Ventilation suggestions Please!

[86Garage]

I just put up my first metal building and already wishing I had done things a little different, but here I am. I would like some ventilation suggestions please. Shop is 30x45x12 foot side walls. Metal tube frame building with bubble insulation heat barrier laying directly against the metal with no air gap. I wasn’t aware that’s how this contractor was doing it, but now that’s what I have.

The building is warm already. No soffit vents or ridge vent. That’s something else I wish I would have done. Planning on installing a ceiling at the truss height inside that’s about 14ft high.

I was thinking of putting a motorized exhaust fan with louvers at one gable end and intake vents at the opposite end? They would be above the interior ceiling that’s about 14 ft. Is this the correct way considering what I currently have? At what height should the intake vents be? I am trying to avoid putting anything in the roof directly as I am afraid it will leak into the ceiling/attic area and if it does by the time I figure it out too much damage will already be done. Any suggestions appreciated! Oh, location is central Tennessee. So warm humid climate.

 

[86Garage]

Just put up my 1st metal building. Already wish I had done some things differently, but here I am. Located in middle Tennessee. 30x45x12. Bubble insulation that the installer put the metal directly of the bubble wrap with no air gap. It is already warm inside. I plan on putting a ceiling in it at the truss height which is about 14 ft. It’s a tube frame building with 4ft on center posts. No ridge vent or soffit vent, that’s my fault. Is my best option now a motorized lover fan on the gable end with air intake vents on the opposite gable end? How’s that effect the ceiling and blow in insulation I was planning on doing? Any suggestions appreciated!

 

[Hank11]

Are you going to heat and cool it?

What will you use the building for?

 

[86Garage]

Yes to both. Car restoration. Thanks.

 

[jack stand]

The additional fans that you mention can probably be added later without holding up most inside finishes.
It's ******** hot out and summer time, there's a point where you're hopeless fighting it. You might have a little different judgment with a less extreme temperature week.
But ventilation is the right track up until the air your pushing through is at blast furnace temps.
Have you ever ridden a motorcycle at 100*+/-? No matter how fast you go, it only gets worse .

 

[bluedog225]

If the bubble insulation is aluminum coated, it only needs an air gap on one side or the other. About 3/4”. Emissivity versus reflectivity. If you insulate, it would be good to incorporate a gap.

The fans will work. Though the ridge and soffit vents will be automatic passive airflow. And quieter.

 

[NUTTSGT]

Threads merged.

 

[86Garage]

I was told if the bubble insulation is installed tight against the outside sheet metal you don’t want an air gap to the insulation or you have A pocket between the bubble wrap and the insulation that could accumulate moisture And mold could start?

 

[bluedog225]

I was told if the bubble insulation is installed tight against the outside sheet metal you don’t want an air gap to the insulation or you have A pocket between the bubble wrap and the insulation that could accumulate moisture And mold could start?

It gets pretty complex depending on your climate so the answers will vary.

A gap does prevent heat flow. If you have a metal wall, aluminum bubble insulation, gap, traditional insulation, then interior wall, then it will have to dry to the inside. The outside is double impermeable. This means your interior finish must be permeable to moisture.

I can’t think of any reason the gap would create a moisture issue. No water coming in from the outside.

And the bubble wrap and exterior metal wall will all be outside the traditionally insulated envelope. So cold air should not get through to that layer.

Others may know better.

 

[86Garage]

I was planning on finishing the inside with steel as well. So it won’t really allow moisture through it either.

 

[bluedog225]

I was planning on finishing the inside with steel as well. So it won’t really allow moisture through it either.

I don’t think that’s a viable idea. I believe it has to have the ability to dry to one side or the other.

Random article explaining this stuff.

Understanding Vapor Pressure, Permeance, and Permeability in Building Assemblies

Moisture management is one of the most critical yet misunderstood aspects of high-performance building. Every builder and designer has encountered mysterious condensation, peeling paint, or damp insulation inside wall cavities that should, by all logic, have remained dry. At the heart of these...

build-construct.com

 

[CraigStu]

I like your idea of fans in the gables vs roof. I think a fan will help but it will help more once you have the ceiling in. The idea is that all the heat coming off the roof into the attic area can be reduced getting into the area where you are below the new ceiling. Until you install a ceiling you could also try two vents vs a vent and a fan. BTW consider average local wind direction when figuring which end to put the fan in.

 

[86Garage]

Thanks. I guess insulating it also should be considered. I wanted to eventually heat and cool and use steel on the inside as well for its durability. But since the bubble wrap was placed directly below the outside sheet metal, I am not sure what to do? Short of cutting it all out again to add furring strips. That’s a lot of work I would like to avoid.

 

[Firebrick43]

I was told if the bubble insulation is installed tight against the outside sheet metal you don’t want an air gap to the insulation or you have A pocket between the bubble wrap and the insulation that could accumulate moisture And mold could start?

That is not how radiant barriers work. They have to have an air space to reflect into. That being said, double bubble is sold with all kinds of snake oil claims and is little more that a condensation blanket at best to keep the warm moist air from hitting the bottom of the roof and dripping on your head.

Are your R panels on the walls and roof installed vertically? Many of the tube building that is an add on option that requires purlins and girts installed before the tin.

If it is installed vertically the R panels ribs actually provide enough natural airflow to allow moisture to dry in the cavity. If installed horizontally there is usually water leaks and seeps that I would be very careful what insulation you do use, polyiso/XPS foam sheet or vinyl encapsulated fiberglass is all I would dare to use and preferably the polyiso.