Options for covering kraft faced insulation?

[FLman]

First time post from a guy that is relatively clueless but trying to figure things out and do things himself when possible...

I have a detached 2 car garage with second floor loft here in north Florida. It's being used for mixed purposes (storage, eventual car, "indoor" pet tortoise enclosure). Because of the latter the garage has to be somewhat climate controlled with some cooling in the summer and some heating in the winter. I was hoping I could slap a minisplit (MrCool 27K BTU, dual zone, 18K downstairs, 12K upstairs loft) in there and get away with that without insulation but of course I was wrong. I just had insulation put in yesterday and the installer used kraft faced batts.

I'm now at the point of figuring out what I do about covering this.

1. Of course the installer told me with the kraft paper I do not need a vapor barrier. Googling gives me mixed opinions but it generally sounds like a true vapor barrier may still be needed. Is that true?

2. What can I cover this with? I'm by no means handy but like to learn how to do things myself if possible. I'm not looking for this to look pretty but just functional and I'm watching expenses so as not to tick off my wife. If it was an option I'd just throw some OSB over it on the lower level and leave the storage loft space uncovered. I'm pretty sure that's not an actual option though. Am I stuck with drywall?

I'll be doing this all with just myself and my young apprentice (10 yo son). I appreciate any wisdom you guys can give us. I attached pictures of the unfinished walls and then the downstairs and upstairs with insulation.

Mike

 

[Ultradog MN]

No offense but I don't get why people are so adverse to drywall.
It's cheap, simple to install and can be taped even years from now if you can't afford it now.
PS,
Really nice looking space you built.

 

[FLman]

Totally get it. Honestly, this space was never really supposed to look “finished” and I’m afraid an amateur drywall job will just look like I aimed for that and it came out like ****. OSB could be put up less than perfect and it would still look fine, cause it’s just OSB and no one cares.

 

[mm08822]

It's the asphalt on the craft paper that actually is the vapor barrier. As long as the paper flanges are nailed tight to the joists and studs it will be pretty good.

The other method is to use unfaced and then cover it afterwards with 6mil poly. This also helped a little better with drafts.

Sheetrock is a good choice. If you are essentially working alone, you can rent a sheetrock lift for the ceiling and upper walls.

There are plenty of one man tips to hang drywall. Search YouTube.

Buy yourself a screw gun and a 50# box of drywall screws. Have at it.

 

[mike93lx]

Totally get it. Honestly, this space was never really supposed to look “finished” and I’m afraid an amateur drywall job will just look like I aimed for that and it came out like ****. OSB could be put up less than perfect and it would still look fine, cause it’s just OSB and no one cares.

Get a quote to have it hung and taped. Might be surprised that the cost is pretty reasonable.

 

[NUTTSGT]

Why isn't OSB an actual option ?

Granted, plywood would look nicer but is going to be more cost.

 

[wandrur]

I did OSB in my shed build, and I think it looks great. I caulked the seams and painted it, but you could easily leave it as is.

 

[Ultradog MN]

Totally get it. Honestly, this space was never really supposed to look “finished” and I’m afraid an amateur drywall job will just look like I aimed for that and it came out like ****. OSB could be put up less than perfect and it would still look fine, cause it’s just OSB and no one cares.

Okay, you win.
But if you paint it add a little color.
Im just finishing mine.
5/8" type X (fire rated) drywall throughout.
And some "oops" paint from Home Despot mixed together.
It won't win any color awards but at least it ain't prison white.

 

[danski0224]

Like most installations, that insulation is installed improperly. There is compression along the studs where it has been stapled.

Of course, doing it properly means that you can't see the studs and the drywall glue isn't sticking to studs.

The insulation on the roof plane in the second picture is a bigger problem. The insulation should be put on the wall of the room in attic truss, and then the back (roof facing side) needs to be covered with an air barrier. Can't see how the details are on the "ceiling", but I suspect there are issues there too. This will cause issues with trying to maintain cooling and heating.

Hopefully those trusses were ordered to carry the added loading of drywall.

The paper facing is flammable, it needs to be covered.

If you haven't done drywall before, I would suggest getting a few quotes for a complete job- hanging and taping.

 

[Ultradog MN]

Like most installations, that insulation is installed improperly. There is compression along the studs where it has been stapled.

Of course, doing it properly means that you can't see the studs and the drywall glue isn't sticking to studs.

The insulation on the roof plane in the second picture is a bigger problem. The insulation should be put on the wall of the room in attic truss, and then the back (roof facing side) needs to be covered with an air barrier. Can't see how the details are on the "ceiling", but I suspect there are issues there too. This will cause issues with trying to maintain cooling and heating.

Hopefully those trusses were ordered to carry the added loading of drywall.

The paper facing is flammable, it needs to be covered.

If you haven't done drywall before, I would suggest getting a few quotes for a complete job- hanging and taping.

Is gluing drywall to studs customary or required (code) where you live?
It is simply Not Done here.
They did experiment with gluing back in the 1980s. I've seen it in a couple homes of that era but it is simply not done here.
Just wondering...

 

[danski0224]

Is gluing drywall to studs customary or required (code) where you live?

It is customary.

It may be code, but I would have to verify that if I wanted to be sure. The assumption is because I usually see it being done, then it is likely code, because the extra money for product and time would not be spent.

 

[billconner]

Am I the only one bothered by vapor barrier face being on wrong side for Florida? Warm moist air will hit back of paper cooled by AC and condenser.

As far as stapling on the side of stud facing interior or the side facing cavity, I believe either is acceptable per the manufacturer. Some inspectors will have a preference. People that glue drywall have a strong preference. Drywallers in general don't like it on interior. (I don't use faced and add a 10 mil poly vapor barrier in my very cold climate.)

 

[danski0224]

Am I the only one bothered by vapor barrier face being on wrong side for Florida? Warm moist air will hit back of paper cooled by AC and condenser.

Keep in mind that paint can be classified as a vapor barrier.

I would always suggest that the Building Science website be checked out for the most recent information about best building practices in a specific climate zone.

 

[billconner]

Keep in mind that paint can be classified as a vapor barrier.

I would always suggest that the Building Science website be checked out for the most recent information about best building practices in a specific climate zone.

Some paint can perform like a vapor barrier. PVA based paints on drywall not much of a vapor barrier.

I believe BSC will say no vapor barrier or on exterior side.

 

[coldh2o]

It is customary.

It may be code, but I would have to verify that if I wanted to be sure. The assumption is because I usually see it being done, then it is likely code, because the extra money for product and time would not be spent.

How does the drywall get glued if a continuous poly vapour barrier is used?

 

[danski0224]

How does the drywall get glued if a continuous poly vapour barrier is used?

I don't know.

I haven't worked in a house in Canada.



I should have added the words "in my area" to prevent others from assuming that I made a blanket statement about all drywall installations...

 

[Leaflessshadetree]

In that space I'd do drywall. I find it easier (and more forgiving) than OSB or other sheet goods. It also costs less than just about anything other than cheap paneling.

 

[coldh2o]

The insulation on the roof plane in the second picture is a bigger problem. The insulation should be put on the wall of the room in attic truss, and then the back (roof facing side) needs to be covered with an air barrier. Can't see how the details are on the "ceiling", but I suspect there are issues there too. This will cause issues with trying to maintain cooling and heating.

Why is this the case? As long as the roof has been vented behind the batts, the building envelope is maintained. It's the same as any other conventional building sans attic trusses - insulated roof and walls.

It also allows the full attic space to be conditioned - the space under the roof behind the truss walls can be used for storage without worries about temperature, humidity etc.

 

[danski0224]

Why is this the case?

Fiberglass insulation must be in contact with an air barrier on all 6 sides.

If it isn't, the R value is significantly reduced.

Every house that I've been in that has a former attic space with insulation in the roof rafters has significant issues with heat gain in the summer, because the insulation is not installed properly.

 

[billconner]

I agree it makes more sense to insulate at the roof rather than the knee wall if for no other reason than it reduces the area size of the thermal barrier thus reducing heat loss/gain. Simpler is better. The ability to use that area for storage is a bonus.

 

[Ultradog MN]

In that space I'd do drywall. I find it easier (and more forgiving) than OSB or other sheet goods. It also costs less than just about anything other than cheap paneling.

Mine is all 5/8 type X drywall so you're preaching to the choir.
But I think of the average fellow here --- who is very savvy about a lot of things like Ford tractors, Studebakers, school board meetings, Harleys, HVAC, electrical, parenting,
El Caminos, fine bodywork and paint,
snowmobiles, collecting cool tools, banjos, machining and woodworking, writing code, gunsmithing, drinking copious amounts of liquor, cutting up a deer, Briggs and Strattons, turning clay pots, holding seances, exercise and the miriad other things they do in their garages --- He will do almost Anything to avoid having to tape drywall.
C'est la vie

 

[Firebrick43]

Is there full length ventilation channels on the roof deck behind the insulation? Is there soffit vents and ridge vents on the roof? If not you will have rot/mold in the cavities.

 

[billconner]

I wouldn't put Indiana experience on buildings in Florida..

 

[billconner]

Here's an article that seems pretty to close to o.p.'s situation. It suggests you may want to spend a little time sealing roof at eaves and ridge. Still not crazy about craft paper inside - I'd probably slash it - but not sure it's a real concern. If roof deck and underlayment - felt or synthetic - is good - I think you could use whatever you want for interior sheathing, though I'd lean towards boards or t&g or something that allows drying inward. If drywall, pva paint to maintain permeability.

RR-0981: Vented and Sealed Attics in Hot Climates | buildingscience.com

buildingscience.com

 

[danski0224]

I agree it makes more sense to insulate at the roof rather than the knee wall if for no other reason than it reduces the area size of the thermal barrier thus reducing heat loss/gain. Simpler is better. The ability to use that area for storage is a bonus.

Then the roof deck isn't properly ventilated. And the insulation isn't air-stopped

Well, the air will move through the insulation and significantly reduce the stated R value.

 

[Firebrick43]

I wouldn't put Indiana experience on buildings in Florida..

Seriously??? You’re going to GL like that?

Condensation and ventilation doesn’t know state lines.

And it’s worse in hot humid climates not better.

Unventilated and insulated roof decks will condensate and not dry out no matter where you live except maybe the desert.

The only way to keep it from happening is to ventilate the roof deck or not have an airspace(hot roof) with low permeability foam (typically closed cell)sealed directly against the deck.

It’s been part of building science classes for at least 2 decades now and is in the IBC code for 15 plus years.

The IBC allows hot roofs only if the insulation itself has a low permeability. Only closed cell foams will meet this requirement or open

Can be found at R806.5

The Florida building code is based on the IBC. The FBC is behind paywalls but here is passed legislation in Florida that took affect in July 1 2024.

https://www.flsenate.gov/Session/Bill/2024/1185/Analyses/h1185a.RRS.PDF

It specifically deals with the part of the code for hot roofs and lays out even what the previous code was. Neither allow fiberglass only without ventilation.

Even has pictures for some people

 

[billconner]

Then the roof deck isn't properly ventilated. And the insulation isn't air-stopped

Well, the air will move through the insulation and significantly reduce the stated R value.

It's just like insulation in a wall. Read linked BSC article. I'll go with Joe before code anyway.

 

[billconner]

Condensation and ventilation doesn’t know state lines.

Sure it does. Heating climates moisture inside. Cooling climates moisture outside. A lot easier to make a roof deck a vapor barrier, most are, especially with synthetic underlayment. With cooling, the air inside is going to be drier.

 

[billconner]

Here's another take on it, including about FL codes.

Unvented cathedral ceiling assembly for Florida - GreenBuildingAdvisor

Hi All, I've read a lot on this site to learn as much as I can, but I still have some persistent questions about the particulars of my situation. I've gutted a 325sqft room. It's down to the concrete block walls, slab floor, and existing roof assembly(2x4 rafters, 1x4 decking, felt, metal roof).

www.greenbuildingadvisor.com

 

[Firebrick43]

Here's another take on it, including about FL codes.

Unvented cathedral ceiling assembly for Florida - GreenBuildingAdvisor

Hi All, I've read a lot on this site to learn as much as I can, but I still have some persistent questions about the particulars of my situation. I've gutted a 325sqft room. It's down to the concrete block walls, slab floor, and existing roof assembly(2x4 rafters, 1x4 decking, felt, metal roof).

www.greenbuildingadvisor.com

Your “proof” is a discussion about insulating in a way that specifically is noted to violate the building code and subsequently stated that the OP on that discussion was aware and knowingly going to violate it anyways?

Sure it does. Heating climates moisture inside. Cooling climates moisture outside. A lot easier to make a roof deck a vapor barrier, most are, especially with synthetic underlayment. With cooling, the air inside is going to be drier.

There is a significant portion of the year where heating takes place even in Florida and is cool and damp, and that moisture will be trapped.

And it’s not about sealing the outside of the roof deck at all. ??? It’s about sealing the bottom side of the roof deck and having the dew point in the foam itself, which does no harm because moist air cant reach that point, not in the fiberglass which precipitates out.

 

[beltfeed]

Bill what's your thoughts on smart vapor retarders. Here's a cut and paste from Fine Homebuilding and a link to an article on smart vapor retarders from the Journal of light construction. In climates that temps range from 0 to 95F I would think this might be a good idea. Thanks for your construction comments, with you being in the business it's nice to see some tried and true methods.

The membrane’s vapor permeance rises and falls​

When conditions are dry, a smart vapor retarder is relatively vapor-tight (in other words, it has a relatively low vapor permeance). When the air or the building materials adjacent to a smart vapor retarder get more humid, however, the membrane becomes more vapor-open — in other words, its vapor permeance increases. Under dry conditions, it acts like a vapor retarder; while under humid conditions, it opens up and allows moisture to pass through it.

In the U.S., the best-known smart vapor retarders are CertainTeed’s MemBrain and two Pro Clima products: Intello Plus and DB+.

According to CertainTeed, MemBrain has a vapor permeance equal to or less than 1 perm when dry, and 10 perms when damp.

According to Pro Clima, Intello Plus has a vapor permeance of 0.17 perm when dry and 13 perms when damp. In other words, Intello Plus is a more effective vapor barrier when dry than MemBrain, and is more vapor-open when damp than MemBrain.

According to Pro Clima, DB+ (a smart vapor retarder that is less expensive than Intello Plus) has a vapor permeance of 0.8 perm when it is dry and 5.5 perms when damp. That means that the vapor permeance range of DB+ is not as great as that of Intello Plus.

https://www.jlconline.com/how-to/insulation/understanding-smart-vapor-retarders_o

 

[danski0224]

It's just like insulation in a wall.

No, it isn't.

 

[billconner]

beltfeed-

No opinion. I tend to be old fashioned. I prefer asphalt paper over house wrap and synthetic underlayment; pine boards instead of OSB - though occasionally use.plywood; and so on. I just like the science of building, learning through reading and conferences.

Thanks for asking!