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How to Insulate Walls and Ceilings

Insulating walls is good.

Insulating ceilings is good.

But when you can do both?

You should high five yourself…

…because your home will be SUPER comfy.

Today you’ll learn how to insulate walls and ceilings the right way.

These tips instantly cut your utility bills and aren’t hard to do.

Let’s dive in.

Today’s Backstory

My buddy Bill put an addition onto his house.

Let’s just say his family is expanding.

Bill's Family

The walls and ceilings in Bill’s addition are open.

This presented us with a great opportunity to show you how to insulate a home.

Here are the supplies you need:

  • R-21 for 2 x 6 Walls ($58 per bag)
  • R-38 for Ceilings ($58 per bag)
  • Gloves ($10)
  • Eyewear ($10)
  • Utility Knife ($5-$10)
  • Insulation Knife (optional)
  • Dust Mask ($3-$5)
  • Carpenter’s Square ($6)

Adding insulation is pretty easy.

But you can mess it up.

That’s one of the reasons we made this tutorial…to show you the right way.

How to Insulate Walls 

What’s your first step?

Measure the distance between studs.

Most homes have 16 inch on-center studs.

You might have 24 inch on-center studs, you gotta check.

Pretty sure my 11-year old daughter could handle this.

Measure Studs

Insulation should fit snug agains the studs to prevent drafts.

We chose Kraft-Faced R-21 for Bill’s walls because it’s the best option for 6″ studs.

R21 Insulation

Kraft-Faced insulation also helps prevent mold and mildew.

For cold climates, like Pittsburgh (GO  STEELERS), you should have the paper face the interior of the house.

Kraft Paper

I personally like Johns Manville because it’s formaldehyde-free.

If you value your health this is the way to go.

Does anyone else get grossed out at just saying formaldehyde…reminds me of dead frogs floating in jars.


Measure the width and height of your stud bays.

If you need to trim batts of insulation, do it with a utility knife and carpenter’s square.

Cutting Insulation

All holes in studs should be sealed with fire-rated caulk.

This goes for wire holes, too.

Hey, this is a great excuse to use the caulking gun!

Sealing Holes

Insulation should fit snugly at the top and bottom of the stud bay.

Snug Fit at Top

Split insulation and feed it behind and in front of the wires.

Split Insulation

Electrical boxes present a different challenge.

You should cut out a section of insulation for the box.

But make sure the insulation still fits tight against it.

I joked with Bill that he looked like a character from the Walking Dead…

…beards and knives automatically trigger a Rick Grimes reference

Electrical Box

Our insulation’s Kraft paper had tabs on it.

You should staple the tabs every 6-8 inches on the inside of the stud.

This keeps a nice tight seal and prevents the drywall from having bumps.

Stapling Tabs

Cut odd size pieces of insulation so that they fit nice and tight.

Cutting Odd Pieces

Okay, that pretty much does it for the walls.

We have a few extra tips in the video tutorial, don’t miss that.

So, how should you tackle ceiling insulation?

Ceiling Insulation…Not as Hard as You Think

Bill was a bit nervous to insulate the ceiling.

Until he realized the insulation was cut into 24″ by 48″ batts.

Anyone can install this size of insulation.

Bill's R38

Here’s one of the most important ceiling insulation tips: don’t block air vents.

This stops proper airflow into the attic.

And can lead to problems.

Watch the video to see

  1. Bill’s cute daughters
  2. how to insulate
  3.  our COOL SURPRISE at the end


What’s Next

Many thanks to Johns Manville for sponsoring our project.

Good insulation combined with a solid foam backer board like KERDI-BOARD can make for a cozy bathroom, too.

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.

Thanks as always for reading, watching and adding your 2 cents.



Interior Insulation

  1. Robb c says:


    Thanks I have a garage that needs to be insulated. Thanks for the video.

    Robb in Detroit
    PS I will use jm insulation for my project

    1. What’s in that garage Robb?

      Something with lots of horsepower I hope!!

      1. Cami says:

        Aloha! Thank u for ur video. I got a question: in hawaii with warm weather should i use same insulation or would the house become really hot? Where i live is humid n rainy but not hot. The other question is do i need to calk wire holes on the ceiling too? Or just on walls? Do i need to have that checked by inspector before putting the insulation or just go for it ? Many thanks!

  2. Adam Drummer says:

    Hey Jeff~
    Thanks for the great insulation tips, esp. about caulking the wiring holes and sealing the insulation seams with tape. I’m hoping to insulate my garage by the end of the month if the weather allows. It’s getting colder and colder in Oregon and I’m tired of having to run multiple portable heaters all the time! Now I just need to move all the boxes, shelving, and tools out of the way.

    1. Oregon…I’d love visit.

      I’ve been wanting to get out West.

      Don’t worry, I have plenty of stuff in my garage, too. Funny how things pile up.

      Glad these tips might help you out, keep me posted 😀

  3. Char says:

    Jeff, great video but need to know: floor of my attic [which is used for storage] is insulated with similar product but the ceiling is not. Should the ceiling be done as well?
    Also have a free standing garage that could really use insulation, has none anywhere.
    Thank you,

    1. Good question Char, as long as your joists are packed with insulation you should be ok. About 18 inches of insulation would be good but lord knows we don’t have that in our house. So I’d focus more on the joist bays 😀

  4. simplydab says:

    We would insulate the floor joists under our office – it’s over the garage so it stays SUPER cold in there!!! Also the closet is a bump-out addition to the side of the house so it’s not insulated either, we suspect…. we’re seriously thinking about poking some holes in the interior walls and doing blown-in insulation. I have a lot of clothes stuffed in there but they only insulate so well, ya know?

    1. Here ya, and I think the blown-in insulation is a great option for you. Especially if you want to keep your walls intact 😀

  5. Lee Wells says:

    Hmm. Looks like you were taking a break from home repairs to do some bow hunting, thought I saw a bow in the back seat of the car. 🙂
    I got a old house…ceiling I can do from the doing the walls cant use that..wonder if you can refill them? reinsulate them? it appears that the insulation in my walls is loose stuff not like the new stuff.
    any suggestions.

    1. Anthony says:

      Yes you can refill your walls with blown in. You can do that a single way in three different locations depending on what is easiest. The idea is that a circular hole is drilled into each study bay – This hole can be done from the exterior, the interior of the room or from an attic through the top plate. Although you will want to be careful with that last one depending on your house’s structure. All you do is purchase the blown in insulation and a blower (most home improvement stores will loan you the blower for free if you buy enough insulation) then put the hose up to the drilled hole, blow it in as tight as you can, patch the hole and you are done!

      1. Great tips Anthony, totally agree with your approach. Thanks for helping Lee

    2. No bow, just lighting for our video, haha.

  6. Rex Card says:

    Thanks for another great video. I’d like to insulate my sub porch in hopes of using it during winter or early Spring.

    1. That’s cool Rex, good thinking 😀

  7. TC says:

    When cutting with a utility knife it helps to press down as hard as you can. I’ve used a 2×4 before and pushed with most of my weight. The harder you push, the easier to cut through. It was briefly mentioned in the video, but I thought I’d raise the point again since it’s really hard to cut if you don’t squeeze it down. Cheers!

    1. Thanks TC, also doesn’t hurt to have a fresh blade. We probably should have mentioned that, too.

  8. Nicole says:

    I would like to insulate my home office. It’s the coldest room in the house in the winter time.

    1. If you’re like me you spend a lot of time their Nicole. So insulating would be a great option 😀

  9. Darlene says:

    Thanks for the tips. I have a second story addition to insulate. I will use JM insulation

    1. Awesome Darlene, it’s easy to use. Are you going to start with your attic?

  10. Ingrid says:

    Great video. My home is quite old and recently I found that the walls lack insulation. How can I address this problem without taking down the walls? Wish it was as simple as your video.

    1. Thanks Ingrid for your question.

      Lee asked the same one earlier.

      Your best option is to use blown-in insulation. You’ll have to cut holes into the stud bays and fill them with the insulation. Then, you have to patch the holes with joint compound, sand, prime and paint. Way out all these steps and see if it’s worth it to you 😀

  11. Deb says:

    Need to add insulation to a family room that was once a single car attached garage. This would be a good option.

    1. Cool Deb, I’d rather have a family room than a garage 😀

  12. Laura Z. says:

    I am currently in the process of insulating the exterior of my house. You are lucky to have uniform 16″ stud sections. On my 1950 house, they are all different widths, ranging from 8″ to around 15″. Each has to be separately cut to width. A total pain! Where was the building inspector in 1950? Did they even have one? This wasn’t an amateur built house, but part of a post-war cookie-cutter subdivision. I guess they were building “fast and loose” in those days! Anyway, I’m going section by section and have used two brands of insulation. One brand is easier to cut and less itchy than the other. I’ve never used Johns Manville and hadn’t thought about the formaldehyde issue, so I’ll give that a try.

    1. Anthony says:

      Laura, try the Roxul brand of insulation if you haven’t already. It’s a little pricier but, MUCH easier to handle and cut. Downside it is not readily carried by Home Depot or Lowe’s in my area. (except for their soundproofing 16 on center batts) I just go to Lowe’s website and have it shipped to store.

    2. It would have been interesting to see the construction of those homes back in the 50s. I wonder if there was an inspector. Good questions. It is a paint to cut lengthwise, you could use the route we chose or blown-in insulation Laura

  13. Matt palazola says:

    Thanks Johns Manville!

  14. delruel says:

    I’ve installed insulation before, but now I know how to do it the right way. Seriously great tips. Thanks!

    1. Thanks, there are some small details that add up to a big deal if installation is done wrong. But overall, it’s pretty easy.

  15. Jean says:

    Although I am not astute with skills like your own I enjoy getting your emails. This video gave me some information about insulating. I will be sharing this video with all of my family (I come from a large family) who do home repairs all the time. They will love it! I hope sign up for your emails as well.

    1. Awe, thanks Jean. I really appreciate your kind words. Hopefully your family likes the video and tutorial. If you have any requests for videos let me know. I’m always happy to help 😀

  16. Christopher Dean says:

    Thanks for the video!

  17. Gloria K says:

    Well I learned something today…

    1. Awesome, thanks Gloria. Insulation isn’t too bad, can actually be fun once you get going

  18. Liisa says:

    Great info, I will be replacing discolored insulation in my garage your way, Thanks!

    1. You’ll like those small batts Liisa, very easy to use

  19. Bill Brennan says:

    Good suggestions….time to get to work!!

    1. Seems like there’s always work to be done Bill…the life of a homeowner!!

  20. Sandra Lea says:

    Great info, I need to reinsulate my basement ceiling after a plumbing leak.

    1. Ugh…plumbing leaks are the worst Sandra. I hate them with a passion. Hope it wasn’t too bad.

  21. Brandon says:

    Enjoyed the video. I’ll be using these tips as we finish our basement next year. Somewhat related question for you: As far as heat/cold/moisture are concerned is it better to build the wall/insulation right next to the basement’s cinderblock wall or leave a 6-12 inch gap?

    1. Anthony says:

      No need for a gap unless you want to lose area off your finished space.

      1. Good question Brandon, if you follow your local code for basement walls you should be good.

        1. Brandon says:

          Thanks Anthony and Jeff. I’ll see what our local basement code is.

  22. Kevin says:

    Great video and very helpful tips! Last summer my dad and I installed JM insulation in my garage walls. It has really helped keep both the winter and summer temperatures very manageable. Thank you for all the fun videos and podcasts!

    1. Thanks Kev, really appreciate your kind words. It’s cool that you and your Dad do that kind of stuff together. Projects are always more fun with family and friends.

  23. Ed says:

    Like the video, short, to the point and informative. Now have to tackle my garage ceilings with the 4 ft units. Hadn’t seen them before.
    Have a question, what are the black stud attachments I see in the film? Can’t figure them out. Keep up the good tutorial info.

    1. Lol, I asked Bill at the house but can’t remember his answer Ed.

      I’ll get you a the info…

      1. Got the answer Ed, they are for low voltage wires like the internet, speakers for TV, medias wires, etc.

        Bill thinks of everything when it comes to new wiring, he’s an electrician 😀

  24. Michelle says:

    I’d use JM to insulate my garage. It’s freezing in the winter. I’ve used a couple of left over pieces from the attic. Those couple of insulation pieces in the garage, just don’t make a difference. Plus now I know the right way – how to insulate around wiring, cut to fit and attach it. The pieces I have aren’t attached. At least I got the paper facing the right way. lol

    1. Sweet, glad the vid helped Michelle. Yah, paper facing can be tricking. Once you get the entire garage insulated you’ll notice a big difference!

  25. Shawn says:

    Beefing up the attic insulation and air sealing would be my first priority for adding insulation.

    1. Me too Shawn. I have to do that myself. Our house gets too cold in January and February!!

  26. Matt says:

    Good video.
    Haven’t had to work with insulation yet, but this gives me a little more confidence.

    1. You can do it Matt, once you get started it’s easier to finish.

      Let me know if you have any questions.

  27. Tammara says:

    Good tips, thanks! I will be removing ceiling paneling soon to insulate.

  28. michael sklar says:

    As always – great video. So helpful.
    I’d be glad to complete the insulation on our crawlspace.

    1. Ah, crawl spaces. Not for the faint of heart.

      Thanks Michael, keep me posted on your project buddy.

  29. Myrna Ball says:

    Very helpful video, I learn so much from them. Doing some finishing in our home, needed this, thanks

    1. Glad to help Myrna, let me know if you have any questions 😀

  30. Myrna Ball says:

    thanks again. see above comment

  31. maureen says:

    very good information on insulation. I have a question . I had I believe it is called ridge vents. Well I had the idea of putting vent on both front and back to cut down on heat in the summer time. It works but it is winter and I have an idea of covering these vents on front and back with plastic for the winter. There is no flooring per say just insulation blown in on the floor. Would this be a good idea or maybe build a wood box around it and put a hinged door on the box ?

    1. Maureen, if your ridge vent is in the roof you want to leave this alone. It allows the air to flow into the attic and ventilate the space. But could you post some pics over in our Facebook group? I just want to make sure we’re both thinking of the same thing.

      here’s the link to join

  32. Debbie How says:

    Hi Jeff:

    Question: I live in Ontario, Canada and it gets pretty darn cold in the winter. Our problem is with both our front and back doors during the winter months. Neither my husband or I are handy and we need help. We feel the cold coming into the house and the sides and bottom of these doors. What can we do to fix it?

    Thanks so much for your help.

    Debbie : )

    1. You can add door sweeps to the doors Debbie. That’s not a bad project.

      There are a variety of different sweeps, too. If you know how to measure, drill and cut wood you can do that project no problem.

      Also, if the sides of the doors are drafty you can check the seals on the doors. Chances are good that you might need knew ones.

      You can get feedback from our group over on Facebook and post some pictures of your doors

      Here’s the link to join

  33. Hank says:

    Crawling under the house today to insulate the crawlspace. What timing! You didn’t specifically look at floor insulation, but some of the basics still apply.

    REALLY excited about sliding around on my back, installing insulation above my face! With only 1.5-2ft of crawl, it’s pretty tight.

    Thanks for the video and story (and surprise!)!

    1. Lol, yah I wouldn’t be excited either Hank. Good luck my friend.

      You’re a brave man!!

  34. Rebecca Davis says:

    Great video as usual. I don’t have any open walls but could use the gift certificate to help pay a professional to blow insulation behind my existing walls. I have an entryway that get down in the low 50s during cold winter months! Builder forgot the insulation??? Brrrrrrrrr!

    1. Whew, that’s cold Rebecca.

      Sounds like you sure could use new insulation in your entryway. That or a new door.

      Funny thing is we need a new door, that sucker is terrible at insulating 🙁

  35. Joanne De Lisi says:

    I think you have ESP, Jeff because every time I get MANIC thinking about HOW to approach a repair in my very OLD home, there you are posting the video I need. . Due to medical circumstances, I was unable to do needed repairs for decades. I have been freezing here. In fact, the last time insulation was done here was when I was a child well over 50 years ago. This video couldn’t have been better – simple and clearly explained. Thank you a million times for all this help.
    With a hug & kiss for Bill’s adorable children,

    1. Thanks so much Joanne, hope your doing better now.

      Bill and I had fun making the video. Glad it could help you see how easy this project could be.

      Please let us know if you have any questions.

  36. Jackie says:

    Great timely video — it’s chilly in the ‘Burgh today! 🙂 I would love to insulate the ceilings in my basement, but wonder what products might be best: the floors are hardwood laid directly on the joists. (1950’s home) This means that any water/dirt that falls between the cracks in the hardwood floors ends up in the basement. UGH. I have no clue how to insulate this without major work and/or potential for mold issues later….any ideas?

    1. It sure is getting cold Jackie, what’s up with the weather here?

      I know exactly what you’re talking about with the hardwood floors. Do you have an unfinished basement? If so, you’ll be able to add some insulation to the joist bays. If you’re super worried about mold then you could use mineral wool.

      It’s great stuff and Johns Manville makes it. Or your could use the insulation we used and make the Kraft paper face the finished part of your house, e.g. the upstairs. I’ve never done this project but some people use chicken wire (not pretty) to hold the insulation in place.

      1. Jackie says:

        Thanks for the ideas, Jeff. Yes, the basement is unfinished. What I worry about with kraft paper faced insulation is if (or rather, WHEN) I spill something on the floor, then that liquid seeps between the floor boards onto the kraft paper. Don’t know if that will mold or not, but if the liquid is anything other than water, then maybe mold or insects could find the soaked kraft paper appealing. I only use a damp mop on my original oak floors anyway, but accidents will happen. Do you think I am being over-cautious? Anyway, I will investigate mineral wool.

  37. Joyce says:

    thanks, for all the tips on insulation! I didn’t know they had a safe kind
    for people to work with,since I’m not a frog lol that’s a concern.

    1. Well, you should always wear protective gear…goggles, gloves, long sleeves, and a dust mask. But the fact that it’s formaldehyde free is a HUGE benefit.

      Yah, it’s good to not be a frog in a glass jar, haha

  38. Jackie says:

    By the way, what is fire-rated caulk?

    1. Fire-rated caulk withstands flames for up to 4 hours and expands when exposed to heat. It’s better than just your normal silicone sealant. We actually didn’t have any on hand for the video 🙁

      But I wanted to mention it anyway

  39. Melinda Wilson says:

    Very timely. I was just asking a handyman about insulating the ceiling of the unfinished part of my basement. I think I can do it myself, but am wondering about insulating over/around water pipes.

  40. Renee Pedersen says:

    We have been talking about insulating our garage for the past couple of years. We have it partially done but never have gotten the rest done. You know, one of those projects!

  41. J. M. says:

    Great video – need to winterize the home.

  42. dan says:

    How about insulating a drop ceiling? Blow it or batt it? Or batt just the bottom layer and blow in rest above in case you have to open back up? We still have insulation in attic too so is there a condensation problem doing the drop ceiling area too?

  43. Nigel says:


    Great video!!!

  44. Corinne Gracie says:

    Thank you for the tips. Going to be insulating my home soon so was glad to get to watch this video.

    1. Awesome Corinne, glad the tutorial helped. Let me know if you have any questions.

  45. Jason says:

    Thanks for the tips. In my home here in Texas they didn’t put insulation over the garage or laundry room. I’m assuming I can just lay the insulation down directly over the dry wall from the attic in both areas. Any pointers about dealing with recessed lighting fixtures?

    Also, are there any issues regarding the insulation with using plywood to floor the attic? This would in affect sandwich the insulation between the drywall of the ceiling and the plywood.


    1. Awesome question Jason, you can add the insulation to your attic.

      If it’s paper faced make sure the paper faces the conditioned room, it this case your laundry room or garage. You don’t have to use paper faced insulation.

      In fact, I personally like mineral wool insulation from Johns Manville or Roxul. Both are good.

      In terms of the plywood, we have the exact same setup in our house…insulation between ceiling drywall and OSB.
      I explain the pros and cons in my podcast episode 234

  46. Cheryl says:

    Thanks, easy to follow tutorial, I have some unfinished basement areas that are framed out but not insulated. Would it really help to insulate this storage area of the basement? Thank you again!

  47. Nicole C. says:

    We are insulating and well all the way around remodeling an older house, at least 35-40 years old! Do i have the room I’m starting with stripped down to the framing of walls and ceilings. My question is should I do any reframing or add any new studs to the existing framework & will this alter how I will do my insulation job??

  48. Dave says:

    Thanks for the turtorial(s) Jeff. Always helpful. Question about insulating a basement. I’m finishing my basement that is all poured concrete. I read some (numerous) turtorials online that say to put XPS on the walls to prevent condensation behind the fiberglass, and use unfaced fiberglass in the studs. I did the XPS and now I want to put fiberglass in the studs, but I can’t find 2×4 unfaced insulation at a reasonable price. Am I safe using faced, maybe put the facing against the XPS instead of the drywall? Unsure of what to do. Thanks!

  49. Meredith Thompson says:

    I’m new to all of this but want to learn how to work on my house. I have a laundry room that the washer & dryer is on an outside wall. The water stub leaks cold air. How can I insulate this room. As well as under my kitchen sink. Do I need to tear out the drywall and start over?

    1. Thanks Meredith for your question. If your walls already have insulation you may not have to tear anything out. I’d first start with trying something like Great Stuff foam insulation. It’s easy to use and is at most home stores. Plus it’s not too expensive, under $10.

  50. Tom says:

    Installed drywall in my new home. Taped and floated joints. Primed, textured and then primed again. Sprayed walls & ceilings with interior latex. Have not insulated attic yet. Been seeing cracks in ceiling now. Is this due to not having any insulation in my attic?

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