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emocrat
Feb 28, 2007
Sidewalk Technology

So, it seems there are some people posting in here that actually know about insulation and the dangers of doing it wrong. I don't though, so I wanted to get some advice. I have googled around a lot on this subject and I just keep finding contradictory information so, maybe a discussion in here can help me out. Rather than making GBS threads up someone elses cool project thread though, I figured I would start my own and maybe other people will find it useful. Anyone else with questions feel free to post and maybe it can become a resource.

So, here is my situation and questions:

I live in a split level brick rancher built in 1972, in the central Virginia area. The basic structure is pretty common, concrete slab basement floor, basement walls are concrete block, 1st floor walls are wood framed. and the entire thing is clad in brick veneer. The entire house sits on a moderate slope that runs diagonally across the footprint of the house, meaning, from a birds eye view the top left corner the first floor is at grade, and on the bottom right corner the basement is a walk out.

About 65% of the basement square footage is finished living space, with the other 35% being laundry, mechanical and small workshop space. I don't plan to change that ratio. There are no current water issues, and we cannot find any signs of prior water issues. The concrete and the block are dry, they do not sweat, the framing is in good condition, with no signs of ever having been repaired or replaced. We discussed with the prior owners, post sale, who I have reason to believe are honest and I have a continued relationship with and who lived there for 32 years, and they confirmed that they have not ever had water intrusion issues.

However, the entire basement is completely un insulated. In the unfinished space the exterior walls are bare concrete block. The rim joist is exposed and visible with no insulation anywhere. In the finished spaces 2x4 walls are erected with either wood paneling or drywall over them, but nothing else. No foam of any kind, no batting, no vapor barrier etc.

So, how should I go about insulating this space? I have complete access to the unfinished area right now. In the near future I will redoing a huge portion of the finished space which will be an opportunity to get behind all the walls there. My goal is basically to improve efficiency and comfort. Cost is always important but I am willing to spend the necessary money to do things well and with the most effective materials.

My understanding is that the most important part is the rim joist and the best way to do that is to use XPS foam board, but I want as much info as I can get. Also an important note is that due to the slope, a very significant amount (I would estimate 35%) of the square footage of the basement walls are above grade, and these walls are just concrete block with brick veneer.

So, suggestions? Use 2 inch XPS directly on the block walls and seal it up? Fiberglass? Rockwool? I am all ears, also let me know if pictures or further info will help. Thanks.

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Some Guy From NY
Dec 11, 2007


My basement was bare cement block walls before I finished it with drywall. I insulated using Roxul Comfortbatt (rockwool). I also have this insulation throughout the rest of my house (house was completely gut rennovated in 2013, basement was finished in '14). Roxul Comfortbatt is amazing. Easy to work with and has made a huge noticeable difference in insulating and sound deadening. Before the basement was finished, during the winter it was extremely cold in the basement, you could literally see your breath on some days. It was uncomfortable to be down there without a hoodie/sweat shirt. Now that the basement is finished/insulated, during winter it is only slightly colder than the rest of the house.

Also, Rockwool is naturally fire resistant which is a huge plus, especially in the basement where my natural gas boiler and hot water tank are located.

Some Guy From NY fucked around with this message at 19:59 on Jun 14, 2016

Slugworth
Feb 18, 2001

If two grown men can't make a pervert happy for a few minutes in order to watch a film about zombies, then maybe we should all just move to Iran!


You're a monster for suggesting rockwool as easy to work with. I mean, I guess on a technical level, but it's made of poison ivy coated bee stings.

Ultimate Shrek Fan
May 2, 2005

by FactsAreUseless


Slugworth posted:

You're a monster for suggesting rockwool as easy to work with. I mean, I guess on a technical level, but it's made of poison ivy coated bee stings.

Roxul isn't itchy at all. Theres green pipe insulation that looks exactly like Roxul which feels like fibreglass on pcp.

Slugworth
Feb 18, 2001

If two grown men can't make a pervert happy for a few minutes in order to watch a film about zombies, then maybe we should all just move to Iran!


Some googling seems to agree with you, which is kind of blowing my mind. We used rockwool for firestopping on a project about ten years ago, and I swear to god it was ten times itchier than fiberglass. I dreaded touching the stuff.

emocrat
Feb 28, 2007
Sidewalk Technology

Yeah I have heard good things about Rockwool, and I am planning on using the Roxul Safe n Sound stuff for noise reduction in the ceiling (although I haveealso read that any claims of superior sound deadening are... specious).

I guess the thing that is holding me up is that I do not really understand the way the various insulations and installation methods affect moisture, how that interplay's with the materials of my house and the local climate, and I get worried that I am going to set myself up to find out I soaked the other side of the wall and ruined it in a year or 2.

Some Guy From NY
Dec 11, 2007


I live DIRECTLY next to overhead subway tracks...I used Roxul Safe n Sound in the ceilings, along with ComfortBatt on the exterior walls. Before the complete renovation, there was fiberglass insulation in the exterior walls and the subway was so loud it sounded as if you were standing on the train platform itself. With the Roxul, it makes the sound of the subway train sound like a car passing.

Picture for reference:



I also had all the windows replaced with triple pane windows, and the through the wall AC units were removed, the holes bricked up, and I had Mitsubishi ductless AC installed.

I don't think you'll be disappointed with rockwool.

And for the guy who said rockwool is itchy? not in my experience at all. Nothing compared to fiberglass...





If you have to trim the Roxul, the secret is to use a cheap bread knife. Cuts through the batts with ease.

Some Guy From NY fucked around with this message at 14:30 on Jun 15, 2016

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emocrat
Feb 28, 2007
Sidewalk Technology

Well, thats a pretty solid endorsement, thanks man.

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