Home Improvement → [Insulation] Basement insulation recomendation/process

In the process of finishing basement and it's time to insulate. First off can someone recommend and particular or decent brand or does it not matter. And second, so my brain has me thinking about a thermal barrier between the insulation and the foundation wall and moisture. From what I have seen the insulation is paper backed on 1 side. The side that will be between the foundation and the insulation will be open to the insulation. Do I need somethong protecting it from condensation?

I used the pink 1" rigid foam against the concrete, then mineral wool insulation betwwn the studs. I am very happy with the result.

Um, before I answer a few questions please.
Is the basement framed? Or are there 5/4 strips nailed to the walls? Or are you going right to concrete walls?
Tell me that and I can tell you which insulation to use.

Also, vapor barrier. I personally am not a big fan of wall vapor barrier (the plastic) (at all)
I have seen so many times that the plastic actually holds the moisture in, causing mold /mildew (i have seen both black and green mold caused by vapor barrier holding either water or just moisture in.
No, I think it best to seal the concrete walls with ThoroughSeal (very good product)
»www.thoroproducts.com/pr ··· fing.htm

Again, depending on how you are lining up the walls will tell the story on which insulation to use.

Basement is already framed. Was framed when I bought the house. The studs are about an inch or so from the foundation.

And also I get zero water in the basement. Not a drop. The soil has good drainage and my house in about the middle of ther block at the peak of the hill

Camelot One's suggestion is spot on if you're concerned about moisture. I did the same along a basement wall that has the chimney behind it. Water was running down the brickwork and saturating the insulation, etc.

I've remediated the leak, but used the rigid insulation as a water shedding plane just in case, with mineral wool behind it. Benefit of mineral/Rock wool is that it won't compress like fiberglass if wet and won't rot.

That one inch gap between the foundation and the studs is standard practice her in Michigan. I would just put fiberglass between the studs and leave the gap. This will eliminate possible future problems with moisture. There will be enough air movement to carry moisture away and this will allow you to use a dehumidifier to lower the moisture between the foundation and the finished walls. I also would use green board drywall.

Have you looked into spray foam? With that 1 inch between the stud and wall it would make for a great complete envelope of the basement. Even doing 1 or 2 inches and then filling in the studs with wool or fiberglass.

If the walls are already framed, your product options are a little more limited. I suggest looking at what problem you need to address, and go from there.

If the basement is dry, then the issue would be warm/humid air from inside the room contacting the cold concrete walls, which would create condensation. You can deal with that either by preventing the warm air from contacting the concrete (vapor barrier), or by allowing airflow behind the wall to dry the condensation.

Personally, I am not a fan of plastic vapor barrier for something like this. I like the rigid foam, with all the seams taped and sealed. But that would be impossible to do with a framed wall in place. Spray foam would do the trick, and give you the best R value, but it is expensive.

The problem with the paper faced insulation is that the paper becomes mold food. Without a vapor barrier, I would worry the moisture present would allow mold to grow. I think you would be fine using just 3.5" un-faced mineral wool, and leaving the 1" air gap behind the walls open to allow airflow to dry any condensation. Menards has some good quality stuff that goes on sale every few months.

Yea. Spray foam is gonna be too much. The walls I think will have some air flow because of the way the floor joist run and because part of the basement where the boiler room is will not be finished. So air will get over there to a point. As I had said I have zero water leaks. The basement floor and foundation walls are bone dry.

Then I would think just some non-mold/mildew friendly insulation will be enough. Fiberglass or Mineral Wool would work, but the mineral wool will stand up in the wall cavity by itself. Fiberglass will need to be attached somehow, usually by way of paper facing. And I don't think I would want that in this situation.

»www.menards.com/main/bui ··· 5780.htm

Home Depot sells a no R-value version by Roxul, but it isn't as thick or as dense, and doesn't stand up on its own very well.

Unfortunately there is no me are close to me. I'm in nj. The closest one is in Ohio. I See home depot sell denim insulation. I need to compare the prices. Now I just need to figure out what r value to buy. Time to do price. calculations.

Just came from home depot. Seems everytime I go there i spend $100 (Costco too. Thats tommorow). I saw that Roxul stuff. Gonna compare price per square foot. But it's def an option.

so I was just evaluating stuff in the basement and something else came to mind. The house is a ranch so there is 1 support beam running down the enter if the house. At either end the foundation sticks out further to support the load. Thing about when I Sheetrock. The Sheetrock would be sitting right against the foundation. What do I put up to protect the Sheetrock. Or does it matter for that small spot I looked at Sheetrock prices and the mold resistent one is only 3 more a sheet so I might do that on the entire basement

I think the few extra dollars is worth the reduced chance of mold/mildew. Laying Sheetrock of any type directly over concrete is a no-no, for the reasons already discussed. I'd make sure the plastic vapor barrier extends down over the curb as a little extra protection (at minimum).

I went with Roxul R15 in my basement finishing, you can get it at Lowe's for about $40/batt.

Definitely stands up on it's own easily, and yeah, it's mold resistant if you're worried about condensation or water issues.

I don't believe my contractors put up a vapor barrier, and I wish they did and going back I woulda paid the extra moolah to get it done.

Had to go with fiberglass. That roxul stuff wasn't in the budget. Still working on low voltage wiring. What a pain in the ass.

Unfaced fibergaalss? You do not want any paper on the walls below grade.

Every thing I gave seen online show single side faced insulation. On the Sheetrock side

You wouldn't have much of a choice on that. The purpose of the paper facing is to give you a way to attach it to the studs. It would be pretty difficult to staple it from the back side with just a 1" gap.

But I do agree that using paper facing below grade seems like a bad idea.

What problems could I have?

Just some additional background info. Even on the coldest days we had lest year the temp I. Th basment never went below 58. During the summer I think the hottest I ever saw it was 66.

The problem is that the concrete will always be colder than the air temperature in the room. The warmer air will contain more water, so when it contacts the concrete, it will cool, causing condensation. Mold and mildew require water and food. The paper becomes the food.

So the fact that there is a gap between framed wall and the foundation and the air will be able to flow because the way.the floor joists run to the boiler room. I'm thinking I should be ok. If the roxul wasn't 3x the price I would have done that.

Isn't that why we use plastic vapor barrier; to keep the condensation away from the wall cavity/insulation, etc?

My understanding is that the plastic vapor barrier is more to keep the moisture wicking through the concrete from entering the room. It probably helps with the condensation problem, I just don't know how much.

That's a big non-no, you have what looks like untreated lumber in contact with concrete, you will get rot at the contact point which will eventually have sagging in the floors above

Haha. That's been like that since the house was built in 1960. There are steel support columns along the stretch too

Everyone assumes doom and gloom based on what are "best practices"... I chuckle a little with each post.

Even though you've stated that your basement is bone-dry multiple times, everyone assumes your home will rot out and cease to be.

Sounds like you have a good handle on it. Vapor barrier should be hung to keep moisture from migrating into and through the Sheetrock. Water vapor is crafty stuff.

Yea, nothing is going to rot there. Your not supposed to use treated above the water line anyway.
Judging from the pic, some R13 or R15, sheetrock and your done.
No need to over think this.

Could you fur that support area using lath strips, and use 1/4" sheetrock there, maybe with some thin rigid foam in between the lath strips? Just an idea to keep the finished drywall flush with the adjacent walls.