I just wanted some advice and opinions on basement insulation. I finished part of the basement a couple of years ago, and want to finish the rest. The original part I finished with 2x4 studs, 16 inch centers, and R-12 pink fiber insulation. I'm going to do the rest with 2x4 24 inch centers this time (why pay for more wood when its not structural?). Anyway, I've seen some guys that have put rigid insulation against the wall and build the wall against that rather than the wall against the foundation with fiberglass between the studs. I suppose the theory is, you are insulating where the wood would be, studs have what an R value of 2 or something? You don't have to put vapor barrier up against the foundation side. But, the rigid insulation I've seen doesn't hold a candle to what you can get for either fiberglass or a rock whool product, (even though I used the lowest R-12). Where I come from, we have a grant from the electricity company that'll pay for insulation. Which is the better way to go in your opinions?

Keep in mind although doing both would kick butt, I doubt the grant would be approved, and I'm doing it myself, and I don't need the headache. Thanks guys!

If you put R30 in an old house that has studs every 12 inches, you get the best of both worlds. Here, you get to pick both the stud size, spacing and type/thickness of insulation. I think the most pertinent questions are how temperature stable do you want the basement to be? And how important is quiet. Other considerations are mainly financial.

In regards to temperature stability, I want the best option to keep the basement warm in winter. I live in a cold climate, think North Dakota, only farther north! I'm also installing baseboard heaters to keep it warm. But I don't need it to be cozy, maybe just south of room temperature.

In regards to noise, it doesn't matter at all.

The reason I am looking at 24 inch studs is to save on lumber costs, but also to reduce the bad R-value that wood studs have. And since its not structural, it doesn't matter. I can get 16 or 24 inch insulation so that's no problem. I do have somewhat of a space issue, which I forgot to mention. I think R-7 pink rigid, is 1 inch? I can't remember. So, two inches will double that, which is close to the R-12 of the insulation I got last time. When you take into consideration the studs, I think that drops to like R-10 or something. I'm not sure. So two inches of rigid would be better, but I'd lose 2 inches of wall all around. My basment is about 700 square feet, so space is an issue. On top of that, I can get a higher R value fiber or whool insulation. The rigid idea I like because I can put up the insulation first and not pay more to heat my main floor before I gather the money to build the walls.