A BIG question that seems to be on a lot of my students minds these days is “How do you insulate a basement correctly?” This is a very good question!
There seems to be so many variations of the right and wrong way to insulate basement walls on the internet…it’s a no wonder why there is so much confusion. There are also a lot of different insulating products (membranes, foams, panels, barriers…you name it!) that have surfaced over the last few years it’s no wonder it’s so damn confusing.
So let me tell you exactly how I do it and how you should be doing it too…and it’s a very simple procedure as well…I use the good old fashion never fail-you R-13 3.5″ fiberglass insulation in all my Exterior Walls…PERIOD! let me tell you why…
There’s no need to first add 2″ Styrofoam with adhesive to the masonry walls as many would tell you. Or hang add a plastic Vapor barrier on the backside of your new framed exterior walls or any of that craziness! That is all un-needed effort that just steals your money and your time.
As a matter of fact vapor barriers cause Mold! Did you know that? Yep…vapor barriers can create a moldy environment behind your new framed walls. This in time can and will destroy your basement walls and occasionally can make you very sick as well!
Basement exterior walls need to “breath” so they stay dry and mold-free. Adding these extra “layers” of insulating protection creates a moist environment because now the backside of your exterior walls can no longer breath properly. This is what causes new mold spores to be born behind your walls.
Think about it…you have an existing dark cool space behind your new framed exterior walls, and a heated new space on the other side of that wall. Then….you go and add a vapor barrier (a piece of plastic or Styrofoam) behind the wall what’s going to happen?
Well I’ll tell you…the vapor barrier is going to begin to sweat and become very moist and that my friend is the perfect formula a mold farm! (D+D+ZV = M) Dampness+Darkness+Zero Ventilation = MOLD
Now…the controversy starts with “well you can’t use fiberglass insulation because everyone knows that basement walls occasionally get damp and wet and fiberglass insulation can’t get wet.”
This is True!…But…and this is a BIG BUT,…”but you shouldn’t be finishing your basement at all until you have 100% CORRECTED ANY AND ALL WATER OR MOISTURE ISSUES IN YOUR BASEMENT…PERIOD! So if your basement has a water or dampness issue, you MUST fix it NOW before you even think about basement finishing! I can’t stress this enough!
Once you have guaranteed that your exterior walls will never get wet or damp again, Fiberglass insulation in your new framed walls is the BEST way to insulate your basement. And that’s where the buck stops for me! Okay…I’m done ranting. Glad to finally get that one off my chest once and for all.