Insulating a basement shop

[Andy Pratt]

I am insulating a below-grade basement shop in upstate NY and wanted to get some advice. I'm in a bit of a time crunch on ordering materials so any thoughts are appreciated.

The walls are cinder block 7-8 feet tall and my endstate is to have full, covered stud walls to have something to affix cabinets/ducting/electrical conduit to, and insulate to allow me to keep the shop heated year round.

I dry-locked the walls and put an epoxy coating on the floor, so there is already a vapor barrier there. My dilemma is that if I throw a stud wall over that and insulate the cavities, hot air from the shop is going to be condensing right on the inside of the vapor-sealed concrete and I might have a moisture problem in the wall.

Any thoughts on how to insulated/wall this space without doing something foolish that would cause moisture in the walls?

Thanks,
Andy

[Richard Jones]

Andy,

I guess you've seen these?

http://www.eere.energy.gov/buildings/building_america/pdfs/db/35017.pdf

http://www.buildingscience.com/index_html (then type in "basement insulation" or similar in the search function at the top right)

Hope this helps.

Rich

[Paul Saffold]

"The No-Mold Finished Basement" in March 2005 Fine Homebuilding. It is viewable online if you subscribe to FHB.com.

[John Coloccia]

I am insulating a below-grade basement shop in upstate NY and wanted to get some advice. I'm in a bit of a time crunch on ordering materials so any thoughts are appreciated.

The walls are cinder block 7-8 feet tall and my endstate is to have full, covered stud walls to have something to affix cabinets/ducting/electrical conduit to, and insulate to allow me to keep the shop heated year round.

I dry-locked the walls and put an epoxy coating on the floor, so there is already a vapor barrier there. My dilemma is that if I throw a stud wall over that and insulate the cavities, hot air from the shop is going to be condensing right on the inside of the vapor-sealed concrete and I might have a moisture problem in the wall.

Any thoughts on how to insulated/wall this space without doing something foolish that would cause moisture in the walls?

Thanks,
Andy

You can go down the rabbit hole on this one.

I ended up sealing the wall with Sanitred, and using Wallmate insulation. It has slots for furring strips built in. The stuff is not cheap by any means, but it works. My problem was that I was converting a garage, the entry door to the house was right up against the wall. I only had 2 5/8 inches to work with. I used 2" insulation with 5/8" drywall :)

If I had more room, I would have built a wall several inches away from the cement wall. This allows any moisture to condende on the concrete harmlessly, and allows for airflow across the wall and sill.

If you ask ten different people, you'll get 20 different answers on the right way to do it.

[Justin Florentine]

I have a very similar problem. Hundred year old house, below grade basement. Fieldstone foundation walls, dirt floor, poorly covered over with concrete. Exposed ceiling about 6' + high. I'm 6'1", so I slouch.

I was cleaning out down there after having been out of the shop since spring. Getting ready for the "inside" seasons, you know? Anyway, it's been really rainy this summer and it is taking its toll down there.

The deck of my jointer is showing first signs of rust. I'm kinda in a panic about it, because I'm really not sure if sealing up a 100 year old basement is gonna be possible.

[Ken Garlock]

Hi Andy.

What I would do is to keep the stud walls an inch or two away from the basement walls. Then I would have urethane foam sprayed to fill the space between the studs and fill in the small gap between the two walls. Urethane insulation gives you an R-8 per inch, so temp differentials should not be a problem. Example, 2x6 stud wall: 5.5 inches, one inch offset from wall gives you 6.5X8 = R-52 and that is great in anyones book. The urethane gives you fantastic insulation, and will help seal the basement walls. Wall sweating is a non problem, given you did a good job sealing the walls.

[phil harold]

http://www.buildingscience.com/documents/information-sheets/5-thermal-control/basement-insulation/


just for your info dri-lock only last about 5 years this all depends on how much water is trying to come into the basement

[David Christopher]

I think Ken hit the nail on the head......cant go wrong with urethane

[Scott T Smith]

I think Ken hit the nail on the head......cant go wrong with urethane

+2. Spray foam is an excellent choice for insulation.

[Steve Goetz]

Andy,

Follow this link and it will tell you exactly how to insulate you basement walls properly. www.homeconstructionimprovement.com/how-to-insulate-basement-walls/ (http://www.homeconstructionimprovement.com/how-to-insulate-basement-walls/)

I am currently finishing my basement and am doing just as the link suggests. Foamboard, studs, insulation, drywall. Using spray foam is nice, but it's expensive and it does not allow you to add electric or anything else in those walls down the road without major deconstruction. The foam works well and is easy to apply with foamboard adhesive. I used 1" foam which gives an added R value of 5.

Hope that helps, Steve

[Ryan Stagg]

Moisture in the walls is inevitable if you have a warm living space - plan for it instead of trying to avoid it.

The Building Sciences treatise posted above is excellent. I just went through this myself - 2" XPS directly against the slab, framed wall directly against that, and unfaced batting in the framing - although I think spray foam, as others have mentioned, in the cavities would be better if you're willing to pay for it.

Additionally - all of my bottom plates basement-wide sit on strips of 1" XPS. Makes a nice thermal break and keeps you from having to use treated lumber.

[Anthony Whitesell]

Ummm, that's funny. When I called Dow's help line about the same project, I was told that there's no guaranteed way to prevent mold from occuring in the space between the concrete and the insulation. I was told by their "expert", I would be better off leaving it un insulaed for maximum airflow to reduce the chance of mold forming.

At the same time, spray insulation was not (5 or so years ago) as popular as it is today for the DIYer.

[Gary McKown]

My basement shop (which is only about half underground) is concrete block and uninsulated. I realize the Phila. area is not upstate NY, but mine stays quite pleasant with only one vent off the main HVAC duct and a simple electric space heater running occasionally.

I have never had any indication of moisture through the walls or floor, but I will leave it uninsulated. There are ways to affix whatever to the walls, such as hanging temporary panels from a cleat over the top of the blocks, with a few added anchor screws.

[Anthony Whitesell]

My basement is completely unheated and is atleast 60% underground. Last December we had a power outage that last lasted 2 days (others were out for almost 2 weeks!). So what little heat the furnace in the basement provided wasn't there. The basement dropped to 55 degrees and never recovered until spring.

I also run a dehumidifier 24-7-365 and it fills the bucket atleast every three days. More this past spring when it rained every other day.

I have also come to the realization that the concrete used to make the foundation wasn't exactly top or atleast the mix was a little off. The metal pins that held the forms all rusted out and leaked, in addition to the high moisture levels. I ended up driving out them out with a piece of 1/4" drill rod and filling the holes with some quickrete repair stuff that comes in a chaulking type tube. So far so good.