Ceiling ventilation questions

[HuskerCO]

I have a 40x48x16 pole barn and I want to finish the interior by insulating and drywalling the ceiling. I am concerned about ventilation and need some help. I am not an expert and appreciate any advice.

Underneath the metal roof and above the purlins, I have an insulated vapor barrier. I also have soffits, they are not vented, but they are not airtight either - I can see some daylight. There is a ridge vent, but it is not open to the interior, the insulation covers it. I am in Colorado and throughout the winter I have had zero condensation inside even after snow/melt cycles - we typically have very low humidity.

I want to know if I will have any ventilation issues if I add unfaced insulation (no vapor barrier) to the bottom cord of the scissor trusses and then drywall?

 

[Kaizen]

Why is a ridge vent not open to interior? You sure it’s not just the roof cap? Pics will help


Sent from my iPhone using Garage Journal

 

[HuskerCO]

It looks more like a ridge cap, now that you mention it. I was supposed to have a vent....

 

[HuskerCO]

Had to get another post in before I could post a pic. What do you think? View media item 110014

 

[ericm]

Some vents are really low profile. Pull some insulation away and see what's under there.

For ventilation you need vents both down low and up high so warmed air will rise and exit. The code is a minimum net ventilation area of 1/150 the area of the vented space. Can be 1/300 under some circumstances (see below). For fire safety get vents with 1/8" mesh or designed to resist entry from embers in some other way. Embers entering vents are a major way that buildings catch fire. I like the BrandGuard vents. Some vents including some BrandGuard models have special coatings inside a honeycomb that swell up when exposed to heat, closing off the vents. I plan to use those on the under eave vents which will see more heat in a fire than the vents up high.

https://iibec.org/attic-ventilation-101/

https://www.brandguardvents.com/vent-products/

https://www.firesafemarin.org/home-hardening/vents

 

[HuskerCO]

Thanks for the advice and the links, super helpful.

So I don't think it's a ridge vent. I pulled back the insulation and I can see some daylight from the ends, but sides have semi ridgid foam blocking it out. So would you recommend putting in some soffit vents and then gable vents?

View media item 110016

 

[ericm]

Some vents use open cell foam to keep stuff out but that looks like closed cell foam.

Soffit and gable end vents are what I plan to use for my stick built shop with metal roofing. Gonna need some big *** gable vents to get my 1/2 of 1/150 (for a 36x44). Hopefully it won't look too bad. The eyebrow style roof vents are popular here but I don't like the looks, adding places for leaves to collect and putting additional holes in roof panels. Also it'd be a pain to seal around ag panel.