Adding more insulation?

[Hobby_Man22]

So I'm in zone 2 and I think I need to add more than just R30 to my metal building. Right now I have mineral wool batts in between the perlins held up with metal straps that are screwed to the perlins. I'm thinking about getting some r15 fiberglass rolls and just lay it over the perlins. The perlins get pretty hot and probably create a bunch of heat gain. Any suggestions? I also want to cover it with vinyl.

 

[Hobby_Man22]

I know they have vinyl backed insulation, but not sure if they have the kind that covers the perlins

 

[Hobby_Man22]

Isn't most heat and cold lost through the roof?

 

[Hobby_Man22]

I know on a cloudy day the ac does ok and says off for a lot longer in between cycles vs a sunny day where it stays off for only about 10 minutes.

 

[Hobby_Man22]

It's not really a cooling issue, more of a not retaining the heat/cold air long enough. After 10 minutes it's already raised back up 2.5 degrees and the ac is kicking back on again. Grant it its 95 degrees outside I still think it should do better. The house stays off for 18 minutes in between cycles and it only raises 1 degree before kicking back on.

 

[Firebrick43]

Are you just trying to get your post count up? You know there is an edit function right?

 

[Hobby_Man22]

Are you just trying to get your post count up? You know there is an edit function right?

Not everyone has to pertain to your likes and desires my friend.

 

[billconner]

Confused by "over the purlins" . Would it in fact be under the purlins? Not sure how you "lay it over" purlins. Picture? And are purlins metal or wood?

I do believe most heat is lost through roof, most by convection, least by conduction. Heat gain through the roof is primarily radiation, so insulation under the roofing and the structural members it's attached to makes sense. I think you'd have to add furring perpendicular to the purlins to effectively get insulation under them, or use a rigid insulation. I'd look at vinyl faced 4x8 rigid fiberglass. It will take some hunting to find a dealer - not a Home Depot kind of product.

 

[Hobby_Man22]

Confused by "over the purlins" . Would it in fact be under the purlins? Not sure how you "lay it over" purlins. Picture? And are purlins metal or wood?

I do believe most heat is lost through roof, most by convection, least by conduction. Heat gain through the roof is primarily radiation, so insulation under the roofing and the structural members it's attached to makes sense. I think you'd have to add furring perpendicular to the purlins to effectively get insulation under them, or use a rigid insulation. I'd look at vinyl faced 4x8 rigid fiberglass. It will take some hunting to find a dealer - not a Home Depot kind of product.

Attached to the bottom with screws. I mean so they're covered up. The perlins get hot. I saw the vinyl faced insulation, but I don't think they intend for that to cover the bottom of the perlins. When I say bottom I mean the part inside of the building.

 

[Hobby_Man22]

The perlins are metal

 

[billconner]

I still then suggest rigid insulation on the purlins or furring strips - like 3 1/2" metal studs - and vinyl faced insulation.

 

[Hobby_Man22]

I still then suggest rigid insulation on the purlins or furring strips - like 3 1/2" metal studs - and vinyl faced insulation.

Well they have vinyl insulation sheets you can buy that are like 12ftx85ft. I'm thinking of getting r15 or r19 insulation rolls then cover it all up with the vinyl cover.

 

[billconner]

Can you get a stand off at the purlins so you are not compressing it?

 

[Hobby_Man22]

What do you mean stand off?

 

[Hobby_Man22]

Can you get a stand off at the purlins so you are not compressing it?

It's only going to be compressed on the bottom in the areas I screw it down.

 

[billconner]

How close do you plan to place screws.

 

[Hobby_Man22]

How close do you plan to place screws.

Not sure yet. As far apart as possible without it sagging a bunch. A lot of these rolls are only 15in wide.

 

[billconner]

it just seems like the batt will be compressed quite a bit along lines of purlins.

 

[jmdirk]

Normally you would have done insulation over the frame of the building before putting the roof panels on. Yes, it compresses over the purlins, but it still creates a thermal break between the roof deck and the purlins.

Sounds like you have more of a retrofit install already. But sure, I don't see why you can't get some rolls of faced insulation and wrap the purlins.

Maybe contact a company like Silvercote and see what they recommend.

 

[billconner]

I think a photo would help. I'm no longer sure of what the conditions are. I thought a steel shape of a size like 2x4 or maybe 2x6 on edge across trusses and parallel with ridge. Maybe "z" shape. Roofing attached to them, batts between, guessing no vent space. Batts held with strapping. And you want another layer of batts under purlins.

 

[duneslider]

How good is the air sealing in the building. My house is well insulated but when my kids leave the doors open it doesn't matter how well the insulation is the air exchange is high and the ac has to keep running. If your building is leaky then nothing is holding back the the tempered air. I was running a water line to my garage fridge the other day and there was a small hole along one of the walls in the drywall roughly the size of a quarter and I could feel the air movement coming out that little hole.

 

[Hobby_Man22]

How good is the air sealing in the building. My house is well insulated but when my kids leave the doors open it doesn't matter how well the insulation is the air exchange is high and the ac has to keep running. If your building is leaky then nothing is holding back the the tempered air. I was running a water line to my garage fridge the other day and there was a small hole along one of the walls in the drywall roughly the size of a quarter and I could feel the air movement coming out that little hole.

I sprayed the seams before I put in the batts that are currently in there.

 

[Hobby_Man22]

Normally you would have done insulation over the frame of the building before putting the roof panels on. Yes, it compresses over the purlins, but it still creates a thermal break between the roof deck and the purlins.

Sounds like you have more of a retrofit install already. But sure, I don't see why you can't get some rolls of faced insulation and wrap the purlins.

Maybe contact a company like Silvercote and see what they recommend.

Normally, but the guy who built this building was too cheap to do that. I bet back in 2018 the vinyl backed insulation they typically put in red iron steel buildings would have only been like $4500. Also silvercote does make vinyl covering like 12ftx85ft rolls and that's what my plan is to use for the final coverring. I may give them a call and see if they have an actual kit that covers the perlins based on building size.

 

[Hobby_Man22]

Nobody wanted to do anything but spray foam since the building was already put up so I put these batts in myself. I've been inside these spray foamed builings and it's like being inside a tin can. Loud *** he'll. I'm very happy with the mineral wool batts.

 

[Hobby_Man22]

I think a photo would help. I'm no longer sure of what the conditions are. I thought a steel shape of a size like 2x4 or maybe 2x6 on edge across trusses and parallel with ridge. Maybe "z" shape. Roofing attached to them, batts between, guessing no vent space. Batts held with strapping. And you want another layer of batts under purlins.
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Here's a pic. I just put it up with some 1" steel straps. These are 23"x47"x7.25" thick R30 Rockwool batts. There's about an inch of space in between the roof and the insulation for air circulation. So what I want to do is find some vinyl face insulation rolls that are like r15 or 19 and just lay it over the exposed purlins because the r30 isn't cutting it and this stuff needs to be covered.

 

[Hobby_Man22]

They also didn't quite fit so there is a space as you can see in the photo. The batts are about an inch short. That's why I think if I just cover it with another layer and make sure has no cracks it will make a difference.

 

[billconner]

No doubt it will make a difference, and probably a significant one. My comments were aimed at maximizing the difference.

 

[Hobby_Man22]

No doubt it will make a difference, and probably a significant one. My comments were aimed at maximizing the difference.

Kind of a bummer. It was a ***** putting those straps up.