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Did you recently complete some renovations and had to replace the attic insulation? Or probably you’ve just purchased a house without any insulation in the attic, and you're wondering how to install one quickly. Well, you’ve come to the right place because we researched this question, and we have the answer right here.
Here are the steps to insulate an attic before installing the ceiling:
- Install the baffle rafter vent on the base of the rafters where it meets the wall plate.
- Measure the distance between the joists.
- Trim your batt insulation based on your measurements, adding an inch or two to the original measurements.
- Place the batt insulation between the joists with the paper facing the inside of your house.
- Open the paper flap of the batt insulation and fasten it to the joist parallel to the floor.
- Repeat steps 2 to 5 until you have covered the entire ceiling area with the batt insulation.
- Install a layer of polyethylene sheet over the insulation.
- Install the drywall to cover the batt insulation.
But what if the drywall ceiling is already installed? And how do you insulate the attic door? Read on and learn about all these in detail from the succeeding sections.
Attic Insulation 101
We have two possible scenarios when it comes to installing attic insulation. We covered the first scenario on the steps we provided above—installation of the batt insulation when the ceiling has not been installed. The second scenario is the installation of batt insulation after the ceiling drywall has been installed.
Let’s take a closer look at the steps above first. Then we will go through the installation of insulation after the ceiling has been installed.
How to install batt insulation in the attic before the ceiling drywall is installed
Here is a more detailed take on the steps that we've listed above. We will start with safety precautions, then we will move to the materials that you will need.
Have the following equipment ready and wear them before you start to work with the batts. Never remove them until you have completed working with the batts.
This set of equipment will help prevent particles from the insulation from getting to your clothes and prevent you from bringing the particles into your home.
The particles from a fiberglass batt insulation can irritate the skin, eyes, and throat. The particles from a rock wool batt, on the other hand, are like asbestos but not as dangerous. Thus, it is still best to prevent yourself from inhaling them by equipping yourself with the following:
- Disposable coverall suit with hood
- N95 respirator
- Eye goggles
Clean the area thoroughly once you’re done working with the batt.
Remove the coverall suit carefully and dispose of it properly.
Tools and materials needed
Here are the tools that you will need to install the batt insulation:
- Staple gun
- Extra staple wires (just in case you run out)
- Measuring tape
- Cardboard cutter
The insulation materials to be used include:
- Baffle rafter vent (width should be equal to the distance between rafters)
- Rock wool batt or fiberglass batt (it should have an R-value that matches what you need)
- Polyethylene sheet
Follow these steps for installing insulation in the attic before the ceiling is installed.
Installing the baffle rafter vent
- Measure the vertical perpendicular distance from the wall plate to the bottom of the roof deck, measuring an inch or two from the edge of the wall plate facing the inside of the house.
- Measure 1 to 2 inches from one end of the baffle rafter vent and make a pair of cuts on both sides. This is so the baffle rafter vent can easily be folded.
- Measure a distance from the first pair of cuts that is equal to the perpendicular distance from the wall plate to the bottom of the roof deck.
- Make another pair of cuts at this point, on both sides of the baffle rafter vent.
- Align the first pair of cuts on the side of the wall plate facing the inside of the house. Fasten it with staples.
- Position the baffle rafter vent on the roof deck perpendicular to where one end of the baffle rafter vent was stapled on the wall plate. Fasten the baffle rafter vent with staples.
- Repeat the same steps until you have covered the area where the rafters meet the wall plate with the baffle rafter vent. This is to protect the soffit vents from getting covered by the insulation.
You might as well watch this video below for a demonstration of the detailed installation steps:
Installing the insulation batts
- Measure the distance between the joists with your measuring tape.
- Add an inch or two to your measurements and trim the batt based on the modified measurements.
- Position the batt between the joists. The paper moisture retarder should face the inside of the house.
- Open the paper flaps along the side of the batt insulation and fasten it to the side of the joist that is parallel to the floor. Staple the paper flaps every 6 to 8 inches.
- Repeat steps 2 to 4 until you have covered the entire ceiling area with your chosen batt insulation.
- Install a layer of polyethylene sheet over the batt insulation on both sides—the side facing the floor and the side facing the roof. Polyethylene sheets are classified by Energy Saver (the U.S. Department of Energy's consumer resource on saving energy) as a Class I vapor retarder, although it has a secondary, yet equally important, purpose in our installation. The polyethylene sheet will prevent any batt insulation dust or particles from mixing with the air. Thus, it protects the air quality inside your home.
- Install the drywall over the batt insulation.
How to install batt insulation in the attic after the ceiling is installed
Watch the video below for some helpful attic insulation pointers:
The steps for installing the batt insulation after the ceiling has been installed are similar to the steps we provided above. There is one additional item, though, that you will need for this installation: a polystyrene insulation spray adhesive.
If you are not planning to install drywall on the attic floor, then you need to keep in mind that you should keep your feet on the joists. If you accidentally step on the ceiling board, you could fall through the ceiling and into the room below.
You can use a scrap of 3/4 inch plywood that you can place on top of the joists so that you’d have something to step on while installing the batt insulation.
Follow the same steps for installing the baffle rafter vents where the rafters meet the wall plate. Complete this part of the installation before proceeding to the installation of the batt insulation:
- Install the batt insulation on the areas with the baffle rafter vent first. Remember that the side with the paper moisture retarder should face the inside of the house, not the roof.
- For this kind of installation, there is no need to staple the batt insulation to the joists since the paper side is not reachable and the joists and the ceiling drywall will keep the batt insulation in place.
- Continue the installation around the baffle rafter vent, making sure that the area around the attic door is the last area where insulation will be installed.
- Install a layer of polyethylene sheet over the batt insulation. Fasten it with staples.
- Once you have completed installing the batt insulation and the polyethylene sheet on all the areas of the attic except the attic door, measure the width and length of the attic door.
- Trim an insulation batt to match the length and width of the attic door.
- Trim a polyethylene sheet to match the length and width of the attic door.
- Spray an even layer of polystyrene insulation spray adhesive on the inside of the attic door.
- Install the trimmed batt insulation onto the inside of the attic door, making sure that the paper moisture retarder will be facing the side of the floor when the attic door is closed.
- Install a layer of polyethylene sheet over the batt insulation and secure it with staples.
What happens if insulation is installed backward?
With the completion of the instructions on how to install batt insulation on your attic before or after the ceiling is installed, you might be wondering what will happen if the batt insulation is installed the wrong way.
The paper side is also called the paper moisture retarder side because there is a thin layer of asphalt between the paper and the batt insulation. The combination of paper and asphalt serves as a moisture barrier.
If the paper moisture retarder is facing the roof when the batt insulation was installed, there will be nothing to stop possible moisture buildup between the ceiling and the batt insulation. Moisture buildup can cause mold growth and structural deterioration of the wood that gets exposed to moisture.
So, if you’re thinking of installing unfaced batt insulation for your attic, don’t do it. There is a purpose to the paper face of batt insulation that can save you hundreds or even thousands of dollars in repairs in the future.
The installation of batt insulation for attics can be a simple DIY job. What’s important is knowing and following all the safety precautions for working with insulation materials that can have an impact on your health no matter how small the effect might be. Next would be to know what kind of installation to do—whether you already have the ceiling installed or not.
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