Garage insulation

[cmbicycles]

I am teaching from home in my garage for the foreseeable future and I need to insulate it to take the edge off when it gets cold, and keep the heat in when I run a heater. I had planned to upgrade the electric and insulate down the road to make a year round workshop. Need to do that sooner now. It's just served by a 20a circuit, so planning to add some more capacity now as well. You can see all the electric is flexible metal conduit, so could just leave that exposed on top of the walls as well, since it's just a workshop.

It's a 16x24 detached garage, 2x4 walls and 2x6 roof, everything 24"oc. I plan to insulate and drywall the side walls and replace the garage door, but am torn on the upper end. We use the rafters for storage so I'd need to either sister some ceiling rafters and make a door to get the thule box up, or install baffles between each roof joist and insulate the roof. I'm leaning towards doing the roof, laying baffles from the soffit to the ridge vent to leave room for air flow, and just leaving the vapor barrier exposed.

Anyone done this? Am I crazy to consider it? I'm thinking I'll leave the roof insulation uncovered as drywall would be a pain up thru the rafters. Other options or advice welcome.

Picture of the bike corner attached.https://uploads.tapatalk-cdn.com/20200924/dba38f69d8bb26c3ca73450e33a4c1c7.jpg

[Louis]

These folks had a "room above the garage," but perhaps it isn't that different from your situation, if you're going to heat the garage:

https://renosemipros.com/insulating-room-over-the-garage/

[el cheapo]

In my state if you make improvements where additional heated/ac space is added it will increase your property taxes if the tax office finds out.

[fogrider]

In my state if you make improvements where additional heated/ac space is added it will increase your property taxes if the tax office finds out.

how would the tax office find out?

[dgauthier]

The smartest advice I have heard for do-it-yourself refinishing of a garage is to call your local building inspector out. They can tell you what approaches make sense and are up to code.

[Davist]

how would the tax office find out?

you should pull permits in general.. we had someone do something next door, and got a tax bill for a shed (we had already lived here 10 years and it was there when we moved in) that we had to dispute.

[Tandem Rider]

Go see the building inspector first, not second. S/he will be able to give you a lot of advise on what you are trying to do. The LAST thing you want is to be enemies with the inspector. They can and will make you de-construct to allow for inspection. They will tell you what permits are required and what inspections are required and at what stage each inspection is required. As far as what you need for electrical, heating, A/C, structural, etc a permit allows you to work with the utility company and a contractor. No utility and very few contractors will touch an un-permitted job.

That being said, since you are going use the space for more than storage, you probably will have to cover the insulation with sheetrock, both for fire code and to protect your lungs from fiberglass. The side benefit is you may be able to wire the shop with romex wire since you are putting up sheetrock.

Sounds like a great space with lots of uses, have fun with the build out!

[batman1425]

Another datapoint - you may want to bring in a structural engineer to take a look at your roof construction. Many garage roof structures are really only designed to support the live and dead load of the roof itself and keep the walls of the garage from bowing outward. Lots of variables factor into this but the chords (2x6 in your case) may not support much additional weight safely. Even drywall and blown cellulose can add up quickly in the weight department. An engineer should be able to give you a lb/sqft recommendation.

Some don't realize this and pack the ceiling full or close them up not paying attention to how much weight they are adding with the finishing materials. That can lead to sagging ceilings and in a worst case, collapse if you're not careful.

Once you've got an idea of what the chords will support, you can figure out what makes sense from a function, performance, and aesthetic perspective - drywall and lightweight insulation, spray foam on the underside of the roof deck, etc. If the chords will handle it, you could finish it out and make provisions for a storage space with pull down stair access.

In your climate, think about vapor barrier too. Lots of contentious information out there, but if you will be heating the space, think about where condensation is likely to form and how to control it.

[adampaiva]

Wow you guys love to make a project more expensive. He doesn’t seem to be creating a new bedroom or anything. I’d personally not bother with all of this inspector/permits stuff if this was mine.

Why will Sheetrock be particularly difficult on the roof underside? Doing it yourself or hiring that out? You could pop in rigid foam insulation to the underside and choose to cover or not? Not sure if there are sufficiently fire retardant options to leave exposed. Or add nailer strips and just sheetrock between the roof 2x6’s.

[lzuk]

Easiest insulated ceiling might be rigid foam on top of the ceiling joists. If you go with drywall you should fir the undersides of the joist at 16” center. Shouldn’t need a permit unless you add electrical and or plumbing as it would still be a garage and not living space

[Dave]

Building inspectors are not your personal construction consultant. They only come out after permits are granted and you've reached a stage of construction that requires an inspection. For example, if the wiring is modified, it must be inspected before drywall is applied.

It's not hard to find info about the acceptable span for 2x6 ceiling joists, assuming that drywall is applied. The weight per square foot is really small, under 2 lbs per square foot.

I the ceiling is to be dry walled, then the electrical wires can generally be moved to the side of the joists and flexible conduit is not required, but there are areas where codes are more strict than NEC requires.

[batman1425]

Building inspectors are not your personal construction consultant. They only come out after permits are granted and you've reached a stage of construction that requires an inspection. For example, if the wiring is modified, it must be inspected before drywall is applied.

It's not hard to find info about the acceptable span for 2x6 ceiling joists, assuming that drywall is applied. The weight per square foot is really small, under 2 lbs per square foot.

I the ceiling is to be dry walled, then the electrical wires can generally be moved to the side of the joists and flexible conduit is not required, but there are areas where codes are more strict than NEC requires.


OP says 16x24 footprint with 2x6 ceiling joists 24”OC. Assuming the joists span the 16’ there’s probably not a lot of dead load wiggle room there. Probably enough for drywall and insulation, but that’s it. I wouldn’t use it for storage and that. If it was me I’d have an engineer look at it just to confirm the load limits before putting rock up but yvmv


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[Dave]

A brief search yields some relevant info.

https://www.mycarpentry.com/joist-span-tables.html

[HenryA]

Spray foam the whole thing?

https://www.greenbuildingadvisor.com/collection/spray-foam-insulation

Your structure may or may not be suitable. Best part about it is its over and done in a day when you hire it done.

As to the need for permits, etc. Read your county/city regulations and find out. Every place is different. Everywhere from no permit needed to extensive architect and engineer stamped plans and strict inspections. The only rules that matter are the rules where you live.

[robt57]

Get batting of correct width with vapor barrier one and staple it to the roof rafters. Vapor barrier facing down. I'd get 2x6 even though you really should have some air under the sheathing. But 2x6 in 2x6 rafters spaces will sink a little in time and leave a little air space to the wood in time.

Your real issue IMO will be the concrete sucking the heat outta your feet. Decide on a corner for your desk and put a few 3/4" horse mats down over the cement there, and a small heat pad made for under a desk for your feet while you sit.

Make sure the weather stripping on exterior doors is good/new/tight, insulate the garage door panels if only thin Aluminum one sided.

Get a third horse mat for your bike trainer area... ;)

[cmbicycles]

Get batting of correct width with vapor barrier one and staple it to the roof rafters. Vapor barrier facing down. I'd get 2x6 even though you really should have some air under the sheathing. But 2x6 in 2x6 rafters spaces will sink a little in time and leave a little air space to the wood in time.

Your real issue IMO will be the concrete sucking the heat outta your feet. Decide on a corner for your desk and put a few 3/4" horse mats down over the cement there, and a small heat pad made for under a desk for your feet while you sit.

Make sure the weather stripping on exterior doors is good/new/tight, insulate the garage door panels if only thin Aluminum one sided.

Get a third horse mat for your bike trainer area... ;)

Yeah, the concrete floor will get cold in winter. Eventually I thought about putting in something like Dricore flooring and a rubber mat over top, but that will be a later project. I also do a little welding out there, so have to consider the floor for that as well... maybe just get a nice welding blanket to throw down or just plan to make all my sparks outside. I have some 1/4" rubber mats out there now in the half where the bike stand resides. I dont actually have a desk out there, I'm working off my table saw... just making sure to not run it through my laptop in the frustration of teaching online.

Going through plans for everything on wheels (storage/shop tools/etc)to reconfigure the space when I need to work on different projects.

I was planning on r19 for either ceiling or roof, r13 in the walls. Vapor barrier on both

To the above for difficulty of installing drywall on the roof, there is only 41" between peak and ceiling, and half of the length has boards already nailed down for storage, so getting full sheets of drywall up would require some effort. Nothing terribly heavy is being stored, wheel/bike boxes, thule box, some beach stuff, vintage cannonball collection, etc. It's just me doing the work. I need to get it done as economically as possible, but also want it right, as doing it wrong would be even more expensive.

Plenty to think about. I'll see if I can identify the type of wood based on the span chart linked above to see what load it can support. Maybe I'll have to find a different place to keep the cannonball collection.

[HenryA]

OK, no exposed spray foam for you if you're welding out there. Whatever insulation you pick, how about metal -- like roofing or inexpensive siding? Already painted from the factory. Screw it up just like you would drywall, but be neat about it. Its much lighter than drywall.

[cmbicycles]

I had considered doing metal roofing for the ceiling, or underside of the roof itself. Maybe drywall on the walls and that up top, or just do the whole thing in corrugated metal something. Could run the electric over top of the metal using the flexible metal conduit. A friend is an electrician and offered to take a look to make recommendations so I'll see what he thinks as well.

[dgauthier]

Wow you guys love to make a project more expensive. He doesn’t seem to be creating a new bedroom or anything. I’d personally not bother with all of this inspector/permits stuff if this was mine.

Why will Sheetrock be particularly difficult on the roof underside? Doing it yourself or hiring that out? You could pop in rigid foam insulation to the underside and choose to cover or not? Not sure if there are sufficiently fire retardant options to leave exposed. Or add nailer strips and just sheetrock between the roof 2x6’s.

Every time I hear about a structure collapsing in some 3rd world s__thole resulting in scores of deaths and injuries, I say a little prayer of thanks that I live in a country with building codes.

[batman1425]

OK, no exposed spray foam for you if you're welding out there. Whatever insulation you pick, how about metal -- like roofing or inexpensive siding? Already painted from the factory. Screw it up just like you would drywall, but be neat about it. Its much lighter than drywall.

The first house we owned, the previous owner did a neat trick finishing out the basement. The basement ceiling was engineered I-beam 16OC. They bought some nice looking vinyl siding, cut it to about 15" wide, and popped it in between the beams so it would rest on the bottom flanges of the I's. Coat of paint on the exposed surfaces and you're Robert's nephew. Looked really nice, was light, you could cut holes in it for pot lights where needed, and was super easy to remove a panel to get to utilities. Pretty clever.

The 24" centers might make this a non-starter for the OP's application. The panels probably aren't rigid enough and would sag in the center. Also for sure wouldn't support the weight of insulation.

[Tandem Rider]

OK, no exposed spray foam for you if you're welding out there. Whatever insulation you pick, how about metal -- like roofing or inexpensive siding? Already painted from the factory. Screw it up just like you would drywall, but be neat about it. Its much lighter than drywall.

A friend of mine did this inside his shop, be aware, there is no noise dampening with this. It may not matter to you but grinders, drills, etc get louder with an odd echo. He regretted it in his case.

The last shop I built for myself I put T-111 on the walls, just the least expensive I could find, and sheetrock above. I would do that again. That might be an option for you as well, once the T-111 is nailed up it's finished unless you really want to paint it.

[Dave]

Codes may require a minimum R38 ceiling insulation. Local codes should also be considered for the wall and ceiling coverings. Sheet rock is usually required for fire protection. Other decorative materials go on top of that.

I acted as the general contractor when I built my home and 1800 square foot shop. With the high wind potential in the foothills of the front range, the roofs and walls had to be anchored to withstand 110 mph winds. A licensed engineer had to sign off on the design. In Larimer County, all builds must be designed by a licensed architect or engineer. Heated workshops must have R10 foundation insulation. I even have R10 foam panels under the 6 inch thick concrete floors in the workshop. I bought garage doors with the highest R value sold by Clopay, at the time.

[Bob Ross]

Easiest insulated ceiling might be rigid foam on top of the ceiling joists.

I was wondering if anyone would suggest this; wasn't sure it was still a thing.

Back in the 1970s my Dad was in the plastics industry, he worked for the polystyrenics division of Arco Chemical selling the raw plastic material to molders and fabricators. So we got a ton of finished product to "beta test" in our home, including the then-nascent rigid foam insulation. Did our attic and garage entirely with 1" foam. I guess it worked.

But since I've lived in apartment buildings for the 40+ years since and rarely hang out in Home Depot, I wasn't sure if expandable polystyrene foam was still a go-to for insulation materials.

=====
Amusing story albeit thread-drift: When I was 18 and needed a job my Dad hooked me up with one of his clients who manufactured this aforementioned 1" rigid foam insulation. The way they make those 4'x8'x1" sheets of foam insulation is they mold a 4'x8'x3' block of solid foam -- fill the mold with loose polystyrene beads, blast it with steam to get the beads to expand/congeal -- and then they use an industrial hot wire knife to slice off 1" sheets. Anyway, the steam expansion process creates a lot of static electric cling, and so getting the 4'x8'x3' block out of the mold after it's been expanded is a bit of a chore. The job that I was offered involved whacking the side of this giant mold with a baseball bat to loosen the foam block until it fell out! $2.15/hour to smack a giant aluminum block with a baseball bat for 8 hours a day.

I declined the offer. :banana:

[HenryA]

A friend of mine did this inside his shop, be aware, there is no noise dampening with this. It may not matter to you but grinders, drills, etc get louder with an odd echo. He regretted it in his case.

The last shop I built for myself I put T-111 on the walls, just the least expensive I could find, and sheetrock above. I would do that again. That might be an option for you as well, once the T-111 is nailed up it's finished unless you really want to paint it.

Agreed.
My first pick is T111 as well. I like the somewhat rustic look when unpainted. Kinda like a fancy show horse stable look.

[NHAero]

Building engineer here...FWIW...

41" to peak seems marginal storage for the cost of putting the thermal boundary at the roof rather than the ceiling joists. If you have stuff to store up there that gets used once/year, think about an end wall access in the gable, above the thermal boundary.

You want to make this enclosure airtight (and then consider a small energy recovery ventilator). The occupancy you describe won't generate much moisture and a vapor retarder is less critical than an air barrier, especially at the ceiling level. If you have the floor to ceiling height available, and because you have minimal insulation depth available under the existing storage "floor" in the attic, unless you remove them, I might put up a 1" layer of foil-faced polyisocyanurate insulation on the underside of the ceiling, tape the joints as an air barrier (foil takes care of the vapor issue too), strap over the foam with a true 1" thick strapping to run wiring in without penetrating the foam. Avoid recessed lights - use surface mount LED lights, some don't even require a shallow electrical box.

I'd rather blow-in cellulose than batts, fills all the nooks and crannies. If using batts, mineral wool batts are stiffer and fill cavities better than fiberglass - Roxul is one brand. Same for the walls. Cut the batts carefully around wiring, and use an outlet cover gasket to limit air leakage.

1" of foam on the floor will make a big difference in comfort. You can get Huber Zip-R with OSB laminated to 1" foam (or more) and maybe glue it down. You'll need an additional surface on top of that for welding though! Maybe 1/2" cementboard, such as Durock.

If you use a vapor retarder, in your climate I would choose Certainteed MemBrain, which is a variable permeability product. Tape it if it's the air barrier, otherwise not needed.

Finally, a single zone minisplit heat pump will provide heating and cooling, and if you do a decent job on the thermal enclosure you can likely get away with a 9,000 BTU/hour unit, or even a 6,000 BTU/hour. The brands I use are Mitsubishi and Fujitsu.

[robt57]

Yeah, the concrete floor will get cold in winter.

The other issue is the evaporating moisture off it. Evaporation is how cooling works if you'll recall 9th grade science and health classes.

Truth is probably closer to it won't change that much in temperature year round. But it's mass and evaporation process and your feet so close will be subject to temperature transfer.

So sealing the surface, and wearing wool socks and good weather insulate shoes for prolonged standing help as much as anything. Unless you put a thermal reflective layer on top of an insulating layer, an 220v electrical heating mat grid and and convection friendly flooring layer.... ;)

The shoes and socks route will eat into your chi chi zoot bike budget less though....

[HenryA]

For all but the floor, NHAero has presented some very good ideas. The frugal solution to a cold concrete floor is wool socks.

If you heat and cool it even moderately, the air will exchange enough to keep humidity at an acceptable level. I have a dehumidifier running in my garage and its around 30% humidity in there now. No rust, no funk growing, reasonably comfortable and I live in a humid place.

[cmbicycles]

Building engineer here...FWIW...

41" to peak seems marginal storage for the cost of putting the thermal boundary at the roof rather than the ceiling joists. If you have stuff to store up there that gets used once/year, think about an end wall access in the gable, above the thermal boundary.

You want to make this enclosure airtight (and then consider a small energy recovery ventilator). The occupancy you describe won't generate much moisture and a vapor retarder is less critical than an air barrier, especially at the ceiling level. If you have the floor to ceiling height available, and because you have minimal insulation depth available under the existing storage "floor" in the attic, unless you remove them, I might put up a 1" layer of foil-faced polyisocyanurate insulation on the underside of the ceiling, tape the joints as an air barrier (foil takes care of the vapor issue too), strap over the foam with a true 1" thick strapping to run wiring in without penetrating the foam. Avoid recessed lights - use surface mount LED lights, some don't even require a shallow electrical box.

I'd rather blow-in cellulose than batts, fills all the nooks and crannies. If using batts, mineral wool batts are stiffer and fill cavities better than fiberglass - Roxul is one brand. Same for the walls. Cut the batts carefully around wiring, and use an outlet cover gasket to limit air leakage.

1" of foam on the floor will make a big difference in comfort. You can get Huber Zip-R with OSB laminated to 1" foam (or more) and maybe glue it down. You'll need an additional surface on top of that for welding though! Maybe 1/2" cementboard, such as Durock.

If you use a vapor retarder, in your climate I would choose Certainteed MemBrain, which is a variable permeability product. Tape it if it's the air barrier, otherwise not needed.

Finally, a single zone minisplit heat pump will provide heating and cooling, and if you do a decent job on the thermal enclosure you can likely get away with a 9,000 BTU/hour unit, or even a 6,000 BTU/hour. The brands I use are Mitsubishi and Fujitsu.

If we could vacation without the thule box I'd get rid of it, but don't have another space to store it off the car. So while the amount of space isn't much, its what I have to work with. If I cut into the gable wall, I will probably need to replace the siding on the whole garage... which also matches the house. That is not a project we want to tackle right now. It is older, faded and somewhat brittle, and I don't think it would survive removing some sections to cut an exterior access door on the gable. There are also diagonal braces that go from the gable wall sill plate to the ridge beam that would block an access door. I was considering sistering a couple of the ceiling joists, cutting one joist in between and making a drop down access door to gain access, but need to do a little more thinking on that regard.

I dont know that I'll be able to make it completely airtight on the first phase as the windows aren't in the plan and aren't exactly airtight. I will be replacing the metal garage door with an insulated door, but windows will be phase two. The hope is just to make it comfortable enough to work in efficiently for now and leave some upgrades, like flooring and a mini-split system for later. There is only 95" from floor to bottom of the ceiling joists so can't do too much layering of floor and ceiling without bumping my head, I'd also need to reframe the side door to clear any raised flooring.

I am not planning on recessed lighting. Its a workshop but was going to look into some more basic LED light options.

Thank you for the options to consider. I appreciate it. Maybe I need to just knock it down and make it bigger... that seems the most economically sound(less) choice, but would let me net what I need from the space more easily. All it takes is money. lol.