Go Back  DoItYourself.com Community Forums > Electrical, AC & DC. Electronic Equipment and Computers > Electrical - AC & DC
Reload this Page >

Need advice on insulating with discovery of knob and tube wiring

Need advice on insulating with discovery of knob and tube wiring

Reply

  #1  
Old 11-08-05, 05:15 PM
nipa
Visiting Guest
Posts: n/a
Need advice on insulating with discovery of knob and tube wiring

I'm looking for advice on how to proceed with an attic insulation project for an attic with knob and tube wiring. I just purchased a home in Maine which only has 3-4" of loose attic insulation without any vapor barrier. I want to add a vapor barrier along with another 8-10" of insulation but have just discovered there is some knob and tube wiring buried within the existing insulation. We already knew there was a mixture of romex and knob and tube wiring in the house but didn't realize the knob and tube was in the attic also. We were planning on eventually replacing the knob and tube but can't afford to take on a full house electrical project at this time. I'm thinking that I will have to follow the following steps for this project and would appreciate any input on this from the forum:

1) Remove knob and tube wiring from attic and replace with romex. It looks like the knob and tube in the attic services the ceiling lights in the second floor bedrooms. Will this be safe to replace if other parts of the house are still knob and tube?

2) Remove existing insulation so a vapor barrier can be added. My thought was to methodically move from one end of the attic to the other by first removing the existing insulation from between one run of floor joists and replacing it with faced R-30 (= 9.5") and then pour a couple of inches of the old loose insulation on top of the R-30. Is there value in re-using the old insulation? There was a leak at one point in the roof so I know some of the insulation got wet.
 
Sponsored Links
  #2  
Old 11-08-05, 05:37 PM
Bonehead's Avatar
Banned. Rule And/Or Policy Violation
Join Date: Nov 2005
Posts: 202
It's really too late, for vapor barrier. You'd never be able to do a decent job, and it's not really economically feasable. According to some new codes, a couple coats of paint or at least a vapor barrier ceiling paint is sufficient.

Regarding knob and tube. IMO...this is the safest, not the dangeroust, as one is led to believe, forms of wiring ever invented! Why? The hot and neutral wires are separated, insulated, sheathed thru tubes or ceramic as it goes through bored holes! The wire inself si wrapped aroudn ceramic insulators on the joists or rafters.

Squirrels have eaten Romex wiring and caused houses to burn (I'd venture to guess, anyway). But this wouldn't happen with knob and tube, due to the separation of each wire.

You can insulate right over it, no problem. I work with rental properties over 100 years old, with knob and tube, and we, along with other properties, have no problem with the stuff. For some reason, inspectors have issues with this form of wiring, but I have a feeling it is a job security thing.

ONE of the problems (if you want to call it that) is that knob and tube is only a 2-wire, non-grounded system. But that is no big deal, as most interior outlets today, with all the plastic insulated equipment don't really need a ground. And gfci's can protect ungrounded situations.
 
  #3  
Old 11-08-05, 05:50 PM
nipa
Visiting Guest
Posts: n/a
Originally Posted by Bonehead
It's really too late, for vapor barrier. You'd never be able to do a decent job, and it's not really economically feasable.
Could you explain why it is too late? What is wrong with my suggested approach of shoveling out all the loose insulation and replacing it with faced R-30? With regards to economics, there really isn't any because I will be doing the work myself.

Originally Posted by Bonehead
ONE of the problems (if you want to call it that) is that knob and tube is only a 2-wire, non-grounded system. But that is no big deal, as most interior outlets today, with all the plastic insulated equipment don't really need a ground. And gfci's can protect ungrounded situations.
We eventually plan on using many modern 3-prong appliances and equipment in the house so thought we would need to remove the knob and tube in order to support the 3-prong load on the system.
 
  #4  
Old 11-08-05, 06:23 PM
Bonehead's Avatar
Banned. Rule And/Or Policy Violation
Join Date: Nov 2005
Posts: 202
Because it is hard to secure the facing. The facing extends only about 1 inch over the insulation. It is applied to the underside of the ceiling joists, overlaped at each joist... Or, stapled up the edge, by stapling from below. How you going to secure it?

I suppose where you have to have the 3-prong systems, then you'd have to, I guess. I guess that with computers, especially, you really should have the 3-prong. And with refrigerators..they too should be 3-prong, technically.

I have a frugal mindset because of all these old rentals I work on, where we have gotten by on several of the homes that only have 2-wire systems. But if you can afford the conversion...go for it.
 
  #5  
Old 11-08-05, 06:28 PM
Bonehead's Avatar
Banned. Rule And/Or Policy Violation
Join Date: Nov 2005
Posts: 202
In theory you could use sheet plastic and drape up and over joists. But then you may have problems burying electrical junctions...and getting around all the wiring could be difficult. That is why I have always heard that vapor barrier isn't really necesary, if you accomplish it with vapor barrier paint.
 
  #6  
Old 11-09-05, 08:44 AM
Forum Topic Moderator
Join Date: Feb 2005
Location: Near Lansing, Michigan
Posts: 10,537
Re-using the old insulation is a waste of your time in my opinion, especially if it has gotten wet. It's useless.

Knob and tube itself is a fairly safe wiring method. According to code, you are allowed to leave k&t wiring in your house untouched. If you upgrade any portion of a k&t circuit, you have to upgrade the entire circuit. The main issue is that k&t is ungrounded and it is not permissible to extend an ungrounded circuit.

Personally, I would replace all of the k&t with romex before proceeding with the insulation. This would be a good opportunity to pull some more circuits too as you probably only have a couple 15A circuits supplying the entire house now. You will need more power availible if you want to use modern appliances on your upper floor. One 1800W hairdryer is capable of maxing out an entire 15A circuit.

I believe that you are not allowed to insulate over k&t; you'll have to call your building inspector's office to get a firm ruling on this for your area.
 
  #7  
Old 11-09-05, 06:22 PM
nipa
Visiting Guest
Posts: n/a
Thank-you both for your advice and direction. I never heard of vapor barrier paint before. Is that a specialty item or can it be purchased at one of the local super chain stores (i.e., Home Depot).

With regards to the electrical, we plan on doing all the electrical work ourselves since we received a quote from an electrician for $18K to upgrade the electrical. We are fortunate to have a friend who is an electrician who has offered to teach us the ropes for drawing up the electrical plan, running the wires and making connections. He will make all the main box connections for us too.
 
  #8  
Old 11-09-05, 07:36 PM
Bonehead's Avatar
Banned. Rule And/Or Policy Violation
Join Date: Nov 2005
Posts: 202
Originally Posted by nipa
Thank-you both for your advice and direction. I never heard of vapor barrier paint before. Is that a specialty item or can it be purchased at one of the local super chain stores (i.e., Home Depot).

With regards to the electrical, we plan on doing all the electrical work ourselves since we received a quote from an electrician for $18K to upgrade the electrical. We are fortunate to have a friend who is an electrician who has offered to teach us the ropes for drawing up the electrical plan, running the wires and making connections. He will make all the main box connections for us too.
Yes, you should be able to find it there. Zinsser is one brand name. The best paint is the stain-block sealer paint/vapor barrier paint that has shellac as one of the ingredients. It is excellent for painting over knotty or other bleed-through wood, so you don't have to keep painting and painting multiple coats for your top coat paint.. But somebody told me that just two coats of latex paint also does the job. But I don't see how, actually. Latex 'breathes'. The more coats you apply, though, the more of a polarizing effect gets created. For ecxample, if one coat allows air permeation that will cure let's say a caulk in 1 day...two coats will take 2 days, and 3 coats will take 3 days (just to illustrate my point). I know this is true from my experience with covering up the ends of opened up caulk tubes with a latex "condom". One condum would delay the setting up of the caulk in the nozzle. But two, three or four condems would add much more delay time. I'm sure latex paint is going to work the same way. But I believe if you REALLY want to stop the migration of vapor...to use the shellac-based stain block/vapor barrier paint.
 
Reply

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Thread Tools
Search this Thread
Display Modes