Input on my plan to insulate my shed shop

[Michael Yadfar]

I had a thread earlier about heating it, but now I realize I would be better off insulating. My shed is my temporary shop, temporary as in 3 years, so I guess insulation would be worth it as long as it's not too over the top expensive. The shed is pretty small, only 16'x9', but I make it work because it's what I got. When I work it there, it involves moving the machine I want to use in the middle, then putting it back against the wall, and for plywood, I cut it outside on my contractor saw.

As far as my plan goes, so far I would plan to put r-13 insulation in between the wall studs, throw a vapor barrier over top, and cover over with 1/2" OSB. The roof is a bit tricky because people recommend r-19 insulation, but from what I see, r-19 is made for 2x6 rafters. My shed has 2x4 rafters, so I would assume I would have to go with the r-13 for that too, throw a vapor barrier over, and also cover with 1/2" osb. The floor is also a bit tricky, because it sits on 4x4s with plywood over top, so I really have no room to work under. For the floor, my plan would be to put a vapor barrier over the existing plywood, put 1" foam panels over that, and put 1/2" OSB over top of the foam. For the doors, I have two side doors and a front double door. My plan for those would be to do the same thing as the walls as far as insulating, and put some kind of weather stripping on the openings. For the windows, I was thinking single hung windows.

For the copula and ridge vent, I guess what I do is cover that over too. The roof also overhangs the building a few feet in front, and there are little "cubbies" there which I will show a picture of. My assumption would be that I have to completely block those off?
289710

This picture was from before it was a shop, so most this junk is no longer there.

The walls and windows are pretty straight forward, the doors are a bit of a concern, but my biggest questions are with the roof and floor. With the roof, I don't know if they make r-19 for 2x4 rafters... With the floor, I don't know if my plan is sufficient. I also don't know if OSB is an acceptable floor material, and I would also be concerned of the wheels of my 700 lb planer going through it. As far as doors go, I would need some recommendation.

Other questions I have are what to do about those "cubbies", and if I would only use vapor barrier on the interior side of the insulation

[Mark Kornell]

For your walls, OSB won't add anything significant for insulation value. So if the look of vapor barrier over insulation doesn't bother you, you could skip the OSB on the walls.

For your ceiling, you can use foam board between the rafters. More money than fibreglass, but you can easily achieve R-19 in 3 1/2". Vapor barrier underneath. I would use OSB or gypsum board on the ceiling if only to keep the insulation from sagging down. And painting it white will help with increasing the lighting.

How you deal with the ridge vent depends on how you insulate the roof. If there is a gap between your insulation and the roof sheathing, then you keep the vent. If your insulation is pushed up against the sheathing, then you block off the ridge vent.

And yes, vapor barrier belongs only on the "warm" side of insulation.

For your floor, you'd want to use plywood rather than OSB. You are correct, 1/2" OSB is a little soft for heavy equipment. Not that 1/2" plywood is great, but it is better than OSB.

Insulated doors are pretty easy - sandwich 1 1/2" foam board between 2 sheets of OSB/plywood, with a 2x2 frame at the perimeter.

Regardless of how well you insulate, it is just as important to air seal. Any hole or gap gives warm air a straight conduit to the outside. You need some ventilation, though, if only to bring in oxygen to small space.

[Matt Krusen]

I would suggest possibly using Roxul insulation for the walls and ceiling. The stuff made for 2x4 construction is actually R15. Not a huge improvement but every bit helps. Its also great for soundproofing and is more fire and pest resistant. Its good stuff.

[Michael Yadfar]

For your walls, OSB won't add anything significant for insulation value. So if the look of vapor barrier over insulation doesn't bother you, you could skip the OSB on the walls.

For your ceiling, you can use foam board between the rafters. More money than fibreglass, but you can easily achieve R-19 in 3 1/2". Vapor barrier underneath. I would use OSB or gypsum board on the ceiling if only to keep the insulation from sagging down. And painting it white will help with increasing the lighting.

How you deal with the ridge vent depends on how you insulate the roof. If there is a gap between your insulation and the roof sheathing, then you keep the vent. If your insulation is pushed up against the sheathing, then you block off the ridge vent.

And yes, vapor barrier belongs only on the "warm" side of insulation.

For your floor, you'd want to use plywood rather than OSB. You are correct, 1/2" OSB is a little soft for heavy equipment. Not that 1/2" plywood is great, but it is better than OSB.

Insulated doors are pretty easy - sandwich 1 1/2" foam board between 2 sheets of OSB/plywood, with a 2x2 frame at the perimeter.

Regardless of how well you insulate, it is just as important to air seal. Any hole or gap gives warm air a straight conduit to the outside. You need some ventilation, though, if only to bring in oxygen to small space.

I noticed that fiberglass insulation is typically "vapor retardant". Would that mean that I wouldn't need a vapor barrier? And also, would foam board work for the floor and would r-10 be alright for that?

[Doug Ladendorf]

I would suggest possibly using Roxul insulation for the walls and ceiling. The stuff made for 2x4 construction is actually R15. Not a huge improvement but every bit helps. Its also great for soundproofing and is more fire and pest resistant. Its good stuff.

+1 for Roxul. I'm putting it in my garage now and it's great to work with, adds like 15% more r-value, sound deadening, fireproof etc. worth the extra cost. Use a vapor barrier no matter what you choose.

[James Conrad]

Vapor Retarder is the correct term and a VR product is used most commonly in construction. They are classified by a permeability rating. The term barrier was used early on and was often a misnomer as most products did not actually 100% stop vapor transmission as the term implies. Although, vapor barrier products are used in some building applications they are not common in most residential construction.

What are you conditioning the space with? I would be concerned with proper ventilation for such a small place, where I would install a simple oneway vent that provides fresh makeup air to the space.

Roxul gets my vote as well for its higher R value, resistance to absorb moisture and bugs and rodents don't like it. It is better at stopping vapor transmission than fiberglass as well. Apply a simple 3-4 mil poly over that, caulk and tape all edges and seams. Wall covering over that. Should be more than sufficient for a small space. If you want more R value, apply 1/2" rigid XPS foam board over the walls, 2" on the ceiling in place of the poly, again caulk and tape.

For the floor, 2" compression rated XPS, at least 25psi, over the existing floor with 3/4" Advantech on top.

[Michael Yadfar]

I was looking at the doors last night, and it may be a bit trickier than I thought to seal around the openings. They are typical barn style doors, and don't sit completely flush against the wall as they're not really meant to. I would assume that I would want to shove some material in there to both insulate and cause the door to be flush, but I'm not sure what material to use

[James Conrad]

You could make stops from 1x and use some weather stripping that butts up against the door frame on the interior. A little air leakage is not necessarily a bad thing in this case.

[Jeff Duncan]

What about spray foam? Only reason I'm thinking of it is b/c the shop I'm moving into just got sprayed top to bottom with it and it's supposed to be a pretty good R rating. Plus it gets every nook and cranny. I know they make do-it-yourself spray kits, just not sure how expensive they are?

good luck,
JeffD

[Mark Kornell]

Typically, closed cell spray foam is in the R-5 to R-7 per inch range, so for a 3 1/2" cavity you could expect R-17 to R-24. And it eliminates the need for a vapor barrier (retarder...). DIY kits are available, but not sure if they'd be cheaper than hiring someone. For example, the first site I found for a DIY kit has an estimator which calculates almost $1300 to give you 3" of foam on your walls. And a bit more than $600 for 3" in your ceiling.

You can get rigid foam board in a similar R-value per inch. Price is less than spray foam, but you also need to add vapor barrier.

Compare that to the R-15 of a 3 1/2" Roxul batt, much less money than spray or board foam. Your cost for Roxul would be $350 (plus tax) or so to do your walls and ceiling.

How much do you plan to use your shop? And when you are not using it, do you plan to keep it heated? If you only use it a couple evenings a week and you don't need it heated otherwise, I'd think it would be hard to justify the cost to upgrade to the spray foam. The extra insulation doesn't do you any good when there's no heating. And even at R-15 with a tight vapor barrier, it would heat fairly quickly when you want to use it.

[Michael Yadfar]

Typically, closed cell spray foam is in the R-5 to R-7 per inch range, so for a 3 1/2" cavity you could expect R-17 to R-24. And it eliminates the need for a vapor barrier (retarder...). DIY kits are available, but not sure if they'd be cheaper than hiring someone. For example, the first site I found for a DIY kit has an estimator which calculates almost $1300 to give you 3" of foam on your walls. And a bit more than $600 for 3" in your ceiling.

You can get rigid foam board in a similar R-value per inch. Price is less than spray foam, but you also need to add vapor barrier.

Compare that to the R-15 of a 3 1/2" Roxul batt, much less money than spray or board foam. Your cost for Roxul would be $350 (plus tax) or so to do your walls and ceiling.

How much do you plan to use your shop? And when you are not using it, do you plan to keep it heated? If you only use it a couple evenings a week and you don't need it heated otherwise, I'd think it would be hard to justify the cost to upgrade to the spray foam. The extra insulation doesn't do you any good when there's no heating. And even at R-15 with a tight vapor barrier, it would heat fairly quickly when you want to use it.

Since I'm going to college, I will probably use it heavily during the summer and winter break, but during the school year, just weekends. I'm going to school local and I'll be home on weekends and breaks. I would plan to use a small electric one room or camper heater which I would think would be sufficient for the space. I'm more worried about insulation for winter use, because most my hobbies revolve doing stuff outside so I just mostly sit around all winter, so I plan to use the shop heavily then. Like some people said, working around tools in my carhartt isn't necessarily the safest practice, and a lot of finishes won't work as well if at all in the cold.

Another thing I wanted insulation/vapor barrier for is to protect tools from humidity, I would like to run a dehumidifier in there. Humidity isn't a huge issue where I am, because I'm not in a coastal region. Here in southeast PA we have a relatively mild climate. I've had my jointer for 4 months, never waxed it and I don't even have any surface rust. I'm assuming the previous owner may have treated it with something, but it's not too bad. Reason I'm worried about humidity is for the long run. I invested way more money than I originally anticipated on my tools, and right now I have about $4,000 worth of equipment and I'm still upgrading.

Im not looking to spend a huge amount of money but I still want to do it right. Reason for this is that this is temporary and I don't own the shed, it's my parents shed. Once I move out, they could really care less whether the shed is insulated or not. I actually just spent money to run 240 volts in there too. As far as how long "temporary" is, I plan on about 3 years. I'm going to a free college with a 100% job placement rating within the past 15 years, and I also hold a part time job now, so I plan to be able to rent somewhere decent once I start working, a place with a good sized garage. At my house now, we have a fully insulated 2 car garage, but it holds my parents vehicles. If it was my house, cars would be outside and tools would be in the garage, but it's not my house. I atleast get to keep my hand tools in there

[Mark Kornell]

I'd base my decision on whether or not you needed to keep the space above freezing. If not, the Roxul or fibreglass is probably your best choice. If you need to keep glue, finishes, etc from freezing - which means you need to maintain a heat level for a good chunk of the year - I'd lean toward the spray foam.

Humidity control could be very important during the summer months. But remember that your de-humidifier is only as good as your vapor barrier and sealing.

[Rick Potter]

Michael,

I have a 10X12 shed, and used insulation and OSB as you were suggesting. I am always surprised how cool it is in the summer, and warm, in our mild winters. The OSB is a great way to hang stuff on the walls too. My shed has open vents at the peak. I painted the OSB white for more light.

Rick Potter

[Michael Yadfar]

Michael,

I have a 10X12 shed, and used insulation and OSB as you were suggesting. I am always surprised how cool it is in the summer, and warm, in our mild winters. The OSB is a great way to hang stuff on the walls too. My shed has open vents at the peak. I painted the OSB white for more light.

Rick Potter

Thats nice. If you don't mind I have a few questions from your experience if you don't mind answering. I'm wondering what you used for the floor and how you sealed off the doors. Also, does this help control humidity issues in your shop?

[Jim Andrew]

Personally, I'd use the kraft faced r13 fiberglass, and staple the edges to the face of the studs, so the insulation is expanded to the whole 2x4 space, and skip another layer for vapor barrier. Lots of homes are built with the kraft faced insulation only. Fiberglass will not burn, so why spend more? R13 fills the space well, and r 15 is much more expensive. When I did my addition, I bought r11 on sale half faced and half unfaced, and put the unfaced in first, then another layer of faced, and stapled it. It fit fairly tight, but stopped air coming through the wall from cracks along the bottom of the wall where corrugated metal leaves a gap. Old pole shed with 2x4 walls framed inside.

[Rick Potter]

Michael,

It is on a slab, and the floor is concrete. The door is a 36" pre-hung steel door from HD...about $125 (I will never build a shed door again). It came with weather stripping. About the humidity....this is SoCal, and humidity is rarely an issue, so I can't help you there.