Building a garage-shop , need help

[Cyle]

I haven't looked a lot into the hot roof system, but offsetting the cost of a vented raised heel truss with blown in attic insulation would take a lot of efficiency in the way hot roofs are constructed.
Lots of times it's layers and layers of rigid insulation or spray foam (which also loses benefits vs. cost after certain thickness) to gain a certain r value determined by your climate or the building energy code
Another option for that type of roof is SIP type systems which are also not cheap.
An R50 or R60 blown in attic should be pretty efficient and to upgrade blown in to better values isn't overly expensive the last time I checked into it.

I don't get why people are trying to re-invent the wheel. Blow attic insulation in vent the roof and soffits like everyone has done for decades and stop trying to fix chit that isn't broken FFS. The dumbasses with these ideas lose more hot air out of their heads then a properly blown in attic at R60.

 

[lilduke]

Real shops have flat roofs. No attic Haha

 

[Frosty19]

And flat roofs are also sloped at the plumbers grade of about 1/4" every foot too lol

 

[Lund]

So I'm perplexed, looking at building a shop , 40x40 with two side 12x40 open storage bays

I've got two quotes that are outrageous for prices in wood framed 130-160000.00 , which includes the pad and footings

Looked at a metal 42x44 commercial building ( 80000.00 ), but then would have to build the side storage bays extra like pole sheds , and wood walls inside with insulation, work benches , plywood to hang stuff on walls ect , plus the pad and footings cost


160000.00 for a garage is crazy is it not ???


Need advice , know there was a thread I kinda lost where it went

View attachment 249664

Hey, my shop is insured for a little more then $300k, no content just replacement cost to rebuild.
You've been in my shop and you know what it is so it will be a huge investment for sure.

 

[Cdnfireman]

I don't get why people are trying to re-invent the wheel. Blow attic insulation in vent the roof and soffits like everyone has done for decades and stop trying to fix chit that isn't broken FFS. The dumbasses with these ideas lose more hot air out of their heads then a properly blown in attic at R60.

Theres lots of data showing that unless you perfectly seal the Vapor barrier and have the right number and size of vents to the size of your soffits that you won’t be able to properly vent the moist air from the structure. Lots of pics of rusty gang nails and moldy insulation to prove that. Temperature delta and wind speed also are factors. Just because that’s the way things have always been done doesn’t mean technology hasn’t changed to improve things. Kinda like trailer braking systems.

 

[Cdnfireman]

I haven't looked a lot into the hot roof system, but offsetting the cost of a vented raised heel truss with blown in attic insulation would take a lot of efficiency in the way hot roofs are constructed.
Lots of times it's layers and layers of rigid insulation or spray foam (which also loses benefits vs. cost after certain thickness) to gain a certain r value determined by your climate or the building energy code
Another option for that type of roof is SIP type systems which are also not cheap.
An R50 or R60 blown in attic should be pretty efficient and to upgrade blown in to better values isn't overly expensive the last time I checked into it.

Agreed. The concern is that blown in will settle over time and any moisture that does condense on it will degrade its insulative abilities, and that no plastic vapour barrier will ever be tight enough to have zero loss. The theory of the hot roof is the 4” of closed cell spray foam under the roof deck creates an air impermeable layer that prevents hot air from escaping.
I see the logic of it and there’s enough studies proving it, I’m wondering if any spray foam contractors are familiar with it here.

 

[JayT]

Agreed. The concern is that blown in will settle over time and any moisture that does condense on it will degrade its insulative abilities, and that no plastic vapour barrier will ever be tight enough to have zero loss. The theory of the hot roof is the 4” of closed cell spray foam under the roof deck creates an air impermeable layer that prevents hot air from escaping.
I see the logic of it and there’s enough studies proving it, I’m wondering if any spray foam contractors are familiar with it here.

That would still trap all the moisture in your attic space. It's an interesting concept but you would have to have an exhaust fan in your attic space to pull the moisture out. You would still end up with Rusty gang plates on your trusses if you didn't vent it properly

 

[TDR]

I’ve got 2 shops and a large garage on my house. House garage has in-floor. Small shop has forced air and big shop has radiant. If you are building a large shop with high ceiling I would recommend radiant tube. Mine is about 40’ long and it heats the building in a hurry with good recovery when the doors are opened. Couple that with a few ceiling fans for circulation and a properly sloped floor to a good drain and you will be just fine. I like my in-floor but boilers are expensive and costly to properly maintain. Forced air works ok on a smaller building but it blows a lot of dust and doesn’t heat evenly or quickly.

 

[Frosty19]

A lot of the pitched residential type hot roofs I've seen examples of are using the concept for vaulted ceiling height or where the "attic" becomes useable for storage or room space with properly designed trusses.

It's essentially the same concept with spray foam to the underside that we do low slope ("flat") roofs to save the need for cross ventilation and allow for shallower roof trusses. Can also do outboard insulation with the exterior 2% slope built in to it and your barrier is above the roof

 

[Cdnfireman]

That would still trap all the moisture in your attic space. It's an interesting concept but you would have to have an exhaust fan in your attic space to pull the moisture out. You would still end up with Rusty gang plates on your trusses if you didn't vent it properly

From the research and testing I’ve read, the moisture doesn’t condense out in the attic because the air temperature isn’t colder up there. The entire air volume inside the walls and under the roof deck is conditioned. Running a dehumidifier for the whole building might be necessary because the normal warm moist air leakage into the attic space doesn’t happen. There’s nowhere for the moisture to go. The gang plates have to be completely coated in the spray foam to prevent thermal bridging down the metal.

 

[Cdnfireman]

I’ve got 2 shops and a large garage on my house. House garage has in-floor. Small shop has forced air and big shop has radiant. If you are building a large shop with high ceiling I would recommend radiant tube. Mine is about 40’ long and it heats the building in a hurry with good recovery when the doors are opened. Couple that with a few ceiling fans for circulation and a properly sloped floor to a good drain and you will be just fine. I like my in-floor but boilers are expensive and costly to properly maintain. Forced air works ok on a smaller building but it blows a lot of dust and doesn’t heat evenly or quickly.

Where in the building did you install the tube heater? Is it parallel to the overhead doors or perpendicular across the shop in front of them?

 

[Frosty19]

From the research and testing I’ve read, the moisture doesn’t condense out in the attic because the air temperature isn’t colder up there. The entire air volume inside the walls and under the roof deck is conditioned. Running a dehumidifier for the whole building might be necessary because the normal warm moist air leakage into the attic space doesn’t happen. The gang plates have to be completely coated in the spray foam to prevent thermal bridging down the metal.

The biggest thing is because of usual construction methods when people say attic here a lot of people assume it's cold.
You're correct - This method makes the attic conditioned and its within the building envelope. The spray foam is the vapor barrier and the conditioned air in your house never meets the condensing point from the outside [this is where I was mentioned having a proper r value for the spray foam (and someone can correct me if I'm wrong but spray foam starts to lose its effectiveness much over r30 or so) is important and also tough justify the offset with a blown in at r60 especially in a shop environment with a standard pitched roof.]

 

[JayT]

From the research and testing I’ve read, the moisture doesn’t condense out in the attic because the air temperature isn’t colder up there. The entire air volume inside the walls and under the roof deck is conditioned. Running a dehumidifier for the whole building might be necessary because the normal warm moist air leakage into the attic space doesn’t happen. There’s nowhere for the moisture to go. The gang plates have to be completely coated in the spray foam to prevent thermal bridging down the metal.

I get what you're saying. There would be no condensation because there are no cold spots for it to condensate on. it would still concern me that humidity is trapped up there since you would obviously want to finish the bottom cord of your trusses with either drywall or tin. I guess you could leave it wide open but that does not look finished at all. Your attic space would be a sealed airspace. I suppose you could put vents in your ceiling to allow air to move through the attic space as well

 

[JayT]

Where in the building did you install the tube heater? Is it parallel to the overhead doors or perpendicular across the shop in front of them?

I think it was mentioned earlier in this thread, you don't want to install your tube heaters across perpendicular to the doors. Then you can't back a tall fifth wheel or motorhome in without some part of the roof being near the tube heater and potentially melting it. Definitely something to think about

 

[pistoncontracting]

And that's one of the company's I gota a quote from

From my experience, I wouldn't pay them to build a dog house.

They seemed to have outgrown what started them, and are on to bigger, better things.

I chose them thinking they would be worth the added money.

I was wrong.

 

[S.W.A.T.]

Open canopy, problem solved for attic moisture

 

[tex78]

Well got a quote from csd metal out of golden

75000 grand for 40x40 with 12 foot open side covered sides, 12 high , 14 foot walls , 12x12 garage door

Be about 125000 with taxes for them to build , shop pad , screw footings , insulated


Could save a bunch of labor if I put it up myself , as it all bolts together , figure about 10 grand , thinking pad is 16000 ish , and 4 grand for screw footings

Just would need to hire out the screw footings , and concrete pad



So question of the day , is metal or wood better , as we are close to the same price now , if I don't do much

 

[tex78]

Oh and a 40x70 shop , with 2 12x12 doors ect was same price for building


The labor to build was way more as span is bigger ect , also said take in a few grand to build a partition wall , and them extra costs

 

[niner]

Oh and a 40x70 shop , with 2 12x12 doors ect was same price for building


The labor to build was way more as span is bigger ect , also said take in a few grand to build a partition wall , and them extra costs

A 40x70 is 40’ wide and 70’ long. How is the span bigger than a 40’x40’ Did you price out a 70’ truss?

 

[tex78]

A 40x70 is 40’ wide and 70’ long. How is the span bigger than a 40’x40’ Did you price out a 70’ truss?

Metal building guy Said its way harder to build because it's twice the span , said probably twice the time to build it