Oh, blow it out yer…

15 Jul

Wow, what a season this has become.

Extended road trips, “bumps and thumps” and just general mayhem! LOL!

I’m back home now, finally.

(My 5 year old son threatened to take my truck keys away from me. “NO MORE COLORADO!” he shouted as he literally threw himself into my arms and scolded me for being gone so long. I literally teared up to know that he’d missed me so much. Autistic kids don’t “attach” like “normal” kids. So, when he throws himself into my arms and tells me that he loves me or that he missed me terribly, it’s really an event.)

Okay… deep breath…

While I’m getting resettled, I thought I’d address a question that I have been asked several times lately.

MANY ISBU families install a dropped ceiling in their containers to allow for ductwork, electrical runs and plumbing.  Most of the time, this dropped ceiling is made of OSB (Oriented Strand Board) sheets suspended using rafters. This is a very conventional/typical method easily handled by building families.

Many of these families are building in “my neck of the woods” (the Northern US) where temperatures drop dramatically in winter.

So, this leads to a review of insulation practices.

Regular readers KNOW that I prefer SPF (closed cell Spray Foam) insulation over literally EVERYTHING else, when it comes to keeping that box warm and cool. SPF fills in all the nooks and crannies, creates it’s own vapor and moisture barrier, resists insects and rodents and even makes the box stronger. You shoot it on, it stays where you shoot it and it doesn’t break down, settle or drift.

At R6-7 per inch, applied SPF simply can’t be beat. You spray it on, cover it up (siding or paneling) and forget about it. It’s just about as “low maintenance” as you can get.

However, it doesn’t come without a price. It IS decidedly more expensive.

That said, some families elect to insulate the old fashioned way using fiberglass batts or cellulose (either blown in or “broadcast”).

“Ronin, I can’t afford SPF, but I need a high performance insulation package that I CAN afford. Got any tricks?”

Regular readers KNOW I despise fiberglass batts. They break down over time. They don’t respond well to moisture should you accidentally get them wet (say… in a bad storm) and they don’t respond well to diverse temperatures.

Fiberglass batts aren’t really anything more than really thick furnace filters, IMHO. Warm air migrates through them. Falling temperatures cause them to lose their R value (by -20F they lose half their installed value).  While fiberglass is “cheap and easy”… you get what you pay for.

Many opt for cellulose. Cellulose actually GAINS R value as temperature drops. But to do a big ceiling, you have to buy a LOT of it… That adds up.

So… if you’re on a really tight budget, I’d submit that you can COMBINE fiberglass and cellulose to build r values inexpensively.

Are you gonna get away from using  SPF? Nope! LOL!

Get a spray can or two of SPF (spray foam) and seal up every crack you can find in your ceiling on the OSB surface. Then install your fiberglass batts in the traditional manner. THEN…

… blow in or broadcast a layer of  cellulose OVER the top of the installed fiberglass batts.

You can buy bags of cellulose insulation at the big box stores inexpensively. Blow it into your ceiling cavity or just cut the bags open and then “broadcast” (spread by hand) it yourself over the fiberglass batts to build the R value you require.

TIP: You CAN usually rent a cellulose blower from the same store you buy your cellulose from. It isn’t that  expensive, and it’s not rocket science. If you can rent a blower, DO IT. It’s going to help insure that you get good insulation loft and good coverage at a very high rate of speed. Doing it by hand is possible, but it’s slow and tedious. 😉

Loose cellulose spreads at a rate of about 1.5 pounds per cubic foot. I’d personally add at LEAST a foot (thickness) of cellulose to the top of the fiberglass batts, if it were me making the call. I want as much R value as I can get into that space.

You’ll need to do some math to figure out how many pounds of cellulose you’ll need, dependent on your ceiling size.

Insulating your ceiling in this manner will GREATLY improve your (basic) fiberglass insulation R values.

I can’t stress highly enough that you want to seal up all the leaks into the ceiling from below. The more hot air movement you stop, the better your insulation will perform.

It is very important to have very good seals around the edges of your ceiling structure. In winter, the greater the temperature differential between the house and attic, the more “stack effect” air leakage there will be. In other words, the better you insulate, the more tendency there will be, for house air to rise, and the much colder attic air to drop down, through the cracks. So definitely, give that proportionate attention. Use that SPF in a can to seal up the area around your ceiling electrical boxes in the attic.

For sunken ceiling fixtures we build a small insulated enclosure using rigid insulation (you can buy it by the sheet at the big box stores) to box them in. You can use duct tape to build your  box, but we then turn it upside down and then shoot some SPF into the seams to insure that it stays air-tight and together. (The SPF will “glue” the rigid insulation box together.)

Note any requirements for venting and any collected heat distribution as you do this. Some sunken fixtures require a way for collected heat to be exhausted safely. Pay attention to the little details and they won’t come back to bite you on the butt later! 🙂

More later, stay tuned!

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One Response to “Oh, blow it out yer…”

  1. observeandreport69 July 15, 2013 at 12:24 pm #

    Big Fan- Please find the attached in regards to a heating solution. I am not a salesman, there are a few brands that offer similar products. Heck, all the low resistance films may be made in the same factory in China. Bottom line: its cheap to operate and install. No moving parts . Low energy densities . Good Luck!


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