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Jerry LaBelle
03-01-2008, 7:12 AM
In the process of building my new basement shop (just moved in to our new house). Got my permit from the inspector and when I mentioned insulating my basement walls he said it would be a waste of money. He said that with the 1" foam board on the outside of the poured concrete walls that I would already meet an R11 insulation value. Once you get below the frost line the temperature stays pretty constant and I would not gain anything by adding more insulation on the interior. He also suggested not to use a vapor barrier since you want the concrete walls to breath and not have moist air trapped between the walls and concrete. I intend to put 1/2" OSB on my 2x4 walls.

Any thoughts?

Jerry

Eric Haycraft
03-01-2008, 9:59 AM
Definitely don't use a vapor barrier.. You will probably end up with mold if you do. The only good ways to insulate concrete that I know of are spray foam or foam sheets. At my sister's place we put up unfaced mold resistant fiberglass and that should hold up well too. Since you already have foam on the outside of the wall, I would tend to agree that it probably isn't worth putting more up. The best insulating property about concrete is that it prevents all air from passing through it, so it is pretty energy efficient just by itself.

Victor Stearns
03-01-2008, 4:48 PM
To Insulate or Not To Insulate, Oh The question.
Anyway, all of the walls in our basement, which is 90% finished have the walls studded with 2X4's and 3-1/2" of insulation. I do know that you can feel the difference. When we added a 12x22' addition to the house, we had to also put a full depth basement in due to the grade of the lot. This has sense become a bedroom for our son. Prior to adding the studding and insulation it seemed to feel chilly. Afterward the chill is gone.
So I would insulate without a question. It will also help with deadening the sound of the shop equipment. I would also insulate the ceiling.
Victor

Eric Haycraft
03-01-2008, 4:58 PM
I'll soften my answer a bit.. If you are studding out the walls, why not. It costs next to nothing for fiberglass insulation and you can't (easily) add it later. Just make sure to get unfaced mold resistant insulation.

Rob Will
03-01-2008, 10:27 PM
Jerry,
I used a DOW styrofoam product called WallMate in my basement. It works very well and creates a strong, solid-feeling wall.

http://www.youtube.com/watch?v=uecMuy7b7-Y

As far as the insulation on the outside of your house goes, I would suspect that as time goes on, the styrofoam will accumulate a bit of moisture and become less effective as an insulator. One thing for sure, energy is not going to get any cheaper. I would definitely insulate the interior walls.

Rob

Kev Godwin
03-02-2008, 12:27 AM
Jerry,
Eric H. gave you some very good advice. If you do plan to build stud walls on the inside of your foundation walls, it could be viable to insulate between the studs without a vapor barrier or vapor retarder (they are not the same). The rigid insulation you said was on the outside of your foundation walls is likely extruded polystyrene, not expanded polystyrene. (In laymans terms - you likely have a colored insulation board on the outside, not a type that will break apart in very small white beads if broken down.) Fiberglass insulation without a facing will permit natural soil moisture to evaporate through the system to the interior with minimal risk of building up too much relative humidity, or worse; creating a mechanism permitting water saturation.

Extruded polystyrene will give you many years of thermal performance beyond expanded if used in contact with exterior grade. The hygrothermal performance difference between these two insulation boards is great. Expanded polystyrene is not a good product to be used in contact with grade and will break down in fairly short order.

If you do plan to add studs on the inside of the foundation walls, it is okay to add more batt insulation given your climate location.

Kev Godwin, AIA, NCARB
Building Solutions, PLC

Joe Chritz
03-02-2008, 4:40 AM
What Kev said but I would add that if you can swing it have 1" of spray urethane foam sprayed onto the wall, either before or after studding out.

Expensive but worth every penny.

Joe

Jerry LaBelle
03-02-2008, 6:48 AM
Jerry,
I used a DOW styrofoam product called WallMate in my basement. It works very well and creates a strong, solid-feeling wall.

http://www.youtube.com/watch?v=uecMuy7b7-Y

As far as the insulation on the outside of your house goes, I would suspect that as time goes on, the styrofoam will accumulate a bit of moisture and become less effective as an insulator. One thing for sure, energy is not going to get any cheaper. I would definitely insulate the interior walls.

Rob

Rob,
What's the price on these panels and are they found at HD or Lowes?
Thanks
Jerry

John Keeton
03-02-2008, 7:25 AM
When we built our home, we had the spray urethane applied to the entire basement, after studding up the walls. Hold the studs back at least 1/2" from the concrete. The basement is dry, warm, and comfortable. Make sure to get the closed cell foam, it has a near zero perm rate. It is more expensive, but you will get that back in no time. I also used it on my shop which is a stand alone metal building. I had the whole interior sprayed, ceiling and walls. I is tighter than a drum! The wind can be blowing 40mph and virtually no heat loss.

Darryl deHaan
03-02-2008, 8:06 AM
I just finished my basement after a flood, and researched this tirelessly. What I ended up with was extruded (closed cell) polystyrene glued to the foundation and then a studded and insulated 2x4 wall covered with drywall. The whole thing is moisture control. If it is coming through your foundation, you have to deal with that first, otherwise you might be wasting your money. The poly styrene is permiable, so moisture will eventually pass through, but very slowly. Occasional seasonal moistness can be ok with this system.

The typical polystyrene is around R5 per inch. I put 1" all around and tuck taped all the seams to create a moisture barrier. I used mineral fibre insulation (brand name Roxul up here in Canada) because I find it alot easier to work with and it is resistant to water and fire. The trick is to not trap moisture in the wall. By using drywall (aka sheetrock) and using a latex paint on the surface, you allow any moisture to pass into the room. The use of a dehumidifier is key in this solution.

The US department of energy did a pretty good study, and spells it all out in this document: http://www.eere.energy.gov/buildings/building_america/pdfs/db/35017.pdf

Good luck,

Darryl

Thom Sturgill
03-02-2008, 8:14 AM
The mineral fiber (rock wool?) insulation is also a better sound blocker than fiberglass (for the ceiling!) and is not as irritating to work with if you are installing it yourself.

Lee Koepke
03-02-2008, 8:40 AM
I have a basment with poured walls and it does stay a pretty constant temp all year-round. In the bar/gameroom, I did not add any additional insulation on the furred walls, and the shop area is still exposed concrete. Its a daylight basement so the entire rear wall is framed and insulated.

I am in Georgia, so my temp variations will not reach the extremes you have in the North, but the gool 'ol Earth is a very good insulator.

It boils down to personal preference. Its not ALOT of money, if you do it while framing. Change your mind later .... different story.