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Old 06-17-2014, 11:10 PM   #1
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Attic blown in insulation


Hi all. Been working on a 1904 fixer upper in Chicago for the past year and am now in the midst of new roofing/attic insulation phase. I have about a 600sqft unvented attic (2x4 rafters, no soffits) that previously had batts in the rafter bays and was somewhat partially finished with a wood panels on the rafters and walls and a plywood floor.

I took out all wood panelling and old batts (man that was a chore--2,500 lbs of materials), had my rafters strengthened in preparation for a new roof and will be pulling up plywood floors after the roof is done and blowing in insulation. (FYI will have power vent in attic installed during roofing project)

I'm probably going to use attic cat. Had a few questions:

-I have one area with a main plumbing stack and electrical conduit--besides sealing any exposure with Great Stuff, would you recommend putting a barrier around this area so blown in insulation isn't all around it or is it better to have settle around that area?

-do I need to protect any wiring here that leads to 2nd floor? Electricians did run new wiring to 2nd floor through attic floor (no can lights in attic floor)

-I have an attic pull down ladder. After doing some research it seems like building a box around opening might be my best bet. I was thinking 1x12s--resting on 2x4 joist would give me up to 16"

-it looks like r49 is recommended for this area. 16" wouldn't quite get me there. Is it a huge leap between r40 and 49? Whatever r value should be a huge improvement to not condition my large attic area.

Sorry for the long post. This is only my second so can't quite post pics yet.

Jay

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Old 06-18-2014, 07:44 AM   #2
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Attic blown in insulation


Shouldn't need to protect wiring as long as it is good shape. The foam is basically plastic and non-conductive.

You can build the box out of foam if you want. They don't need to be that sturdy as long as you don't abuse them.

R40 is ultimately sufficient but going from R40 to R49 is cheap, cheap, cheap. Just do it.

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Old 06-18-2014, 05:41 PM   #3
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Attic blown in insulation


Thanks for the reply. What kind of foam would you suggest for building up around the attic stair opening? Also, would you recommend just having a batt over the top? Owens Corning sells a pup tent looking cover but it's only r-10. Regardless, I have to have a 12 to 14 inch high box around the stairs unless I want insulation spilling out when I open the hatch next.

Also--do you recommend just blowing all around the plumbing stack or building a box around that for less messy access in the future. Will be sealing any exposure to the 2nd floor around the stack either way. I do plan on replacing old cast iron stack in a couple of years and also running up an additional stack for the future when I can afford to turn my attic into living space. Would be a little easier to access existing stack without insulation covering it but i suppose it can easily be raked aside.

Thanks much.

Jay
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Old 06-19-2014, 12:38 AM   #4
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Attic blown in insulation


Rigid foam for the box.

Done bother with the boxes on the plumbing stacks. Just seal them.
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Old 06-20-2014, 12:45 AM   #5
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Attic blown in insulation


Following, thanks
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Old 06-20-2014, 02:04 PM   #6
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Attic blown in insulation


Is there a reason that you are using blown fg? Cellulose is cheaper and will deliver a superior r-factor. At 3.7 per inch you get r-59 from that 16".
Re: the electrical, its all good as long as you don't have any active knob and tube wiring left in the home (given the age I'd suspect that it did at one time).
On the attic hatch, see what you can do about adding some weatherstripping in addition to the box and insulation.
Wow's recommendations are spot on.
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Old 06-20-2014, 02:29 PM   #7
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Attic blown in insulation


Don't bother with Great Stuff. Get the two part foam and airseal the entire attic. Rim joists, light fixtures, all wiring, etc. The tanks look like propane tanks, and you run a double ended hose to them. No point in insulating if there is still air being exchanged between your upstairs and the attic. The stuff stinks to high heaven (you'll need a GOOD respirator), but is absolutely worth it. I did the entire attic a few years ago, before using blown in cellulose. It made a huge difference.
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Old 06-20-2014, 04:46 PM   #8
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Attic blown in insulation


Quote:
Originally Posted by mnp13 View Post
Don't bother with Great Stuff. Get the two part foam and airseal the entire attic. Rim joists, light fixtures, all wiring, etc. The tanks look like propane tanks, and you run a double ended hose to them. No point in insulating if there is still air being exchanged between your upstairs and the attic. The stuff stinks to high heaven (you'll need a GOOD respirator), but is absolutely worth it. I did the entire attic a few years ago, before using blown in cellulose. It made a huge difference.
Good advice....
I'd also add that an energy audit would not be a bad idea testing before and after the work. There is a host of safety issues that you can run into when you seal up your home from the ramifications of combustion appliances to indoor air quality. It should only cost you a few hundred bucks but it will be huge peace of mind, and perhaps prevent a dangerous situation. Doing the insulation/air sealing DIY is where you save the $$$.
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Old 07-07-2014, 02:18 PM   #9
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Attic blown in insulation


All,

After much work in the attic pulling out old insulation and plywood flooring, I'm ready to air-seal before blowing in insulation onto the attic floor. When pulling up the plywood floor I encountered a few areas where the plaster and lathe doesn't extend flush against the joists in the attic. See attached pics. The first is I believe a look at the closet ceiling and the second is against the exterior wall. What is the best way to air seal these sections?

Attic blown in insulation-image-230166498.jpg



Attic blown in insulation-image-1435137257.jpg
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Old 07-07-2014, 02:42 PM   #10
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Attic blown in insulation


Rigid foam cut to size, seal around the perimeter.
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Old 07-07-2014, 02:43 PM   #11
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Attic blown in insulation


I wadded up newspapers and stuffed them in the hole, then put the foam on top of the newspaper. This gave the foam room to expand without endangering my plaster and lathe, but also didn't waste the foam.

How deep are the notches in the joists for that conduit?
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Old 07-07-2014, 04:22 PM   #12
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Attic blown in insulation


Most of the notches just exist in furring strips on top of the joists. There are a few locations where a hole was drilled into a joist. The attic had been partially "finished" for years on top of 2x4 joists with batt insulation underneath LOTS of wood panelling in the rafters and walls. Took a lot of elbow grease to get rid of all that work. I eventually would like to turn this into a master bedroom but that is many years down the road. Will do it right with properly sized joists etc when I get there. The attic in our 1904 home is def not engineered for a liveable space as currently built. Here's a pic of some of the initial demo to get it that point. I'm only 37 but man my body took a beating getting to this point!

Attic blown in insulation-image-2193123540.jpg

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