Spray Foam vs Fiberglass Insulations: What Are the Differences?

Poor insulation can be one of the main causes of your utility bills skyrocketing in different seasons throughout the year. If you believe your house gets chillier in winter and hotter in summer as compared to other houses in your region, the reason possibly lies in your walls. Yes, we’re referring to house insulation. You see, your house’s insulation properties determine how much heat or coolness gets inside. If your house is not insulated properly, you’ll obviously be spending loads of money on keeping your loved ones warm or cool in rough weather. Why not opt for a permanent solution for this problem? You can get your house insulated and set up a proper barrier between you and the harsh climate conditions of the outside world.

Now that you know why it’s necessary to insulate your house, you must have knowledge about which type of insulation to go for. In general, you have multiple options but your top two choices are fiberglass and spray foam insulation. Both have their different characteristics but both have one goal, which is to make your house prone to tough weather. So, allow us to thoroughly guide you throughout this insulation-choosing process by differentiating between spray foam and fiberglass. However, before we continue, it’s necessary to explain the term “R-value” that you’ll be coming across a few times throughout this read.

What is R-Value?

The R-value of a material tells its capability of resisting thermal energy. Commonly used as a value to measure insulation, the R-value can give you an insight into the insulative material’s abilities to withhold thermal energy. However, it is not the only factor that should be considered when you’re choosing an insulation solution. Since the R-value of fiberglass, for example, may reduce with time, it is best to evaluate other features of an insulative material than simply judging it by its R-value. Also, the R-value might slightly vary from region to region depending on the climate conditions and on the surface, you want to be insulated, but it helps estimate an idea of the material’s insulative properties.

Let us now proceed to the detailed comparison between fiberglass and spray foam insulation.

Comparison of Spray foam and fiberglass insulation

Here is a comparison of the various aspects of spray foam and fiberglass insulation materials.

Fiberglass InsulationSpray foam Insulation
Is made of tiny glass particles tightly backed together with plasticA combination of chemicals that react with each other
Affordable costCostlier than fiberglass insulation
Insulation can have air gaps that reduce its effectivenessProvides very effective insulation
R-value of 2.5-3 per inchR-value of 3.5-4.5 per inch
Lasts for around 25 yearsLasts forever
Easy to installDifficult installation in comparion
fiberglass vs spray foam insulation

Composition

As the name suggests, Fiberglass insulation basically comprises tiny glass particles tightly backed together with plastic created to trap heat, cold, and sound waves within them. In either way, fiberglass greatly trims down the overall heat and provides a well-insulated building. As far as the working is concerned, fiberglass catches warm or chilly air from the outside world and keeps it trapped within its microcompartments. However, the extent to which fiberglass works does not reach a full 100%, this means that most of the air that passes is not let through but some of it might.

Spray foam insulation is done by mixing certain chemicals that react immediately when they come into contact with each other. Their mixture creates a foam-like substance that is used to insulate structures. Spray foam is used to tightly fill gaps between walls and other building components. It expands quickly wherever sprayed and seals the break effectively. Not only does this foam keep out air, but it can also filter out allergens, soundwaves, and moisture. Hence, minimizing the chances of mold growing on the foam. The two main types of spray foam are closed-cell and open-cell. 

Cost

Unlike most of the insulation options you have out there, fiberglass is relatively affordable and does not break the bank. A square foot sheet of fiberglass would cost you no more than 0.50$ at best. Furthermore, fiberglass does not need anything special during installation which makes the installation procedure pocket-friendly. So, if you’re looking for an inexpensive way out of the insulation problem, then look no further; Fiberglass is the way to go. 

Perhaps the only factor that stops spray foam from being as popularly used as fiberglass is the price tag that comes with it. Although it varies on the type of spray foam you’re going for, spray foam can leave your wallet empty. Moreover, the installation cost is quite heavy as well due to the blowing and mixing part. However, the return you’ll get on the investment is worth it since you’ll be saving loads of money due to low utility bills. 

Effectiveness

As mentioned previously, fiberglass does not completely put a full stop on the airflow from the outside world. It can stop most of it but if you’re looking for a fully effective solution, then fiberglass would likely disappoint you. If you leave out even an inch of space empty between the fiberglass sheets, it would greatly impact the overall efficiency of insulation. Nonetheless, fiberglass can still get the job done.

The effectiveness of spray foam is not up for debate. Since it is first warmed up before being sprayed, the foam is capable of spreading into even microscopic gaps. Once it dries up, the chances of air coming in are reduced heavily. You can expect much better performance from spray foam in terms of effectiveness as compared to fiberglass since spray foam boasts a higher R-value.

R-value

For fiberglass batts, you can expect the R-value to be around 2.5-3 per inch. Whereas for loose-fil, expect it to be around 3.5-4 per inch.

The R-value of open-cell spray foam lies somewhere around 3.5-4.5 per inch. Closed-cell spray foam can get you a whopping R-value of around 6-7 per inch.

Longevity

If you don’t plan on staying in the house for more than a couple of years, fiberglass insulation is recommended for you. Since it’s effective to some extent and inexpensive, it can definitely give your loved one protection from the weather for around 25 years max if it is not damaged throughout this time.

Spray foam is a highly sustainable insulation option. It can last for ages if applied properly. Studies have shown that spray foam can serve your house for up to 100 years in a slightly above-moderate climate. So, if you’re going to be investing in spray foam, rest assured it will guard your house against extreme weather for a good while. 

Installation

Commonly produced in the form of batts (sheets) and loose-fill, this insulating material can either be fitted between beams or simply blown through a blower. The hassle-free installation of fiberglass makes it one of the top insulation solutions for over 80% of homeowners in the US. You can make it a fun DIY project through fiberglass batts and call it a day. However, if you go for loose-fill, you’ll need to seek the assistance of a professional since loose-fill requires to be blown on the surface through a blower.

Unlike fiberglass, spray foam requires a professional for installation. Since it involves mixing and warming chemicals before application, you cannot attempt at spraying the foam yourself. As far as the installation is concerned, spray foam insulation is made by combining isocyanate and resin. One barrel for each chemical is bought and warmed up before being mixed and sprayed on the surface. Through a spray foam gun, the mixture is sprayed and sticks immediately to the exterior. As time passes, the foam dries completely and stops external airflow along with sound waves. 

Conclusion

At the end of the day, your house’s insulation is what matters. Both fiberglass and spray foam bring their own sets of benefits and advantages to the table. There’s no denying that there are dozens of factors varying from homeowner to homeowner that must be taken into account before passing a judgment. When it comes to efficiency, spray foam takes the win, but when it comes to price, fiberglass is the victor. In any case, the final verdict is dependent on your insulation needs. 

Charles John

A novice DIYer who learns about home ventilation. I am a mechanical engineer and have a basic knowledge of HVAC systems but I learn continuously to make myself the best blogger in that space.

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