Limited Attic Space, no insulation, need help fast

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What? Afraid of a toaster in the attic.
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'What? Afraid of a toaster in the attic. '
ROFL.
For the OP:
Either don't insulate, or have your wiring upgraded. Also, try to find a way to get access to the attic, other then via the roof.
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Chas Hurst wrote:

IIRC knob and tube used insulated wire, but I can see some validity in the its getting more convection cooling because it was free standing between the insulators (knobs) whereas romex is usually stapled against wood and often covered by insulation too.
Wouldn't bet on it without seeing the old specs myself though.
Jeff
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Jeffry Wisnia

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Knob and tube is insulated. It's exactly what I said. The gauge of the wire is thicker. K&t used 12 gauge wire for 15 amp circuits. Most 15 amp circuits now use 14 gauge wire.
Dimitri
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D. Gerasimatos wrote:

You are right that it is insulated. Of course by now a lot of it is not all that insulated.
However you are at least a little off on the wire gauge thing. I am not quite old enough to know if they originally required or used larger gauge wire for a circuit. The stuff I have worked with did not. In fact it used smaller gauge wire. The physical separation and the ability to dissipate heat allowed it to carry the additional current per wire size.

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Joseph Meehan

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My house is wired with knob and tube and it is a bigger gauge. However, don't take my word alone for it:
http://www.webcom.com/~malin/knob.html
http://www.home-inspectors.com/knobandtube.htm
Dimitri
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Matt wrote:

The additional physical separation of the wires allowed a greater ability to dissipate heat and that allowed for the greater capacity.
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The fusing current of 12 ga copper wire is 235 amps...
Nick
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Generally you would want to have vents along the eaves of the roof, then vents at the peak of the roof and a clear path for the air to flow as pictured on the following web page.
http://www.owenscorning.com/around/ventilation/roofandattic.asp
So best to have this type of air flow and to not block that air flow with insulation.
So far as the knob and tube wiring, I would have it all replaced with romex if it is acceptable to cover the romex in your area with insulation, then not to worry about that.
So far as the recessed lighting, no matter what the label says, these can get *very* hot and damage/melt the insulation on the wiring. I would have the electrician verify that these are wired with appropriate new high heat rated wiring. Then I would also be sure to not cover them with any insulation so the heat can dissipate.
So far as how much insulation, with the current high energy costs, I would add as much insulation as possible to the attic and also add the roof top insulation. It will probably be worth it in the long run. I don't know what your heating and cooling costs are, but if you want to lower them, then consider the cost of this work -vs- the cost of added insulation.
And so far as spray foam around the existing electrical boxes for ceiling lighting, again these can get to be quite hot as heat travels up. I would re-wire with appropriate new high heat wiring and ask the local building inspector what is allowed. I have seen these where the heat from a regular light bulb has caused the insulation on old wiring to fall to pieces leaving bare wire (was not high heat rated wiring). Personally I would tend to want to leave a little ventilation above these just like the recessed lighting.
Overall, your area may require a building permit to install insulation. Good idea to get a permit and discuss your plans with a local building inspector before the work is done, then have it inspected after the work is done. If no permit is required, might want to see if you can pay a building inspector to check it out in their spare time or something - make suggestions as to what would be best.
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Hi - Kelly. I'll make my comments inline below...

Good idea here. Your climate may see less benefit and a longer payback period but it couldn't hurt.

Ventilation is very important in attics and will prolong the roof life and eliminate rot, etc. I would make sure there is some airspace between the roof sheathing and the insulation AND that there is a way for air to enter and exit.
Given that this is a flat roof, there are products that can be added on top for insulation. they are not 1/2" thick, they are about 3 or 4 inches thick urethane. Here is one of many http://www.insulateonline.com/index1.htm?flatintro.htm~main

If I insulated the 'attic' I would leave airspace and add vents.

That pipe may or may not be adequate. There should be a place for air to enter and exit under the entire roof.

That would be best answered by a heating AC guy. Are you getting hot or having trouble staying warm or both ? You may never see a payback or ROI. You could in a year. Too hard to tell.

Its about R5 per inch. They are most likely talking about a 3" product. make sure they are then that price may be OK. its definitely not for a 1/4" product.

They are cheap - Just get an IC rated can if you are adding the insulation and venting. Do not mess with non-IC in an insulated area.

Don't worry about it - Very little, if any, will leak out.

So - To sum it up. If it were me. I would add a 4" ridged foam on top of my roof sheathing before I had my new flat roof installed. Before it was installed I would have some sheathing removed so my K&T wire could be looked at. If the insulation was crumbling off I would have it replace with romex. If it was fine I would leave it alone. Maybe at this point I would have my recessed light installed. I can use the one I have because I'm not putting insulation in my 'attic'.
Our advice is free, take it for what its worth.

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I'd replace all the knob and tube wiring with romex while you have access to that area. I'd only use IC rated lighting. I also would not fill the entire space with insulation. There should be air space with vents for a way for air to enter and exit above the insulation. This keeps the temps down and prevents moisture problems. Plus in your area with milder climate, you can get by with less insulation.
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How about the p2000 foam insulation: http://www.p2insulation.com /
For 1 inch, installed with seams properly taped and an air space like you have, you can get close to R-40. Yes... 1 inch... r-40. It's expensive but great for limited space. A number of the timber framers around here are starting to use it since it's so useful for limited space areas. The 1 inch of p2000 gives better r-value than the regular rigid foam they used to use. I understand it's been used commercially for some time and is just now getting onto the residential market. From the literature it seems it gets it's high r-value by addressing radiative and conductive heat along with a vapour barrier all at the same time.
- Scott
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