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Venting and Insulation for Semi-Vaulted Ceilings


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I inspected a 120-year-old house today with semi-vualted ceilings on the second story. Inspection of the attic revealed blown-in insulation packed in the vaulted portions of the ceilings and piled over the flat section of ceiling. There are no roof vents of any kind.

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This shows the insulation.

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At the edge of the flat section of ceiling, the insulation is packed into the rafters diagonally down along the vaulted portion of each ceiling. Yes, I see the knob-and-tube entering the insulation. It is reported by the owner as being disconnected. I'll recommend an electrician inspect it.

This is the first situation like this I have seen. Is it recommended to pack insulation into a vaulted ceiling like this? What sort of venting would you recommend? Anything else you might suggest?

THanks!

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If it's new construction it's a disaster, but I've not found major issues with this situation in old buildings.

Old growth lumber, the generally loose nature of construction (drafty, easy vapor transmission), minimal to no vapor retarders to retain moisture, etc., make for few problems related to condensation. That's my experience anyway.

I'm reasonably sure there's some condensation in there somewhere, but I'd tend to doubt it would be a big problem.

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Yes, I see the knob-and-tube entering the insulation. It is reported by the owner as being disconnected.

Regarding the knob and tube, I have heard that more times than I can count, and it is often not true.

The lack of venting is probably not a big deal. A couple gabled end vents may be worthwhile.

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If it's new construction it's a disaster, but I've not found major issues with this situation in old buildings.

Old growth lumber, the generally loose nature of construction (drafty, easy vapor transmission), minimal to no vapor retarders to retain moisture, etc., make for few problems related to condensation. That's my experience anyway.

I'm reasonably sure there's some condensation in there somewhere, but I'd tend to doubt it would be a big problem.

I agree. Older houses are very forgiving of this kind of thing. The spaces between those sheathing boards allowed for ample ventilation when they were covered with wood shingles. Even now, with plywood and asphalt shingles, there are so many holes and gaps up there that it's like a sieve.

The packing of insulation in the rafter bays is wrong, but in a house like this it never seems to cause anything bad to happen.

As for the knob & tube, I've started recommending that they have an electrician remove all of it, even when it's no longer energized. For one thing, it often turns out that it really is still energized. It also causes confusion in the future. I've been surprised to find that people are actually having it removed.

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Try to remember to bring a voltage sniffer into the attic on an older house like that. The ceiling fixtures especially on the first floor are often left on the K&T wiring, because the sparky doesn't want to break thru lath and plaster to string new cable.

I recently had an old attic that had new cable to the bedroom fixtures but 2 porch lights were still on K&T. K&T should not be buried under insulation and these porch attics are not insulated. I inspected the wire for damage to the rubber insulation. If it is cracking off, it needs to be replaced.

Always try to locate the transition from old K&T to new cable. Sometimes it is a flying splice, not in an enclosed junction box. Have a qualified electrician repair the splices for safety. Have the electrician replace any K&T that is damaged or unsafe.

Jim is the most correct. It should all be replaced to reduce any doubt and replacing it will reduce their insurance costs.

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Try to remember to bring a voltage sniffer into the attic on an older house like that. The ceiling fixtures especially on the first floor are often left on the K&T wiring, because the sparky doesn't want to break thru lath and plaster to string new cable.

I recently had an old attic that had new cable to the bedroom fixtures but 2 porch lights were still on K&T. K&T should not be buried under insulation and these porch attics are not insulated. I inspected the wire for damage to the rubber insulation. If it is cracking off, it needs to be replaced.

Always try to locate the transition from old K&T to new cable. Sometimes it is a flying splice, not in an enclosed junction box. Have a qualified electrician repair the splices for safety. Have the electrician replace any K&T that is damaged or unsafe.

Jim is the most correct. It should all be replaced to reduce any doubt and replacing it will reduce their insurance costs.

I will keep all that in mind. This house was stripped to the studs and re-wired from the box-out and then sheet-rocked a few years ago.

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Try to remember to bring a voltage sniffer into the attic on an older house like that. The ceiling fixtures especially on the first floor are often left on the K&T wiring, because the sparky doesn't want to break thru lath and plaster to string new cable. . .

I can't count the number of times that voltage sniffers have lied to me.

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I can't count the number of times that voltage sniffers have lied to me.

I've had many false positives but never, ever a false negative.

I get lots more false positives, but I've had some great false negatives. The best was a cable hanging from the ceiling in a basement. The agent was standing next to me and asked, "Is that live?" I pulled out the voltage sniffer, which remained obstinately unresponsive as I ran it along the length of the cable, and I said, "The volt sniffer says it's dead. . ." Now before I could complete the sentence (which I had intended to say, ". . . but you can never trust these things), she reached out and grabbed the live end of the wire.

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I like the sniffers but of course they are not infallible. So carry 2. The adjustable type can be set so that they don't detect less than about 90 VAC.

I have a cheap one that is too sensitive so it goes off on low voltages such as induced current in dead K&T.

If I get a positive on one side of K&T I check the other wire, which should be a neutral, dead if fixture is off.

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I get lots more false positives, but I've had some great false negatives. The best was a cable hanging from the ceiling in a basement. The agent was standing next to me and asked, "Is that live?" I pulled out the voltage sniffer, which remained obstinately unresponsive as I ran it along the length of the cable, and I said, "The volt sniffer says it's dead. . ." Now before I could complete the sentence (which I had intended to say, ". . . but you can never trust these things), she reached out and grabbed the live end of the wire.

I don't use it on cables, only individual wires.
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HI's, or anyone else. That's not a bad reason. It's actually a pretty good reason.

I mostly asked because I am curious. Why wouldn't one tell folks to take out old K&T wiring?

It could be intensive therefore expensive labour not really accomplishing anything. A few abandoned wires strung through ceiling joists and partly buried in insulation, who cares?

Certainly if there is a fear that the old wire could become re-enrgized, or if it wasn't bypassed properly, sure, remove it.

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HI's, or anyone else. That's not a bad reason. It's actually a pretty good reason.

I mostly asked because I am curious. Why wouldn't one tell folks to take out old K&T wiring?

It could be intensive therefore expensive labour not really accomplishing anything. A few abandoned wires strung through ceiling joists and partly buried in insulation, who cares?

The next home inspector, and the one after that, and the one after that. . .

Certainly if there is a fear that the old wire could become re-enrgized, or if it wasn't bypassed properly, sure, remove it.

That fear is present on every house with abandoned wires.

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