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Old 03-11-2013, 11:56 AM   #1
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Insulation question


I am going to be adding additional batt insulation to my attic. Currently there is not much barely meeting the top of the 2x4 joists. I know your supposed to add additional perpendicular to what is there but can I go parallel? Also, for ceiling boxes for fans and lights can I go right over it with insulation?

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Old 03-11-2013, 12:14 PM   #2
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You would be best to air seal around the bath fan, any places that wires come through the top plate, and around any lighting fixtures or boxes that are up in the attic. After that is done, then have more blown in, until you either meet or exceed the R value, that is required by your area for insulation.

Adding batts can trap moisture if done with the wrong ones, or not even do anything at all other than drain your pocket book, if not done with the proper R value.

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Old 03-11-2013, 12:16 PM   #3
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You would be best to air seal around the bath fan, any places that wires come through the top plate, and around any lighting fixtures or boxes that are up in the attic. After that is done, then have more blown in, until you either meet or exceed the R value, that is required by your area for insulation.

Adding batts can trap moisture if done with the wrong ones, or not even do anything at all other than drain your pocket book, if not done with the proper R value.
I am adding unfaced batts so trapping moisture is not an issue. Ok as I said i am using batt not blow in. So, can you answer my question about adding it parallel or does it have to be perpendicular? I will using acoustical sealant around the boxes and recessed housings.
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Old 03-11-2013, 12:16 PM   #4
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Insulation question


there are clearances that MUST be maintained around pot lights and bath fans etc for the electrical and fire code/safety. I am not an electrician but you may want to post a question in the electrical forum at the top of the page about what they are. there are also forums for carpentry and construction for the insulation question. may speed up the time it takes to get an answer if you post there too.
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Old 03-11-2013, 02:11 PM   #5
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Insulation question


I am not an expert but my 2nd layer of insulation is going the other way, i think it would be better. i am also going to blow in some to get up to R-60.

As far as lights go, and fans boxes keep the insulation back about 3 inches unless the light has IC stamp on the top then you can cover it.
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Old 03-11-2013, 02:28 PM   #6
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Insulation question


If I was adding batts to an attic, it would be perpendicular to the joists to eliminate insulate the wood to prevent thermal bridging.

Also, I wouldn't be laying batts in my house and would get it blown in.
Its cheaper to just get it blown in than batts because batts are more expensive, it would be done in a couple of hours, etc. (after all the sealing ofcourse)
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Old 03-11-2013, 03:32 PM   #7
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Merged threads.
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Old 03-11-2013, 04:24 PM   #8
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You can put it in any way you want. The reason for going perpendicular is to minimize thermal bridging at joints. There are no joints in blown in so its not an issue, thats what the others are trying to tell you.

I suspect you are talking about the lower chord of trusses being 2 x 4's. I did not think that anybody put R-11 in ceilings, even with trusses. House must be really old or minimally built.
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Old 03-12-2013, 09:35 AM   #9
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If you are glutton for punishment, do the batts. If you want to do it easier, just get it blown in.
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Old 03-12-2013, 12:13 PM   #10
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If you are glutton for punishment, do the batts. If you want to do it easier, just get it blown in.
cost is too much.
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Old 03-12-2013, 12:59 PM   #11
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http://www.energystar.gov/index.cfm?...sulation_table
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Old 03-13-2013, 08:12 AM   #12
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cost is too much.
How much is your time worth?

You will need to figure that into your analysis of cost vs. expense.

Blown in insulation is also a bit better (cellulose) at preventing convection and getting installed properly.

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