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Attic insulation

15392 Views 12 Replies 5 Participants Last post by  creamaster
Not sure this is the appropriate room but...

Last year about this time in my newly purchased 35yo home I was dismayed to see how hot my attached 540sq attached garage would get. The drop-down to the attic is in there so I poked my head up.

Yep. No insulation. There appeared to be plenty of pink blown in for the rest of the house so I took myself off to Home-Despot to get some batts. I installed R-38 over the entire garage over the course of an afternoon.

I then called into work the next day recovering from heat-stroke LOL....!

But it dropped the temp in the garage alot. Somewhere in the range of 15-20F.

My electricity bills that summer were ridiculous. Or should I say outrageous?! In the range of $300+ a month. Anticipating this for the upcoming season I climbed back up there to inspect the duct-work and insulation. Besides the ducts needing repair I discovered the piss-poor application and depth of the blown in. In most areas it is 3" deep but in some spots it is much less and others about 5".

I'm toying with the plan to get some more R-38 batts and lay them cross-ways across the existing insulation over the main living area (500sq) where the thermostat is. This is where everyone spends 95% of the time anyway. I then plan to do the rest later.

One of the rationals for the batts is that I can do it by myself, it is easy, cheap, they can be moved around and they provide a more uniform application.

Ideas? Opinions?

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Since the blown-in insulation over your living space isn't very deep, look around underneath it to see if the attic was sealed before the insulation was added.

Batts of fiberglass really aren't as effective as blown-in cellulose. The cellulose fits into every little nook and cranny, which is not true with the batts.

I found that the fiberglass batts were more expensive than adding cellulose. That may not be the case where you live.
I checked already. No not sealed. If it was a blank slate I'd go with a 1" foam application and then an insulation. I saw some sort of blown in radiant barrier in my google searches. My situation is not ideal.

Could I use a leaf-rake to spread out blown in type insulation?


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I think it would be worth the effort to move the insulation around to seal things up. After I sealed my attic this past winter, I noticed a big difference in the temperature of the rooms on the main floor. It had been very cold near the floor, but sealing took care of that problem. That was even before adding any insulation to what was there.

I could be wrong about this, but I don't think it's too late to use the spray foam if that's what you want to do. You would just have to move the existing insulation out of the way, which would make it much easier to see everything that needs to be sealed.

This is just a thought (maybe not a good one, lol) but is it possible to move all of the loose insulation over to the space above the garage? Maybe you could use an electric (definetly not gas powered) leaf blower to push it?

Is the drop down access to your attic in the garage insulated and does it have a good seal on it?
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Got back from Blowes with 13 bags of the Greenfiber and 7 bags of R-30 batts. When it cools down after midnight I'll get up there and start with the Geeen-fiber.

Should be enough for R-13 over 500sq and then with the batts over that I should be pushing R-50 over the main living area.
Check all ceiling penetrations and caulk them, first. It will be a lot harder after the new insulation. Tape the duct work with foil tape, including the elbow joints. Insulate them as well. Tie batts on any skylights, caulk around any pipes, except gas flues. Don't cover can lights unless they are rated IC, OK to cover.

Use air chase baffles next to the roof sheathing, from the exterior wall in 4'. Be sure your soffit vents have a clear path to the baffles.

As GM said about the access door: Be safe, G
It sounds like you're in a hurry to get the insulation in. I can't blame you, but the insulation isn't really the only important issue here. Without doing all the things GBAR and I have suggested, you won't get the full performance out of your insulation. And because of that, your electric bill won't go down as much as it should.

I really don't know how much needs to be done, how much you've already done or how much you know about insulating your attic. Sealing it and adding baffles are important, but they're not life-threatening issues. But....what GBAR said about not covering the can lights (if you have any) is very important. Also, maybe this doesn't apply to your situation, but if your attic has a flue that vents the gas water heater or furnace, be sure that no insulation comes within a couple inches of it as it is a fire hazard.

I don't mean to lecture or rant, but it took me several months to get my attic to the point where it was ready to be insulated (I admit I'm a little slow, but there was a LOT to do). I'd hate to see you go to all the trouble and expense of insulating and not get the financial benefits or comfort level proper prep work will give.

Good luck with it. Let us know how it goes.
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My attic had the similar situation you are going through. Prior owners had spread some older wool type insulation between the joists but not uniformly and had stopped about 1/2 across the attic. The original batt insulation is 3". What I did was place in foam baffles in all the rafter spaces so the attic can breathe. Then took the greenfiber celluose insulation and hand ground it/bagged/lugged it up and used a wooden flat rake to speard it evenly acorss the entire attic to the top of the joists. Then I laid perpendicular to the joists, R 19 batt insulation over the enitre attic.

Im glad I didnt just use all blown in celluose, becasue my ceiling drywall had begun to sag somewhat just form the added weight of what I put in between the joists and I had to place more drywall screws, shoddy construction , also built in the 1960's.

Good luck with your attic, it lowered are heating bills alot and made the temps more uniform throughout the house.


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Good thing I didn't get very far in my efforts Saturday night. LOL I laid out 3 bundles (by hand) of the Greenfiber which was a PITA and then 11 batts. I left some space between the roof angle and the batts to encourage air-flow (thinking I don't need no stinkin baffles!) and called it a night.

Sunday I started checking the ceiling with the infra-red. With 95F outside the north-facing side of the ceiling was 80F. The South side with existing insulation was 80 also- and under the added insulated part was 78! But I was disturbed to find that on that side at the edge of the ceiling up to about a foot inwards the temps were 85!

I went and bought 20 baffles (will make 40?) and I'll redo what I've done so far. I'll install the baffles and push some blown in up against the angle and then push the batts further up against the roof- much like the pics creamaster posted.

Any special approach? I'll staple the baffles first. The baffles split length-ways. Can I use both or should I just use one as creamaster's/B] pics show?


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I'm not sure if it really matters one way or the other, but I used both. And since my roof doesn't have a very high pitch, I added another half of a baffle (cut sideways) on to the end of the full-length one. In the picture below, you can see the horizontal lines where they overlap. I did that so that when the insulation was being blown-in, it wouldn't get inside the baffle. With just one full-length baffle, there was only about 14" or so from the top opening of the baffle to the top of the batt insulation below.

Don't forget to block the gaps around the bottom of the baffles (like in the picture below) so the cellulose insulation doesn't work it's way down into your soffit. If you were in a colder climate, you'd want to make sure to insulate over the top plate of the exterior walls as well. I'm not sure that's an issue where you are in Texas. But maybe.

BTW, I'm curious as to how you spread the Greenfiber stuff around. Did you just break it up and toss it in place? Can you post some pictures?
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Manually spreading that Greenfiber is a real PITA. I would try to maneuver the block out to location and would try to break it up and spread it out with a rake. This didn't work very well and would leave big chunks. I'll do the garbage bag thing in the future. I'll see about some pics.
I did 3 bags manually over 1 cold room last fall, just to test the effect . I need about 35 bags and a blower is free for a day at HD if you buy 30 bags or more.
Best deal in town , with about $400 in material , I qualify for about a $750 energy rebate just for the attic upgrade from our Gov't.
No qusetion it's hard to fluff the stuff while breaking it by hand but I had a trick that helped. Since I have a 4- 12 roof pitch and can't stand up in the attic, I grabbed an 8' piece of 2" pvc pipe to sweep level with, using it like a big wand. This also broke some of the chunks by batting them but it did get a bit dusty. I also found it handy for holding down the batts above my top plates while tucking baffles over them.
Don't forget to check soffit ventilation in addition to the baffles. If you have the old style grilles which I still do, you may want to enlarge or increase the number of openings, there and at rooftop. There is a correct ratio of soffit to roof openings based on pitch and surface area and when done right it will help cool the attic properly, otherwise you will be fighting a funnel effect after all your insulating efforts.
Just think how hot your parked car gets in 5 minutes in the sun with the windows closed. It only cools when the air escapes.
The batts above your top plates should be maintained to help insulate the wall below.
Lowes should have the calculation table for venting in the roofing materials aisle where they sell the vents.:thumbsup:
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I went through aboutt 15 bags of the greenfiber, chunking it by hand, took along time! I used a yard cart and would break off handfull chunks then use a small handheld pronged weed rake to break it up into smaller peices then I would also use a regular metal pronged rake about 12" in width to really break/stir it up and fluff it. I went through several packages of N95 masks, you dont want to breath that dust too much. I would then dump it into a large garbage bag and lug it up to the attic. I would do like 4 bags then go up and spread it, rinse and repeat. Looking back now, I would have rented the blower, got a friend and blown/raked the crap and saved myself weeks of doing it by hand. My attic is roughly 1000 sq ft. Live and learn :)
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