Shop Buildout: Part 4 – Wall and Attic Insulation

Welcome back to Farbulous Creations! I’m Ron Farber-Newman, and this video is the fourth video in my garage shop conversion series, as I work to convert a standard two garage into my dream shop. In this video, we’ll focus on insulation, both wall and attic insulation. A contractor who does this type of work everyday could probably have this work done in a weekend, but for me it was a multi-month process, as 1) I was doing the work in my spare time in the evenings, and 2) many parts of the garage process were happening asynchronously.

But let’s head back to August when I kicked off this work, and I’ll give you some more background on my the decisions I made along the way!

So in my last shop video, I talked about how I had some experience with electrical work, giving me the confidence to do that work myself. Insulation work seemed un-intimidating enough, but I had never done it before so I did plenty of research and YouTube learnin’ to make sure I knew what I needed to know to make educated decisions along the way.

One of the first decisions I needed to make was how exactly I wanted to insulate the attic space of the garage. A few YouTubers I follow, such as Jay Bates, decided to insulate their shop’s attic space with spray foam insulation directly on the roof sheathing. That seemed appealing to me, as it would have allowed me to leave the attic space open to the rest of the room below without a formal ceiling in there, allowing me to potentially store lumber up there. However, I decided it wasn’t the best option for me despite being a good option for him.

One reason is my location. Jay is in Mississippi, where the primary goal most of the year is to keep the extreme heat from the sun beating on the roof from getting in. And, since it doesn’t get as cold, warming an enclosed space in the winter isn’t very hard there.

For me, being in Minnesota, we get both extremes of temps, from high 80’s and 90’s in the summer to low teens and negatives in the winter.

Since you’re battling the thermodynamic fact that heat rises, you want as much insulation R-value between the non-conditioned, non-heated air in the attic and the heated room below as possible. Spray foam insulation, even sprayed thick at 5 inches would only provide an R-value of around R-35. And it can be expensive since it’s not really a task you want to DIY. I didn’t have any formal quote performed, so this could be wildly inaccurate, but from searching around, it seemed like it would have cost around $2500 or so to have my roof spray foamed. Using fiberglass batt insulation, I could achieve a higher R-Value of R-49 AND do it myself, for only around $900 – the cost of enough R-49 insulation for my sized attic. The other option for attic insulation was blown-in insulation, which might have actually been a bit cheaper than batts, but I decided that while I don’t ever plan on needing to get back in the attic for additional electrical or duct work, it would be a lot easier to take a batt or two down to get access to the attic than the inevitable mess that would result from trying to cut through the plastic barrier holding back blown-in insulation.

So… that was a lot of background on my decision without really explaining what I’m doing in this footage you’ve been watching. In my research on how to properly insulate, I learned that attic ventilation is arguably the most crucial part of the insulation process. Without proper airflow into and out of the attic, all kinds of problems can arise – the biggest issue is that during the summer, your roof can get so hot that shingles start warping, which will seriously shorten the lifespan of your roof. In the winter, if the heat that does manage to escape past your insulation is allowed to build up, it causes the surface layer of snow to melt and cause ice dams and icicles along the roofline. While pretty and festive, they’re a sign of an attic space that isn’t properly ventilated. To account for this much-needed airflow up there, one of the best ways to get it is to have vents on the soffits of your roof’s overhang that bring fresh air into the attic to create the positive pressure needed to push the warm air that would otherwise accumulate up through the vents in the roof.

The roof overhang on our house has vents precut and built into the eave sheathing itself, but the garage did not, so I had to install them, and that’s what I’m doing here. I ordered these 4 inch by 16” white eave vents to match the white paint of the eave itself. I then determined the center-point between the roof joists and cut a roughly 2 inch by 15” rectangular hole in each joist bay. I would have liked to make a bigger hole, but because of the pitch of the roof and the limited overhang, that’s the maximum hole size I could muster without running into the 2×4’s of the framing itself. Since this was such a repeatable process – and I had to do it 22 times, I made myself a “story stick” with the hole’s width and distance from the house cut into it to easily mark my location on the eave for where I would drill my starter holes, before coming at it with my reciprocating saw. These rectangular holes at times came out a bit ugly and not perfectly rectangular, but since they would be covered up with my eave vent, I wasn’t super concerned about how perfect they looked. I used small self-tapping screws to secure each vent in place. It’s worth noting that these particular vents have a built-in screen on the backside to prevent bugs from getting in too.

Back on the inside of the garage with all of my eave vent holes and covers installed, it was time to install some rafter baffles. These are also super important to proper ventilation. What they do is provide an unobstructed channel for that air to travel up into the top of the attic. You may be wondering, why is that necessary? Well, once insulation is installed, that insulation could very well block the flow of air from the eave vents up into the top of the attic where it’s needed, as it’s not uncommon for the insulation to get pressed right up against the roof sheathing. With these installed to keep the insulation from blocking the path of airflow, the eave vents can do what they’re designed to do.

After the rafter baffles were installed, I could get started on the wall insulation – but not before doing some quick spray foam behind the outlet boxes and various places that could use a little sealing up. I don’t know if there’s a better way of working with this stuff that I don’t know about, but it was pretty messy for me, haha. I also underestimated how large it would expand to, requiring me to cut a bunch of it away later once it cured. Oh, and I didn’t realize that there’s a special version made for door and window casings that expands slower, so by putting it around the door frame here like I did, my door didn’t want to close properly later after it had expanded and cured. I had to install a few screws on the inside of the door frame to pull it back in the other direction. Live and learn [AND THEN GET LUVS?].

Okay for real this time, time for wall insulation! Few things in life are as satisfying as opening a package of fiberglass insulation, as it quickly expands to its full uncompressed size, after being oppressed by the plastic bag for who knows how long. The installation is fairly straightforward and quick with this stuff, as it comes in the varying widths to fit the type of construction you might be dealing with. In my case, I was working with 2×4 framing on 16 inch centers. So I used 15 inch wide insulation in R-15 – the highest R-Value available for 2×4 framing – with kraft backing. All you do to install it is place it snuggly in the wall cavity and staple the kraft paper wings to the studs on either side, pulling to stay taut and tight the entire way up and down the wall. I used a combination of a hammer stapler and a regular stapler where I didn’t have enough room to be accurate with a hammer swing, such as at the bottom of the walls.

In wall cavities that had wiring running horizontally, I split the insulation in half and sandwiched the wire between the two halves. In cavities that had an outlet, I used my utility knife to cut away the kraft paper and the insulation to make room for the outlet.

One other consideration I had to make regarding wall insulation was the fact that my walls in the garage are 9 feet tall. Just one panel of the R-15 didn’t cut it, as the pre-cut batts only come in 93 inch lengths (that’s 7 and 3/4 feet for those playing at home), meaning I was 15 inches short at the top of every cavity. Now sure, I could have just cut the 93 inch batts that come pre-cut, but the R-15 insulation I was using here also came in 24 foot rolls, so I wanted to figure out which one made optimal use of materials so I didn’t order more than I needed. Being a pretty visual person, using my planning document, I performed the Adobe Illustrator equivalent of counting on my fingers and toes and determined that three 24 foot rolls would serve me better (and be cheaper) than buying additional 93 inch precut packs AND produce less waste, so that’s what I went with.

Cutting the insulation to fill these 15 inch voids was pretty straightforward. I found it easiest to press the insulation as flat as possible along the cut line with one board against another board, and then use a utility knife to make multiple scores until it was fully cut. One thing I can’t recommend enough for this type of insulation work is to get a utility knife with easily swappable blades, as fiberglass can dull a blade in no time. I bought a nice pocket-knife style folding utility knife that made it super easy to swap out blades. Just maybe reinforce the spare blade canister with some packing tape like you see here, as I dropped mine off my ladder at one point, causing the new, unused blades to go everywhere, and then I carefully had to repackage them in the case without cutting myself.

Installing these mini pieces of insulation went just as quick, and I overlapped the kraft face from the top panel slightly over the edge of the bottom panel, just like you would do with shingles or siding.

In some areas that were otherwise tricky to work with, such as below the breaker panel, I disassembled the insulation and installed it piecemeal – installing a few back panels of insulation between the horizontal 2x4s before covering the whole assembly with a thinner than usual kraft-backed piece.

After getting all of the wall insulation up, I could finally start getting the ceiling insulation up, which was important if I wanted to be able to start using the heat function of my new ductless mini-split unit as our autumn temperatures started to drop.

And as I began to open the outer shrink wrap of the ceiling insulation, I made a startling discovery, that’s especially frustrating when I look back at how I’ve lamented about pre-ordering all the supplies that then got in my way. And you know what that was? The ceiling insulation that has been in my way for the past 11 months was the wrong size! I accidentally ordered 16 inch wide R-49 instead of 24 inch wide R-49, which is how wide my joists are. They are not a sponsor, but thankfully I ordered all of these supplies with my Home Depot credit card, which meant the normal 180 day return window got extended to a year. So I got really lucky, as that would have been around a $900 mistake. Sure I could have probably sold it on Craigslist, but I doubt I would have got what I paid. So I returned it and promptly ordered the correct width, which got delivered a week later.

Getting the R-49 installed was pretty easy, and a very similar process to installing the wall insulation, except you’re stapling up above you, rather than straight out on the wall in front of you, making it awkward at times. I did observe that the “accidentally ordered R-49” was 16 inches wide instead of 15” wide like the wall insulation was, and that this was 24 inches instead of 23 inches – I think for wall insulation they take off an inch to make it exactly fit the space between the studs, but for ceiling applications, they leave the extra inch to make the fit nice and snug so it’s not falling down at you while you try to install it. The first strip of R-49 was kind of annoying, as it was the end joist space, and not as wide as the standard 24 inch bays, which meant I had to cut it down the long side. But otherwise, it was a breeze, and easy to maneuver despite its increased volume compared to the R-15 – thankfully they limit it to 4 foot lengths, as I imagine it would be too heavy to easily manipulate if it were made in longer lengths. So the R-49 outfitted the center-most parts of the ceiling, but the pallet I ordered was only able to cover 384 square feet, and my garage ceiling was slightly larger than that. Here’s how I decided to contend with that. The very edges of my ceiling against the two walls where the roofline tapered downwards weren’t tall enough to receive the full height of R-49 insulation anyway, so I decided to buy a few rolls of R-19 insulation in the same 24” widths to fill these remaining spaces – quite like how I used rolls of the R-15 to fill in my gaps at the top of the walls. But the R-19 insulation, while it fit closest to the wall, still had a decent amount of space above it on the edge where it met the R-49 insulation. To account for this, I got a little scrappy, literally, and used all of my cut scraps from the wall insulation and ceiling insulation – which I had saved in a garbage bag along the way – to fill in these voids before moving onto the next joist bay. I thought this was a good way to use my scraps while optimizing the insulation in these areas.

For the final two end pieces – the keystones of my ceiling insulation if you will, I used a spare R-49 piece, cut in half, and then into two very crude trapezoids to fill in the space in a similar way, without being able to access it from the side.

And right as I was finishing my ceiling insulation work – I got to see its effectiveness in action. We got about 5-6 inches of snow when I had just 1-2 joist bays left, but since it was a tad chilly, I had the heat on in there, despite not being all the way done. Looking at the garage roof from the house, you could clearly see the outline of the joists bays with no insulation melting the snow, and the rest of the roof was otherwise unmelted. After sealing those final bays up, the melting stopped and I could finally start leaving the heat on low in there to make it always ready for me to come out there to work.

So that was a doozy, filled with what might have seemed like too much information, but I figure there’s enough DIY videos out there on this type of topic that tell you what to do or what they’re doing, without really telling you WHY they’re doing it the way they are.

So hopefully you found my thought process useful if you find yourself doing this type of project or needing to make these same decisions for your own DIY insulation project.

With that, let’s end this video here, and in the next video in the series, we’ll cover wall and ceiling coverings, as well as touch on the mini split briefly. I know a lot of the plywood work was done and visible in some of my footage throughout this video, but a big, multi-faceted project like a garage finishing often has many parts happening at once, so if it sometime seems like we’re taking a step back to look at something that already appeared done in a previous video – it’s because we kind of are. Hope that’s okay.

So stay tuned for that, and until next time, cheers!