How to Insulate a Wall without Removing the Drywall
There will be no huffing and puffing to blow these walls down
Be it your finished basement or those drafty walls that give you the chills in your living room, one thing’s for sure—knocking down drywall to install insulation can be a major pain (and come with a high price tag). Before you crank out the hammer and start busting through your drywall, you have a few options to avoid the mess and hassle. Use this guide to help you get started on learning how to insulate a wall without removing the drywall.
Why Insulate a Wall without Removing the Drywall
Insulating a wall without removing the drywall, also called retrofit insulation or re-insulation, is useful for homes with existing drywall. Instead of knocking down the existing drywall and then installing new drywall, you can save on the cost of your project by navigating around your drywall.
How Much Does It Cost to Insulate a Wall without Removing the Drywall?
The average cost to insulate a wall is between $1 and $4 per square foot, depending on the type of insulation used. Cellulose and fiberglass cost the least, while blown-in insulation blankets and spray foam insulation cost the most to install. Drywall installation costs an extra $1.50 to $3 per square foot, so avoiding these extra steps can greatly decrease the total cost of your project.
How to Prep for Insulating a Wall without Removing the Drywall
Preparing for insulating a wall is an important step that you don't want to overlook. You'll want to lay down drop cloths for an easy cleanup when you drill holes into the drywall and when you install the insulation, as both of these steps can be a messy process. It's also a good idea to wear safety glasses, a mask, long sleeves, long pants, and closed-toed shoes when handling insulation to protect yourself from insulation particles.
How to Insulate a Wall without Removing the Drywall
Insulating a wall without removing the drywall comes with a few essential steps that you won't want to skip. Here is everything you need to know to successfully DIY your wall insulation project without removing the drywall.
Find the Right Place to Drill
Though you won't be removing the entire drywall to insulation, you will need to make a series of holes to fill the walls with insulation. But one wrong move can cause electrical issues or needless repairs. The last thing you want to do is drill into wires or receptacles or start drilling only to hit a stud and have to repair your wall.
Fortunately, a thermal camera can easily be used to scan the walls for electrical lines, pipes, and studs. Using your thermal camera, find free spaces in the drywall to drill the holes and mark them off with a pencil.
Aim for at least one hole per panel—or roughly every 16 to 24 inches. Each hole can go directly in the middle of each panel you plan on insulating. If you want to prevent settling and gaps, then you can mark one top and one bottom hole for the most coverage.
Drill the Holes
Now that you've marked the location of the halls, it's time to start drilling them. Follow these steps to complete this section.
Make note of the diameter of the nozzle on your insulation kit or blowing machine.
Use a hole saw with the same diameter as the applicator or slightly larger to drill a hole into each marked spot.
If you plan on reusing the drywall cut-outs for patching later, set aside the pieces for the end of the project.
Add the Insulation
There are several different types of insulation and materials you can choose when insulating a wall without removing the drywall. Three of the most common types of insulation include loose-fill insulation, spray foam insulation, and blow-in blanket system insulation.
Loose-Fill Insulation
Loose-fill insulation is made from either cellulose or fiberglass. Cellulose is cheaper per board foot, has a higher R-value, and performs better in northern climates. However, fiberglass requires less material to fill the wall cavities, is less likely to settle, and stands up to the tests of time with its long lifespan of up to 100 years. Both materials are DIY-friendly, so follow these steps on how to install loose-fill insulation into your home's walls.
Put on your safety equipment, including gloves, a mask, goggles, and long-sleeve clothing.
Insert cellulose or fiberglass into the blowing machine.
Ensure the drop cloth is beneath the work site.
Place the end of the blowing machine tube into one of the holes you drilled.
Have a helper on hand to continuously reload the blowing machine as you run out of loose-fill insulation.
Then, evenly fill the walls, going from hole to hole until each panel is full.
Spray Foam Insulation
Spray foam insulation is another type of insulation you can install inside drilled sections of drywall without removing the drywall entirely. You can find a spray foam insulation kit at your local hardware store. But this doesn't mean that spray foam insulation is the easiest installation method for DIYers.
Polyurethane spray foam comes in closed-cell and open-cell options and is the most common type of spray foam insulation. Only closed-cell polyurethane insulation is available in DIY kits. If you decide to use open-cell spray foam insulation, then you'll need to work with a professional to install it.
With this in mind, here's what you need to know on how to DIY spray foam insulation into a wall without removing the drywall.
Double-check that your home is protected from contact with spray foam insulation.
Be sure to wear complete personal protective equipment to protect your lungs, skin, eyes, and clothes from damage.
Insert the nozzle sprayer hose into one of the top holes you drilled.
Evenly inject the spray foam to fill the stud or joist space.
Then, go in from a bottom drilled hole to fully fill the cavity and avoid gaps.
Stop filling the cavity once you feel pressure on the end of the nozzle, as the foam will continue to expand, and you don’t want to overfill the wall.
Use a paint scraper to carefully remove excess spray foam.
Allow the spray foam to cure for about an hour.
Blow-In Blanket System (BIBS)
Using the blow-in blanket system to install insulation into the walls gives you the tightest and best installation, which is one of the reasons blown-in insulation costs the most. For this method, you'll need to hire an insulation installer near you to do the job, as BIBS requires specialized equipment to successfully complete the job.
Patch the Walls
Once you have filled the walls of your home with insulation, it's time to repair the walls to cover any unsightly holes. You can patch up the walls by using the existing drywall discs that you cut when you initially made the holes or by using new drywall plugs entirely. Here are the steps:
Insert the drywall discs into the holes.
Secure each drywall disc using drywall tape.
Coat the disc and surrounding area with spackle.
Wait for the spackle to dry.
Scrape any extra spackle off the wall using a putty knife.
Sand the area until it is smooth and even.
Paint the Patches
The holes might be out of sight, but spackle has a way of turning even the smoothest drywall into a splotchy canvas. After you've patched the wall, you'll want to paint the wall for a seamless look. Use a roller or a paintbrush to give your newly insulated wall a paint job. Apply two coats for full coverage, allowing for each coat to dry completely.
Clean Up
Insulation can be a messy project, especially if it's your first time using a blower machine or spray foam. Be sure to thoroughly clean the project site while wearing protective equipment to prevent insulation particles from causing irritation. Do not sweep the area, as this can lead to dust particles entering the air. Instead, use a wet mop, wet cloth, or vacuum cleaner with a HEPA filter to remove fiberglass or cellulose particles.
Tips for Choosing the Right Insulation
The right insulation can make all the difference when it comes to keeping your home's temperature the way you want it. Here are a few tips on how to choose the best insulation type for your home.
Consider the R-value. Not every insulation performs equally. If you want insulation that will keep your northern house warm in harsh winters, choose BIBS or cellulose insulation over fiberglass.
Look at the complexity of the installation. If you want to install BIBS or open-cell spray foam, then you'll want to work with a pro.
Determine your skill level. Sometimes, doing it yourself can prove to be too tricky. Working with a professional can help you choose the best insulation and installation method for the project.
DIY vs. Hiring a Pro
Knowing if you've properly filled the cavities when you can't see inside the wall makes this project more advanced than simply laying batts or rolls of fiberglass into a wall cavity. If you use spray foam, you run the risk of overfilling the cavities, which can cause the walls to buckle or crack and the joists and studs to become damaged from the pressure.
On the contrary, underfilling the walls with spray foam or loose-fill insulation can make the insulation less effective, increasing your energy bills and leading to a drafty, poorly insulated home.
To install the right amount of insulation, only complete this project if you feel confident knowing how to tell if you’ve filled the cavities correctly. Leave room for the spray foam to expand, pack loose-fill insulation well to avoid settling and gaps, and of course—when in doubt, contact a local insulation contractor for the best installation.
Frequently Asked Questions
The cheapest way to insulate a wall is to use cellulose or fiberglass and install it yourself. If you can avoid having to knock down existing drywall, you can save up to $3 per square foot of insulation space. If you do need to hire a professional, you can lower the cost by cleaning the area and making it easy to access.
The best insulation material depends on your method of installation, where you live, and your budget. If you're looking for an insulation material that has a low cost and a high R-value, then cellulose insulation may be the best option for your home. If you want insulation that is easy to install, then you might want to choose fiberglass. For insulation that won't settle over time, blown-in insulation or blanket insulation works the best.