Installing insulation myself. Couple questions

[Hobby_Man22]

I'm going to get some rock wool mineral wool insulation to insulation my red iron metal building. I can't find any contractors that answer the phone and I don't think it takes much to shoved some panels up in between steel girders anyways.

Question one: Do I need to put some kind of plastic covering over the insulation like you see on many steel buildings, or cab it be left exposed. It's going to be inside the building just fyi.

Question two: Since the building is already built, do they make some straps to help hold the insulation in? Primarily on the roof?

 

[mepstein]

I just put rock wool into my workshop. It's pressure fit between the studs but you might need strapping between metal. I would cover the batts with something. I'm going to use a peforated moisture barrier behind my interior metal walls to keep the dust from coming through. It's not as bad as fiberglass but still not good to breath.

 

[marineman]

I can't see your location on the mobile app but vapor barrier goes on the warm side. In cold climates thats inside, in warm climates thats outside.

Sent from my SM-G970U using The Garage Journal mobile app

 

[Hobby_Man22]

Houston. I don't think the mineral wool needs a vapor barrier. I was talking about is it okay leaving the insulation exposed. I guess it could get dusty after a while, but who cares about that. It's a shop.

 

[Hobby_Man22]

I'm going to rent a scissor lift so I can reach the roof.

 

[Hobby_Man22]

I just put rock wool into my workshop. It's pressure fit between the studs but you might need strapping between metal. I would cover the batts with something. I'm going to use a peforated moisture barrier behind my interior metal walls to keep the dust from coming through. It's not as bad as fiberglass but still not good to breath.

I looked at that stuff. I don't see how I can use that stuff with the beams already in position. I think ill just get some insulation strapping and put straps over them after squeezing them in place. It looks like they make metal strapping that hold batts in place.

 

[mike93lx]

vapor barrier goes to the warm side.

are you air conditioning the space? if yes, you would want the barrier to the outside. placing it inside will allow moisture to condense on the plastic inside the cavity.

if no, i would not use a vapor barrier at all.

 

[Hobby_Man22]

vapor barrier goes to the warm side.

are you air conditioning the space? if yes, you would want the barrier to the outside. placing it inside will allow moisture to condense on the plastic inside the cavity.

if no, i would not use a vapor barrier at all.

Yes but mineral wool does not need a vapor barrier.

 

[mike93lx]

Yes but mineral wool does not need a vapor barrier.

Insulation type doesn't matter, unless the insulation itself Iis a vapor barrier, like closed cell foam. Trapped moisture can create mold

 

[rlitman]

Insulation type doesn't matter, unless the insulation itself Iis a vapor barrier, like closed cell foam. Trapped moisture can create mold

And vapor barriers trap moisture.

 

[mike93lx]

And vapor barriers trap moisture.

That is why you out them in the right place

 

[matt_i]

The vapor barrier is an interesting question, I think its different for climates...

In winter things like cooking, showering, indoors while its cold outside is a prime soruce of the moisture.

In summer when its humid outside and a person is air conditioning the inner space then its concentrated outside.

Two different scenarios.

The main thing is to stop air infiltration which carries the moisture with it. In dead air the humidity has a very difficult time "moving".

If you draw a temp gradient graphic as if you could measure the temperature every 1/16" of an inch from outside to inside, eventually there's a place where the dew point is crossed and that's the layer where the moisture will condense, collect, and drain.

In a southern climate I'd place it on the outside. Much more likely for that abstract "plane of dew point" to be much closer, in distance to the outside siding surface.

The beauty of rockwool (and dense cellulose) is it naturally excludes air movement, and, if you get it wet, it just stays wet and won't harbor organic growth.

Given the materials in a steel building, much less likely to get damaged by moisture vs. SPF wood framing.

However, with a reasonable effort at air-sealing, using rockwool, I wouldn't use it in a shop that's not going to be cooled 100% of the time.

 

[mepstein]

I used Rock Wool and Tyvek. Tyvek is an air and water barrier but vapor permeable.

 

[rlitman]

That is why you out them in the right place

While I would love to agree with you, I just can’t bring myself to do it.

Every year, I read new vapor barrier suggestions, and read about how the last way of doing it was all wrong and caused major problems. And every couple of decades, every insulation company seems to go **** up in bankruptcy due to lawsuits, and starts all over from a clean slate, but still using the same name.

Anybody still remember EIFS?

The problem as I see it is any system will appear just fine when it is installed. It is only when it gets torn out that we start to see the inherent flaws. By then, the contractor is long moved to an island without extradition, and the manufacturer has disavowed any liability from its former self, and the customer is left to hang out and dry.

For my part, I’m not having anything to do with vapor impermeable membranes. No way, no how. There are plenty of systems that slow the movement of vapor without completely blocking it, and those, I’m all for. Rock wool, tar paper, tyvek, etc, I’m all fine with. Foil, solid PE sheeting (not perforated), closed cell foam, etc, all trap moisture, and must be used in a way where they do not trap moisture where it shouldn’t be. Yet too many times, they do just that.

 

[rlitman]

The vapor barrier is an interesting question, I think its different for climates...

In winter things like cooking, showering, indoors while its cold outside is a prime soruce of the moisture.

In summer when its humid outside and a person is air conditioning the inner space then its concentrated outside.

Two different scenarios....

Different indeed. I live in a climate where we both heat AND air condition. If you’re fortunate enough to live in a climate where you only do one of those, then perhaps conventional vapor barrier recommendations will work for you. Here, ha!

 

[Hobby_Man22]

We use both heat and a.c. in Houston. We think 60 degrees is cold.

 

[toolchaser]

As far as the strapping question, I used the narrow plastic duct support strapping, but the web type would work as well My trusses were 36" o.c. so it helped significantly reduce sag. If yours 24" o.c. or less it may not be needed

 

[Hobby_Man22]

No mine are steel beams measuring 43.5in. I can kind of squish them in between to hold them in place on the walls, but the ceiling I'll probably do a couple straps per bat.