Eco-Friendly Insulation: Pros and Cons of the Top 5 Types [+1 in Development]

When it comes to increasing the energy efficiency of your home, the type of insulation matters. But conventional forms like fiberglass and polystyrene — composed of fossil fuel-derived plastic or other chemicals — are not environmentally friendly. So what’s a climate-conscious homeowner to do?

Fortunately today, there are several eco friendly insulation alternatives available. Not all are suitable for certain regional climate conditions, and some are better in new vs. older homes, so it’s important to become well-informed on the pros and cons of each type.

Here you’ll find the complete guide to the 5 major eco-friendly home insulation options on the market today. At the end, there’s a table of five factors to weigh when choosing eco-insulation and how the 5 types stack up. 

You’ll also get a peek into the newest kid on the block in the eco-insulation world plus a mention of another type of eco-insulation available in Europe.

Green consumers will find our listing of eco-friendly aspirants that don’t really fit the bill — and reasons why they don’t — very enlightening. Here’s what to watch out for so you won’t get greenwashed.

Finally, we share some tips on how to increase the mileage of your eco-insulation energy efficiency by taking a few additional steps — before, during, and after installation.

Why is insulation so important?

The organic architect, green builder, and sustainability expert, Eric Cory Freed, says it best when it comes to insulation:

“The more, the better!”
– Eric Cory Freed

Although it is possible to overdo insulation in rare cases, having more rather than less is preferable.

In line with this view, we present several key reasons why insulation is vitally important to your home.

1. Insulation lowers energy bills

In most places, for the majority of the year, keeping your home comfortable requires major energy inputs in the forms of air heating or cooling. In fact, over 50% of your total energy costs are for HVAC (heating, ventilation, and air conditioning).

To keep costs down, it makes sense to install insulation in your ceilings, walls, and floors. Like a layer of security against temperature fluxes, insulation will buffer you against receiving high heating and cooling bills. 

2. Insulation makes your home quieter

Who likes noise?

Insulation will protect you and your family from experiencing unwanted sounds coming from outside — like traffic or lawnmowers. In fact, high-quality and ample insulation could make your home so quiet that you may hear a pin drop!

In our hectic modern society, that’s not so bad.

Insulation will also damper the sounds coming from other parts of your home. With the soundproofing effects of insulation, young kids can get as rambunctious as they like without bothering other family members who may work at home. Likewise, teens can play music above a “tolerable” level without distracting anyone else. (Of course, “too loud” varies from family to family.) 

3. Eco-insulation is toxic-free

A unique feature of eco-insulation that isn’t shared by its traditional counterparts is that authentic eco-insulation contains no synthetic chemicals or is made with fewer, less toxic chemicals. 

The chemicals used in standard insulation types include flame retardants and volatile organic compounds (VOCs). Three common toxic chemicals in conventional home insulation are:

• Isocyanate
• Formaldehyde
• Hexabromocyclododecane

Who wants these toxins causing hormonal disruption, cancer or off-gassing into your child’s lungs all over the deep recesses of your home?

Pre-insulation tips 

Whether you’re designing a brand new home, retrofitting a historic home, or upgrading the insulation on an older one, there are several things you can do before installation to make the process more streamlined and the results more effective. When you do, the eco-insulation will perform even better for you.

1. Determine where the air leaks are

Do you know that heat leaks out all over your home? Cold air sneaks in easily, too. It all adds up to 25-40% of your total heating and cooling bill…escaped!

Some of these places may surprise you. Here’s a breakdown of where air leaks can occur:

• Electrical outlets
• Switch plates
• Doors 
• Window frames
• Baseboards
• Ductwork
• Outside water faucets
• Fireplace dampers
• Attic hatches
• Window air conditioners
• Internet/Cable and phone lines
• Dryer vents

So do some sleuthing to find the hotspots!

One way is to scan all of your home’s nooks and crannies with an inexpensive heat leak detector. If you want more precision and full-color images at a significantly higher price tag, go for this type of detector.

With the valuable information that detectors provide about how heat is escaping, you can better pinpoint exactly where you need to insulate your home. And when you’re more airtight, your home will retain cool air inside much better during hot summers.

2. Seal all air leaks in your home

Unless you’re an expert with a caulking dispenser or spray foam equipment, hire a professional to do the sealing before you install insulation. This way, you’ll be starting off one step ahead in terms of reducing heat escape and cold air infiltration, maximizing energy efficiency, and lowering energy bills.

Be aware that most spray foam is made with fossil fuel-based polyurethane and other harmful chemicals. A toxic-free spray foam called AirKrete works wonders in filling all the crevices and won’t adversely affect your health. If you’re a DIY pro, you’ll need specialized equipment and the AirKrete liquid foam maker.

Since heat rises, start at the highest level of your house and work your way down. Pay special attention to areas around windows and doors, lighting fixtures, studs, joists, electrical boxes, wiring, pipes, fan housing, and ductwork. Junctions where walls meet ceilings or floors are often places where heat escapes or cold air penetrates, so take extra care in those areas to avoid what’s known as thermal bridging.

Since AirKrete is non-flammable, you won’t need to worry about sealing the chimney perimeter or any cracks there.

3. Use a programmable thermostat as a cost-cutting strategy

When you’re not at home or prefer a cooler environment for sleeping, a smart thermostat will enable you to set the desired changes without lifting a finger each time.

With one of these gadgets, it saves you the hassle of making the change manually. And you don’t ever have to worry about forgetting when you’re in a hurry. 

As a result, no surprises on your next energy bill, thanks to a programmable thermostat.

4. Upgrade windows for greater home insulation

Although it may be costly and time-consuming to do major renovations of walls and floors to improve the energy efficiency of your home in terms of its insulating ability, windows are an easier fix.

Installing double or triple pane windows with or without argon or krypton gas inside them will make a noticeable improvement in both insulation and soundproofing. Upgrading windows reinforces the beneficial effects of eco-installation everywhere else (including around the window perimeters), too.

What does the R-value of insulation mean?

A common term you’re sure to hear tossed around a lot by home insulation companies is known as the R-value. This number is used to rate and compare different types of insulation. 

Although R-value is an important consideration when choosing home insulation, it is not the only one. See the table below for a list of factors to take into account.

An R-value is a measure of the resistance to heat flow that a particular material possesses as heat moves through it, fiber to fiber or granule to granule. Specifically, this is conductive resistance due to heat loss from air leakage.

The higher the R-value, the greater will be the effectiveness of the insulating material. 

Besides differing by material type, R-values also vary depending on thickness and density of the insulation. Thicker and denser material means higher R-values. Age, temperature, compression, and moisture content usually reduce an insulation’s R-value.

By contrast to conductive losses, your home also loses heat by convection of air currents, like in drafts around windows or under doors. Technically a factor in your home’s total heat loss, heat escape from convection is not included in R-values.

The United States Department of Energy (DOE) calculates the amount of insulation measured by R-value that consumers should use to insulate their homes depending on their climate zone. 

The DOE’s Home Energy Saver website has tools for consumers to use when insulating their homes. 

Although the DOE has published extensive tables listing R-values for the traditional forms of home insulation as well as other information about them, this government department provides very little information about the eco-insulation types described in this article.

Here is a table of R-values that an academic researcher compiled from DOE and HUD (Department of Housing and Urban Development) data. We’ve enhanced it with information about eco-insulation taken from other sources and presented elsewhere in this article.

Insulation Type	R-value per inch
Sheep’s wool batt	4.3
Cork batt	4.0
Hemp batt	3.7
Loose-fill cellulose	3.5
Dense-fill cellulose	4.0
Denim batt	3.5
Loose-fill fiberglass	2.5
Fiberglass batt	3.8

It’s important to keep in mind when weighing your insulation options that R-values do not tell the whole story. Note especially that plastic foam insulation is known to shrink over time leaving gaps, thereby lowering its R-value. Particularly relevant is that some building experts testify that spray plastic foam is often poorly installed, sometimes unknowingly. This creates air leaks and, in some cases, moisture issues. 

How do I know how much insulation I need?

When comparing your eco-insulation options, you need to figure out how much you need and which type will give you the biggest bang for the buck over the long term. The climate where you live, the type of house you have, (new or old), and your fuel source(s) figure prominently into the equation.

To determine specifically how much you can save on home energy costs, depending on the specifics of your home and region, consumers may find this calculator helpful.

What are the best eco friendly insulation materials?

Novel eco-friendly insulation types are coming on the market all the time. Here are the best ones currently available or undergoing research and development in the lab.

1. Sheep’s wool

Not to be confused with rockwool or mineral wool, which are manufactured from fossil fuel-intense processes using mining waste products or basalt rock, sheep wool insulation is 100% all-natural, renewable, recyclable, and biodegradable. 

Excess wool is sheared directly from live animals and undergoes minimal processing before it’s ready to be installed in your home to keep it as cozy as it does its living bearers.  

Wool has an incredible ability to control moisture, absorbing any excess up to 35% of its net weight. Since condensation often happens naturally inside your walls and ceilings especially in humid environments, wool is excellent at keeping mold and mildew at bay. 

Keratin, a protein naturally found in wool, prevents wool from getting moldy, like some of other forms of insulation may become, when exposed to water or high humidity.

When ambient humidity levels are too low, wool releases the stored moisture back into the air. This natural give-and-take continues during the lifetime of your sheep’s wool insulation. 

But moisture control is not the only advantage from sheep’s wool home insulation.

The wool acts as an air filter, too. The amino acids that make up wool irreversibly bind with several chemical nasties that could be floating in your indoor air — like cancer-causing formaldehyde or nitrogen oxides and sulphur dioxide. 

Formaldehyde is an off-gassing chemical found in many building materials. Nitrogen oxides and sulphur dioxide are common air pollutants found in car exhaust and power plant smokestacks due to the combustion of fossil fuels.

Wool’s R-value, up to 4.3/inch, is comparable to or surpasses synthetic insulation varieties — even when wet. And it will maintain that R-value for 50 years, unlike many synthetic counterparts. 

Sheep’s wool is also extremely resistant to fire and is self-extinguishing. It is resistant to insects and rodents, too, due to 8% boric acid added to it. Derived from boron, a naturally occurring earth mineral, boric acid and similar chemicals made from it known as borates, are considered non-toxic. 

You may know of borates in Borax, a common laundry cleaner on your shelf at home.

Green consumers interested in purchasing this type of eco-insulation should be aware that some sheep’s wool companies use a synthetic insecticide called Larvanil which contains bifenthrin as the active ingredient. 

Bifenthrin is a type of pyrethroid. It’s a lab-made analog to natural insect repellents called pyrethrins found in chrysanthemums.

Available in batt (large blocks) or blow-in fill, sheep’s wool maintains its elasticity, doesn’t clump easily, and resists compression. It is 2-3 times more expensive than conventional insulation, although synthetic closed-cell foam is more expensive.

In the United States, Nevada-based Havelock Wool is a major retailer for sheep’s wool insulation.

2. Cork 

You’re probably familiar with cork if you drink wine. Cork bottle stoppers are not very popular any longer ever since plastic foam stoppers hit the wine scene.

But there’s a whole lot more that you can do with cork — including insulating your home.

Do you know that cork is a natural tree product? Its harvest and manufacture as eco-insulation are completely sustainable practices, calculated, in fact, to be carbon-negative. 

Learn more about how cork is harvested in this short video below: 

Harvesting the outer bark layer from a type of oak tree every nine years is analogous to shearing sheep’s wool for eco-insulation. 

These practices do not damage the living organisms. In fact, periodically removing the excess bark or hair is a good thing — for them and for us!

Removed by hand in a time-honored, family tradition passed down from generation to generation in Western Mediterranean and North African countries, cork bark intended to be home insulation first spends time in the sun to dry thoroughly.

Then, it is minimally processed, beginning with a mechanical separation of impurities that generates dust. It is this dust that provides over 90% of the energy needed for cork insulation manufacture.

Ground up cork shaped into blocks is blasted with extremely hot steam, causing the cork to expand. A binder chemical found in cork called suberin activates from the steam treatment, holding tiny cork granules together. As a result, no additional chemicals are required.

Cork has an R-value of 4 per inch, which is as good or better than many of its fossil fuel-derived competitors. It is very fire resistant and allows water to pass through it without causing damage.

Guaranteed to last 50-60 years in your home, cork is a leading contender for the best eco-insulation on the market today.

More common as a home insulation in Europe, cork is slowly catching on in the United States. Prices are still high for comparable R-value thicknesses. For example, cork insulation may cost 5-10 times more compared to plastic foam boards.

3. Hemp

The non-psychoactive (0.3% or less THC) cousin of cannabis, hemp has gotten a bad wrap over time. In fact, it was illegal to grow hemp in the United States until 2018. This means that companies have been wary of utilizing it as extensively as it could have been in past decades as an agricultural commodity, but this is slowly changing.

Given its versatile qualities, hemp is perfect for making rope, sails, clothes, toilet paper, biodegradable plastic, paint, and biofuel — just to name a few. 

But hemp isn’t just for things. It has great potential as a food ingredient and dietary supplement.

In fact, hemp is very easy to grow, not needing pesticides to impede weeds. Its roots reach down deep to groundwater so it does well in dry areas. And it sprouts up really fast — like a weed — although it’s not one! In a mere 2 ½ months, hemp goes from seed to harvest.

In terms of sustainable green living, hemp wool is an eco-friendly home insulation. In the United States, Idaho-based Hempitecture is a leader in the field of hemp home insulation. They also produce Hempcrete (an eco-conscious concrete alternative).

Although HempWool is 92% hemp, the remaining 8% is polyester, a fossil fuel-derived plastic that is not biodegradable. Other brands may contain up to 40% polyester. This is unfortunate, and has a negative effect on the sustainability of hemp insulation. 

After the useful life of hemp insulation, it could be ground up as mulch and reused as fertilizer. Grinding up polyester in the hemp insulation produces microplastics and nanoplastics which are harmful to marine life and ecosystems and possibly to humans.

All the stats on hemp insulation are stellar. For example, it’s R-value is 3.7/inch, running side by side with the conventional insulation contenders. 

Hemp insulation is extremely fire resistant, and not prone at all to microbial growth.

Like wool and cork, moisture passes through hemp and spreads out instead of collecting in one area and causing a mess — like fiberglass, cellulose, or denim. Hemp also absorbs excess condensation without becoming moldy.

Unlike fiberglass and often different from cellulose and denim depending on how densely packed they are, hemp insulation won’t slump (due to gravity) over time in walls, so you’ll continue to receive its insulating benefits for the entire duration of its long (50+ year) life.

HempWool cost? In some forms and against certain rigid foam board insulation types, hemp wool is price competitive. However, it can be up to twice as much as conventional fiberglass. Green building experts predict that this price differential will drop in the U.S. once more farmers start growing hemp. 

To find out more about HempWool, HempCrete, and the future of green buildings, you can listen to a podcast with Hempitecture’s founder, Mattie Mead.

By the way, if you’re wondering which is better: sheep’s wool or hemp wool insulation, this short video may help you decide.

4. Cellulose

Cellulose is a tree product, usually composed of about 80% post-consumer newspaper. The newsprint is likely made of petroleum-based inks.

The rest is non-toxic borate, a chemical compound that acts as a natural repellent to insects and rodents. Borates also resist fire and mold.

The R-value of cellulose is 3.5-4.0/inch, making it competitive with other types of eco-insulation as well as fossil fuel-based alternatives.

In terms of price, cellulose costs about the same as traditional fiberglass.

When dry and very tightly packed, cellulose is a great home insulator. When it is packed very densely, it won’t settle like fiberglass tends to do. 

However, the situation changes drastically if it gets too wet.

When water-logged, cellulose sags and clumps up. As a result, it loses its insulating ability.

Worse, moisture interacts with certain chemicals in cellulose insulation which could be used as a fire retardant or insect repellent like ammonium sulfate.

 As a result of the interaction, corrosion sets in. The corrosion could affect other parts of the infrastructure of your home, including piping and wiring. Any metal fasteners used to hold the cellulose in place could corrode, too.

On the other hand, borate compounds, when used alone in insulation, do not lead to corrosion. 

There are two types of cellulose eco-insulation: blown-in and damp-spray.

Blown-in cellulose

Ideal for open attics since you don’t have to remove walls to install it, blown-in cellulose is simply shredded newspaper sent through the hose of a blowing machine into the space you wish to insulate. If the air pressure is set on high, the resulting cellulose will be packed in very densely, allowing for minimal air leaks — if any.

If you’re in a house with some fiberglass already present, it doesn’t need to be removed before adding blown-in cellulose (or any type of eco-insulation).

Often, for outside walls, cellulose is blown in from holes made into exterior siding. On the other hand, if cellulose is installed from the inside, the work is very dusty, requires masks and goggles, and is best left to professional installers.

Damp-spray cellulose

For new home construction projects or home additions, damp-spray cellulose is easier to fill open cavities than blown-in cellulose. You’d have a real mess everywhere if the cellulose were dry!

In the damp-spray version, the same recycled newsprint is used but it is dampened with a precise amount of a fine water mist (about 30% by weight). Just enough is needed to make the cellulose rigid and hold its shape — but not enough to be a breeding ground for mold or possibly wood rot. For this reason, leave it to a pro. 

Sometimes, synthetic glues are added to the mix to make the cellulose stick better to your home’s walls or ceilings. 

After spraying, the cellulose must remain exposed to the ambient air until its moisture content drops to 25% (usually 2-3 days depending on your climate zone). Then it’s safe to enclose it permanently.

Research shows that cellulose eco-insulation is approximately 40% more effective at stopping air infiltration than traditional fiberglass insulation. 

5. Denim

Constructed of 80% recycled cotton from industrial and post-consumer waste, denim insulation diverts a huge amount of fast fashion waste from winding up in landfills every year. 

However, note that most clothes today — even blue jeans — are composed of several different types of materials woven together (like cotton, polyester, and spandex). It is costly for recyclers to separate out the fibers. So, it’s more likely that 100% cotton remnants discarded from clothes factories — and not unwanted clothes — are used to make denim insulation. 

If old clothes are used as is, that means the final product contains less than 80% cotton.

Furthermore, it takes huge amounts of water and synthetic (fossil-fuel-derived) pesticides to grow cotton. This means that cotton is not as sustainable a textile as hemp or sheeps’ wool, for example. 

Remember there are petroleum-based inks used to dye the denim, too. This reduces denim’s overall eco-friendliness.

However, don’t think organic cotton’s off the hook. And it’s probably not in denim insulation since there’s so little of it compared to conventionally grown cotton.

Borate compounds are added to denim to impede mold growth, insects, and rodents as well as resist flames.

Like other forms of green insulation, denim carries an R-value of 3.5/inch and is sold as batts and loose fill. Denim is about twice as expensive as its conventional counterparts. 

If you’re interested in this type of eco-insulation, UltraTouch is a leading brand. 

A new development in eco-insulation

Green building materials are exploding in popularity compared to just a couple of decades ago. Research is active and ongoing. Here is one of the most promising types of eco-insulation under investigation.

Nanowood

What is there not to like about nanowood? It’s nature’s best-kept secret developed in 2018 by Dr. Liangbing Hu at the University of Maryland in collaboration with researchers at the University of Colorado, Boulder and KTH University of Technology in Sweden.

This team subjected wood — by itself an excellent insulator — to three simple and readily available chemicals you may even have at home in other products: sodium hydroxide (lye), sodium sulphite (food preservative), and hydrogen peroxide (antiseptic).

That chemical trio removes lignin from the wood. An effective heat conductor by itself, this major wood component is currently being developed as a clean energy source.

Without lignin, however, nanowood is much more insulating.

Made entirely of tree matter, nanowood is a super insulator, besting the industry standard, polystyrene (often referred to by the brand name, Styrofoam). It’s also extremely thin and lightweight but at the same time very strong. To top it off, it’s biodegradable. 

Best of all, nanowood is relatively inexpensive to manufacture. Researchers estimate that it will cost $0.70/sq. ft. once it finally gets to the commercial production stage. (For comparison, fiberglass averages $0.65-$1.20/sq. ft.)

Being extremely thin, nanowood is also easily rolled and folded. Its versatility means it has many potential uses that require greater maneuverability like pipe insulation.

NeptuTherm

Manufactured in Germany, seaweed eco-insulation is apparently available in Europe since the company website appears live (German language only). But it’s not — yet — sold in the United States that we could tell. Articles in English state that this insulation type is 100% natural from beach-strewn seaweed with minimal processing. Let’s hope it catches on and arrives on U.S. shores because it seems to hold much promise as a genuine eco-insulation!

Home insulation marketed as eco-insulation

Many companies offer insulation products that appear sustainable but are not as eco-friendly as the five types profiled in this article plus nanowood (under development) and NeptuTherm.

1. EcoBatts

EcoBatts is very similar to fiberglass. As such, it’s still itchy to install and hazardous to be around because of the tiny glass shards.

Fiberglass is made partially of plastic with interwoven glass particles. As such, it is difficult to recycle and reuse except as a filler in cement or asphalt after it is ground up. This use results in microplastics introduced into the environment causing harm to animals, plants, and ecosystems and possibly to humans, as we saw in the case of hemp insulation.  

Described as “phenol- and formaldehyde-free mineral wool” — typically these toxic chemicals are used in fiberglass manufacture — by its manufacturer, EcoBatts is 61% recycled glass. So, it is a small step up from conventional fiberglass which doesn’t contain as much recycled glass (if any). 

Details on what is used to make it and how aren’t posted on the company website.

2. Aerogel

Touted as a space age wonder with extreme insulating properties, Aerogel is mostly made up of air by volume. At this point, it’s mainly used for industrial applications including oil and gas pipelines.

Synthetic amorphous silica (SAS) is the base chemical in Aerogel, giving it the nickname “puffed up sand.” According to the company website, the other “major” ingredient is E-glass (a type of fiberglass) sometimes blended with petroleum-derived polyester.

Because of its synthetic and fossil fuel-based ingredients, Aerogel is not a truly sustainable eco-insulation.

3. AgePan

Called “ecological and sustainable” on the company website, little information is given as to what exactly AgePan is or how it’s manufactured.

Other sites state it is made of wood fibers coated in petroleum-derived paraffin wax with a polyurethane-based binder holding it all together.

With these added ingredients, AgePan (and similar brands) are not sustainable types of eco-insulation.  

4. Icynene

Known as an open cell polyurethane spray foam, the manufacturers of Icynene state it is safe. It is a petroleum product — so not green. 

We have gleaned from other websites selling this product that it is made from castor oil as well as petroleum-based ingredients and contains no chlorofluorocarbons (CFCs) or hydrochlorofluorocarbons (HCFCs) like some spray foams contain to blow in the insulation.

CFCs and HCFCs, when burned or exposed to UV radiation, release phosgene, a poisonous gas similar to the chemical weapon, mustard gas. 

In this sense, since Icynene uses water instead when it is blown into your home, it seems more environmentally-friendly than other spray foams.

However, the fact that there are lawsuits against spray foams raises doubts about whether you’d want it in your home. 

Tax credits and other incentives for home insulation

The Biden Administration recently extended through the end of 2021 a small tax credit up to $500 for home installation. It covers materials only (not labor).

Here is information from the Energy Star website:

“Typical bulk insulation products can qualify, such as batts, rolls, blow-in fibers, rigid boards, expanding spray, and pour-in-place. Products that air seal (reduce air leaks) can also qualify, as long as they come with a Manufacturer’s Certification Statement, including:

– Weather stripping
– Spray foam in a can, designed to air seal
– Caulk designed to air seal
– House wrap”

Your state may offer other tax advantages, so check out the national database to see how much money you’ll save — on top of lower home heating and cooling bills — with eco-insulation.

Summary table on eco-insulation: 5 factors to consider

Here’s a handy guide to the leading types of eco-insulation commercially available in 2021, scored against each other based on five key points to consider:

Wrap up on Eco-Friendly Insulation

Fortunately for climate-conscious homeowners, traditional insulation materials, like fossil fuel-based fiberglass and polystyrene, are no longer the only options you have. Several environmentally-friendly alternatives are available today to insulate your home. Sometimes higher in upfront costs, the energy savings they provide will last for the life of the product which could be 50 years or more. 

Most of these materials are comparable in insulation ability to conventional types as measured by R-value but without the huge fossil fuel input needed to make them or the toxic chemicals applied to them.

So if you’re looking to reduce your carbon footprint while saving energy and money, choose one or more of the sustainable types of eco-insulation profiled in this article for your home.