated space. That's what I was told and that's what I'm doing.
CD

 

[mwmx54]

Thank you so much for the response. I have read so many different contradicting things online that I can't tell which would be correct. Your reply is swaying me towards faced glass with face against the drywall. Do you plan on using a vapor barrier along with the faced insulation? Some people say do, others say absolutely not. From what I understand the Kraft paper is a barrier/retarder in itself, same with painted drywall, would it be necessary or beneficial to have all 3? I'm over keeping the trusses open, I just want it done and Saturday is tomorrow. I need a plan! I'm not worried about what costs more or less, short of way more in the case of spray foam, I just want it done right. One other thing, the styrofoam soffit things, how do you keep the soffit vents open without using them? Or do you just cut the insulation short of the soffit and leave it open that way? Unless we are talking about two different things.edit again, I meant only using the soffit baffle things for the first couple feet, to give the insulation something to back against. Not all the way up.

 

[cybrdyke]

I stopped the insulation batts right over the header board. But i had to cut down the first six inches of the batt to 3" so that it wouldn't block the air flow from the soffits. You can use the baffles as you suggested. That seems sensible.
I am only relying on the kraft facing as the vapor barrier. I will be using metal material for the ceiling, and drywall on the walls. no other barriers.
Bummer you're in a hurry cuz there's a bunch of insulation guru's on this forum. They just prolly haven't checked in recently.
CD

 

[mwmx54]

Yeah, I've done a ton of research, I hope I'm making the right choice, it's funny reading some of the info on the net, there are many people that say never ever use a vapor barrier in a vent elated unheated attic, and so many that say it's an absolute must. Some have also said just the Kraft facing is ideal, it's a retarder more than a barrier, so it still allows some breathing, which sounds better than plastic against what has been termed a "water vaper translucent" drywall material allowing water in and against the drywall, no Bueno. Almost all have said its a must to use a plastic vapor barrier in walls though, the argument against the walls was the fact that most homes are house wrapped, meaning there is a vapor barrier against the outside of the home, then sandwiching insulation between that and another vapor barrier. I'm confident my attic has adequate ventilation, so I am going with either blown in cellulose or blown expanding fiberglass from HD, and no vapor barrier. They are both the exact same cost including the blower machine. I will decide which to use when I am at Home Depot tomorrow, im leaning towards glass though. Stuffing recycled paper doesn't seem like a good idea. Paper molds right... And absorbs water.