Go Back  DoItYourself.com Community Forums > Interior Improvement Center > Insulation, Radiant and Vapor Barriers
Reload this Page >

Ceiling Insulation in Finished Garage / Floored Attic

Ceiling Insulation in Finished Garage / Floored Attic


Old 09-09-05, 10:39 PM
Visiting Guest
Posts: n/a
Ceiling Insulation in Finished Garage / Floored Attic

I apologize if this post is a dupe (and a long one at that)... i've looked through the forum, but haven't found the answer that i think best fits my situation. so here goes...

----- BACKGROUND -----
My wife and I have a 1 story home built in Nashville, TN in the 50's, and are in the process of slowly finishing the 1 car garage into a laundry/exercise/storage room. The previous owners took care of bricking in the garage door, but left us w/ a fixer-upper. We've since had the electrical replaced, insulated all 4 walls, and sheetrocked the walls w/ 5/8" sheetrock (since it's a laundry room, we figured insulating between the room and the rest of the house, and the 5/8" sheetrock would cut down on the noise of the washer and dryer). We are going to have a new HVAC unit installed, and are upping the tonnage to add ducts to heat/cool this room.

The space above our garage is the only portion of our attic not currently insulated. I have a few questions on the best way to get this done, and i need some help from ya'll.

The area itself is about 264 square feet of floored attic. Spacing between the individual joists is approximately 15" wide, and there is about 8" of height between the sheetrocked ceiling of the garage, and the plywood flooring in the attic. I'm going to have to take up the flooring to move one light fixture and install another, so cutting holes and blowing insulation in isn't really an option.

-----QUESTIONS -----

1) Do I need to install insulation w/ a vapor barrier? if it is unfaced, can i just put down a sheet of poly between the sheetrock and the insulation?

2) Should I install the thickest insulation I can in this area, faced or not? If so, it looks like an R-25 will fill the space from the sheetrock ceiling to the flooring... but the owens-corning i found doesn't have a vapor barrier. Or should i just settle for the thickest faced insulation i can find that will fit in that width? Don't want to underinsulate or blow $$ and overinsulate.

3) Will I run into a moisture issue if I install insulation and then put the flooring back in? We store several items in the attic, and don't want to give up the space. (our attic is vented, if that is a factor)

4) Should this insulation be stapled in, or is it ok that it just lie between the joist and on the ceiling below?

I certainly hope that with a post this long, i haven't forgotten anything... but if i have, and you want to point something out to me, please do. no offense taken.

thanks folks!

Sponsored Links
Old 09-15-05, 05:57 PM
Visiting Guest
Posts: n/a
Hey 209dave,

I hope this works this time, I typed all this out once then it didn't post but here goes one more time, lol.

I have done several jobs just like yours but down here in FL. The best and easiest way we found to do this was to cut about an 18" run out of the plywood in the attic right down the center. Then we stuck our blow hose almost out to the end of each truss runn then turned on the machine and filled up all the cavities, 1 at a time. Then we replaced the plywood when finished. When using blown insulation a vapor barrier is not required in FL., I'm not sure if it's suggested in your area or not.

We have also done this type of install with batts (blankets) in the same manner. We used a long flexible pole to push the batts into each truss run. The only problems we hadd with that were the wires, the batts don't slide past them if they aren't at the top or bottom of the trusses. If you use batts definately use kraft faced (with a vapor barrier) and the thickest size you can get that will fit in the 8" without compacting it.

Stapling is definately not needed on a ceiling. The only reason it's needed in flat ceilings is to hold it up until the sheetrock is installed, walls and sloped ceilings are a different story. Moisture will not be a problem either as long as your attic is very well ventilated, plywood will not hold moisture in you ceiling.

I hope this helps
Old 03-16-10, 12:02 PM
Join Date: Mar 2010
Posts: 1
Thanks for your very informative reply to Dave's question. We have a similar situation, where our garage was finished as a bedroom in the 1960's and the attic space above was floored with 1" x 8" boards. There has been insulation between them, but now it is old, deteriorated and compacted. We hoped to replace it using the batt method you mentioned. However, the joists between the bedroom ceiling and the attic floor are 2x6's so they are only 5 1/2" high. We found that R-19 rolls, or batts, are 6 1/4" and wonder if this would end up being too compressed? Also, are we wasting our time & money with the R-19, since R-38 is usually recommended? We live in southeast Virginia and don't know what R-value is recommended for this area.

Any advice or suggestions will be greatly appreciated.

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