How To Insulate Existing Interior Walls

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Sometimes you may want to install insulation to existing interior walls, particularly if your home is over 100 years old. While this may seem pretty difficult at first glance, it is actually fairly simple if you have the right tools and insulation type. But what’s the best way to do this? We’ve researched the answer to this question for you, and in this post, we’ll go over it.

The best way to insulate your interior walls without removing drywall involves filling the interior walls with blow-in insulation. While blow-in insulation is typically used in attics, basements, and other crawl spaces, it works perfectly behind established walls to create a solid barrier for thermal insulation.

Here are the steps to install insulation behind interior walls:

  1. Locate the wall studs
  2. Drill the insertion holes
  3. Feed the insulation in the wall
  4. Do drywall patchwork

Sometimes older homes can be prone to cold drafts and other temperature issues that can cause high energy bills in both the warmer months and colder months of the year. Effective insulation is a great way to prevent these types of issues, especially when it comes to cold drafts. Continue reading to learn how to install it when your interior walls are already established.

A room at a newly constructed home is sprayed with liquid insulating foam, How To Insulate Existing Interior Walls

Steps to Install Insulation Into Established Interior Walls

Things you’ll need:

  • Blow-in insulation and machine
  • Worker’s gloves
  • Protective goggles
  • Drill with large bits
  • Stud finder
  • Wall repair kit
  • Trowel or putty knife
  • Cleaning towel
  • Ventilation masks
  • Tarp

Worker Spraying Expandable Foam Insulation between Wall Studs, Spray Foam Temperature Settings [Cold And Hot Climate Issues]

1. Locate the wall studs

Using your stud finder, go over the entire wall behind which you plan to install the insulation. Next, use a piece of chalk or pencil to mark the areas to outline the width of the studs. You’ll typically find that there will be anywhere from 14 to 16 inches between each stud in the wall. The distance may be shorter between the windows.

Find this stud finder on Amazon.

2. Drill the insertion holes

Next, grab a stepladder and mark the locations on the wall where you will place your drill holes. These holes should be centered between the studs in the wall, and they all should be at least 8 inches below the ceiling. First, check behind the first few drill holes to ensure that no plumbing or electrical wires are running behind your other drill points.

It may also be a good idea to shut off the power to the room for extra safety. Set up a work light if needed. Then, take your drill and place two-inch holes in the drywall on the areas that you’ve marked. You’ll want the holes to be as high as possible on the wall so that the insulation will naturally pile up to create an even layer behind the wall.

3. Feed the insulation into the wall

Take your blower’s nozzle and place it in the first drill hole, making sure to point it downward. You’ll want the nozzle to go as far as possible. Next, place a large towel or another large piece of fabric around the hole opening to create a barrier. This will prevent insulation from flying out of the hole while the blower is in operation.

Turn on the blower and feed the insulation between the studs. Continue feeding the insulation into the wall cavity and shut off the blower when you feel resistance from the insulation backing into the hose. Keep in mind that a lot of dust and debris will be kicked up during this process, so you’ll want to ensure that you throw on your goggles and ventilation mask ahead of time. Complete this process until you have filled all of the walls in the room with insulation.

4. Do drywall patchwork

After the room’s walls are filled with insulation, take your drywall repair kit and go over each hole to apply mesh and spackle as needed to cover the holes back up. After the spackle dries, apply primer and paint to the areas, making sure that it looks uniform to the surrounding wall.

More of a visual learner? Check out this video to see how it’s done:

How do you insulate an old house without tearing down walls?

There are a few different ways that you can insulate an older home without removing walls. Let’s look at how.

Insulate the interior walls

The most common way to insulate an old house without breaking down the walls is to apply insulation behind the walls themselves. Blow-in insulation is best for this. This will require drilling holes into the wall and feeding the insulation between the joists behind the wall structure. You can perform this task yourself if you have basic carpentry skills and are comfortable handling blow-in insulation.

Or, you can hire a contractor to perform this task for you. A contractor may charge anywhere from $400 to over $800 for this type of project, depending on the room size, the backing structures behind the drywall, and the amount of insulation needed.

Double insulate the attic and the roof

For most homes, the attic and roof are the most common areas where heat is lost–this is because heat rises. Rather than insulating your entire home and potentially causing issues such as excessive humidity and structural damage within your walls, you can add an extra layer of insulation to your roof attic for just a few hundred dollars.

The type of insulation you choose will depend on the current insulation in your attic and the area’s layout. You can also add sealant and weather stripping to provide even more insulation to these areas.

Repair exterior brick base

Even homes with vinyl siding will typically have a brick base that’s about five to six feet high. Over time, the mortar between the brick can disintegrate, causing gaps and holes, leading to drafts and water leakage. This is also referred to as “weep holes.” It’s best to have a contractor patch up these holes to improve your home’s insulation and keep your energy costs down. Repairing the area can cost anywhere from $250 to over $500, depending on the square footage that needs to be repaired.

Seal the windows

It’s also a good idea to double-check all of the windows in your home. Windows are the second most common area of energy loss. Whether you have single or double pane windows, it’s always a good idea to check the seals around the windows to make sure that there are no gaps, holes, or damaged frames.

You can also use window film to insulate the windows if you only have single-pane windows. Another step that you can take to insulate the windows is installing a thermal curtain or blind covering. You can typically find these window dressings at your local home improvement store or online.

Seal crawl spaces

If you have a basement or crawl space beneath your first floor. Check the existing insulation, if applicable, to see if there are any signs of mildew, mold, or dampness in the area. This can also be a contributing factor when it comes to energy loss throughout the year.

Overall, it’s better to have a full-throttle plan of attack when it comes to completely insulating your home.

Can I put insulation over drywall?

Yes, you can place insulation over drywall. However, this is typically not recommended. The main reason is that the insulation will cause the room to be smaller, and it will typically need to be covered with a barrier unless you don’t mind having it visible.

You can, however, consider building a false wall in front of the insulation. But keep in mind that this will reduce the size of the room even more. If you are determined to insulate the wall specifically, consider applying other thermal barriers such as thermal blankets or other fabrics.

Check out this thermal blanket on Amazon

Does it make sense to insulate interior walls?

It can make sense to insulate your interior walls if your home is on the older side and you are experiencing serious issues with temperature regulation. However, it’s always best to consider other areas of insulation first. This includes insulating the roof, attic, basement, and windows of the home. These are typically the most common areas of energy loss.

Is it better to insulate walls from the inside or outside?

It is typically better to insulate the home from the outside. This means ensuring that the home’s exterior (be it brick or vinyl) has a solid surface that is free of gaps and cracks.

Wrapping Things Up

A room at a newly constructed home is sprayed with liquid insulating foam, How To Insulate Existing Interior Walls

We hope that this post has been helpful and illustrating how to insulate interior walls without removing drywall. Remember to always check for the studs before drilling your installation holes.

Be sure to check out some of our other posts before you go:

How To Cool An Attic Bedroom [6 Methods To Try]

Does Vinyl Siding Make A House Warmer?

This Post Has One Comment

  1. Shelter4GreenDeal

    Love this post. Thank you for giving such an interesting article.

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