How to Insulate an Attic: DIY Attic Insulation

worker installing basement insulation
  • 3-4 hours
  • Beginner
  • 100-400
What You'll Need
Staple gun
Face mask
Safety goggles
Utility knife
Tape measure
Spray foam insulation (optional)
What You'll Need
Staple gun
Face mask
Safety goggles
Utility knife
Tape measure
Spray foam insulation (optional)

If left uninsulated, homes can experience around 20% of heat loss, while also trying to deal with issues such as flooding, mold, and dampness.

Many mistakes are made in the process of insulating, however, as not all homes are made the same, and different insulation can achieve various results. Here are some tips on how to insulate an attic. At the end, we'll head downstairs and cover insulating basements.

Types of Insulation

ceiling insulation with window

If you decide that your home will benefit from insulating the ceiling, then you may wonder what insulation is best. This also depends on the space being insulated, and what your goals are, as all forms of insulation will come with different attributes.

Typically, for basement ceilings, you’ll want a combination of mold and fire-resistance, soundproofing, and decent R-value. R-value is the insulation’s ability to resist heat flow, and different R-values will be recommended for different applications.

Other materials like drywall, glass, and are also given R-values. Always check building codes for specific restrictions and rules, especially if you will be covering the insulation with drywall and finishing the space.

Fiberglass Insulation

Made from spun glass, this type of insulation is usually the cheapest and most commonly used for ceilings and walls as it comes in batts or blankets that can be rolled into place. The loose-fill variety would not be ideal for ceilings, as it would fall down.

Fiberglass comes in a variety of R-values, with various soundproofing, mold, and fire-resistant capabilities.

Wool Insulation

Can be made of sheep or mineral wool, and like fiberglass, come in batts that are designed to fit between typical dimensions of studs and joists. Wool insulation is usually denser than fiberglass and can achieve higher R-values.

This tends to make it more fire-resistant, which may make it ideal for ceiling application. Wool insulation tends to be better at soundproofing, as well, but it depends on the manufacturer.

Foam Boards

worker installing insulation panels

Foam boards come in large sheets or in lengths similar to batts for easy installation. Foam boards may fit tight between ceiling joists, but often you would need to glue or attach them, so they don’t fall out. They can be used in conjunction with other types of insulation, giving more R-value to the space.

They won’t be irritating to skin, eyes, or lungs when installed like fiberglass and wool batts are. Installing large sheets over joists filled with batts can be an easy way to add extra R-value, but you would still have to cut around electrical boxes and ceiling lights and make sure they are accessible.

Spray Foam

Spray foam insulation is an excellent insulator, but it's also more expensive. It’s usually done by professionals as the job can be messy if you don’t know what you’re doing. It’s extremely hard to clean up or cut off any spray foam that ends up where you don’t want it.

For this reason, it’s not recommended for ceilings where there are electrical boxes, wires, water pipes, or vents, as these need to be accessible for repair. Since most basement ceilings are home to these important elements, spray foam is usually not used.

The application may be beneficial when sealing up crawlspaces or unobstructed ceilings.

Insulation for Soundproofing

Soundproofing is one of the main reasons homeowners may want to insulate, especially if they are planning to renovate the space or create extra living space. Sound can travel easily through exposed joists, and insulation meant for sound blocking will decrease noise when installed properly.

Soundproofing is a great idea if you want your basement to be a rehearsal space, kids' playroom, workshop, extra bedroom, separate apartment, or home office.

The best way to soundproof your basement ceiling with insulation is to use high performance mineral wool batting or dense panels meant specifically for reducing noise.

Many brands boast soundproofing qualities, and some will also be water and fire-resistant. Talk with a professional about which brand will work best for your situation if you aren’t sure.

The common pink fiberglass batting will help reduce sound, but not as much as higher performance varieties. Spray foam is not ideal for soundproofing, but some brands have been modified with moderate soundproofing capabilities.

That said, buyer beware of advertising slogans, as any insulation is meant to insulate, not soundproof. Specific brands may be better than others, but the best way to completely soundproof is to use insulation in conjunction with other practices.

Adding thick drywall, or even doubling up on sheets will soundproof more than insulation will. Acoustic tiles utilize the principle of creating space between the two living areas. Headroom may be a concern, so the decision on how best to soundproof your basement ceiling will depend on the space and your goals.

Insulation for Heating and Cooling

As mentioned, if you are insulating your ceiling in order to cut down on heat loss and to keep the home conditioned, you should insulate the walls and basement floor, as well. Many homeowners think that insulating the ceiling will help create warmer main floors, but the science doesn’t work that way.

If the room below is cold, the floor above will be cold, and ceiling insulation doesn’t stop that – even if it’s professional grade spray foam. In fact, it would be better to insulate the walls and floor of the basement and leave the ceiling exposed since there is no heat loss between the main floor and the basement.

The main loss of heat is from exterior walls and floors. Be wary of contractors who tell you that you need to insulate the ceiling without any specific reason for it.

Insulating your basement ceiling may help with keeping your main floor warmer if the basement space is unfinished and is colder than the rest of the home. Still, merely insulating the ceiling won’t do the trick, completely.

The entire basement space would have to be insulated and heated properly for temperature not to transfer between the ceiling space, even if spray foam is used.

How To Install Batting

worker in basement with insulation roll

When using any kind of batt insulation, you want to apply it so that it fits snug between joists without leaving any space un-filled. Squishing or condensing any types of batting renders it useless for any of the intended purposes.

Empty space means sound and heat will escape. A utility knife is generally used to cut batts into place, especially when going around electrical boxes or vents. You can cover up any electrical wires or water pipes that aren’t damaged or leaking, but may have to cut out small portions of the batts to make them thinner so they fit.

Ideally, the entire batt stays as unaffected as possible. If there are small spaces where batting won’t fit, use a small can of spray foam to fill in, or cut batts into small, but snug pieces that aren’t squished into place.

While installing batts are fairly straight forward, remember you are working overhead which can be cumbersome and more time consuming.

Ladders or scaffolding may help the job go a lot easier, and two people are always better than one when holding the batts in place, especially with insulation that has paper sides to be nailed into joists. Safety glasses, gloves, and full body clothing are always recommended whenever you are installing any insulation.

Vapor Barriers and Mold Issues

If you are experiencing mold issues in your basement, it’s unlikely that ceiling insulation is going to solve this problem unless moisture is finding its way up through the ceiling into the main floor somehow.

This happens more commonly with crawl spaces or basements with an excess amount of moisture problems, and often smells can seep up into the main living space.

In this case, insulation along with a proper vapor barrier may be a solution, but it’s very important to install both of these properly or to hire professionals for the job if you aren’t up for the task.

Crawl spaces are notoriously difficult to work in, and if the insulation or vapor barrier is not installed correctly, your mold issues can be multiplied, and the cost of removing and fixing the problem will be, too. Crawl spaces are either vented or un-ventilated, which will affect whether they need to be insulated.

This will also depend on your climate and whether moisture is a concern. In larger basements where bad smells from moisture and mold are a problem, vapor barriers and insulation will merely provide a band-aid solution to a bigger problem that needs to be dealt with.

Costs of Insulating Your Ceiling

Measure your ceiling space to get the square footage (length multiplied by width) and then cross reference with the type of insulation you want to use. Most brands will have some basic calculations for square footage coverage on the bag or company website so you can do your own quote.

As with most installations, add around 10-15% extra to allow for waste, which is always a factor no matter how well you install. You could also ask a company to come by and give you a quote, but unless you plan on using them, you should ask any questions over the phone, so you don’t waste their time.

If you are wondering what the cheapest way to insulate a basement ceiling is, the most common approach is to use basic fiberglass batting and install it yourself. This doesn’t necessarily mean it’s the best option, however, as you could be paying for materials on a labor-intensive job that won’t give you the desired results.

Should You Insulate Your Basement Ceiling?

Before you can know whether it’s a good idea to insulate basement ceiling, you need to know what kind of basement you have. Basements vary between full, partial, and crawlspace areas, and can be made of various building materials, though the most popular foundations are poured concrete or masonry blocks.

These factors will play an important role in deciding whether to insulate your basement ceiling. Other factors include your climate and whether you experience extreme temperatures and floods, as well as any foundation or grading problems.

Insulating a ceiling will not help retain heat, reduce flooding, stop mold, or add any integrity to the home if larger problems are not addressed first.

If you have a typical below grade cement wall and floor basement that gets relatively cold and damp, then insulating the ceiling will help reduce substantial heat loss and keep the space drier. It will only be worth doing, however, if you insulate the entire space.

That means walls and even the floor. Otherwise, the amount of work and money that goes into insulating ceilings will be for nothing, as the heat loss and dampness will seep through the other unsealed areas.

If you want to insulate for soundproofing reasons, then yes, insulating your ceiling will help. You do not need to soundproof the walls and floor of the basement to achieve the goal of reducing sounds from below, although every bit of insulating will help create a soundproof space.

If you are renovating the basement to make it into liveable space, there are codes requiring a certain thickness of drywall on the ceiling to make it fireproof. Check your local code to see if there are restrictions or specific types of insulation that are made for this kind of application.

If you aren’t experiencing any particular problems, or you live in a climate where heat loss isn’t a concern, then there isn’t any reason why you should insulate your basement ceiling.

There are no rules or codes that say basements must have insulated ceilings, it’s only a good idea if you want to finish the space, or have specific issues. Still, there are pros and cons to insulating versus merely using drywall which we will dive into more specifically.

Other Considerations

exposed ceiling with pipes

The basement ceiling is where many of the home's main water lines, pipes, electrical wires, and HVAC vents are located. When these are exposed, it can be easy to find where lines run to, which is especially helpful when doing renovations anywhere else in the house.

Keep this in mind if you are thinking of insulating the ceiling, as covering these essential lines up means they aren’t as easy to access. Usually, insulation is covered up by drywall, meaning any leaks or electrical issues contained inside the ceiling would mean cutting open the drywall and messing about with the insulation.

Spray foam is not recommended around these lines so that they can be accessed. Electrical wires can also start a fire in batt insulation, so make any repairs to wires, pipes, or vents before insulation is installed. Always check building codes beforehand.

Another consideration is mold and pests. Insulating a wet space traps that moisture in and intensifies mold growth. Air flow allows a space to breathe. If you have any problems with mice, squirrels, or bugs, deal with an infestation before you do any work.

Squirrels and mice love to live in batt insulation, creating a mess while they nest during the winter. Mice can make their way through almost anything, and can even nose their way through hard spray foam.

Roaches and other insects don’t particular like insulation to nest in, but if you need to spray or eradicate them from the home, best to insulate and seal up exterior spaces after remediation is done.

Alternatives to Insulating Basement Ceiling

Ultimately the goal is to keep your basement dry and free from mold or allergens. Insulating your basement ceiling does not automatically fix any of these issues, and in some cases, it can exacerbate them.

Other ways to combat basement moisture include using dehumidifiers and fans, though this is only helpful for low-grade dampness. You’ll need to install sump pumps to help with flooding, or fix any problems with foundation walls.

Properly grading the exterior of the home can sometimes be an easy fix to direct water away from seeping into the foundation and creating moisture issues. Increase airflow with properly installed windows which will also add natural light to a dark, dank space.

If there are no flooding or foundation issues, properly insulating the entire space will have the most benefits, as will adding HVAC venting so that the space is conditioned similarly to the rest of the house.

Before insulating, you must remove any sources of mold by professional remediation. Any water issues like leaks and flooding should also be dealt with first before insulating, which can include fixing retaining walls, concrete foundations, basement floors, or installing sump pumps.

While there are many reasons to insulate a basement ceiling, just remember that when it comes to keeping temperature in check, the basement walls and floor are the most important spaces to insulate.

It would be more cost-effective to properly install flooring on a cement basement and insulate exterior walls than it would to insulate a ceiling when it comes to heat transfer.

If you want to soundproof, add fire-resistance, or have some areas of a ceiling that are exposed to the outside world, then it’s a good idea to insulate your basement ceiling. Just do your homework before you take on the project, and weigh the pros and cons of the added expense and effort.