insulating new basement

[bebobalue]

we just added a family room to our house with a basement under it.. it was just blocked in and is yet to be sealed... I wanted to add insulation inside the brick but it was capped off with a 1/2 block (4" solid cement bricks) so that option is out .. the mason mentioned putting 4x8 sheets of 2" foam on outside before it is back filled.. so I bought 13 of them but I have been told that it is a waste to put insulating foam( R-10 value) outside the walls that it will do little to nothing towards help[ing to keep basement warm??? what say everyone..if it is not ok what do you sugest , interior walls with fiberglass inside?

[suemarkp]

To me, that is the best place to put it, as the concrete block will be a thermal mass in the basement near the temperature that you wish to maintain. You do need to insulate the concrete that is above ground in a way that complies with termite and moisture rules, and find a way to cover what styrofoam is exposed to protect it and make it pretty.

[bebobalue]

:) I have just started reading all these concerns over insulating inside your basement and ending up with mold problems / condensation problems .. with foam on outside wont that help prevent any condensation as a result of finishing the inside of a basement?..if not any recomendations for finishing..I actually care more about reducing sound transferance..ie: sound proofing as much as posible as I will be using this room for band practices...thanks in advance for any ideas............................................. .....

[xkvator]

exactly as Mark said - and don't let anyone talk you out of insulating the outside of your basement walls - put a waterproofing membrane on the block first, then the styrofoam. make sure you have 4" drain pipe/gravel/filter fabric at the footer and unless you have a sandy soil that drains well, i like to backfill with 2B gravel almost up to grade level. clay soil against the foundation will freeze in winter because it's not getting any heat from your insulated basement and could push and crack/bow the wall. any styrofoam above grade needs protected - look at www.permabondws.com - for 1 idea.

[Ron]

If you haven't put a structure on top of this block wall you might want to consider filling the cavities of the block with sand or vermiculite to help with sound transmission reduction and insulation.

[Timothy]

This link is to an excellent article about basement insulation systems and related mold concerns. Anyone contemplating insulating a basement should consider reading it.

http://www.eere.energy.gov/buildings/building_america/pdfs/db/35017.pdf

It essentially says that outside foam insulation is ideal although making the exposed (above grade) portion aesthetically acceptable and yet durable is problematic. The article also gets into detail about different methods of insulating from the inside.