Get Nrdly Free Trial Built with Nrdly

Roxul Insulation (lower utility BILLS)

Roxul insulation was my #1 choice for our master bathroom remodel. I’ll explain why.

It’s made of Basalt rock and recycled slag. If you don’t know, slag is a by-product of steel production. I live in Pittsburgh, so it’s kinda second nature to know about slag.

Little side note: I was a geology major in college for about 1 year…then switched to chemistry. So I geek out on cool things that make your home a better place to live.

Today you’ll see why I chose Roxul for our wonky 100 year old bathroom remodel.

Plus I’ve got a surprise at the end of my video. Who doesn’t love good surprises?

What is Mineral Wool

Why is mineral wool so awesome?

Reason one: Roxul won’t catch on fire until about 2000F. I don’t know about you, I want a chance to run if my house catches fire.

Reason two: Roxul is inorganic and therefore not a food source for mold. Mold in a house is BAD, unless it’s in the form of blue cheese.

Reason three:  it’s water repellent. If Roxul gets damp it won’t lose it’s R-rating, meaning it won’t lose it’s ability to insulate.

Cool stuff.

Here are the supplies you need to install Roxul

Roxul is especially helpful in old homes that don’t have normal stud bays!!! You’ll see what I’m talking about.

Roxul Insulation…important concepts to remember

Whatever insulation you use, wear protective gear.

The little fibers are not good for your body. Plus it gets itchy and nobody likes being itchy. Remember Chickenpox?

Roxul ComfortBatt can be used for exterior walls, basements, and crawlspaces.

Roxul for exterior walls

ComfortBatt is R-15 rated and should be used in 16″ on center stud walls

R-15 Rated

How much Roxul should you buy?

It’s simple. Measure the dimensions of your wall, length x width, and get your square footage.

Obviously you don’t need to be a genius. But deduct for doors and windows.

I like to buy more than I need then take back what isn’t used. Each Roxul bag covers 59.7 square feet.

Roxul Square Footage

I feel like this is super important to keep in mind. So I’m repeating myself…the reason I love Roxul is because it’s fire resistant and water repellent.

Not every insulation out there can say this.

Roxul is fire repellent

In my video I mention that we’ll be using Schluter KERDI-BOARD to waterproof the shower surround. It’s an awesome waterproofing material. But no matter what waterproofing you use, you’re still going to get water vapor in the stud bay.

The fact that Roxul won’t lose it’s R-Value because it’s water repellent means it’s a great option for bathrooms.

After all, if insulation loses it’s R-Value your bathroom won’t be well insulated and your utility bills will go up.


How to Install Roxul Insulation…it’s like cutting bread

Hopefully if you remodel your bathroom it’s a bit easier than my project. This situation is strange because the bathroom is over 100 years old and the framing is a bit wonky to say the least.

Fortunately the exterior wall had framing that’s 16 inches on-center. No matter what your situation you’ll have to cut insulation to size, unless of course you’re using blown-in insulation…which is messy.

I like starting at the top of the stud bay and placing Roxul flush with the header.

Start at the top

Roxul should sit flush with adjacent batts and studs, there shouldn’t be any gap.

There should be no gaps
No gap near studs

Roxul is super easy to cut. Seriously, it’s easier than cutting bread. Use either a utility knife or drywall saw to cut it. A drywall T-square will help you make clean, straight cuts.

Cutting Roxul is easy

You can slice or groove out the Roxul and fish electrical lines or pipes into it.

Slice Roxul for electrical or pipes

Like I said, this house has strange framing…but that’s not a problem. You can cut Roxul to any size you need. For example, this little cheese slice.

Cutting weird pieces of Roxul
It's a Roxul Cheese Slice

Windows are one of the worst culprits when it comes to losing heat or cool air. Roxul made it easy to insulate around our new window and make this bathroom even more energy efficient for our tenants.

Add Roxul around windows

Remember how I said Roxul is fire resistant. I decided to try and light it on fire.

Roxul won't light on fire!!

I was unsuccessful. Which was cool…don’t try this at home!!

Watch my video for the complete step-by-step Roxul installation instructions.

What’s Next

Many thanks to Rockwool for sponsoring today’s video.

We installed KERDI-BOARD in the shower area to add additional R-Value to the bathroom. This was also a very straight forward project.

If you’re doing a bathroom remodel and need help, join one of our online courses – they’ll make your bathroom renovation much easier!

Let me know if you have any questions and I’ll do my best to help.



Roxul Insulation

  1. John Atkins says:

    Wow I hadn’t seen Roxul before. Thanks for sharing. My wife and I are planning to take on some insulation work throughout our house Later this summer to help with energy savings after our replacement windows are installed. I always enjoy watching your video Jeff. Thanks!


    1. Thanks John, really appreciate your kind words. Yah, I think you’d like Roxul. It’s easy to cut and the fact that it’s fire resistant makes it a great option for older homes or younger homes. It’ll definitely help cut down on your utility bills.

  2. Matthew Clemente says:

    We’ve got an insulation project lined up for later this year. We have two rooms with exposed floors – just plywood/laminate over crawlspaces that are exposed to the outside. Needless to say, those floors were very cold last winter, so we’ll be insulating. We’d already planned on using Roxul, so seeing your video was a great confirmation of our choice. I’m not sure when I’m going to start the project, but hopefully before it gets much hotter. The insulation safety kit would be really helpful!

    1. Yah, insulating while it’s 200F outside is no fun. You’ll have to keep me posted on your project. We don’t have a crawlspace but I’d have to imagine it could be easier with something like this. I’ve read about crawlspace projects and seen people use chicken wire to hold it in place.

  3. Liliana Wells says:

    This looks great. I could do it myself. I wish I had known about this when we were doing repairs to an investment property years ago. I love learning about new products.
    Thanks for entering me in the giveaway. What kind of respirator is it? I would like to buy one too.

    1. Thanks Liliana, the one I like is up in the supply list section. It’s a 3M model and I’ve been using it for years. It’s served me well and kept me safe. So many nasty things you can inhale when remodeling

  4. Sherry Rybczynski says:

    This is awesome! I want to insulate our unfinished basement ceiling because you can hear everything going on upstairs when you are in the basement. I see Roxul says it is an acoustic insulation, so does this mean it works well for sound as well as insulation for heat/cold? Thanks for the great video, it looks so easy to install and I look forward to getting started.

    1. Roxul makes two different kinds of insulation. The ComfortBatt is for insulating exterior walls and Safe N Sound is for interior walls where you want to cut down on noise. I used the former in my bathroom on interior walls and found it to cut down on the adjacent bathroom noise. So both are great options Sherry

  5. Larry W. Lee says:

    I had never heard of Roxul until your latest video today. I have seen other products like Cellulose, that’s better than fiberglass. I live in a very hot area of southern CA and it’s starting to warm up with my electric bill already at $350 a month and we haven’t run the AC yet! I’m going to start Insulating the attic and I’m going to use Roxul. Need to find out if Lowe’s or Home Depot have Roxul. Thanks for the great video’s Jeff. Please enter me in your give away. Thanks,

    1. Thanks Larry, and boy that’s a high electric bill. Home Depot carries Roxul here in Pittsburgh. The price was about $48 for a bag, so not bad. I need to add extra insulation to our attic. Our upstairs gets muggy compared to the first floor. Keep me updated on your project 🙂

  6. Celene R says:

    Delightfully timely! We have a crawl space that we would like to make into useable storage which means adding additional insulation to cut down on the extreme heat of the summer (triple digit temps predicted for this week). The builder put in blown insulation which was great until we had a damp winter this year and I noticed the adjacent room is no longer as cozy as before. This insulation definitely seems to be the insulation solution I was seeking; now I just need to figure out how to deal with all the blown insulation and putting down a workable floor for light storage.

    1. Ouch, triple digit. That’s hot Celene. Not looking forward to that in Pgh. The nice thing about Roxul is that it’s water resistant. So if it gets damp it won’t lose it’s R-Value. And if you live in a humid area the insulation is bound to get damp!!!

  7. Patricia says:

    We have a home that is over 100 yrs old and desperately needs insulation in the attic. Like your bath remodel the attic has all sorts of weird angles and spaces. We have always used fiberglass insulation but you have sold me on this product. I had never seen it before but oh my it will make this project so much easier. Thanks Jeff.

    1. Thanks Patricia. I think you’d like Roxul. Cutting it is easy and I like that it’s structure maintains its rigidity so that you can fit it tightly in framing. Old homes are so neat but a slight pain when it comes to remodeling, lol

  8. David Bruno says:

    Another great video – being a total DIYer this safety insalation kit would be an awesome addition to my work room! Keep the great info coming and hopefully choose me to win!!!!

    1. Thanks David. What kind of projects are you working on this week?

  9. JAMES BERAN says:

    When we did some insulation work, we found out it pays to shop online. We had a deep area.. At that time, there was mostly fiber glass. I remember that buying a roll of faced and a roll of unfaced to put on top of it was cheaper than buying the same R value of thicker insulation that was faced.

    Often times, online, tile is listed at a crazy price. By going to the store, I found out that the price was for a box of 5 and not the price of a single tile. I got b/w marble tile from China for $3.59 for a 12×12 to cover my faux fireplace.

    1. Tile is tricky, be careful buying the cheap stuff. Steve and I have talked about this quite a bit. Sometimes what you save initially is eaten up when you go to cut the tile and it starts to break. Then you have to buy more to make up for the broken ones. So some times it’s better to buy the better tile. Especially if you’re putting in a new bathroom and plan on living in the house for the next 30 years 😉

  10. Dan says:

    And I just bought R-13, R-19 fiberglass which loses R value when moisture condenses in the wall. I heard cellulose is air-sealing and doesn’t lose R-value. Is Roxul also?

    1. Dan says:

      BTW–Good you foam sealed the horizontal sheathing (exterior boards). I did the same and it cuts out a lot of drafts. I could feel wind from the next rooms until I sealed it out.

      1. Yah, I didn’t foam seal the boards in this house for fear it would push the slate roof. Don’t want to replace any more slate than I have to, haha. Spray foam is certainly awesome but costly. I might have to do a cost comparison down the road to get specific numbers. That would be a great thing to see on paper or a Google doc

  11. Renee says:

    Another great video Jeff! My husband and I have used Roxul to insulate our interior wall in our attic. You are correct – Roxul is very easy to cut. We have plans to insulate the rest of our attic and your giveaway would be very much appreciated! Thanks Jeff!

    1. No better time to insulate the attic Renee. I have to do the same thing. It helps cut down on heating and cooling bills. Plus makes the house more comfy. Have to get on that right away…

  12. Lorraine Newman says:

    Hi Jeff
    Thanks for taking the time to make these videos and news letters to help us all out. I work with my brother on his home repair and maintainence business. I am always passing along your emails to him for the great DIY and tips. We will try Roxul on the next insulation job and the insulation kit would help us out. Thanks again Lorraine

    1. Thanks Lorraine. Roxul is worth checking out. Plus one person can install it no problem. Which makes for a more efficient work day. Really appreciate you passing on my videos, thanks a million 🙂

  13. Dan Hedman says:

    This is great information. I’ll be retiring from the army next year and will be building our final house at that time. I am constantly researching products to make our final house as energy efficient as I can, so thanks for sharing. And like you, I try to do as much as I can myself so the right equipment is always a big help.

    1. Congrats Dan on your retirement. And thank you for serving our country. Let me know if you have any questions about materials or tools. I’d be happy to help in any way.

  14. catherine Brown says:

    That’s great product.It very easy to do.I live house that was built in1907.It would be great to use this product.

  15. Eric S says:

    Hi Jeff, thanks for the Roxul installation explanation. I am going to be finishing a basement and part of an outbuilding, so I was really happy to find your blog to learn about best practices and products. I would use the safety kit for both the renovations, of course. Have a great summer! Your Pens knocked out my team in the playoffs. =/ But Consol’s a pretty cool place.

    1. How cool Eric, are you making your basement into a game room?

      Sorry to hear about your hockey team. The Pens are tough this year.

  16. Lynn K says:

    WOW I have never heard of Roxul. We are going to replace a shower some time here in the next 6 to 12 months. I am sure going to look into replacing the fiberglass insulation in the wall with this. Looks like a GREAT product and I bet it is much better to work with then fiberglass.

    1. That’s exciting Lynn. What kind of bathroom remodel are you doing?

  17. Marzette says:

    Hi we are building our house paying for it as we go. We still have a couple of rooms to insulate and the attic. I have never heard of this type of insulation till now. Thanks for the informative articles and videos.

    1. Congrats Marzette. Roxul in the walls would help a ton. And if you do it yourself you’ll save some money.

  18. Gina Goforth says:

    I would love to have the safety kit. I need to replace the damaged panels in my daughter’s room with wall board. The room has no insulation at all, and has already been getting pretty hot. If I get that done, I’ll probably need to replace and insulate the whole back third of my house once it’s leveled. The walls are already in cracked pretty badly. Anything that can make that process go more smoothly would be greatly appreciated.

    1. Adding insulation will make her room way better. And you’ll hopefully lower the heating and cooling costs.

  19. Douglas Blazer says:

    Thanks for all your repair tutorials. They are very helpful. I am going to put new walls ,just two sides, in my bathroom and Roxul looks great. The reason I would really be able to use the kit you are giving away is that I have had Asthma all my life and I have to be very careful about Dusty environments. Thanks again for all you do.
    Doug Blazer

    1. Thanks Doug, my wife has horrible asthma and allergies. So I can totally understand your situation. A good respirator and ventilation is a must when doing a project like this one.

  20. Squafdonoboles says:

    I used Roxul to insulate my two sheds. Worked like a charm!

    1. That’s cool. Plus the sheds are fire resistant now!!

  21. Margie S. says:

    I really need to insulate my attic and also around some of my windows. My house is almost 100 years old also, so I know what you’re talking about when you say some of the spaces are kind of wonky. My house has plaster and lathe walls with fire walls. We had blown-in insulation done about 30 years ago and there are definitely cold/hot areas on the outside walls. Probably the insulation has settled so it needs to be redone. I am one of the people who has never heard of Roxul …thanks for the information Jeff.

    1. Thanks Margie, your house sounds just like this one. Those pockets are so frustrating but at least blown in is better than nothing in some cases. That said, if the walls are down Roxul makes sense.

  22. James Stinnett says:

    This would work wonders on our crawl space which has high humidity and no insulation

    1. It would be pretty easy to install James. You might have to secure it with something like chicken wire but it’ll serve you well.

  23. Linda P says:

    Jeff, I could really use the insulation safety kit. I’m planning to add insulation to the attic this fall. We have blown insulation now. Would I put this with the paper side up or down? Love your product reviews!

  24. Diego A says:

    Thanks Jeff, I just happened upon your site as I was doing some insulation research and this stuff looks awesome! I moved into my grandmother’s old house and have slowly been remodeling. We found out this winter that the bathroom is in serious need of insulating. The exterior walls are brick and I honestly don’t think there is any insulation at all in there, it get’s COLD! I’m going to have to give Roxul a try.

  25. Roxul is one of best insulating materials but it has its flaws, when you work with him you must use rubber gloves and, half mask with p3 filters, googles and coverall . Those particles which came out from material can cause irritation on skin. I didn’t noticed you used foil to cover close insulation, before installing drywall or wood?

  26. Joe says:

    I have a space above my garage. I’d like,to insulate underneath the roof to keep my garage a little cooler. Can I usebRoxul between the roof trusses? How would I tack it up to the plywood that makes up the roof deck

  27. Mark says:

    Hi Jeff,
    I also live in the Pittsburgh area and came accross your video… I’m looking for a Roxul installer for my basement. Could we discuss live or could you pass along your contact information so we may discuss. I’m also considering a few other options… installing 1″ Kingspan XPS Insulation board on the inside wall directly on block then framing over and filling the stud space with the Roxul R15… comments suggestions are also appreciated.
    Thanks very much.

  28. Ria Jackson says:

    I just watched your video to show me how to self insulate my home. I’m remodeling my master bathroom & main hall bathroom first then I’m having a extra room added. I will love to try out Roxul for my home. Thanks for sharing🤗


    Tyrrell’s Punting Cambridge Co. was set up by locals who know Cambridge and its history inside out. Punting in Cambridge has been a favorite pastime in the UK since the 19th century. The reason it is still popular in London is due to the immense relaxation and peacefulness it brings to the mind of the traveler. Even before the 19th century punting had been utilized for fishing and trading purposes.

  30. jordiary says:

    Before choosing , I was actually in a dilemma whether to choose them or go for another option. But later I made up my mind to make a try. And guess what! This was the best decision that I ever made so far for my trips. Their hospitality left me speechless. And also the chauffeur was not just an expert punter, but also was omniscient about the history and culture of Cambridge. If you are someone who is planning to go for a punting in Cambridge, trust me, Tyrrell’s Punting would be the best option.

Leave a Reply

Your email address will not be published.