Advice on basement insulation and vapor barrier?

9/2/2014 at 9:04:16 PM

I would suggest you start by reading this article. Good info from a reliable source.

http://www.greenbuildingadvisor.com/blogs/dept/musings/how-insulate-basement-wall

9/2/2014 at 9:49:21 PM

Hey Jim,

There are lots of different schools of thought when it comes to basements and insulation. Ultimately, the decision usually comes to budget. Your best bet is to remove the batt and install a 2lbs spray foam insulation. 2 lbs foam is dense enough that it acts as its own vapor barrier, 1 lbs foam does not! This is probably your most expensive option.

If that doesn't sound like the way you want to go, I would remove the 6 mil poly and install another r-12 batt on top along with black tar paper and r-24 batts on the bottom. Your insulation value is now superior to the existing r-12 and your heating bills should reflect that.

But don't stop there! Use a Dri-Core system or alternate on the floor and you will maximize the warmth of your basement!

9/2/2014 at 10:43:55 PM

Hi,

I am going to suggest a cost effective and very effective system I use all the time when finishing a clients basement. (My own as well).

First remove all the plastic, insulation and 2x3 that exist now.

I assume you have steel beams that will need to be boxed in, you can use most of the 2x3's for that.

Now stop at Lowes or another big box store and buy 2'x8' sheets of ridged blue foam core insulation. Buy the R-10. There is a specific glue to use..ask. Glue the foam directly to your concrete foundation. Carry it up over the base plates for your floor joists on the main floor.

Then use tuck tape and close every seam between sheets and tape the outer edges again the top of the foundation. This gives you the first R-10 plus your vapor barrier.

Now 3/4 0f an inch in from the blue board chalk straight lines down each wall. Measure across to be sure the room will be square. Use Blue board 2x4 lumber for your base plates when you build the walls. When you install each section use the 5" wide white foam under each wall and ramset the bases down. After you have finished building all you outside walls, and have run all electrical and plumbing, now you add Roxul R21 green insulation.

You now have R-31 insulation. An extremely good vapor barrier that will never allow moisture to contact you soft insulation.

Now as the previous poster suggested, You install Dri Core 2'x2' subfloor sheets. This way if you evr have water intrusion or even a burst pipe, the water will work under the plastic base of the wood panels and work its way to the drain in your basement. The floor is also insulated by this system. These are not inexpensive, but I swear by them. There are cheaper foam bottomed panels that actually provide more insulation value but water can not travel.

Remember, if you are not an electrician, get a certified one in to inspect all your electrical runs and hook ups prior to installing the roxul. Let them hook all the lines up to the main panel.

Hope this helps.

James