Options to Insulate Cold Bedroom Above Garage

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stevevz

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Hello all, and thanks in advance for any advice offered.

I am about to tackle a notoriously cold bedroom above my garage once and for all. The current batt insulation up against basement ceiling (or under bedroom floor - depending on how you look at it) that is held in place by wire just isn't cutting it. This insulation is not enclosed (no gypsum board over it).

I found a solution I like that was posted by what appears to be an expert on the subject:

https://buildingscience.com/document...al-performance

However, I want to keep the 2" loss of ceiling height that both options in the article require.

I'd like to go with one of the two options as shown in my images. Is one better than the other?

Option A.png

Option B.png
 
Have you considered closed cell sprayed foam insulation? You get complete coverage and depth which is superior in R value to insulation batts. Why use rigid and batts when you can simply fill the entire joist bay with foam.

Look at the charts from this web site showing R-value of materials and depth.
http://www.greatdayimprovements.com/insulation-r-value-chart.aspx
 
Hello. Thanks for the advice. Yes, I have considered the spray foam option. However, I find it far too expensive.
 
''I'd like to go with one of the two options as shown in my images. Is one better than the other?''

the answer lies in the R value of what you have.
1/2'' x 4'x8' is an R value of 3

roll insulation with a 19R value will do just fine if you sheet rock the garage ceiling
your problem rat now is the cold air is allowed to circulate around the insulation.
rock the ceiling, stop the air, you will be fine
 
To meet minimum code there should have been 5/8 sheetrock on the ceiling!
It will stop all the air flow.
Need to seal up anyplace where wires or plumbing was run with through the plates with fire proof caulking first.
 
Both options call for gyp board, however #1 will give you a warmer floor.
 
If you go with #1 the insulation can slip down leaving gaps so I would go with #2 no vapour barrier
 
You also need to look at sources of airflow above the room. Sealing outlets and switches, sealing the penetrations into the attic space to stop airflow up. If you go with option one I'd use an adhesive that is safe for the extruded polystyrene and glue it to the underside of the floor to keep it from falling down and compressing the insulation and providing air gaps. If you go with option two, if you have the head room apply it across the bottom of the floor joists, tape any joints and then cover it with 5/8" rock and do at least the tape coat of drywall compound. Personally, I'd go to finish coat and paint the ceiling as it makes the garage look much better to have the walls and ceiling painted out instead of raw drywall.
 
I would do option 1 with as thick of foam board as I could find and easily cut and work with. I would cut the pieces for a tight fit and then seal them in at the edges with canned spray foam. If I worried about them falling I would use some strapping screwed into the joists to make a ledge to hold it up. I have found using the sheet foam and then sealing it in with spray foam gives the same result as having the more expensive spray job and is DIY friendly. For additional add the fiberglass with no vapor barrier and then 5/8 Drywall. 5/8 is pretty heavy to work alone with and rent or buy a harbor freight lift. I have done double thickness half inch as well.
 
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