Wall Insulation Question

[AtlasRocker]

Hello All,
I am in the process of building my garage and I am completely finished on the outside. (I do plan on posting the build after I get a little further) I am on getting ready to do the 1 st floor finishing and have to figure out how to finish the walls.

The construction of the walls start with 8" block that is 4' high for the whole perimeter. Then I used 2x6 studs for the rest of the wall construction. The 2x6's are flush with the outside of the block which leaves about a 2" offset on the inside. All along I figured I would just have a small ledge all the way around, but now that I am at the finishing stage of the job I'm not sure I want that. The ledge would be to small to be useful and a great place to collect dust. I was planning on studding out the remaining gap and having a flush wall.

How would you handle the wall insulation? If I get fiberglass insulation for 2x6 walls there will be an air gap.
- Should the gap be between the outside wall and insulation
- Should the gap be between the inside wall and the insulation
- Or is the gap absolutely not the right thing to have

Any guidance and wisdom of the group would be greatly appreciated.
Jim

 

[Dan0myte]

Hey Jim!

I know you've already built the exterior so it's far too late for this, but I would have staggered the 2x6's every 32" on center to create a flush wall on both sides. The fibreglass insulation could then be woven between the studs to create a continuous insulation barrier from one end of the wall to the other. This would have avoided the ledge as well as provided better sound proofing.

But as it stands right now, yeah, nailing 2x2 strips to your existing 2x6's will give you 2x8's, which then you should fill with two batts of regular 2x4 wall insulation per gap giving you a full 8" of insulation. Typical 2x4 insulation is R14, so going with two batts per gap will give R28 wall insulation which is enough for life in the Arctic Circle.

 

[a3tripod]

Edit: He beat me to it! Do what Dan0Myte said, or if funds are too tight to pay for the extra materials and the added cost of the bigger insulation, you can use R19 and leave the ledge as it is. This is how my garage is, though i didn't have a choice! the R19 seems quite effective for my 3-car garage. it doesn't get below freezing in there unless its consistently below 0 outside (which happens every year here in IA).

 

[OccupantRJ]

Add a 1 X 4 to the ledge to create a narrow shelf to store all your rattle cans of paint, brake cleaner, etc, to make them easier to find, or just run all your receptacles in conduit along the existing ledge, and they will all be at the 4 foot level, spaced whatever way you like them. Or, you can break a piece of sheet metal to create a sloped trim around the room so dust won't collect as badly. This could be painted as a stripe would in a contrasting color.

RJ

 

[AtlasRocker]

Thanks for all the input. Never thought about staggering. Oh well, it goes with a project this big that there are all sorts of lessons learned. I'm glad I already learned a lot from this forum or there would be many more things I would have liked to do differently.

I thought about making the ledge a shelf, but despite to the garage being 1,100 sqft, it is actually pretty small and narrow and I can't give up the side the side space. Doubling up on 2x4 insulation escaped me and seems like the best choice. I will be insulated from the weather for sure.

 

[bigdav160]

The true answer to your question is dependant on location. What is true in Alberta doesn't work in Louisiana.

 

[61scout80]

what about blown in?

 

[Doug B]

Hey Jim!

I know you've already built the exterior so it's far too late for this, but I would have staggered the 2x6's every 32" on center to create a flush wall on both sides. The fibreglass insulation could then be woven between the studs to create a continuous insulation barrier from one end of the wall to the other. This would have avoided the ledge as well as provided better sound proofing.

But as it stands right now, yeah, nailing 2x2 strips to your existing 2x6's will give you 2x8's, which then you should fill with two batts of regular 2x4 wall insulation per gap giving you a full 8" of insulation. Typical 2x4 insulation is R14, so going with two batts per gap will give R28 wall insulation which is enough for life in the Arctic Circle.

Just thinking out loud here....in the staggered stud design,it would appear that there would be a compression of the fiberglass to 2" at each stud. I don't think this is good for the r-value.

DanO's second option is more viable. Or,you could fur out with 2x2s,and use 6" r-19 in the deeper cavity-airspace to the outside.

 

[nate379]

Why aren't you guys using R-21 for 2x6 walls? That's usually what is used here.

If you can afford it, I would frame it for a 2x8 wall and run 2 batts of insulation.

 

[belvedere]

Just thinking out loud here....in the staggered stud design,it would appear that there would be a compression of the fiberglass to 2" at each stud. I don't think this is good for the r-value.

I was thinking the same.

 

[idunnosh#t]

NEW HERE,,,DIGGIN IT! DEFINATLEY ADDICTED!Wheels are turnin.(Slightly out of balance)...One option is to fur out from that ledge down to the floor with treated 1 1/2"
or 3 1/2 " then use styro foam and whatever finish material you want to cover your block. On top of your now wider ledge you could build a simple shallow cabinet out of a piece of treated 1x for the bottom, then a plywood ripper for the back, then another ripper or a piece of 1x for the top.Heighth and depth are optional.An easy masonite by-pass door could be made by cutting a pair of grooves in the bottom and top pieces on a tablesaw, cut your masonite to fit loose enough to slide nice, drill afinger hole and WALLA, extra storage. Of course plan your work carefully, cut some small mock up pieces, then knocker out.Alot of cool ways you could doll er up for cheaps. I've noticed alot of shops on here with un-insulated knee walls..??? BRRRR.....My 2$ F.W.I.W..($??)

 

[AtlasRocker]

Thanks for all the advise guys. I am going to stud it out and double up on the insulation. Furring out all the way to the floor is not an option for me. I do not want to give up an inch of inside space and most of the block walls are below grade and all of it is filled with vermiculite. Nothing bad about the extra insulation and R rating and it isn't enough extra $$ to worry about.

I too have been thinking about the staggered approach and while that option is long past me, I'm not sure I like the 32" centers. I'm just glad I hadn't bought all the insulation yet.

Thanks again.

 

[kbs2244]

Don't forget a good tight vapor barrier.
You don't want all that insulation getting wet.

 

[Absea]

Vapor barrier...what's that? J/K of course.

 

[bluescat]

The way I did it 30 + years ago (and it's still standing) was to insulate the 2x6 walls as normal. I used paper backed insulation, and slashed the hell out of the paper, then covered the walls with poly creating a solid vapor barrier. Then I ran 2x2's horizontally every 12 inches, and covered it with drywall. There is a 1-1/2" air space between the drywall and the vapor barrier. Over the years I have had to remove some drywall here and there for various reasons, and have never found any type of damage. I live in the northeast so it sees a varity of weather changes. Hope this helps.

 

[tcianci]

I think your choice of the double insulation is the most effective one, just be sure to use unfaced insulation on the first layer and then faced insulation on the 2nd or more unfaced with a poly vapor barrier. Your block wall is good enough..folks seem to forget that 80% of your heat loss is through the ceiling anyway.

 

[idunnosh#t]

NEW HERE,,,DIGGIN IT! DEFINATLEY ADDICTED!Wheels are turnin.(Slightly out of balance)...One option is to fur out from that ledge down to the floor with treated 1 1/2"
or 3 1/2 " then use styro foam and whatever finish material you want to cover your block. On top of your now wider ledge you could build a simple shallow cabinet out of a piece of treated 1x for the bottom, then a plywood ripper for the back, then another ripper or a piece of 1x for the top.Heighth and depth are optional.An easy masonite by-pass door could be made by cutting a pair of grooves in the bottom and top pieces on a tablesaw, cut your masonite to fit loose enough to slide nice, drill afinger hole and WALLA, extra storage. Of course plan your work carefully, cut some small mock up pieces, then knocker out.Alot of cool ways you could doll er up for cheaps. I've noticed alot of shops on here with un-insulated knee walls..??? BRRRR.....My 2$ F.W.I.W..($??)

I think your choice of the double insulation is the most effective one, just be sure to use unfaced insulation on the first layer and then faced insulation on the 2nd or more unfaced with a poly vapor barrier. Your block wall is good enough..folks seem to forget that 80% of your heat loss is through the ceiling anyway.

I must be the obviously misinformed folks you are referring to in your last sentence.Folks should know what their talking about before they start throwing in-accurate statistics and misinformation around and implying other folks are ( forgetful?.) First of all Fact 1 : Thermal Bridging renders vermiculite or any other insulation in concrete block virtually no better than plain old air. No insulation =4' blockwall at ambient outside air or ground temperature.Major heat loss,Waaaay more than a insulated ceiling. Which brings us to this (wtf? forget ? 80% figure?). Fact 2: Every building is different, there is no cut and dried heat loss percentage through the ceiling and an average insulated structure would be nowhere near that % anyway. Windows,doors,and garage doors,not to mention a uninsulated slab, have a much lower R-value than walls or ceilings.The list of variables goes on and on, and I,ve made my point on fact .I'm not on here to act like a know it all or cause trouble but I know when I,m being smack talked .

 

[Kevin54]

2x6 studding with insulation for 2x6 walls will leave you no airspace unless you build out the wall studs. ANd don't forget that if you trim out the walls you will have a baseboard going around so that will use up 1/2" to 3/4" of the 2" ledge. Actually you would probably not even notice the ledge after everything is finished off. A good coat of epoxy paint or gloss floor paint on the ledge will help it blend in and keep dust from collecting. You'll have more dust on tops of cabinets than you will the ledge. Just my $.02 worth on the subject.