fiberglass insulation for 12 oc

[anwalt2]

My basement is accessible with 12in oc joists.  I would like to warm the floor above by insulating the floor joists from below.  

Looking for suggestions other than cutting 24in oc fiberglass insulation lengthwise.  

Paper or foil backing is not necessary in this application.  

Materials other than fiberglass are also of interest.  FC is just what comes to mind. 

anwalt

[MKepke]

You might look into rockwool batts instead of fiberglass..I fear you are still staring at having to split batts to fit 12" OC tho. At least rockwool isn't as itchy as fiberglass.

That would be its other benefit in an (exposed) basement ceiling..no itchy fiberglass fibers falling down over the years...

Or

..cram in traditional 16" fiberglass batts. 'Wasting' the 4" of width may still be cheaper than any other alternative.

-Mark

[KC]

You might look into rockwool batts instead of fiberglass..I fear you are still staring at having to split batts to fit 12" OC tho.  At least rockwool isn't as itchy as fiberglass.

That would be its other benefit in an (exposed) basement ceiling..no itchy fiberglass fibers falling down over the years...

Or

..cram in traditional 16" fiberglass batts.  'Wasting' the 4" of width may still be cheaper than any other alternative.

-Mark

I used a drywall saw to cut rockwool when I did the garage.  While it'd still be a PITA, I'd 'crosscut' it to fit the space before I'd try to cut 4" (or whatever) off the entire length.

[JosephP]

How feasible is it to heat the basement to the same temp as upstairs?  Are the walls insulated or thick concrete?  Are there old inefficient windows down there?

Yes, you will use energy to  heat the basement, but that heated basement will mean less energy to heat the first floor...probably not a wash, but that may also make the basement more usable???

Just asking if that is an option.

[fixtureman]

You might look into rockwool batts instead of fiberglass..I fear you are still staring at having to split batts to fit 12" OC tho.  At least rockwool isn't as itchy as fiberglass.

That would be its other benefit in an (exposed) basement ceiling..no itchy fiberglass fibers falling down over the years...

Or

..cram in traditional 16" fiberglass batts.  'Wasting' the 4" of width may still be cheaper than any other alternative.

-Mark

You don't want to compress fiberglass as the air in it is the insulation

[MKepke]

You don't want to compress fiberglass as the air in it is the insulation

You won't get the *rated* R-value for the batt, but who cares if it's cheaper and faster per R-value than the other options.

If you'll lose say 20% through compression, put in a 20% thicker batt. Is that 20% thicker batt still cheaper and faster than any other option? If so, congrats on being ahead...

-Mark

[Snipe Hunter]

Have you got insulation between the joists on the band boards at the perimeter? It will help. Probably help more than you might expect. You loose a lot of heat there.

[anwalt2]

My basement is accessible with 12in oc joists.  I would like to warm the floor above by insulating the floor joists from below.  

Looking for suggestions other than cutting 24in oc fiberglass insulation lengthwise.  

Paper or foil backing is not necessary in this application.  

Materials other than fiberglass are also of interest.  FC is just what comes to mind. 

anwalt

Looking to warm floor because i three weeks ago replaced a failed 90+% gas, tank, direct-vent water heater with a heat pump.  With the heat pump, heat for the water is taken from the surrounding space, the basement.  Absent a better solution, I will open a heating vent in the basement to indirectly heat my water with nat gas.  

thx for the suggestions

and yes the band joists are filled with 2in of XPS sealed at the perimeter with great stuff, also new thermopane widows.

[Roly]

Looking to warm floor because i three weeks ago replaced a failed 90+% gas, tank, direct-vent water heater with a heat pump.  With the heat pump, heat for the water is taken from the surrounding space, the basement.  Absent a better solution, I will open a heating vent in the basement to indirectly heat my water with nat gas.  

thx for the suggestions

and yes the band joists are filled with 2in of XPS sealed at the perimeter with great stuff, also new thermopane widows.

I was wondering about using a heat pump water heater in a heated space in the winter, can you feel if the area is colder ?     In the summer I can see it is good but what is the full year efficiency.  
  Roly

[EatenByLimestone]

Staple up netting and blow it in.