How To Insulate Basement & Crawl Space Ceilings: Complete Guide

Many people wonder if they need to insulate the ceilings of their basements and crawl spaces. And it is not an easy task to take upon. In this article, I explain the need to insulate your basement and crawl space ceilings, how to do it, and what the best materials for it are. So let’s start;

Why do you need to insulate your basement ceiling?

The main reason to insulate a basement’s ceiling is to prevent heat loss from the upstairs living areas of the house. Ceiling insulation will prevent any heat transfer from the living areas of the house into the unconditioned basement area thus reducing the load on your heating system as well as lowering your energy bills.

During peak winter times the difference in the temperatures between the living areas of the house and an unconditioned basement can be considerable (sometimes as much as 40 degrees or more depending on where you live). This temperature difference will cause the heat inside your house to quickly dissipate through the floor. Properly insulating your basement or crawlspace ceiling can easily reduce this heat loss.

So should you insulate your basement ceiling?

You should insulate your basement’s or crawl space’s ceiling if it is unconditioned to prevent any heat loss from your house. If your basement is conditioned, then there is no need for insulating its ceiling.

Ceiling insulation is needed only for basements that are unconditioned. If you have a heated aka the conditioned basement or crawl space, there is no need for insulating their ceilings since the temperature difference with the other parts of the house would be minimal. Such minimal temperature differences will not cause any heat loss. But in such a case, make sure that the walls of the basement and crawlspace are sealed and insulated.

How to insulate basement and crawl space ceilings?

If you are planning to DIY your basement ceiling insulation, be prepared for some hard work. Here are the steps to insulate your basement/crawlspace ceiling;

Step 1: Choose the right insulation material

You can use different types of insulation materials for your basement and crawl space ceilings. The selection of the insulation material depends on the conditions of your basement and crawl spaces. Two important things to consider are the required R-value of the insulating material and the moisture content in the basement.

Choosing R-value

R-value of a material is a measure of its resistance to heat transfer. The higher the R-value of insulating material is the more effective it is at reducing heat loss. If you are living in areas where the temperatures can drop very low during winter, I suggest using an insulation material with R-values of 25 to 30. For mixed climates, the best R-values are between 13 and 25, and for moderate climates, you can use insulation with R-values ranging from 10 to 13.

ClimateRecommended R-value for InsulationClimate with minimal heating and cooling requirementsR-10 to R13Climate requiring mixed heating and coolingR-13 to R-25Cold climatesR25 to R30

Choosing insulation type

You can use any type of insulation for your basement and crawl space ceilings. However, you need to consider the moisture content in your basement before selecting insulation. If the basement has high levels of moisture contents make sure to choose an insulation that also acts as a vapor barier. In such cases, closed-cell spray form insulation and faced batt insulation are the best choices. If using faced insulation, make sure that the faced part of the insulation faces the living area of the house ie, it should be facing upwards.

If there is less moisture content in the basement area the most preferred option is batt insulation. Batt insulation is very easy to install, and that is the reason why they are everyone’s favorite.

Moisture Content	Insulation Type
High levels of moisture	Closed-cell spray foam or faced batt insulation
Low levels of moisture	Batt insulation

You can also use foam board insulation, but they are harder to install than batt insulation.

Step 2: Wear protective gear

It is important to wear proper protective gear before insulating your basement and crawl space ceiling. Fiberglass is not kind to most people if it gets in touch with your skin. You will have a very bad day if you try installing fiberglass insulation, or spray foam insulation without gloves, a Tyvek suit, and protective eye gear. Once the job is done, make sure to discard all these protective gear. I don’t recommend reusing them once you take them off.

Get the protective gear from Amazon:

• Tyvek suit – https://amzn.to/3juZE42.
• Face cover set – https://amzn.to/3B25Bvi

Step 3: Caulk and seal around the band joists/rim joists

This is an important step many skips when insulating their basement ceilings. It is important to seal around the rim joists of the basement ceiling before putting insulation. Sealing will prevent moisture intake through the rim joints which would result in rots and other damages in the long run.

Step 4: Insulate rim joists with foam board or a closed-cell spray foam

Rim joists are the hoists around the perimeter of the ceiling, and they are in close contact with the outside air. Since they can get a lot of air transfer and moisture transfer, if you put batt insulation on them, the insulation will get damp. This will cause the boards to rot after a few years. To avoid this, you need to install something that prevents moisture transfer, and the best options are rigid foam board insulation and closed-cell spray foam insulation.

Recommended rigid insulation board	View on Amazon
Recommended spray foam	Tiger Foam

Among the two, spray foam insulation is the easiest to do especially if you are going to spray foam the whole basement ceiling. Given below is a video showing how rim joists are properly insulated.

Step 5: Add insulation between the joists

This is possibly the easiest part of the job. If you are using fiberglass bat insulation, cut it into proper sizes to fit between the batts. Make sure that the widths and lengths of the batts are 1 inch more than the space between the joists so the insulation sits tighter between them. When you are putting the insulation batts between the joists, make sure not to compress them as this will affect their heat resistance. Also, make sure to cover the rim joists well. Any ducting and wiring going through the space should be properly covered and no gaps should be left.

If you are using closed-cell spray foam insulation, which is recommended for moist basements and crawl spaces, make sure to start from the rim joists on one side and move to the other. One thing to keep in mind is that, for easy installation, the foam canisters should be kept between 75 and 85 degrees. For this, you can put them in a box with a heater during the whole process. A detailed guide to spray foaming the basement ceiling is given in the video below.

Best insulations for basement ceilings

Given below are the recommended insulation materials for your basement and crawl space ceilings;

1. Owens insulation rolls

This is a product that you can install yourself. It is very easy to work with and you will be impressed by the lightweight, fiberglass material. Every roll is also very flexible so you will not need to work a lot to set it in place just the way you need to so your basement ceiling will be well insulated. The only aspect you will have to pay closer attention to is to wear clothes that prevent the chemicals from the fiberglass to get into your lungs or on your skin and eyes. 

The R-value of this product is R19. I decided on this product as one of the best not only because it is very efficient but also because you can cut it easily to fit the dimensions you need. If you want a higher R-value, you can even use two rolls of this insulation, one over the other in order to double the heat resistance. 

You can choose this insulating product regardless of the climate you live in and it is efficient at repelling moisture and muffling the sound between your basement and the rest of your house. 

2. Owens pink insulation foam

If you are looking for a more budget-friendly option of insulation, but still just as efficient as the rest of them, this Owens pink foam is ideal for you. These foam squares have a low R-value but you can always use more of them, according to how you need so your basement ceiling can be well insulated. 

One of the great aspects of this insulation is that you will not have to worry about fiberglass particles that could affect your skin or your eyes or any internal organs if you inhale them. Plus, they are easy to install and cut so you can use them in any shape you need with no struggle. I have to mention that this insulation will also look good without having the need to cover it. 

However, due to the low R-value, I don’t recommend using this insulation product if you live in very cold climates. 

3. Johns Manville R13 fiberglass insulation

For those who are looking to invest in an insulation with a high R-value, this one from John Manville is just what you need. You will find this insulation in form of rolls and you can choose from different sizes. Even if you don’t find the right size, there is no need to worry as you can cut them very easily, being made of fiberglass. 

This product is one of the best insulations that come at a budget-friendly cost and they are also very efficient. It is ideal for cold and very cold climates thanks to the high R-value and it is also lightweight which makes it easy to manipulate as you need. If you are looking for a soundproofing effect, this insulation will be a good choice for that as well. 

However, if you don’t install it and maintain it properly, this insulation could attract moisture. It can also break during installation as it is so light so it is a good idea to purchase one extra roll in case this hazard happens. 

4. Roxul Mineral Wool insulation

The last but not the least insulation you can choose for your basement ceiling is this Roxul Mineral Wool type. Even if this type of insulation comes at a higher cost, it is also one of the best that you can invest in. It has high-temperature resistance which is one of the main advantages of this product. 

The R-value of this insulation is R4 per inch and it can easily be layered for even more protection, depending on the climate you live in. Actually, you can count on the fact that this material will only burn at temperatures of 1,200 degrees F which is 649.89 degrees C. If you are looking for a high soundproofing quality, the Roxul insulation can assure you of this quality as well. 

If you are planning to install this insulation by yourself, make sure you wear protective clothes to not get any particles in your throat, lungs, eyes, or on your skin. 

Conclusion 

Insulating your basement ceiling is one of the basic investments you will have to do, to keep moisture out of your house and prevent heat waste. The type of insulation that you choose will depend greatly on the climate you live in since cold climates require insulation with a higher R-value. But overall, you can’t go wrong by applying the information in this guide and you will not have to worry about hiring a professional either. All the insulation types I introduced to you are easy to install by yourself and they can protect your house for many years to come!