Insulation: Fiberglass or Stone Wool?

[elm_street]

Winter is coming on fast here in the Great White North and I'm starting to think about insulating my 15x26 detached garage. At this point I'm not totally convinced it makes sense since it is detached but I think that at the very least it will help keep the sound down a little bit and hopefully a small space heater will take the edge off those -5C to -10C (23Fto 14F) days (any colder than that will make any garage time pretty short).

Currently the walls are just studs and plywood sheathing on the outside. Ceiling is 8' 4.5" (8 foot studs + base plate and two top plates). Total wall area to insulate is around 550 square feet (two windows, a man door and a 10x8 overhead door take up the rest).

This would be a job I would do on my own and I am leaning towards using 1/2" plywood for the interior walls. It looks like I can get R14 in the walls.

I have two main concerns. First is comfort of doing the actual job, is stone wool (Roxul) better from that standpoint or is it going to be almost as itchy as fiberglass? My second concern is rodents. The building is fairly tight but I'm sure there are enrty points for vermin. The Roxul website says "does not support vermin", whatever that means.

Cost wise in my area it looks like stone wool is about 25% more than fiberglass(59 sq feet per pack versus around 78 for fiberglass, the fiberglass packs are 10% more expensive). In my case this would work out to around $370 for stone wool or about $315 for fiberglass. I think I may have just answered my own question if the itchy factor is what I think it is.

So which one would you go with in my situation?

 

[Highbeam]

I've been putting up lots of pink (Owens) batt insulationn from HD and it is not itchy at all. I mean really, not at all and none of that itchy dust that gets in your throat that you end up hacking out later. I have been pleasanty surpised at how nice it is to work with.

The FG guys have made huge advancements in the itch department.

 

[dlenkewich]

If you take care of any penetrations and sheet the inside, you have little reason to worry about rodents in my opinon.

Roxul will cause much for skin irritation than regular fibreglass. The fibreglass out now is so refined it causes very little irritation but you'll find it also depends on the quality of product you buy. I also just insulated with owens corning and I found it much better than it was even a few years ago.

Roxul is also much more expensive so I would consider if you really need that product or not.

 

[Architorture]

I like mineral wool... Good sound performance, doesn't support mold, will work when wet, good in a fire

 

[theoldwizard1]

I like mineral wool... Good sound performance, doesn't support mold, will work when wet, good in a fire

You nailed it !

Rodents will shred the fiberglass and use the strands for nesting material. Mineral wool would just crumble if they claw at it.

OP needs to decided if it worth the cost for those feature.

 

[the gypsy]

I would use Roxul. It is a sound insulator it is a fire retardent will not burn as easy as fibreglass (see on the net the difference between fibreglass and roxul you will be surprised) and does not hold water or humidity. Did you ever see what happens to fibreglass when it gets wet? Can you imagine this in your walls. No need to worry about compressing the Roxul as compared to fibreglass (compressed fibreglass is worthless). It stays in place when you install.
Can you tell that I like Roxul.

 

[the gypsy]

OOOOPS the oldwizard took the words out of my mouth. I guess I am a slow typer.

 

[MScott]

I put Roxul in my basement and will put it in my garage. As mentioned, there is no itching as with fibreglass, and it is much easier to work with. I've seen too much of the fibreglass riddled with mouse holes, full of mould and it becomes useless if it gets wet. It was only a couple of hundred more to do my basement with Roxul than it would have been with fibreglass. Well worth the difference.

 

[Ken P]

If you're going with the Roxul be sure to wear a fairly high grade respirator. A paper dust mask isn't good enough. Just sitting there in the wall after install is fine but if you're cutting and creating any dust it's some nasty stuff.

Also rinse in the shower with cold water first. The soap and barely warm water after.

 

[elm_street]

I'm thinking that for my case since the difference is only around $60 that the stone wool is the way to go mostly from the comfort standpoint (I can handle using an upgraded respirator when doing the work) although the fire, sound and water related advantages are good too.

 

[Highbeam]

There are a lot of myths and sales pitches for and against roxul and FG.

Obviously you can compress FG, you will get the same R value per inch if not more.

FG is glass and does not support mold. Mold has to eat something and won't eat FG anymore than it will eat rock wool.

I might have tried rockwool but it is very expensive. Much more than FG. Both have the similar performance otherwise.

 

[Scott H in Wheaton]

There are a lot of myths and sales pitches for and against roxul and FG.

Obviously you can compress FG, you will get the same R value per inch if not more.

FG is glass and does not support mold. Mold has to eat something and won't eat FG anymore than it will eat rock wool.

I might have tried rockwool but it is very expensive. Much more than FG. Both have the similar performance otherwise.

I have used both, and each has their merits.
Roxul is much better at sound deadening.

Fiberglass will melt in a fire, but to quote Owens Corning website
"the insulating materials in PINK® fiberglass insulation are noncombustible. Its natural fire resistance is unaffected by moisture, evaporation, or time"

Neither product will support mold growth without some outside factor, and then they both would.

 

[Architorture]

Roxul is used in rain screen wall designs...that isn't going to happen with fiberglass... It is a better product

 

[Nowater]

Take care of any source of air infiltration while the building is open. You could outline every stub bay with cheap construction adhesive to help with air infiltration and the same for the roof. If you are letting in cold air that little space heater will just make your electric heater spin. Check doors, windows, and any opening.

Put a vapor barrier toward the warm side. Plywood on the inside would be great for hanging tools. I suggest white paint to make it more light, or try for a very light colored mismatch paint from the big box stores or a paint distributor.

 

[elm_street]

Good points, Nowater, thanks.

I'm thinking that my first priority is going to be getting the walls done but I know that in order to be really effective I need to get either the ceiling or the underside of the roof done as well. I have a storage area in the rafters that has a plywood floor that spans the whole building. Doing each of those will double my insulation costs (actually more than double because the ceiling joists are 2x8 and the roof ones are 2x6 while the walls are only 2x4).