New shop, ground-up build (advice and discuss details)

[mickri]

Keeping a building cool in the summer and warm in the winter is more than just insulation. Buildings have to breath to avoid condensation and if there is much snow where you live you have to be concerned about ice dams. The pictures show a one story building. You describe a two story building. The pictures also show that the building does not have conventional framing. Which I think is a possible good thing.
I'll start with the walls. Wood does not insulate very well and actually acts as a thermal bridge transferring heat or cold from the outside to inside and vice versa . This is a problem that occurs with conventional framing and makes a significant reduction in the R value of a wall. There are lots of creative though not always cost effective ways to solve the problem of thermal bridging. One way to do this is to basically have two walls spaced a couple of inches apart. One is structural and the other is just to create space for the insulation. You can get massive amounts of insulation this way and negate a lot of thermal bridging. Based on the pictures I would consider building an inner wall with as big of a gap between the inner wall and the outer wall as is convenient The inner wall being non structural could be made with 2x2's. Cram as much insulation as possible between the walls. The pictures show a gap between the skin of the outer wall and the framing. Don't forget to fill this gap with insulation. I drew a sketch of the wall section to illustrate what I am suggesting.



Since there are no pictures of the second floor ceiling and roof I am going to guess that the roof will be like the roof in the single story pictures. It would be tempting to fill the area between the roof rafters with insulation. Not good because you cut off all ventilation. Your garage won't breath and you will have condensation problems. You will have mold growing and even drops of water dripping from the roof. I know that this will happen from personal experience where I filled the space between roof rafters with insulation. My suggestion would be to put in ceiling joists and put the insulation between the ceiling joists. Put vents at the peak of the roof at each end of the building and include vents in the eaves just like you would in a house. The eave vents have to flow more air than the vents at the peak of the peak of the roof. I am not a fan of the turbine vents you see everywhere. I have seen studies where it was claimed that turbine vents don't flow anymore air than a normal roof vent and in the right conditions will leak when it rains. I know this from personal experience.

Just my two pennies on how I would insulate your garage/shop.

 

[rgray]

I have a building constructed somewhat like that. Posts are 2x6 with a 2x4 on each side and are 6 foot apart.
I installed a 2x4 vertically between the 6' uprights and used 16" wide fiberglass. Stapling one side of each to an upright in the now 3' space and then just stapling the edges of the insulation to each other and covering with OSB and sheet rock for the welding area.
You could possibly do the same but with 24" wide fiberglass. The building in your pics has a horizontal board which means more cutting, but also means more manageable size of insulation to work with also.
8' post spacing would work out nicer for the sheeting than the 6' as far as covering the wall.

The ceiling in the pics looks straight forward for fiberglass. mine had 2x6 laid flat instead of on edge so on the ceiling I installed 2" foam board.

 

[Bob Korves]

Insulating metal external walls and roofs can be quite problematic. If there is ANY way air can migrate into the insulation, it will, and will then condense the water in the air out when it cools to the dew point. That can be on the insides of the metal walls and roofing, or somewhere in the middle of the insulation. It causes mildew, mold, and structural damage. If it was me, I would have a thick waterproof spray coating, that is not moisture impregnable, installed on the inside of all the external metal surfaces, and then a hard and fire resistant layer on the inside surfaces to protect from fire and physical damage. Some of the spray insulation materials available today are non toxic, though some of those will not stop moisture intrusion. Talk to the REAL pros about your choices before making up your mind on what is best for your situation. Avoid moisture problems while also avoiding toxic chemicals, and make sure the package will be structurally sound. Run your electrical in conduit exposed on the insides of the walls so it is easy to modify as needed. If you have a plain and not insulated slab floor, it might be worth adding insulation at the outside edges of the floor slab. Again, talk to the pros, get multiple opinions, and go with what will work best for you.

 

[pontiac428]

Check with an industrial insulator, I'm surprised your building contractor didn't offer an insulation package.

They offered R6 only (they are a very streamlined business) so I declined. Roof insulation is included, but I thought I could do better for the rest.

Lots of ideas have come and gone, but I believe fiberglass aint one of em. Too efficient, too simple, too safe, too cheap

The good stuff is the stuff that works. Fiberglass is the king, no doubt.

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Just my two pennies on how I would insulate your garage/shop.

Thanks, this is what I've been imagining as my first choice. It's also the most costly and the most time consuming, but the results would be worth it. I'd sheet it all in with OSB and surely be happy with the result.

Again, talk to the pros, get multiple opinions, and go with what will work best for you.

Thanks, Bob. I often forget that I'm not alone in this world and that I can hire people to do work that I would otherwise do myself. I work alone and take pride in being self-reliant to the point of fault. The worst for me is time obligation, I don't want to spend my next ten weekends doing a job that a contractor can do in a day or two. In the end, the cost is less of a factor than having more time to work on my own projects in my own palace.

I appreciate the input. This is just one facet of the project, so I'll post progress as things go. I did the first phase of lot clearing already, the permitting is done, the building plans are done, and the material is on order for the pole building. Things should happen quickly from here. The years of waiting are almost over.

 

[bretthl]

It is a good practice to place a poly vapor barrier between the interior sheathing (d-wall or OSB) and the insulation. This will help prevent warm moist air migrating through the insulation and condensing on the metal exterior and causing rust and/or mildew.

 

[rgray]

They offered R6 only (they are a very streamlined business) so I declined.

I assumed you would have that on your walls and ceiling. That would be your vapor barrier for your fiberglass.
If it's not real costly you might want to go ahead and have them put that on the walls also. R6 & R19 even better also. That's how mine is.

 

[rgray]

That would be your vapor barrier for your fiberglass.

I need to clarify that. That outer insulation would be your hot weather vapor barrier.
For cold the plastic sheet goes on the inside, over the top of the fiberglass.

 

[Bob Korves]

I need to clarify that. That outer insulation would be your hot weather vapor barrier.
For cold the plastic sheet goes on the inside, over the top of the fiberglass.

Understand that a vapor barrier contains ZERO leaks. If water gets into an area between two vapor barriers, it is there for good (actually BAD!)

 

[pontiac428]

Got it. Building code requires a vapor barrier in my area, so Tyvek wrapping all around. The R-6 offered for the walls by the builder was a $15k package, hence my decision to do something else. I figured that kind of money buys a lot of pink cotton candy if I wanted to try and sort it out for myself.

 

[jbolt]

Just to add my two cents worth to this discussion.

Having been a general contractor for 35 years with the last 15 as a construction consultant who works on the litigation side of construction defect, I can tell you there is no one size fits all for properly insulating a building. As building codes require more and more efficient homes, new technologies & material have come onto the market along with the drive to keep costs to a bare minimum, including less skilled labor, there has been unanticipated consequences in building performance.

There are many factors that go into the correct selection of materials for a particular building and how that building is used. There is still much debate within the industry on best practices which does not help.

My recommendation is to seek out 3-4 reputable insulation contractors who work in your area and get their opinions and a quote. Your not looking for price, you are gathering information. Ask questions on why they recommend a certain product or method? Have they done this type of building? etc. Educate yourself. Then decide whether to hire a professional or do the work yourself based on the knowledge you have gained.

I have a property in southern Oregon that has a 40 year old shop with T-111 siding, no weather barrier under the siding and no moisture barrier under the slab. Just adding fiberglass bats and drywall would be a disaster. The wall, ceiling and floor systems all have to work together based on the anticipated usage.

After much research, speaking with colleagues with the industry and several local insulation contractors, we came up with a system we believe with be effective without being cost prohibitive. Part of the system requires specialized equipment and factory certification to apply so I opted to hire that part out and will do the other work myself.