Our basement gets incredibly cold. The main part has a walk-out patio, the backroom however is below-grade, unfinished, with cement walls. The one wall that is right up against the earth (townhouse) had some crappy fibgerglass insulation dangling on it when we moved in. I pulled that down cause it was taking up an absurd amount of space, looked ridiculous, and didn't seem to do much as it was just flapping around back there. I was thinking about slapping on some 4x8 sheets of insulation board on that wall but the ones I'm seeing at Home Depot are R5 or R7.5. Are those going to do much for me? We are also going to get one of those electric fireplace heaters down there, just wondering if it's worth slapping that insulation on that wall or not.