insualtion of garage ceiling

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  #1  
Old 10-12-02, 04:06 AM
aabbyy
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insualtion of garage ceiling

I recently inspected above my garage ceiling and found that there was insulation on the garage ceiling of 3 and one half inches. The insulation is on the ceiling and not against the heated space above. the vapor barrier is facing up and there is a dead air space of about 10 inches above this. I was told that this was the correct way. Since the garage is not heated and open constantly in the winter months. I question wheter this is correct or not. The bathroom floor is tile and it is freezing in the winter.

Correct me if I am wrong, but is seems that this is not the best way for this to have been done.

I want to fill the cavity with loose fill insulation. the vapor barrier will now become trapped between the layers of insulation.

What is the correct way for this to have been done?
 
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  #2  
Old 10-12-02, 10:39 PM
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Location: Arlington, WA
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Install a vapor barrier under the bathroom subfloor. Then rmove or at least slit the vapor barrier of the R-11 or R-13 above the garage ceiling. Now you can fill the 10" of dead air space and the bathroom floor shouldn't be freezing cold. With only a 10" space between the garage ceiling and the bathroom floor joists, you will probably have to remove the sheetrock of the garage ceiling to do all of this. Be aware that the garage ceiling is a firewall and needs to be resheetrocked with 5/8" Type "X" 'rock.
 
  #3  
Old 10-17-02, 05:28 PM
rbisys
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Geetings,

From what I understand you have a heat flow DOWN problem from the upstairs bath floor to the garage.

No matter how much fiber insulation you put in that space your floor will be cold. Heat energy flow down is abot 97% and fiber glass is about 98% air space. You can't win

Since you are getting heat loss thru the edges as well as down the best way would be to remove the drywall, remove the batts and relpace with two layer radiant barrier (RB) insulation. The RB Panels should tbe installed down by the garage ceiling and angle up to the subfloor/rimboard intersection. The RB reflects the heat energy back up at a 95% efficency, plus it is a perfect vapor barrier. You will not have to worry about condensation or mold either.

A cheaper, less efficent way would be to paint the ceiling with a paint with insulating ceramic beads. It would still be far better than FG but would not take care opf the edges. See Koolcoat.com.

You might want to consider installing RB in the attic over existing insulation and painting the inside of the exterior walls with the insulated paint. You could save up to 40-50% on energy bills and the house would be much more comfortable.

Thank you for considering my opinion.
 
  #4  
Old 10-19-02, 04:06 AM
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First thing is to determine whether 3 1/2" (R12) is adequate for the part of the world you live in. You can speak to your local building department about that. In order from bottom to top, install the 5/8 fire rated drywall, required insulation value, 6 mil poly vapour barrier. Leaving an air space between the vapour barrier and floor is proper as long as this space is supplied with a heat source, ie. a hot air supply duct, and a cold air return. This application will keep the floor of the bathroom warm and the plumbing will not freeze.
 
  #5  
Old 10-20-02, 08:56 AM
rbisys
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Greetings,

Pipes won't freeze with FG? You must live in deep down South Florida.

Thank you for considering my opinion.
 
  #6  
Old 10-23-02, 12:17 AM
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Location: Arlington, WA
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Pretty sure rbisys has seen frozen pipes that were embedded in FG in St. Louis. They will most certain freeze in CA, fiberglass or no. (Well, MAYBE not in L.A., but in the "real" CA!!)
 
  #7  
Old 10-27-02, 05:00 AM
rbisys
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Greetings,

Will the REAL Ca please stand up.

Thank you for considering my opinion.
 
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