Need some insulation advice

[almico]

I'm starting the task of converting my 28 x 21' garage to a workshop. I'm only planning on parking the motorcycle in there. I'm keeping the 16 x 7' insulated overhead door for now. I need to add weather stripping though. I live at a relatively high elevation in central NJ. The house is on top of a mountain, but the property is heavily wooded so wind is mitigated.

I have two questions (so far). The walls are 2 x 4 studs on block. Should I increase the stud thickness and up the R value. I think I can only get R13 from 2 x 4 studs.



Second question: The house is a ranch with a low pitched roof. Although I can use all the storage I can get (no useable attic or basement), realistically anything I put up there once the ceiling is in will likely never come back down.

Should I insulate the rafters, ceiling joists or both?



If I install 2 x 6 ceiling joists where the old ones are now I would have a 9' ceiling. I'm planning on a wood/rigid foam floating floor which will add 2" to the floor, but the ceiling will still be plenty high.

Need some advice. What would you guys do?

 

[Rookie2]

do you know all your pictures are available to the world ?

 

[almico]

do you know all your pictures are available to the world ?

Everything I post in Photobucket is for the purpose of posting to a web forum. So yeah, they are all for public viewing.

 

[98ssuck]

I can see the pictures just fine. I would increase the stud thickness to increase your potential r-value. You can't over insulate.

 

[Modern Jess]

One way to thicken the walls and raise the R value is by using a Mooney Wall.

In my own workshop, I'm doing a kind of simplified version of this. I'm using conventional bats in the vertical stud bays, and then rigid foam insulation in the horizontal bays. Not as intense as the full-on Mooney wall, but still adds some additional insulation.

It is labor intensive, though.

 

[almico]

One way to thicken the walls and raise the R value is by using a Mooney Wall.

In my own workshop, I'm doing a kind of simplified version of this. I'm using conventional bats in the vertical stud bays, and then rigid foam insulation in the horizontal bays. Not as intense as the full-on Mooney wall, but still adds some additional insulation.

It is labor intensive, though.

That looks neat. How are you extending your electricals thought the foam? I guess I could just tow nail blocks into the original 2x4s and screw the boxes at the back?

 

[Average_Joe]

A much easier solution than a "mooney wall" would be to add 2x2 furring strips vertically to the face of the studs and then use normal r19 batts.

As for the attic, I would only insulate the ceiling joists OR the rafters, not both. If you chose the insulate the rafters, make sure you use baffles to allow airflow

Also, if you are not flooring the attic area, your insulation does not have to match the size of the joists. For example, you can use R30 insulation with 2x6 joists.

 

[Modern Jess]

A much easier solution than a "mooney wall" would be to add 2x2 furring strips vertically to the face of the studs and then use normal r19 batts.

Easier, yes. Definitely. The main point of the Mooney wall, though, is to reduce the thermal bridging that occurs through the studs. Even if you get R19 bats into regular vertical studs, the overall R value of the wall assembly is significantly lower than R19. The wood studs are only R1 (per inch) and so heat / cold goes through the studs fairly easily.

I actually have a mix of vertical (on the upper walls) and horizontal (on the lower walls). This is largely to accommodate hanging cabinets, where the mounting systems usually rely on a vertical stud arrangement.

 

[Modern Jess]

That looks neat. How are you extending your electricals thought the foam? I guess I could just tow nail blocks into the original 2x4s and screw the boxes at the back?

In my case, I used the extra depth of the wall to set some Wiremold 4000 flush into the wall, and I'm running all electrical in that channel, all the way around the room. The outlets are mounted in the channel as well.

 

[almico]

The main point of the Mooney wall, though, is to reduce the thermal bridging that occurs through the studs.

That's interesting. I didn't think of that.

It seems R19 batt is double the price of R13 at my local HD, $25 per 39' roll vs. 12.50. So I had a thought: Since I have extra room on top of the block, what if I put one unfaced batt of R13 against the outside wall, then a layer of that 1/4" fanfold HDPE rigid foam board, then another 2x4 stud as a furring strip and then another layer of R13. The foam would negate most of the thermal bridging and I would end up with R26 + the R1 and extra vapor barrier I get from the foam.

If I skip the foam board I still would get R26 for the price of R19 just by doubling up.

 

[biodiesel]

If you go this route I would offset the second row of studs from the first to further reduce thermal bridging.

 

[almico]

If you go this route I would offset the second row of studs from the first to further reduce thermal bridging.

Excellent idea. Falls under the category of "why didn't I think of that?!"

 

[Radix2]

Why not cover your r-13 (could get r-15) batts with one of the interior rated polyiso foam boards to add r-3 to r-13 ? You can find them at all the box stores - also stops the thermal bridging issue.

 

[Modern Jess]

If you go this route I would offset the second row of studs from the first to further reduce thermal bridging.

This.

The only thing that would make that better would be an air gap in between the two wall assemblies, which also creates a nearly sound-proof wall.

 

[almico]

The only thing I'm wondering is: is all this overkill considering I'm still going to have a 16' x 7' insulated overhead garage door on my north wall?

 

[biodiesel]

This might not be the most cost effective way of saving energy but everything that you seal out does help. You can never have too much insulation (as long as there is proper ventilation to deal with moisture) it just gets to the point of diminishing returns with the cost of materials.

 

[almico]

This might not be the most cost effective way of saving energy but everything that you seal out does help. You can never have too much insulation (as long as there is proper ventilation to deal with moisture) it just gets to the point of diminishing returns with the cost of materials.

Yeah, everything seems to be a tradeoff.

For example, there are very few 2 x 4 ceiling joints now, barely the minimum to tie the walls for snow load. If I insulate the rafters I'll have a 14' ceiling to heat. If I want to install and insulate a ceiling, I first have to buy (21) 2 x 6 x 22' doug fir floor joists at $18 a piece + sheet rock + ply if I want an attic floor for some storage.

This is my first (and hopefully last) time doing this so I have little to no experience and not a huge pot of money to work with. I use this space a lot though and need to get it livable before winter sets in.

 

[shawhite]

For the money u are going to spend on all this why not just do spray foam in the 2x4 wall and call it a day.

 

[almico]

For the money u are going to spend on all this why not just do spray foam in the 2x4 wall and call it a day.

I guess I should at least get a price. I have about 60 linear feet of 8' framed wall above the block.

That brings up a point...what to do with the block along the entire perimeter?

 

[shawhite]

They make diy spray foam kits if u want to go that route. But I would at least get a quote.

 

[Modern Jess]

The only thing I'm wondering is: is all this overkill considering I'm still going to have a 16' x 7' insulated overhead garage door on my north wall?

The great thing about insulation is that -- once you've sealed the space against air infiltration -- almost anything you do to improve the R value will actually be beneficial. So yes, it's overkill. Yes, the garage door won't be as good as it can be, but that doesn't negate the other insulation on the walls and ceiling. It all averages out. Better walls = better average R value.

 

[almico]

Got one price back for closed-cell spray foam. $1300 for 60 linear feet x 8', or about $2.70/sqft. That's 3" thick and R19.

Still waiting for a few more.


If I use R19 faced batting and 2" furring strips the cost is about $425.

I don't think it pays to build out the 2nd wall.

 

[Huntmaster86]

here in upstate ny i got spray foam done for $1 per sqft per 1" thick. That was closed cell. I went with 3" thick in my attic of my house and couldnt be happier. Much cooler in the summer and hopefully much warmer this winter. After i get my garage standing im going to check into getting it sprayfoamed. Sealing all the tiny ari gaps is one of the biggest issues in building and sprayfoam fixes that.

 

[almico]

here in upstate ny i got spray foam done for $1 per sqft per 1" thick. That was closed cell. I went with 3" thick in my attic of my house and couldnt be happier. Much cooler in the summer and hopefully much warmer this winter. After i get my garage standing im going to check into getting it sprayfoamed. Sealing all the tiny ari gaps is one of the biggest issues in building and sprayfoam fixes that.

That's about the same price as here. $1/sqft/inch. $3 /sqft for 3" to get R19.


I think I'm going with 2" furring strips and R19 batt.

Q: can I put like 1/4" or 1/2" spacers in between the existing 2 x 4s and the furring strips to provide an air gap to help with thermal bridging?

 

[shawhite]

Might want to check with your electric company. Here in Florida my electric company gives large rebates for doing spray foam. They even have preferred vendors that will do all the paperwork for u and deduct the rebate upfront.

 

[Modern Jess]

Q: can I put like 1/4" or 1/2" spacers in between the existing 2 x 4s and the furring strips to provide an air gap to help with thermal bridging?

That's an interesting idea. I'm hard-pressed to come up with a reason why you couldn't do that.