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Insulated rim joists, should I add cavity insulation too?

Insulated rim joists, should I add cavity insulation too?


  #1  
Old 09-30-14, 07:54 PM
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Insulated rim joists, should I add cavity insulation too?

I insulated all the rim joists before framing my basement walls. I used foamboard, PL300 and Great Stuff foam to adhere and seal the foamboard to the rim joist area.

I did NOT put cavity insulation back in (most of the fiberglass I pulled out was unusable)

Im now working on lighting in the finished ceiling, so I have access to a lot of the joist bays, albeit from 2' away.

Should I take this (final) opportunity to shove cavity insulation up to the foamboard? Could I use blown in instead (blow it in from the 2' away and fill that 2' with blown in)? Or do I really not have much to gain either way? Note this is a finished basement with a finished drywall ceiling (Im adding another layer of drywall over the existing because I dont feel like trying to patch holes and get rid of texture)

Thanks in advance.

-Chris
 
  #2  
Old 10-01-14, 02:25 AM
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The rim joist and above grade concrete are the coldest areas of the basement wall, so adding more insulation is good. Having everything hidden behind drywall is always a pain for termite inspectors, but those critters are less frequent in CT than down south.

Bud
 
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Old 10-01-14, 05:33 AM
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Thanks!

Since its mostly closed up now, would you suggest blown in (like Owens Corning Atticat) or should I just try to shove some Roxul in there?
 
  #4  
Old 10-01-14, 07:49 AM
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I can't see what you see, but the machine for blowing insulation can be a pain to set up for a small job. Plus blowing into a closed space is sure to blow back in your face. When I install batts in a low slope roof I make a push pole with a "t" on the end, sometimes add a few nails straight out to grip the insulation.

Bud
 
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Old 10-01-14, 12:10 PM
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Yeah thats what I was afraid of.....found specs on the machine HD rents...150' of hose makes me laugh, considering the machine will be right next to me in the basement while I fill one joist cavity at a time...so maybe I need 20' of hose

There isnt much to see right now....every joist cavity is closed. The new walls have been framed and insulated so I cant easily get through there (I could if I had to). The ceiling is finished from when we moved in (I didnt just finish it myself)

So I figured I would drill a hole about 2' off the wall surface, insert the blower tube and fire up the blower. With any luck it would fill the joist cavity up to where the rim is. I assume some would fall back out from the hole but I would put duct tape or screen back over it to keep most of it in there. A happy side effect is that I could get more insulation around the lights I just had to replace since its easier to blow around them than to try and use batts. But again it could just end up being a huge mess and inconvenience for only a little gain. Ive debated blowing insulation into the WHOLE ceiling but I figure with the wall insulation, rim joist insulation and possibly the blown in around the rim joists the basement should hold its own pretty well without ceiling insulation.
 
  #6  
Old 10-01-14, 12:55 PM
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If you add insulation around those lights, assuming recessed cans, be sure they are IC rated (Insulation Contact).

Your hear loss is to the outside and not between floors (up and down), thus concentrate your efforts and dollars towards the perimeter walls.

Bud
 
  #7  
Old 10-01-14, 03:02 PM
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Thanks....i think Ill just stick with shoving some Roxul up to the rim. if I have any left over Ill lay it "up" into the joist towards the interior of the basement.

The new lights are definitely IC....the ones that were there were far from it, Im actually surprised they didnt start a fire (not because of insulation contact, just because they got so hot some of the wires look just about ready to let go). They must be real old school, the j-boxes for them werent built onto the light assembly....there is a j-box for each light about 2' from the light can itself, feeding a jbox for the next light, feeding a jbox for the next light, and on and on for 12 lights.
 
 

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