How To Install Insulation In Basement Ceiling

How To Insulate Basement Ceiling

While it is not mandatory to insulate the basement ceiling, it may help to prevent heat loss to rooms above. It is also an excellent option for soundproofing the basement area, especially if you use it as an entertainment den.

When learning how to install insulation in your basement ceiling, the best method is to use blanket insulation made of mineral oil, cellulose, fiberglass, or cotton. Fiberglass insulation is the most preferable as it is affordable and easily accessible. However, you will need to get around lighting fixtures, basement ceiling joists, wires, pipes, and other protrusions on your basement ceiling.

Below are the steps for installing fiberglass insulation in your basement ceiling.


  • Fiberglass batts or rolls
  • Utility knife
  • Tape measure
  • Staple Gun
  • Protective gear


1. Wear Protective Gear

It is crucial to wear protective gear when handling fiberglass insulation. This is because it causes itching when it comes into contact with your skin or eyes. Therefore, wear goggles, cover your nose and mouth with a dust mask, and long-sleeved clothes to covers your hands and legs. Also, wear gloves.

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2. Take Measurements And Prepare The Insulation Material

Measure the length and width of the spaces between the basement ceiling joists. While at it, take note of areas where there are wires, bulbs, and other protrusions.

While most fiberglass insulation batt material comes cut to fit a standard ceiling joist space, you want to be sure the fiberglass batt will fit the joist spaces in your basement ceiling. The width of the fiberglass batts may be slightly more than the actual width of joist space. That is fine.

The extra-width ensures that the blanket insulation fits snugly between the spaces to prevent it from falling if you do not reinforce them. However, it should not be too wide that the insulation blanket compresses excessively.

On the other hand, if you use a fiberglass roll instead of a fiberglass batt, you will need to cut it up as per the measurements. Use a pencil and a square to mark the cut lines on the fiberglass batts, and then use a utility knife to cut the batt insulation. Add 1-2 inches to the actual width and length for a snug fit in the ceiling joist cavity.

3. Install The insulation

You must install the fiberglass insulation properly when insulating basement walls so that it delivers its full R-Value and insulates effectively. Installing the insulation on empty joist spaces is quite straightforward.

Pick a batt and tuck it into the joist spaces. Push it up straight to the ceiling wall and then pull it back slightly so that the fiberglass fluffs accordingly. Tuck it in tightly into the space where the ceiling meets the walls.

If you need to use more than one butt to fit the length of a given joist space, ensure that you put their adjoining edges snugly together so that no gaps or spaces are left.

Stapling The Insulation

Find out if your local regulations require you to staple faced insulation. If so, open the edge of the facing paper and staple it against the adjacent side of the joist. Allow 8-12 inches between the staples.

Getting Around Lighting Fixtures

Do not cover lighting fixtures on the ceiling as this can compromise fire safety. If the lighting fixture is IC-rated, you can install the insulation as close as possible. Otherwise, leave at least 3-inches away from the fixture.

Some local lighting codes require you to create a buffer between the lighting fixture and the insulation material. Cut the buffer material and install it 3-inches away from the fixture. Then, cut the insulation butt for a customized fit around the outside of the buffer material.

Getting Around Wires

If there is a wire or wires in the joist space, split the insulation blanket into half along its thicknesses. Then, fit the wire(s) between the blanket.

Do not tuck the insulation behind the wire as it significantly reduces the R-Value. Neither should you press it to the bottom and fit the insulation on top. That might pull the electrical wires too snugly, posing an electrocution or electric fire hazard.

Getting Around Junctions And Fans

These call for a custom fit. Cut out a section of the batt to allow room for the fixture.

Working Around Heating Fixtures And Elements

There might be gas flues, water heaters, and HVAC ductwork on the basement ceiling to work around. Allow at least one-inch clearance around the heating fixture. If the space is too tight, e.g., around chimneys, stuff the surrounding area with unfaced insulation during your ceiling insulation.


There you have it, the steps on how to install insulation in basement ceiling. By following these steps, you will have a flat insulated basement ceiling within a few hours.

Frequently Asked Questions

Why do some energy experts recommend against insulating basement ceilings?

Most energy experts recommend against insulating the basement ceiling and instead insulating the walls. Generally, basements are cold. And hot air transmits from the main house to the basement floor.

In most cases, the heat transfer into the basement floor is not significant enough to cause extreme heat. Insulating the ceiling in a finished basement will inhibit any heat to the basement, making it extremely cold, especially during the winter. It can also be hectic as you have to get around different fixtures.

Will Insulating the basement with fiberglass cause mold growth?

Many homeowners struggle with excess moisture and poor ventilation in the basement, creating favorable conditions for mold and mildew. The challenge with fiberglass insulation is that it tends to hold moisture, increasing the chances of mold and mildew growth. Therefore, it is important to resolve the moisture issue before installing fiberglass insulation.

Alternatively, consider applying spray foam insulation on the basement ceiling roof before installing fiberglass insulation. It will create an air and moisture barrier inhibiting mold or mildew growth.

What is the recommended R-Value for basement insulation?

The Model Energy Code recommends an R-value of 11-13 for basement wall insulation. While this number is specific to basement walls, it is still ideal for basement ceilings.