attic insulating question

Old 11-20-14, 01:27 PM
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attic insulating question

My son owns a rental property (a house) in Columbus, OH and it has no insulation in the attic. It is an old house, built in the 1920's, I believe, so I'm amazed that the attic has not been insulated.

The attic has some old electrical wiring in it and my son is concerned about covering the wiring with insulation. I think part of his concern is simply that the wiring would not be visible if the need to replace it arose. If one layer of batt insulation were installed between joists, I think a gap in the batt insulation could be created where wires are running through the joists and another type of insulation, such as foam or cork, could be placed there under the wiring to connect the ends of the batt insulation and prevent a completely un-insulated section. Does this sound practical?

Also, I believe building code here might call for a second layer of batt insulation to be to laid over the first layer, perpendicular to the first layer. If that were done, everything under it - joists, wiring, etc. - would be hidden. If someone needs to enter the attic then to work on wiring or whatever, how do they navigate the attic when they can't see joists?
Old 11-20-14, 01:36 PM
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What type of wiring is in the attic? the old knob and tube wires need to be left exposed ... or better yet, replaced. It's not hard to find the joists when 'crawling' thru the attic, especially if you've been in attics before. The joists are almost always on either 16" or 24" centers.
Old 11-20-14, 01:37 PM
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Are there any junctions in the wiring? If not, I would think it would be ok to cover as long as it's not K&T, as Mark mentioned.

Additionally, the first step should be air sealing since there is currently no insulation in your way to do so.
Old 11-21-14, 07:39 PM
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A few years have passed since the last time I was in that attic and I can't recall for sure whether the wiring is the old K&T. I think it is not, but I'd need to see it again to be absolutely sure.

Regarding "air sealing", I gather you mean searching for air leaks between attic and rooms below and sealing them. Is that right?
Old 11-21-14, 08:15 PM
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Air sealing involves all of the obvious leaks where plumbing and wiring pass through the ceiling plane, but also the many other much smaller leaks that add up to being a big hole. Leaks into the attic are a combination of energy lost and moisture problems in the attic. Those leaks also must be replaced which involves cold air coming in from lower leaks and often basement or crawlspace air reaching the living spaces. Related link attached.

As for burying anything under layers of insulation, simply attach a sign to the rafters above with an arrow and an explanation.

If the old wiring is K&T, now is definitely the time to have it removed and replaced with proper wiring. Leaving it under the new insulation would be a fire hazard and code issue. Even insulating around it, leaving it exposed subtracts from the homes value and will ultimately need to be replaced.

For the code required insulation levels check the following link: How Much Insulation Should be Installed - About Insulation : NAIMA North American Insulation Manufacturers Association

R-38 looks like a bare minimum, especially since half of that would lose r-value being between the rafters. And neatness counts.


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