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[Wubicon]

Long time reader/lurker!
Like many others I stumbled into the site via the 12 Gauge Garage. A few years later I have purchased my first home, with the starting point for my garage. A little about me: I know very little of construction code/methods but I'm not a stranger to swinging a hammer. Like a really good labourer.

I've attached a diagram of it, which is a good approximation of the space. The main structure was built in 1976, the smaller addition built less than 10 years ago. I'm located in southern Ontario, Canada so it get's cold and hot/humid here in the summer/winter months. The walls are insulated in the main part, about 50% of the walls in the addition is insulated but I think the previous owner got sick and couldn't finish it. So I am.

At some point the main part had an insulated ceiling and soffit venting. No ridge vent. The addition was built similarly. Animals got in and the ceiling and insulation was removed and the however the animals got in was resolved.

Now I have a garage with insulated walls but not insulated roof/ceiling. The height of the trusses/rafters (not sure of the difference) is minimal so this could never be an attic space one could walk around in. Currently I have been putting stuff on the the trusses/rafters for storage (unused lumber, doors, coolers etc). I realize though, this is not optimally insulated opening to a risk of ice dams and cooking the shingles in the summer, shortening life span. Plus the soffits are open so any heat I introduce in the winter goes right out.

What I've done for a slightly warmer winter this year is stuff batten into the top plate below the decking of the roof to help keep the heat in, but this can't be a permanent solution.

So I think I have 2 options but I'm sure I have all the details for either. Maybe someone has another really clever idea.

1. Spray foam the underside of the roof decking and preserve the storage space in the trusses/rafters. Probably need to understand some venting and condensation build up with this option. But as I understand it, moisture build up on the inside of the decking is a problem and warming up the shingles when snow is on top causing ice dams is a problem.

I've also considered when the shingles do bake, go to a steel roof? What problems does that pose though?

2. Put some kind of insulation up, vapour barrier and a ceiling. Does this need ridge vent to let hot air out in summer months? I also want to consider losing the storage space...

Thanks,
Wubicon

 

[Lumpy102]

I'm not a builder, so this is just my opinion/experience, others may disagree.
With the age of your house/garage/addition, I would say you likely have trusses, which aren't generally engineered to hold a load on the bottom chord. Your option #2 is likely the best, install those vent things (Durovent or something similar) between the trusses at the soffits first, install a vapour barrier on the bottom of the trusses and then install your ceiling. Blown or fibreglass bat insulation (I've got 16 inches of bat) and cut in either a ridge vent or several roof vents. The cooler you keep the "attic space" the longer your shingles will last.

 

[Wubicon]

I'm not a builder, so this is just my opinion/experience, others may disagree.
With the age of your house/garage/addition, I would say you likely have trusses, which aren't generally engineered to hold a load on the bottom chord. Your option #2 is likely the best, install those vent things (Durovent or something similar) between the trusses at the soffits first, install a vapour barrier on the bottom of the trusses and then install your ceiling. Blown or fibreglass bat insulation (I've got 16 inches of bat) and cut in either a ridge vent or several roof vents. The cooler you keep the "attic space" the longer your shingles will last.

Thanks for the reply!

My intuition is telling me what you’ve described (or very similar) is the best option for roof longevity, heating in winter months and cooling in summer months.

 

[Bessy]

Following, as my wife and I too, just purchased our first home in S.W. Ontario, and we're facing a remarkably similar situation of garage walls being insulated (from what I can tell), but not the ceiling! I've got to spend some time up there and take stock of any pre-insulation work, but very much in the same boat!

Welcome aboard!

 

[Wubicon]

I'm continuing to think about my options as I complete some other higher priority projects in the garage.

 

[racecougar]

Step one would be to figure out exactly what your roof construction consists of. If you can post some photos here, we can tell you.

Welcome aboard.

 

[E1271]

I'm no builder but I'm a professional DIYer with some experience from building homes, garages and barns. That being said, you're on the right track. Install foam insulation ducts from the soffit up the roof sheathing as far as you require for the depth of insulation you'll add. Then install a vapor barrier along bottom of trusses and then install the ceiling. Build an access panel, or ladder, whatever you prefer. If you choose to go the ladder route, you'd be fine storing light weight material in the attic, i wouldn't be afraid of putting a few hundred pounds or more, especially if it's spread out. Cut in a ridge vent, they are superior and less work to add to an existing roof. I personally wouldn't want to spray foam the roof deck itself, I don't want a climate controlled attic. If you were to have a attic room or something like that, I'd say go ahead but that doesn't seem to be the case here. Good luck, I'll be sure to follow along!

 

[CraigStu]

We need pics.

 

[Wubicon]

I'm no builder but I'm a professional DIYer with some experience from building homes, garages and barns. That being said, you're on the right track. Install foam insulation ducts from the soffit up the roof sheathing as far as you require for the depth of insulation you'll add. Then install a vapor barrier along bottom of trusses and then install the ceiling. Build an access panel, or ladder, whatever you prefer. If you choose to go the ladder route, you'd be fine storing light weight material in the attic, i wouldn't be afraid of putting a few hundred pounds or more, especially if it's spread out. Cut in a ridge vent, they are superior and less work to add to an existing roof. I personally wouldn't want to spray foam the roof deck itself, I don't want a climate controlled attic. If you were to have a attic room or something like that, I'd say go ahead but that doesn't seem to be the case here. Good luck, I'll be sure to follow along!

I see requests for pics so I'll follow up with some later. Best I can do is this diagram for now. Ignore measurements. But that is the basic concept of what im dealing with.



I was thinking about cutting into the exterior walls at the front and rear of the structure for vents so I don't have to mess with the roof. Cool air would enter through the soffits and warm air can exit through the new vents. Cutting into the roof and trying to seal some vents seems like asking for a leak...

Next step would be sealing up the ceiling with vapor barrier and a ceiling covering (plywood, wood paneling, whatever) and putting batten on the vapor barrier in-between the trusses. I should leave some kind of access to be able to check on things up there but otherwise it's a sealed, unusable attic space.

 

[racecougar]

That is a rafter system rather than trusses. The reason we'd like to see pics is to:

A. Determine which you have.
B. Identify spacing of your bottom chords, rafter ties, or ceiling joists.
C. Identify the span of said members.
D. Identify the size of said members.

Without this, we can't tell you if what you have will support a ceiling.


As far as adding a ridge vent goes, it is simple to do. It will outperform gable vents, particularly in your building layout shown above (initial post).

 

[E1271]

I see requests for pics so I'll follow up with some later. Best I can do is this diagram for now. Ignore measurements. But that is the basic concept of what im dealing with.



I was thinking about cutting into the exterior walls at the front and rear of the structure for vents so I don't have to mess with the roof. Cool air would enter through the soffits and warm air can exit through the new vents. Cutting into the roof and trying to seal some vents seems like asking for a leak...

Next step would be sealing up the ceiling with vapor barrier and a ceiling covering (plywood, wood paneling, whatever) and putting batten on the vapor barrier in-between the trusses. I should leave some kind of access to be able to check on things up there but otherwise it's a sealed, unusable attic space.

Ridge vent will still be superior to a gable vent and I've seen a lot of critter problems due to gable vents. I'm not saying it shouldn't be done, it's just my experience.

This is a rafter setup and not a truss. Maybe I wouldn't but too much weight up there, trusses have multiple members that tie the top, roof deck, 2x to the bottom cord making it stronger than this.

Sealed unusable is ok, I put an access in my garage (attached to house) but it hasn't been used since climbing down after blowing insulation. You'll need some kind of access to do the insulation but how you cover it up can be as permanent as you like.

 

[ToolsRCool]

So I'm in the same dilema on a full ground-up garage rebuild here in MI, maybe you can use some of these ideas? Warm summers and cold winters. I installed full length ridge a soffit vents on both my home and garage decades ago, and the shingles have lasted forever on both. So, I am a believer in ridge vents.

Given that, I also see any attempted heat I put into the garage fly right up and out the ridge vent. I now have dust webs hanging down from the ridge vent, and can see them moving violently when the heater is on. I could only imagine what a thermal camera would show. Actually, we already know.

So, on the new build, I am making my own closable ridge vent. Will have full length vented soffits with a ridge vent as well, but then also using those rafter baffle trays full rafter length form soffit to the ridge vent, then fiberglass insulation, then vapor barrier (maybe). The top 1 foot of the insulation and baffle trays up at the ridge will be removable in the summer to allow hot ambient air in the attic to vent out. I will put the last 1 foot of insulation and baffle trays back in place in the fall before heating the garage during the winter.

This keeps the underside of the roof sheathing fully vented year round regardless, but does not let any of my heating attempts to simply fly out the roof, literally. I'm using a (used) high efficiency furnace, and since those use sealed combustion, will not be adding moisture to the garage ambient air.

I have also been working on a way to start a high efficiency furnace in the garage from cold and dark, without the need to use heat tape on the condensate drain tube. I simply route the condensate drain tube within the PVC furnace exhaust exit, including an S trap. Has been working 100% on a test basis so far. I deliberately let it freeze, the fire it up the next evening.

You can quickly and easily add a ridge vent if you wanted, then vent your soffits. Use rafter baffles and insulation atop of them if you want the attic space heated. Venting the gable on each end works too, but not as well, as long as there is a powered fan on one end.