Photo Explanation of my Floor, with bonus insulation excitement

[shadesofmauve]

Yesterday I planned to fully insulate my floor, so I could have a framing/insulation inspection done Tuesday, and get actual subfloor down this weekend. Slightly complicating this, I was also engaged in some familial diplomacy/trade, which is to say I was required to employ my brother, funded by my parents, so that he'd be out of the house doing something useful and my mother wouldn't kill him.

Starting the day, I figured I'd have A drive me out to get insulation, then I'd send him out again to get more (since the Escape would be full), with cash or a gift card or something. I was actually pretty pleased to have him driving, 'cause it just exhausts my foot, lately.

Anyway, we ran my grocery errands just fine, then ran into a wall at Home Depot. They didn't have any unfaced fiberglass batt insulation. They didn't have any unfaced 3.5" thick fiberglass insulation at all! Since fiberglass insulation is still the simple, cheap standard, that was unexpected. We trucked off to Lowes... where they also didn't have it.

Apparently no one stocks unfaced fiberglass anymore. Whut.

At Lowes, though, we found a different kind of unfaced batt -- Rock wool. I only knew rock wool as the crappy fluff in old attics. I've shoveled it, but it didn't show up on my research radar as a current thing at all. So I had a bit of a dither in the aisle at Lowes, sitting on my ass (because screw this standing thing), frantically googling 'rock wool batts' and calling emony42 to google rock wool batts and calling my dad and generally trying to figure out if this shit would work or was a disaster.

(Brother did a bit of googling on his phone, then pushed himself around on the trolley. I don't blame him. It looked kinda fun.)

My other options were special ordering fiberglass, using some kind of rigid foam, or potentially blow-in. All would take more time, to research, order, cut-and-fit, etc, and possibly more money.

I should note at this point that my floor assembly is weird, and my standards are high, so I wasn't even exactly sure how to get what I wanted with fiberglass -- I was just going to buy the first few bags and wing it, see where it got me. I bought a bag of the rockwool batts, instead, and we took it home to experiment.

PLOT TWIST: Rock wool works really well for this, actually! Look at the bit laying under the joists nicely there:



That insulation is between 1" and 1.5" thick, and I got it from a 3.5" thick batt by filleting it with a bread knife. The Rockwool is dense enough that it pretty much sorta works. In retrospect, I've no idea how I thought any of my earlier plans would succeed -- I was going to have to rely on stacked 2" thick fiberglass marketed for craft projects to get anything under the joists, and that would've been a pain in the butt..


Here you can see the wall, the joists attached with hangers, and the sleepers running perpendicular to the joists underneath. The black plastic underneath everything is the vapor barrier, which sits on the concrete slab of the original garage floor. The white frosting dribbling along the base of the wall is spray foam insulation, which hopefully does a bit of air sealing between the cement foundation and the wooden sill plate. Another layer of insulation will be laid down in the joist bays, perpendicular to the current one.

That last pic is about as much as I got done yesterday. I knew I couldn't manage to get the whole thing done, since I started hours later than planned, so it made more sense to do a sample section. The inspector will still come out tomorrow to check over the framing, and hopefully he'll give the insulation plan the go ahead then, too. If he doesn't, I'll have less to rip out...

Comments

[tersa.livejournal.com]

SENSE-MAKING.

Also, although having a curveball thrown at you when you've planned things to the Nth degree sucks, I'm glad it may be working out for the better this way!

[shadesofmauve]

Yay!

The end result is looking pretty good, I think! I just wish I had a bit more equanimity when dealing with curve balls, and could work through them a bit faster, rather than wasting 45 minutes wandering around the hardware store. I like to be well researched and prepared, though, and I think that plays into the slow response to sudden changes.

[t-c-da.livejournal.com]

A pity we can't help with the insulation...

Yesterday a friend of ours who works at BRANZ (remember them?) rang to say they had stacks of insulation that remained from some testing they had been doing, and it was free to a good home as long as you took it away by 4pm. I'm supposed to be Working from Home (as our building is still OOB due to earthquake problems alluded to on FB), so a quick trip to the tip to empty the family trailer, collect $wife from her work and blat over to BRANZ to collect a trailer full of loft insulation. Some of which would do very nicely for quilting, being poly rather than fibreglass, thank you very much!

The plan is to install some in the ceiling of our master bedroom RSN (once we have covered the cost of backyard renovation...).

[shadesofmauve]

Yes, the research place! :D Good place to have a friend, I'm thinking. Sounds like a score!

[solarbird]

Rock wool has been on my radar for a little while. In heat-insulation form, it's higher R-value than fibreglass at the same thickness, and as bonus provides some sound insulation! (Fibreglass provides exactly zero sound insulation, so that's not saying much, but I'm told it's enough better to matter.)

In sound-and-fire insulation form, like here (note R-value of zero), it's got a good rep with studios. I'm thinking of buying some to make form-fitting inserts for my studio's windows.

So you might want to consider replacingny fibreglass in the walls in favour of the thermal rock wool version. It's a little more expensive but you get some sound resistance as well as a higher R-value. Maybe you could do a layer of the thermal plus a layer of the sound?

(eta: I overgeneralised; ordinary thermal fibreglass insulation has about zero sound resistance. There are fibreglass-based products which do have sound dampening qualities, however.)

[shadesofmauve]

I read about the studio uses when I was doing research yesterday -- pretty interesting, though reports varied on the sound efficacy. So many noise-deadening products are so ridiculously intensive expensive that even something that goes a little way seems worth it to me. I'm really curious about the R value of zero, though -- the safe-n-sound is smaller than a 2x4 wall, so it leaves an air gap, which makes R value vanish... but that'd usually be counted in the value of the total assembly; it wouldn't count against the product. I suspect it's partly the density -- compress the stuff and the air stops being your insulator and all that.

The R value as compared to fiberglass per inch was kind of funny. Standard fiberglass is worse, but the newer higher density glass has less difference -- both are R-15 at 3.5 inches wide, but the rockwool edges ahead at 5.5. I assume that means that it's consistently just a tiny bit better per inch, but you need it to add up before it 'rates' because they're looking for an integer. :P

Anyhow, if you make studio window inserts, don't believe anyone who tells you won't itch. It should definitely be enclosed somehow, and you should do the normal mask/longsleeves routine you would for glass. It's MUCH easier to cut to shape, though!

[solarbird]

Yeah, it's the compression. Fibreglass is the same way - compress out the air, no insulative value. In both cases, it's about the trapped air space. A rectangular balloon is R-1, more or less; each additional air layer is another R-value, again, ish, and in both cases, assuming no other insulative value in the materials, which, of course, is inaccurate.

And, absolutely, enclosed. The good things about big rectangles are that sleeves are easy to make and cheap fabric is all you need. And I have a sewing machine! Everybody wins. :D

[shadesofmauve]

I responded to the unedited version of your comment; oops!

I'm thinking about rockwool in walls. The bit of vapor retarder the facing on batts provides is actually necessary there, so if I was to use rockwool it'd mean adding a separate layer, but it's doable. Have to see how much the stuff sets me back for the floor, first -- it's not much more spendy, but it adds up. For now, the thermal version is going underneath my floor, unless the inspector says otherwise tomorrow!

[solarbird]

Yeah, you don't need sound insulation in the floor, unless it's above another space where you don't have control over the noise, or you have Mole People or CHUDs or something.

[shadesofmauve]

Pfft, the mole people living under my garage are going to give me sooo much less crap now that I've insulated the floor/slab with rock wool! Those squares must go to bed at, like, 7. They're always complaining about the music.

[t-c-da.livejournal.com]

Just watch out for The Carpet People!!

[shadesofmauve]

I haven't read that one! I'm remiss in my Pterry reading!

I need to put that and the Science of Discworld on the list for when I have free time again. :D