Shop insulating advice

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DentalDart

DentalDart

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I’ve gotten some great advice so far in my car build threat but want some more from others who may have done this. Mainly for sweating in a metal building.

I started with an uninsulated 40x40 shop with a 17ft peak. I have a 30x40 shop but want to use the 40x40 as main shop due to it being much bigger and the roof being able to be raised much higher. Plus it’s a shorter walk from the house.

I started with 2in foam boards on the walls, with spray foam filling the gaps and cracks.

My question- dealing with sweating inside. I plan on doing mini splits in it this spring, raising the trusses to gain more clearance for a lift/lifts inside it. I will also insulate the roof and finally I will cover the walls and roof with OSB.

Do I fill in all of the cracks between the roof and the walls? What about the crack all the way up the peak? Do I seal up the gable vents as well? To prevent any extra air from getting into the building?

Also the big sliding door sucks for sealing up… should I make it a giant roll up door?

FYI… yes I know it’s much harder doing this while the shop is occupied with junk. But… it’s what I am doing.

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DentalDart said:
I’ve gotten some great advice so far in my car build threat but want some more from others who may have done this. Mainly for sweating in a metal building.

I started with an uninsulated 40x40 shop with a 17ft peak. I have a 30x40 shop but want to use the 40x40 as main shop due to it being much bigger and the roof being able to be raised much higher. Plus it’s a shorter walk from the house.

I started with 2in foam boards on the walls, with spray foam filling the gaps and cracks.

My question- dealing with sweating inside. I plan on doing mini splits in it this spring, raising the trusses to gain more clearance for a lift/lifts inside it. I will also insulate the roof and finally I will cover the walls and roof with OSB.

Do I fill in all of the cracks between the roof and the walls? What about the crack all the way up the peak? Do I seal up the gable vents as well? To prevent any extra air from getting into the building?

Also the big sliding door sucks for sealing up… should I make it a giant roll up door?

FYI… yes I know it’s much harder doing this while the shop is occupied with junk. But… it’s what I am doing.

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Would think you would want to screw up a flat steel ceiling to the bottom of those rafters. You can roll out Batt Insulation from a step ladder over the edge of each sheet of steel as you go.

Then you keep the he7at and or AC down in the shop space and let the rafter area (bare), top side, vent out the Gable end Vents.

Edit:
Having soffet vents in the overhanging soffets allows outside air to enter at the lower roof line, then up and out the Gable End vents at the tops.

People also put Ridge Peak Vents on the Outter Roof Peaks to help pull the rafter area air out.
 
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Door Seal Whiskers go here on the outside for Roll Up Doors.

You can put them on the Inside the same way to seal from the inside on the Slider Doors.



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George Jets said:
Would think you would want to screw up a flat steel ceiling to the bottom of those rafters. You can roll out Batt Insulation from a step ladder over the edge of each sheet of steel as you go.

Then you keep the he7at and or AC down in the shop space and let the rafter area (bare), top side, vent out the Gable end Vents.

Edit:
Having soffet vents in the overhanging soffets allows outside air to enter at the lower roof line, then up and out the Gable End vents at the tops.

People also put Ridge Peak Vents on the Outter Roof Peaks to help pull the rafter area air out.
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I don’t know what soffet vents are? Are those the things I filled with foam?

I’m not doing this ceiling yet because I am not keeping the regular trusses, I am going to go to a scissor truss.

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You may not have a soffet area (like on a house) if your roof does not hang out over the siding by more than a couple inches.
 
So, here's the deal with insulation and vapour barrier.....

The goal here is to prevent warm moist air coming in contact with a cold surface. If you keep this in mind, you can't go wrong.

Insulate the walls and insulate the ceiling. This gives you a thermal barrier from the outside. Next, you use 6mm poly to envelope your working space over the insulation.. This gives you the vapour barrier that you need to keep the warm moist air from contacting a cold surface. This cold surface could include any gaps in your insulation etc.

Once the ceiling is insulted and vapour barrier installed, the attic become a cold space ventilated to the outside via soffit, ridge, and or gable vents. Make sure that you use the Styrofoam "channels" between your rafters so that soffit air can enter the attic and not get blocked by the insulation.

Remember, vapour barrier goes on the warm side.

As for insulating the door.........Pretty tough. You'll have to get creative.

Be advised.......In the spring when you open the door to warm moist air, your floor will condensate........"Warm moist air on a cold surface"

BTW......You'll see people sprayfoam the entire inside. The foam acts as a thermal barrier, and a vapour barrier, so all is good.


Best of luck with your endeavour :thumbsup:
 
I like the spray foam, we did the basement of our house in Winnipeg and it made an amazing difference, both in cold and noise reduction. I have been considering doing the current house, but it's not something that I can afford at the moment, the basement is fully finished and I am not willing to strip it out at the moment.
 
CFD244 said:
So, here's the deal with insulation and vapour barrier.....

The goal here is to prevent warm moist air coming in contact with a cold surface. If you keep this in mind, you can't go wrong.

Insulate the walls and insulate the ceiling. This gives you a thermal barrier from the outside. Next, you use 6mm poly to envelope your working space over the insulation.. This gives you the vapour barrier that you need to keep the warm moist air from contacting a cold surface. This cold surface could include any gaps in your insulation etc.

Once the ceiling is insulted and vapour barrier installed, the attic become a cold space ventilated to the outside via soffit, ridge, and or gable vents. Make sure that you use the Styrofoam "channels" between your rafters so that soffit air can enter the attic and not get blocked by the insulation.

Remember, vapour barrier goes on the warm side.

As for insulating the door.........Pretty tough. You'll have to get creative.

Be advised.......In the spring when you open the door to warm moist air, your floor will condensate........"Warm moist air on a cold surface"

BTW......You'll see people sprayfoam the entire inside. The foam acts as a thermal barrier, and a vapour barrier, so all is good.


Best of luck with your endeavour :thumbsup:
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You say 6mm poly to envelope the space? Are you just talking about a 6mm plastic sheet? That’s what I have been putting on the rafters to keep some heat down lately.

I know the foil face creates a barrier as well, and reflects the heat out. I don’t want to do spray foam, it’s to expensive. Have seen people say 30k to spray foam it, shoot I can buy 5 more Mopars for that much lol.

I don’t think I have a soffit ridge?





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Doesn't look like you have soffits on your building. Yes, I think that's what CFD244 was suggesting, to use 6 mm articles sheeting as a vapor barrier, at least that's what we do in cold climates.
 
I would start by figuring out what insulating value (R value) you want for your climate, desired comfort level and energy usage . 2 inch foam is around R12. If you sheet the roof you could add at least R20 fiberglass insulation on top (my garage is R20 walls / R40 ceiling but it gets a lot colder here). Typically there is a plastic vapor barrier between the insulation and interior of the building as mentioned. You're going to need a lot of insulation.
 
Your soffit ventilation would be under the overhang of your roof (it has small holes in it to allow air in). Some metal roofs have a ridge vent along the total length of the peak and does a similar job as your gable vents. Air in through the soffit and air out through the ridge and/or gable vent.

So basically, you would insulate the walls and the ceiling with Roxul or pink. Then you'd cover all of that with 6 mil plastic to give you the vapour barrier that you would need. Then you would board it with drywall, steel siding, or whatever you want. That would give you an envelope that is sealed thermally with adequate vapour barrier to eliminate condensation on the cold outside walls and attic should there be minute breaks in your insulation.

The attic remains dry, cold and ventilated.
 
CFD244 said:
Make sure that you use the Styrofoam "channels" between your rafters so that soffit air can enter the attic and not get blocked by the insulation.
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I'm getting ready to insulate my shop roof (which has soffit vents and a ridge vent) can you post something that would help me understand these "channels"???
 
str12-340 said:
I'm getting ready to insulate my shop roof (which has soffit vents and a ridge vent) can you post something that would help me understand these "channels"???
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Pretty straight forward. It allows the fresh air into the attic from the vented soffit. Without them, you risk having the space between the rafters blocked by insulation, thus blocking the air flow. They are typically the width of your rafter spacing and made of Styrofoam. Internet pic for reference.

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CFD244 said:
Your soffit ventilation would be under the overhang of your roof (it has small holes in it to allow air in). Some metal roofs have a ridge vent along the total length of the peak and does a similar job as your gable vents. Air in through the soffit and air out through the ridge and/or gable vent.

So basically, you would insulate the walls and the ceiling with Roxul or pink. Then you'd cover all of that with 6 mil plastic to give you the vapour barrier that you would need. Then you would board it with drywall, steel siding, or whatever you want. That would give you an envelope that is sealed thermally with adequate vapour barrier to eliminate condensation on the cold outside walls and attic should there be minute breaks in your insulation.

The attic remains dry, cold and ventilated.
Click to expand...

This kind of sounds like what I have been doing, I wasn’t planning on adding another layer of plastic before the OSB but I guess I could do that as well, then I would have 2 vapor barriers.

Ok so maybe I have been foaming in the soffit ventilation along the bottom of the roof where it meets the walls and travels up the roof peak. That is what lets in most of the cold air all day long.

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CDF244 and George Jets - THANKS!!! I think you just saved me a lots of time....
 
First thing I would do is add ventilation fans to the vents you have. You could also add a ridge vent. DIY stores sell these fans as attic fans.

There is an insulation blanket that is made for buildings like that. It fits right to the roof around the trusses.

If you drop a ceiling and add insulation on top of it, you will need soffit vents.
 
Can you post a close up picture of the area under your gutters, against the wall (from the outside)?
 
Doc, be carefully if you plan to modify the existing trusses

They are engineered to carry the loads expected in the geographic area the building is in.

If you are replacing them perhaps replacing the entire building with one designed to your specs would be a better spend?

On the subject of insulation.

Be Careful about traping moisture. Having a 2 vapor barriers can trap moisture between the walls.

Insulation and vapor barriers intent is to make the cold warm transition zone be in the middle of the insulation not on either side.

That way the location that is cold enough to condense moisture into water is inside the insulation and there will not be any moisture there to condense.
 
If you have the room to install a properly designed scissor truss in place next to the original trusses and then sister the two together (screw them together all up and down the scissor truss), then you should be able to cut away the offending parts of the original truss. Be sure that the added height from doing this will actually meet your lift needs!!!

This might be the only place in all this where the lack of significant roof overhang works in your favor.
 
The best I've seen is the spray in foam. My friend Charles has a new shop and that's what he used. It was really expensive, but over the summer it was literally about 15 degrees cooler in the shop than outside. That stuff is slap amazing.
 
From someone that designs and builds freezer enclosures for a living, please don't take my comment the wrong way; You're going about this all wrong.

RRR nails it. Spray in foam is going to do everything you want with a LOT less work. It will seal EVERY little crack and gap with a single, uniform layer of integrated insulation. A friend of mine built a carport, enclosed the ends, and spray-foamed the interior. It was a good twenty degrees cooler than the outside summer day even with an uninsulated garage door, but there was virtually no incidental airflow.

If you have air gaps and still insulated, you're going to push air out when the building heats up, then pull air in when the building cools. The cold air will have humidity in it that will then condense on the cold surfaces inside, and then when the building heats up, warm dry air goes out and....repeat. It's literally a pump bringing in humidity.

As far as condensation goes, remember, it always forms on whatever is cold. Even if you're putting a steel spoon in a blast furnace, moisture will condense on it until it heats up. In the case of spray-foaming it, you are taking everything to a uniform interior temperature, so condensation points are virtually nil. The minisplits will pull any remaining humidity.

Installing the piecemeal foam will make a difference because you're blocking radiation from those nice warm or cold steel panels, but the studs will literally conduct heat the wrong way. By the time you buy a bunch of the little cans of expanding foam, you're probably dollars ahead to spray-foam it, too.

If you decide you want to finish the interior, a hot knife will shave the foam off the studs, and you're ready to drywall or whatever you want to do.

Edited to add: Don't blow your load on soffit vents unless you're planning on creating an attic space.

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