Guide to eco-friendly paints

Beyond choosing a colour, buying paint means selecting from a wide range of paint options available.

Today, the most common interior paints are acrylic-based, sometimes called “latex”, produced from petrochemicals derived from fossil fuels. They are easy to apply, require little maintenance, and allow the surface to be cleaned.

However, it is not all advantages: synthetic-based paints often include a large number of synthesised chemicals that may pose a risk to people’s health.

Although most people with some environmental awareness have heard of the volatile organic compounds (VOCs) present in their composition and know that these can be released into the air in small amounts, posing a risk to people’s health, it is important to bear in mind that most conventional paints also contain other toxic compounds such as binders, pigments, or additives.

For example, alkylphenol ethoxylates (APEs)—a group of chemicals present in acrylic paint used to increase viscosity—are suspected endocrine disruptors that cause hormonal dysfunction in humans and animals, as well as disrupting marine life.

Recent research by the NGO Environmental Action reveals that acrylic (plastic) particles are the predominant source of microplastics in the ocean and waterways, accounting for more than half of all microplastics present in the world’s oceans each year. Moreover, these plastics have also been detected in the human bloodstream. [1]

Healthy alternatives, such as mineral-, clay-, or plant-based paints, are already commercial products marketed on a large scale, many of them as easy to apply and maintain as plastic-based paints.

WHY USE ECO-FRIENDLY PAINTS?

Paint has been with us for approximately 30,000 years. Body paint, cave paintings, murals, and frescoes: there are many practices in which paint has served as a technical tool and/or artistic expression. The use of paint is inherent to human beings.

Today, painting our spaces stems more from an aesthetic or functional need. Interior design trends lead us to cover building materials with plaster and paint, either for aesthetic purposes to add colour or light to a space, or for functional purposes to achieve smooth or waterproof surfaces that are easy to clean.

However, despite being considered the “final touch”, paint is a thin layer over a large surface area that will have direct effects on the indoor environment and people’s health.

In many cases, the paints used contain toxic components that are released into the air in small amounts over long periods of time and are absorbed by our bodies.

In addition, many paints prevent the natural breathability of building materials. Many materials, such as wood or ceramic, are hygroscopic: they absorb and release ambient moisture, helping to buffer fluctuations and reducing the dryness that occurs when we turn on the heating.

For this reason, if we decide to paint, it will be necessary to select natural, breathable, toxin-free paints that ensure a healthy indoor environment.

What is an eco-friendly paint?

The emergence of synthetic materials brought countless changes to the construction sector.

Resins and vegetable oils, which were traditionally used to make paint, were replaced by synthetic chemical products.

Synthetic paints are usually inexpensive, easy to apply, quick-drying, and in many cases waterproof or make walls easier to clean.

However, despite their qualities, synthetic paints contain a large amount of toxic substances that have a significant impact on the environment and on people’s health.

Eco-friendly paint is defined as paint whose composition replaces the chemicals in synthetic paints with raw materials of natural origin.

Paint composition

The environmental quality of paint depends on its composition, so it is important to understand the ingredients it contains. Any natural or synthetic paint is made up of:

1. Binder
2. Solvent
3. Pigment
4. Additive

1. Binders

Binders act like glue: they ensure the paint adheres to the surface to be covered, and they also bind the colour particles together.

Synthetic paints use artificial resins made from naturally occurring substances that have been chemically modified, or made entirely synthetically from petroleum. Their use emits toxic residues that are harmful to health.

Due to their effectiveness, the most commonly used natural binders are those made from vegetable oils, resins and waxes, glue and casein, clay and lime, or potassium silicate.

2. Solvents

The solvent helps dilute the mixture of binders and pigments. It helps spread the paint and allows it to be applied to the surface with a brush.

Synthetic solvents often contain aromatic substances capable of affecting our central nervous system.

For this reason, it is preferable to use natural solvents as accessible as water, white spirit, turpentine (distilled from tree resins), or even citrus oils or orange peel oil.

It is important to note that, although they are of natural origin, some highly sensitive people may be intolerant to strongly scented resinous components.

3. Pigments

Pigments are responsible for colour and opacity. They have the ability to protect the elements covered by paint from UV radiation—the sun’s rays are reflected by the pigment particles.

Most of today’s synthetic pigments come from petroleum: dyes based on aniline, anthracene, and azo compounds, all of which are carcinogenic substances.

Instead, there are numerous pigments of natural origin to choose from: natural earths and minerals such as chalk, slate, graphite, spinel, or plant-based paints obtained by extracting certain resins or roots.

4. Additives

Additives are used to improve the technical properties of paint application. Among other things, they are characterised as driers, wetting agents, stabilisers, antioxidants, fixatives, etc.

This is the synthetic compound that is most difficult to replace. Many eco-friendly paint manufacturers resort to using manganese, cobalt, or zirconium octoates, despite their carcinogenic effects, because they do not emit gases during application or use; they are only present in the dust. For this reason, it is advisable to take precautionary measures to avoid inhaling contaminated dust during the application process. [2]

Benefits of eco-friendly paints

The main drawback of eco-friendly paints is their price. At present, it has not been possible to match the low cost of synthetic paints, but as with all building elements and systems, the cost we save today is passed on to future generations in the form of greenhouse gas emissions or environmental pollution. Added to this is the toxicity they generate in our homes and the impact on our health.

In recent years, natural paints have begun to be produced on a large scale, competing with synthetic paints in both price and ease of application and colour range. Considering the health benefits their use brings, it is undoubtedly an investment that will always pay off.

But beyond comparing costs with conventional paint, let us look at the advantages of choosing a natural paint.

1. Healthy indoor environment

But beyond the effects on those who apply them, paints remain present in our homes for years. Considering that human beings spend most of our time indoors, ensuring healthy, toxin-free indoor air quality is a decisive factor in supporting the health of our living spaces.

Although outdoor air pollution affects indoor air quality, the highest concentrations of toxins and harmful substances measured in occupied spaces are mainly produced by emissions from building materials, paints, furniture, and textiles such as carpets or curtains.

In the case of paints, the highest concentrations of toxins occur during application and in the weeks that follow. Although ventilation helps mitigate these effects, it is impossible to reduce the long-term accumulation of harmful substances produced by smaller emissions over time.

Unlike synthetic paints, eco-friendly paints are safe during application and throughout their entire service life, and they often emit a pleasant smell during the first few days.

In addition, eco-friendly paints are antistatic—they do not retain dust on the surface, reducing conditions such as allergies, asthma, or skin irritation. They also reduce the emission of Volatile Organic Compounds (VOCs) by replacing synthetic solvents with more natural ones, free of these toxic compounds. Choosing a paint with low or zero VOC content is a way to help create healthy spaces that respect the environment. [3]

APEs and NPE

Beyond VOCs, the recommendation has recently become widespread to choose paints without nonylphenol ethoxylate (NPE) to protect human health and the environment.

The Healthy Building Network included alkylphenol ethoxylates (APEs), which include NPE, in its list of compounds that are toxic to health a few months ago.

Alkylphenol ethoxylates (APEs) are a group of chemicals that includes nonylphenol ethoxylates (NPE) and octylphenol ethoxylates (OPE) and are used as surfactants in acrylic paints. NPE and OPE break down into nonylphenols and octylphenols, which are non-biodegradable chemicals that become toxic to aquatic organisms and are also endocrine disruptors. [4]

2. Breathability

Humidity and temperature in an indoor space vary throughout the day and across the seasons. To ensure health, comfort, and wellbeing, it is recommended that indoor humidity levels remain around 50%.

However, due to the use of heating systems and poor ventilation, the average humidity in the indoor spaces we inhabit is around 20%. This humidity deficit translates into a series of negative health effects, such as changes to the protective mucous membranes of the respiratory system—reducing our natural defences—as well as eye irritation and dryness or an itchy sensation on the skin.

A constant supply of oxygen-rich air and the reduction of carbon dioxide are essential for a healthy indoor climate. Despite the different degrees of wall porosity, the air pressure difference between the outside and the inside of a wall is not high enough to promote significant air exchange through the building envelope.

A properly executed building envelope is only able to renew between 0% and 4% of indoor air, when we should be renewing 100% of the air volume several times a day.

It is necessary that coating products do not reduce the walls’ air diffusion capacity. Eco-friendly paints promote breathability—as open-pore paints, water vapour passes from the inside to the outside of the home, preventing condensation damp. Due to their capillarity, eco-friendly paints provide additional surface protection. [5]

3. Hygroscopicity

Hygroscopic building materials and surface treatments have a high moisture-buffering capacity—they absorb or release moisture into the air. They help compensate for and balance humidity peaks in a room, significantly improving indoor environmental quality.

This moisture-buffering effect occurs in the first 2–3 cm of the surface layer, which is why finishes and coatings play a fundamental role in regulating atmospheric humidity in indoor spaces. The thermoregulatory properties of the natural components present in eco-friendly paints support this effect.

Open-pore hygroscopic building materials are not only able to buffer ambient humidity levels, but can also absorb odours and toxins, helping to create a pleasant and healthy indoor climate.

4. Sustainability

In a context of climate emergency, it is clear that choosing products of natural origin that can reduce the ecological footprint of our built environments is essential.

Replacing synthetic building materials with more natural alternatives is one of the key pillars of sustainable architecture.

In addition to their interesting properties and technical performance mentioned above, eco-friendly paints benefit people by avoiding substances that are harmful to health. They are low-impact products—being biodegradable and long-lasting, they contribute to caring for and respecting the environment.

Types of eco-friendly paints

Today, there are two types of 100% eco-friendly natural paints, classified according to their main components: mineral-based paints and plant-based paints.

Mineral paints

Among all eco-friendly paints available on the market, mineral-based paints are classified according to:

1. Lime paint
2. Silicate paint
3. Clay paint

1. Lime paint

Lime paints are composed primarily of air lime derived from the decomposition of limestone rocks, mixed with natural resins, marble dust, or other additives.

This is an antibacterial, anti-mould type of paint that prevents the proliferation of fungi and microorganisms in the air and on walls.

It is particularly suitable for interiors—for exteriors, a protective overhang is recommended. Lime paints are distinguished by their velvety finish. Their natural colour is intense white, although natural pigments can be added to colour them.

2. Silicate paint

Silicate-based paints are the result of a recycled glass melting process and are essentially composed of pure liquid silicate mixed with selected aggregates.

Their application is suitable for interior or exterior use alike, given their durability, high resistance to atmospheric agents, and excellent adhesion to any surface.

Their waterproof and breathable properties make them suitable for damp rooms, promoting the natural flow of water vapour.

3. Clay paint

Clay paints are composed primarily of natural white clay, marble sands, and vegetable casein.

Their use is recommended for interiors, preferably in dry environments with high relative humidity.

Given their high absorption capacity, their use is recommended on kitchen and bathroom ceilings to absorb moisture and odours, but not on walls due to possible unwanted oil absorption.

Despite beliefs associated with clay, its natural colour is off-white, but it accepts the addition of pigments that alter its colour.

Plant-based paints

As for eco-friendly paints of plant origin:

1. Glue paint
2. Casein paint
3. Plant resin paint

1. Glue paint

Glue paints are made with plant celluloses (methylcellulose), chalk, and coloured earths. It is an odourless, stain-proof paint, although not washable.

As it is not water-resistant, it must be applied exclusively on dry surfaces. It has excellent diffusion properties, meaning it covers surfaces very well due to its high dispersion capacity.

If desired, it can be tinted with added mineral pigments. These are the most economical paints on the market.

2. Casein paint

Casein paint, also known as milk paint, uses casein protein as a binder, a protein extracted from milk. It is a paint with great adhesive capacity, as well as being resistant.

Over time, its impermeability and durability are reinforced indefinitely, making it an ideal material for painting home exteriors and/or furniture.

3. Plant resin paint

Plant resin paints are obtained as a result of processing plant-based materials such as roots or tree bark, potato starch, oils, or waxes, among others.

They are products with high coverage and their application on surfaces is quick and easy. Natural resins are water-soluble, providing protection against moisture that offers great resistance.

ECO-FRIENDLY PAINT LABELLING

Eco-labels or environmental labels are regulatory systems that guarantee the quality of marketed products from an environmental perspective. [6]

Five distinctive eco-friendly paint labels stand out, applicable both nationally and internationally:

1. Ecolabel (EU, 1992)
2. AENOR Environmental Management (Spain, 1986)
3. Indoor Air Emissions (France, 2013)
4. Natureplus (Germany, 2001)
5. EMICODE (Germany, 1997)

1. Ecolabel

The “Ecolabel” label is a European system that aims to promote products that reduce environmental impacts. Products with the ECOLABEL label necessarily have a low level of polluting toxins—they demonstrate compliance with environmental and health requirements at European level. [7]

The ISO 14020 standard establishes the principles for the development and use of this type of eco-label.

2. AENOR Environmental Management

This is a label administered by the Spanish Association for Standardisation and Certification (AENOR), responsible for regulating standards regarding environmental management. It is the Spanish member that certifies the ISO 14001 standard.

The ISO 14001 standard is the international environmental management standard that helps companies reduce the negative environmental impact of their products.

3. Indoor Air Emissions

The French label Émissions dans l’air intérieur (Indoor Air Emissions) classifies paints according to their quantity of VOC emissions, with the letter C corresponding to the highest tolerable emissions and A+ to practically zero emissions.

Since 2013, in France, all construction and decoration products, including paints, must compulsorily carry this environmental label.

4. Natureplus

This is a European quality label that certifies healthy and environmentally friendly construction and decoration products.

Products with the Natureplus label ensure that 85% of their composition comes from raw materials and renewable resources.

5. EMICODE

The label is administered by the German association GEV, responsible for certifying products from manufacturers that comply, to the greatest extent, with VOC emission limits.

There are 3 emission classes according to the EMICODE label, with the EC1 categorisation ensuring the lowest emission levels.