Insulation options for garage ceiling (pics)

[Greg Woloshyn]

My new floor has been poured so now I am ready to make more improvements to the inside of my shop. Since I live in upstate NY, the winters here are harsh and my ceiling is not insulated. The walls are, but that doesn't do much good since the heat goes right through the roof. It would be nice to insulate in the rafters so I can keep the additional storage space and have higher ceiling space, but the only problem is I don't have any soffit vents for air circulation. The only other option would be to cover my joists with some kind of sheet goods (and cut holes for my lights) and make myself an attic and throw insulation up there. Again, this will eliminate much needed storage space and head room. Any other thoughts for insulation alternatives?
http://i45.tinypic.com/2vuhvs6.jpg
http://i49.tinypic.com/2ish75h.jpg

[Jamie Buxton]

What's the budget? You might use plastic insulation that's sprayed in as a liquid, and foams up in place. There are kinds that serve as a water vapor barrier, so there's no need for those soffet vents you don't have. That would give you the maximum use of the headroom. Contractors are readily available to install it. It isn't a DIY installation.

[David Hostetler]

Hmmm... Not sure. My garage is finished and I simply rolled out the batts between the joists...

[Doug W Swanson]

I would put in a sheet rock ceiling, insulate above that and then add a plywood floor on top of that. Then put in a drop stairs so you have access to the storage room you just made.

You will probably have to beef up or add more joists to make things easier but then it would make a nice cozy work environment.

JMO
Doug

[Don Jarvie]

The cross beams can be moved up in the ceiling so you can create a catherdral type ceiling. There's information on the web on how high you can go. It depands on the height of the peak and the span of the walls.

Once you know how high you can go, add a beam to each rafter across and this will form you ceiling. Just add your insultaition and sheet rock.

For ventilation, At the peak on each end add a gable vent. There will be enough space between the roof and ceiling for air to move.

The only drawback is I have no storage but I also have 13 ft in the center of my shop so flipping wood around is no issue.

If you want to keep the storage, come down 2 ft of so from the peak and put 2x4s across and attach you sheet rock there. Insulate and put in the vents the same.

I did the same thing to my shop and can provide pictures if you want.

Let me know if you have any questions

[Alan Schaffter]

I agree with Don with some slight changes.

First add collar ties on each set of roof rafters as high up as allowed by the size of the existing rafters and pitch of your roof (check local code). Remove all the ceiling joist (lower collar ties). If the structure still needs a top-plate-height joist (collar tie) or two, investigate using swaged aircraft cables. A house in our neighborhood did that.

I would add a ridge vent instead of gable vents- very easy to do from the outside- peel the ridge shingles off, use a circular saw to remove the top 3/4" of ply roof deck from either side of the ridge rafter, then attach cheap metal or aluminum ridge vent with roofing nails- on that roof should take about 30 min. max. Run cheap pre-formed foam vent channels between the rafters from the soffit area up to the ridge to vent the roof deck - helps keep the ply from breaking down and the shingles will last longer in the summer heat damage. I am sure you can add soffit vents by cutting a strip opening or drilling holes and attaching vent covers.

Fur out the ceiling with 1 X 2 furring strip or 2 X 4 layed across the rafters and spaced 16" on center - makes it easier to drywall.

Wire it for lights, drop cord, air cleaner, etc.

Add R-30 batts, then rock and tape the entire cathedral ceiling and paint it white. Your shop will seem bigger and will be much airier, brighter, cooler in summer, and warmer in winter.

With such a low pitch, it doesn't look like you have much storage there to begin with, but to keep some of it you can add open-ended (easier to store stuff that way) small mezzanines at one or both ends.

You can surface-mount your lights on the sloped ceilings or hang them from chains.

[Stephan Larson]

I think if it were me I'd install little round vents in the soffit say 3 1/2" round you could cut with a hole saw and then get some of those foam soffit tunnels and run them to your peak where I'd install a ridge vent. Then you could insulated say with an r-19 or so and hang sheetrock to the bottom side of your joist. At least that's the way I did it at my shop and although it's more for heat here it should work for the cold to a certain degree there. You might want to go with a thicker insulation if the space is heated.

Stephan C.

[Mike Cruz]

Oh, boy, explaining this one is going to be difficult...

First of all, can you remove the insulation from your eaves?...the pink stuff poking out on top of the walls? If yes, I would remove that, and put in soffit vents. This will allow air to flow up from the eaves up the roof (between the insulation that I'm about to propose) and out the ridge vent (like someone else mentioned).

Next, the insulation that I just installed in my shop worked out GREAT! It is 4x8 sheets of foam insulation that is backed on both sides with foil. Now, at HD, they sell the 2" thick stuff for about $27 a sheet. I found a guy on CL in PA that sells "seconds" from DOW for a GREAT price. I got 3" for $19 a sheet. R-value of 19, I think, but the actual r-value is supposed to be much higher because of the foil AND because you actually get a seal. As opposed to the pink stuff which air can actually travel through. I have a metal roof and believe me, when it would get 80 out, it was 90+ at head height...I have 10' ceilings with 15' at the crest.

Now, with a ridge vent and soffit vents, you just have to make sure that there is enough room between the insulation and the roof for the air to move up. I have 2x4's running the length of my shop, on top of the rafters. I screwed 2x4 blocks to those, and then the insulation to the blocks, leaving a 1 1/2" gap for the air to flow. You have a different set up there. So, what I would propose is putting blocks on the inside of each rafter and screw the insulation to those. The insulation is very ridgid, so I doubt you would have to worry about sagging.

I simply attached the insulation with screws and washers. Basically, you cut the sheets down to 1" narrower than the space between the rafters. You actually want a little gap because you will fill that with spray foam...that comes in cans from the borg.

I couldn't believe my, well, skin, when I walked into my shop on an 85 degree day last week and it was cool, cool, cool in the shop. And I haven't even done the gable ends yet!

Also, when you run the sheets down the roof, run them just past the wall, not all the way into the eaves. Because next, you need to cover the space from the top of the wall to the insulation (where you just took out all that pink insulation earlier). The air needs to be able to flow into the soffit vents up over the insulation, and out the ridge vent.

You COULD leave it alone and not cover those gaps...but it all depends on why you are insulation... If it is just for summer heat and you are not air conditioning, you could leave it be, it would actually be a nice way to constantly vent the air in your shop. But, in winter, that would be robbing all your precious heat... :mad:.

Here are a couple of quick pics I just took. If you have any other questions, I'd be happy to take a stab at answering them.

[Don Alexander]

What's the budget? You might use plastic insulation that's sprayed in as a liquid, and foams up in place. There are kinds that serve as a water vapor barrier, so there's no need for those soffet vents you don't have. That would give you the maximum use of the headroom. Contractors are readily available to install it. It isn't a DIY installation.



this suggestion would be a recipe for the roof decking to rot rather quickly it is essential to have air flow between the insulation and the roof deck it doesn't need to be alot of space but there does need to be some there are styrofoam channels designed to ensure an air space between fiberglass insulation batts and the wood roof deck these are pretty cheap and even cheaper when you consider the massive moisture damage they will prevent

that being said with the obvious lack of space overhead that your picture shows the faced rigid foam board option could be your best bet if you check with a roofing material supplier you may be able to get the type with a flat gray fiber type material coating it as opposed to the shiny foil
this type product gives you pretty good R value while taking up much less space than R-30 fiberglass Batts will require and you really should cover up the fiberglass for health reasons besides. which you do not need to do with the surfaced ridgid foam type insulation

just something to consider :)

[Don Alexander]

one other thing

no matter what type of insulation you go with , you will need some air space between the roof deck and the insulation and that space will need to be ventilated to prevent moisture buildup on the underside of the roof deck
and thus rapidly accelerated rotting of said deck

[Jamie Buxton]

one other thing

no matter what type of insulation you go with , you will need some air space between the roof deck and the insulation and that space will need to be ventilated to prevent moisture buildup on the underside of the roof deck
and thus rapidly accelerated rotting of said deck

Not as I understand it. Ever heard of SIPs -- structural insulated panels? They're sandwiches of OSB, plastic foam insulation, and OSB. The whole sandwich is bonded together. There's no air space. SIPs are regularly used for structures -- both as walls and as roofs. The foam completely seals water away from the OSB, so there's no water to cause rotting. The same thing holds true for several kinds of foam-in-place insulation. They're field installed, but they do the same thing. The foam bonds to the wood, and keeps water away from it.

[Don Alexander]

ok fair enough

whats the cost of that type product? might come in handy if it isn't rediculously expensive

[Alan Schaffter]

Not as I understand it. Ever heard of SIPs -- structural insulated panels? They're sandwiches of OSB, plastic foam insulation, and OSB. The whole sandwich is bonded together. There's no air space. SIPs are regularly used for structures -- both as walls and as roofs. The foam completely seals water away from the OSB, so there's no water to cause rotting. The same thing holds true for several kinds of foam-in-place insulation. They're field installed, but they do the same thing. The foam bonds to the wood, and keeps water away from it.

The one building I saw (TOH?) made with SIP roofing panels, they added sleepers on top, and another decking layer to create the air space and to attach the roofing material. You would need to check the rating of the SIP. Without that air space asphalt shingles degrade much faster.

[Greg Woloshyn]

Thanks for the great ideas everyone. I took a liking to Don's idea about creating a cathedral type ceiling however I do have some questions. If I raise the ceiling higher and put insulation on top of it and add gable vents, what am I to do about all the exposed rafters underneath? They will certainly need insulation also. I would be inclined to use those spacers in between some fiberglass batts and the roof decking but doing this would defeat the purpose of the cathedral ceiling seeing as I could insulate the whole ceiling using this method.

I think what I might end up doing is installing some soffit vents (if I can) on my eave and placing those spacers in the rafters along with some fiberglass batts and cover the whole roof with these.

http://i48.tinypic.com/fthn2q.jpg

[Alan Schaffter]

Unless you add a microlam ridge beam from end to end, you can't have a true "cathedral ceiling." You need ceiling joists or collar ties as shown it the drawing and like Don and I suggest, to keep the walls from spaying out and prevent structural failure. As I said, use the foam air channels and bats between the exposed roof rafters, then cover it all with sheet rock. I would also run furring strip from end to end on the roof rafters to make it easier to attach the dry wall.

But again, you really should talk to a structural engineer or go into the tables to see how high you can move the collar ties. With such a low pitched roof, it may not be very far.

[Don Jarvie]

Alan described it much better than I. I probably put my rafter ties a little higher than I should have but they way the garage faces snow doesn't sit on the roof for more than a few days so the roof collapsing isn't a huge concern. The trees in the neighbors yard would KO the garage 1st.

I also doubled up the rafters on each end and the center and used joist hangers where the rafters meet the ridge beam and hurricane ties where the rafters meet the wall. I also used 3" deck screws to re-enforce all of the walls and rafters.

You will not beleive the difference the insultion makes in the winter, especially the ceiling.

[Greg Portland]

What's the budget? You might use plastic insulation that's sprayed in as a liquid, and foams up in place. There are kinds that serve as a water vapor barrier, so there's no need for those soffet vents you don't have. That would give you the maximum use of the headroom.+1.

I had the exact same problem as you and after researching a ton of solutions I found that spray foam insulation was going to be my best bet. The spray foam chemically bonds to the roof and will NOT allow moisture to accumulate between the insulation and roof. All the other options (structured panels, radiant barrier, insulation rolls, etc.) will result in mold without proper venting. The spray foam also prevents air movement / leaks (gets into all the cracks and gaps). Cost is about 2x conventional insulation rolls but you end up saving quite a bit in heating / cooling costs.

[Jim Finn]

I have installed a suspended ceiling with lift out insulated panels. I used a ladder to access the items stored above this t-bar ceiling. Worked well for me.

[Don Alexander]

the cathedral ceiling method works fine

just don't overlook the spacers between the rafters for airflow between the roof decking and the fiberglass on the slope coupled with eave vents
for each space of course you will need gable ,ridge or roof vents to go along with those eave vents to create the positive airflow

incidently that positive airflow also helps insulate your working space

[Greg Woloshyn]

I understand how the soffit vents are installed, but what about ridge vents? I know what gable vents are but I have never heard of a ridge vent.

[Don Jarvie]

Ridge vents are now used since the even the air flow throughout the roof and the gable vents are a bit ugly.

The 1st photo shows the finished product and the 2nd you can see the rafter tie in the back and I ran the across the whole ceiling. You can then strap across the ties and then set in the insulation.

The space between the ridge and ties is open to allow air flow. I have to put in a ridge vent when I re-roof the ceiling in the fall,

[Greg Woloshyn]

Thanks for the help. This will be the route I'm going to take. If I remember, I'll post a pic of the finished product when I'm done!