Soffit Vents required when no ceiling attic?

[mark2457]

Hi all

Building a new garage/work shop. Will be truss roof. There will be no ceiling, but I will insulating walls and underside of roof and covering with ply/osb.

Do I need soffit vents and ridge vent or are they just required when you have an insulated ceiling?

TIA

Mark

 

[LB-1911]

How do you plan on insulating the underside of the roof deck, closed cell foam?

 

[dfiler2]

I believe roofs are ventilated for different reasons in different parts of the country. Around here it would not be necessary to ventilate the area you described in the manner you described, assuming it is a garage/shop.

 

[mark2457]

regular bats with kraft paper (then OSB/ply)

 

[mark2457]

I'm in Chicago. Will use for woodworking so will be heating in winter and cooling in summer (at weekends)

 

[kbs2244]

I just built a roof where I used 2x10 rafters to give me air flow space between the top of 4 inch batts and the bottom of the sheathing.
The air flow vents from the eves to the ridge.

 

[LB-1911]

Hi all

Building a new garage/work shop. Will be truss roof. There will be no ceiling, but I will insulating walls and underside of roof and covering with ply/osb.

Do I need soffit vents and ridge vent or are they just required when you have an insulated ceiling?

TIA

Mark

regular bats with kraft paper (then OSB/ply)

I'm in Chicago. Will use for woodworking so will be heating in winter and cooling in summer (at weekends)

You should really consider a visit to the Bldg & Zoning Div.
http://www.skokie.org/CDBldgPermits.cfm

 

[mark2457]

I just built a roof where I used 2x10 rafters to give me air flow space between the top of 4 inch batts and the bottom of the sheathing.
The air flow vents from the eves to the ridge.

Unfortunately the cords on my trusses are 2x4

 

[DC73]

regular bats with kraft paper (then OSB/ply)

Unless you are planning to install foam insulation on TOP of the roof deck, you can't put regular insulation in contact with the bottom of the roof deck. The problem is that moisture can move through the insulation and condense on the bottom of the roof deck leading to rot, mold and other issues. One solution is to install a vent chute below the roof deck along with soffit vents and ridge vents . Another is to use a sufficient quantity of closed cell spray foam to stop the potential for condensation and then to finish with regular insulation.

Visit BuildingScience.com and GreenBuildingAdvisor.com for more information on how to properly construct a non-vented roof in your climate zone.

DC

 

[CNGsaves]

^ ^ This. Need to DO IT RIGHT and not take any shortcuts.

In cold Chicago, you'll want plenty of insulation in "ceiling" or whatever area you have to keep heat in the building.

May want to consider costs of different alternatives:

a) spray closed-cell foam directly on underside of roof (most expensive)
. . or . . .
b) install ceiling and have blown in cellulose insulation plenty thick for R value needed in your climate

With option (b) that's when you'd want ridge vents, gable vents, etc.

 

[mark2457]

Unless you are planning to install foam insulation on TOP of the roof deck, you can't put regular insulation in contact with the bottom of the roof deck. The problem is that moisture can move through the insulation and condense on the bottom of the roof deck leading to rot, mold and other issues. One solution is to install a vent chute below the roof deck along with soffit vents and ridge vents . Another is to use a sufficient quantity of closed cell spray foam to stop the potential for condensation and then to finish with regular insulation.

Visit BuildingScience.com and GreenBuildingAdvisor.com for more information on how to properly construct a non-vented roof in your climate zone.

DC

Thanks DC. Wasn't aware of that at all

 

[wssix99]

I'm in Chicago. Will use for woodworking so will be heating in winter and cooling in summer (at weekends)

Are you in the the City of Chicago or "Chicago"? If the former, you have other ventilation issues to worry about.

 

[LB-1911]

Are you in the the City of Chicago or "Chicago"? If the former, you have other ventilation issues to worry about.

Pretty sure the OP resides in Skokie.

http://www.garagejournal.com/forum/search.php?searchid=23138607

 

[brycez28]

Thanks DC. Wasn't aware of that at all

This is a link to vent chute: http://www.menards.com/main/buildin...-plastic-attic-vent-chute/p-137193-c-5776.htm

 

[mark2457]

Are you in the the City of Chicago or "Chicago"? If the former, you have other ventilation issues to worry about.

in Skokie (so just north)

 

[mark2457]

You should really consider a visit to the Bldg & Zoning Div.
http://www.skokie.org/CDBldgPermits.cfm

Been there and got there detached garage requirements. Nothing about insulation (which figures as many people don;t bother)

 

[LB-1911]

Been there and got there detached garage requirements. Nothing about insulation (which figures as many people don;t bother)

I'm in Chicago. Will use for woodworking so will be heating in winter and cooling in summer (at weekends)

How do you plan on accomplishing this, an all in one gas / electric unit?

Hi Guys

Just budgeting my garage build (Chicago). Gonna be a truss roof (2x4 top chords and 24" OC). Will be 22'x24' 4/12 pitch roof (I make that about 556 sq ft). There will be no ceiling below trusses

Will get some guys out for quotes eventually. What would I be looking at (approx in Chicago) for closed cell under roof decking?

TIA

Mark

If this is new construction why don't you check into parallel cord trusses and stuff some r-38 up there?

 

[mark2457]

How do you plan on accomplishing this, an all in one gas / electric unit?



If this is new construction why don't you check into parallel cord trusses and stuff some r-38 up there?

Thanks LB. Not sure about heating yet. My last space (half size) i used a portable propane vented under crack in garage door. Hope to do something better. Will take a look for a used gas furnace (much cheaper than electric, no?)

While I'm trenching for electrical and low voltage, will run a gas line so I'm ready for gas if I decide to use it

Wasn't aware of parallel chord trusses. (Did look at scissor trusses - they were double cost of common trusses) - checked Menards and midwest engineering. Neither have them

If i used the parallel chord ones, are you suggesting i then put some kind of sheet/drywall on the bottom chord?

Thanks

Mark

 

[kbs2244]

BTW
This is the kind of thing many building department just do not care about.
Their main concern is safety.
As long as it will not collapse it is OK with them.

 

[Voi]

Wasn't aware of parallel chord trusses. (Did look at scissor trusses - they were double cost of common trusses) - checked Menards and midwest engineering. Neither have them

If i used the parallel chord ones, are you suggesting i then put some kind of sheet/drywall on the bottom chord?

In a woodworking shop I'd recommend scissor or parallel chord trusses for the extra clearance. Sheet goods or any long board becomes easier to move.

Or are you going to have tall sidewalls to start with?

Also, you'll have more inexpensive options to add a lot of R value over the 2x4 R-19 batt insulation you're considering with your standard trusses.

I'm pretty sure that you'll end up with a well insulated roof for a similar or cheaper price as regular trusses plus spray foam.

Another option if you stick with regular trusses is to put rigid foam with an air gap between the top chords. Some people skip the air gap and push the foam all the way up to their sheathing, thereby making it an unventilated roof. Not sure if that's acceptable in your area.

You mentioned Menards. On their website they carry a roof decking foam called Valutherm that seems priced well compared to expanded polystyrene.

Here is a link to the 3" product which would allow you to install between your upper chords with a 1/2" gap.

http://www.menards.com/main/buildin...decking-insulation-board/p-1485634-c-5779.htm

As far as drywall, again I think you'd like a painted surface for reflecting light in a wood shop. And it's great fire protection.

 

[Voi]

Hi Guys

Just budgeting my garage build (Chicago). Gonna be a truss roof (2x4 top chords and 24" OC). Will be 22'x24' 4/12 pitch roof (I make that about 556 sq ft). There will be no ceiling below trusses

Will get some guys out for quotes eventually. What would I be looking at (approx in Chicago) for closed cell under roof decking?

TIA

Mark

I assume 22' wide and 24' deep. With a 4/12 pitch you'll have about 25' running feet along the underside of your roof sheathing between each truss. Three inches of foam will be about 135 board feet. You'll have eleven truss "bays" to fill so about 1500 board feet of foam.

Reports are $1 to $1.25 per board feet for closed cell around the US so I'd hope it would be less than two grand.

 

[mark2457]

In a woodworking shop I'd recommend scissor or parallel chord trusses for the extra clearance. Sheet goods or any long board becomes easier to move.

Or are you going to have tall sidewalls to start with?

Also, you'll have more inexpensive options to add a lot of R value over the 2x4 R-19 batt insulation you're considering with your standard trusses.

I'm pretty sure that you'll end up with a well insulated roof for a similar or cheaper price as regular trusses plus spray foam.

Another option if you stick with regular trusses is to put rigid foam with an air gap between the top chords. Some people skip the air gap and push the foam all the way up to their sheathing, thereby making it an unventilated roof. Not sure if that's acceptable in your area.

You mentioned Menards. On their website they carry a roof decking foam called Valutherm that seems priced well compared to expanded polystyrene.

Here is a link to the 3" product which would allow you to install between your upper chords with a 1/2" gap.

http://www.menards.com/main/buildin...decking-insulation-board/p-1485634-c-5779.htm

As far as drywall, again I think you'd like a painted surface for reflecting light in a wood shop. And it's great fire protection.

Thanks

My walls are gonna be 9.5' high (can only do single story in skokie). With a 4/12 pitch roof, that's about as high as I can go. Will do final calcs at weekend and may be able to eek out a few more inches. In the end, it will depend on final height of slab. I'm allowed 15' to peak, so walls will be max I can get once I know final height of slab.