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.

 

[86Garage]

Yes, the walls were optioned to be installed vertically! But like I said the bubble is smashed between it and the tubing, Perkins, girts. No air space other than the tallest rib on the paneling , which isn’t much. It’s still very hot inside because they don’t put fire strips on before the metal. I was unaware at the time that is how they install the bubble insulation. At least the company no used does it that way.

 

[zimman]

This will sound very uneducated but I can't see a company putting a bad thing on a metal building. I've seen lots of insulated buildings done this way. I think you're fine and the suggestions above should help.
Rock on man, it's all good.
Zim

 

[bluedog225]

Interesting. Does that bubble stuff have a reflective aluminum surface on the other side? If the side we can see is not “reflective” then the gap isn’t needed. Sometimes the aluminized sheets can be white. The polyiso boards are sometimes silver on one side and look white on the other. But have same reflective/emissive properties.

You have a moisture impervious surface on the outer wall. Whether it’s simply steel, or steel covered with plastic. If it’s ribbed panel, running vertically, there’s an opportunity for some vertical ventilation through natural airflow. I don’t know if that place against the steel is going to be a problem or not.

But insulating the inside will keep the warm moist air off the cold inner surface of the plastic/metal when it is cold out. That will help with condensation.

And it still can dry to the inside.

edit to add: and with a ribbed panel, there’s quite a bit of gap on the other side of that plastic to give you some benefits of reflectivity.

 

[Firebrick43]

Yes, the walls were optioned to be installed vertically! But like I said the bubble is smashed between it and the tubing, Perkins, girts. No air space other than the tallest rib on the paneling , which isn’t much. It’s still very hot inside because they don’t put fire strips on before the metal. I was unaware at the time that is how they install the bubble insulation. At least the company no used does it that way.

That is just the standard double bubble condensation blanket. That is how it’s to be installed and isn’t more that R1 or R2 in performance. I have never seen it installed any other way by a pole or metal building builder. It’s always over the purlins and against the metal. Usually it’s not placed on the walls but?

You will do all kinds of bogus claims by the manufacture that it somehow performs miracle or is the somehow the equivalent of up to R15 in insulation. Those are total lies.

It’s not “insulation” to make a meaningful difference in comfort other than not having condensation drips on your head.

 

[86Garage]

Yes there is a silver reflective side on the side that’s directly laying on the outer skin.

 

[bluedog225]

Nice building. I don’t think you have any issues if you finish it out correclty.

 

[86Garage]

So, is there a way I can still use steel on the inside without trapping moisture? I really would like to have the durability of steel. Do I leave a gap between the inner white side of the bubble insulation and foam board or not? I could easily run 2” foam board against the cross bracing leaving a 3/4-1” gap. But would I want that if I line the inside with steel? I have to do something on the inside and sparks from grinding welding etc I don’t want burning a hole in the foam board or other type of insulation.

 

[bluedog225]

If the inside face of the bubble stuff is aluminized, a gap will help because aluminum doesn’t emit heat well. Put a piece of aluminum foil 1” from the stove flame and then place your finger 1” away from the backside of the foil. Not much heat. It’s big deal in Texas. Probably pretty important in Tenn. as well. I’d do it.

I like the foam idea but then your have impermeable foam trapping moisture between the steel/bubble wrap wall and the foam. It’s got to dry to one side or the other. Bead board might be vapor permeable, but I haven’t checked in a while.

I guess you could have a gap at the top and bottom so there’s airflow up your wall from the floor. That is, airflow in the gap between the foam and bubble wrap. That’s going to make air-conditioning or heating the place interesting. But it would prevent condensation. And you could finish the inside with steel and it wouldn’t matter since you don’t really have a closed space inside the wall.

I’m a little surprised the spray foam people haven’t been by to say foam the whole darn thing right on top of the bubble wrap. Metal on top of he foam and the irregularities in the foam might allow air to circulate underneath the interior steel. Or put in battens somehow attached to the steel frame through the foam to create the gap.

I’m over my pay grade in this conversation. I’ll let others chime in with better advice. There’s a ton of info on this condensation stuff on the web. And there may be special considerations for steel buildings I’m not aware of.

 

[Firebrick43]

So, is there a way I can still use steel on the inside without trapping moisture?

Yes. You have done nothing yet to trap moisture. As long as you don’t foam or seal those ribs you are fine

I really would like to have the durability of steel. Do I leave a gap between the inner white side of the bubble insulation and foam board or not?

The insulation can touch the double bubble. Put your foam board or 4’ wide fiberglass batt in there.

I could easily run 2” foam board against the cross bracing leaving a 3/4-1” gap. But would I want that if Inline the inside without steel? I have to do something on the inside and sparks from grinding welding etc I don’t want burning a hole in the foam board or other type of insulation.

After putting your insulation in, put up girts like the outside, or more if you are going to hang things on the walls but and put up your steel R panels.

Just don’t add a second moisture barrier such as visqueen before putting up the liner panels. That would create a double vapor barrier and trap moisture. Again, do not foam or put clause strips blocking the ribs from breathing and you will be fine. That is how 10’s of thousands of metal sided buildings are done across the country.

 

[MovingAlong]

Did your new building come with a warranty? If so, does the warranty recommend or prohibit certain interior finishes?

Also, if your contractor stands behind their work, I'd ask them what finish material they recommend to use/avoid as well.

 

[86Garage]

I didn’t choose spray foam because my quotes were 15-16k. Thought I could do it for less. So if I put furring strips up on the inside of my framing and attach the steel to that vertically it should breath to the inside through the ribs. Sounds like that would work.

 

[racecougar]

Are you certain that the building is rated to carry the weight of an insulated ceiling?

 

[bluedog225]

The area between the outside metal and the bubble wrap may ventilate just fine with the ribbed panels. I don’t know much about that.

If you put up sheet foam, there’s going to be a closed space between the bubble wrap and the foam. And this will not breathe. No ventilation. And if the temperature reaches the dewpoint and condensation forms between those two layers. It’s got no place to go. Neither one of those materials will let it out.

If you can hang plywood on the inside, that could be pretty robust. And it breathes. If you’re worried about fire, maybe intumescent paint.

it would be good to detail your wall layers here before installing. Steel siding, bubble wrap, gap, etc.

 

[Firebrick43]

The area between the outside metal and the bubble wrap may ventilate just fine with the ribbed panels. I don’t know much about that.

If you put up sheet foam, there’s going to be a closed space between the bubble wrap and the foam. And this will not breathe. No ventilation. And if the temperature reaches the dewpoint and condensation forms between those two layers. It’s got no place to go. Neither one of those materials will let it out.

If you can hang plywood on the inside, that could be pretty robust. And it breathes. If you’re worried about fire, maybe intumescent paint.

Edit-with your string strips, are you running insulation?

it would be good to detail your wall layers here before installing. Steel siding, bubble wrap, gap, etc.

2” foam board is going to have the dew point inside the foam board. It’s not going to happen in between as the double bubble is r2 at best.

 

[bluedog225]

2” foam board is going to have the dew point inside the foam board. It’s not going to happen in between as the double bubble is r2 at best.

Yeah. That’s where it gets a little more complicated than I understand in all temperature scenarios. But there will still be a dead air space in there with no ventilation. That is, foam on one side and bubble wrap on the other side. Maybe it doesn’t matter if it has a little condensation.

Easiest would be fiberglass batts. Gap or not over the bubble wrap. Then a steel interior built on a standoff of some sort that puts a gap between the steel and the fiberglass for air to circulate back there freely. The gap would be part of the air-conditioned space.

 

[86Garage]

I could install foam board or fiberglass batts directly against the bubble wrap and just furr the steel out a little bit with 1x3 furring strips?

 

[Firebrick43]

I could install foam board or fiberglass batts directly against the bubble wrap

Yes

and just furr the steel out a little bit with 1x3 furring strips?

What is the vertical tube spacing? I wouldn’t go above 2’ span with a 1x3 (3/4” thick) strapping. If it’s 4’ span I would use 2”x4” or the same steel girts you used on the outside.

 

[86Garage]

It’s 4 ft span everywhere. Upgraded from 5’

 

[bluedog225]

Agreed. And maybe get away with 8’ of steel for your needs. Thin stuff attached and supported by wall. Thicker stuff resting on floor with little weight on walls. Unfaced fiberglass or mineral wool not going to catch fire from sparks thrown over steel. Flammable plastic will be covered.

Your ceiling insulation matters a lot more than the walls.

 

[bluedog225]

I wonder if 1/8” steel would be ok freestanding on 4’ verticals. Be a hell of a wall and you could attach everything with magnets.

 

[Fav Onefour]

Yes to both. Car restoration. Thanks.

Why did you build a shed?
I know the question doesn't help now, but man. . .

The building is not built to properly work as a conditioned building. Trying to do half remedies is going to be an ongoing challenge.

You have a couple options. Bite the bullet and redo the building envelope to create a functional conditioned space. I don't see that happening because it's a **** load of work and it won't be cheap.

There is a potential workable solution if the bubble wrap qualifies as a thermal break between skin and framing. In that case, the proper layers are well defined.
You would need full cavity layer insulation along with an interior vapor barrier before doing inside skin.
There are a lot of questions about the bubble wrap. Find out if that layer qualifies.

The second option is doing some halfway lining with insulation and deal with the problems down the road. Those problems will be writing bigger checks every time the utility bill comes due and the ongoing issues of condensation and eventual building issues.

I get hot just thinking about these situations. My old man is the king of shortcut solutions. He wants me to come out and help him fix the dang problems. Latest one is ten year old steel skin that rusting through from the inside. The building wasn't designed for heating but he wanted a nice warm building. He spent the gonzo bucks on heat and just let the water drip off the inside.

 

[racecougar]

I'm still curious to know whether or not the building was designed to carry the load of a framed out, insulated, steel ceiling. Insulating the walls won't matter much if you can't at least hit R-38 in the ceiling.

 

[bluedog225]

If not built for it, maybe remove the bubble wrap on the ceiling and spray foam just the ceiling?

 

[racecougar]

If not built for it, maybe remove the bubble wrap on the ceiling and spray foam just the ceiling?

Agreed that that would be an option, but if that's the route the OP needs to take, then I'd steer away from the gable vent/fan setup, as those will be thermal leak points. Hence, I keep circling back to is the building designed to carry an insulated ceiling.