Healthy home: materials and indoor air quality

The U.S. EPA (Environmental Protection Agency) estimates that the air in our homes is 2 to 5 times more polluted than outdoor air. After spending so much time at home during successive COVID lockdowns, the importance of living in a healthy home has perhaps become clearer than ever before.

Healthy home: materials and indoor air quality

Materiales y calidad del aire, claves para los espacios saludables
Figure 1: Example of materials that can affect a home’s indoor air quality [Source: Jose Hevia / H.A.U.S]

The U.S. EPA (Environmental Protection Agency) estimates that the air in our homes is 2 to 5 times more polluted than outdoor air. After spending so much time at home during successive COVID lockdowns, the importance of living in a healthy home has perhaps become clearer than ever before.

What kind of environmental conditions are we looking for in a healthy home? Operative or comfort temperatures of between 20 ºC – 25ºC, relative humidity between 40 % – 60%, and surface temperatures ≤ 3ºC of the indoor air temperature.  With an indoor air temperature of 20ºC and a relative humidity of 50%, interior surfaces need to be ≥ 13ºC to prevent the risk of mould growth, and ≥ 9ºC to avoid surface condensation. Exposure to mould spores can cause health issues such as eye, skin and throat irritation, nasal stuffiness, coughing and wheezing. Alongside healthy thermal conditions, good indoor air quality is key for wellbeing, solved largely by good ventilation, but also by preventing the entrance of outdoor contaminants (such as particulate matter, radon gas etc.) and by reducing the generation of indoor contaminants due to emissions from materials, furniture, and finishes.

If continuous and controlled ventilation is key, we need to get to the root of the problem: to reduce and avoid materials that emit toxic chemicals in our home. In this article Oliver Style explains what to be on the lookout for, and presents three certification systems that are useful for choosing healthy products and materials.

What does indoor air contain?

To live in a healthy environment, we need to look at the products, materials and furniture we have in our home, since we breathe the particles they emit and we are often in direct physical contact with them.

The first step is to choose paints, varnishes, timber, ceramics, textiles, and furniture with a very low emissions of Volatile Organic Compounds (VOCs). VOCs are of both natural and artificial origin. They all share the common characteristic that they are made of carbon and other elements such as hydrogen, halogens, oxygen, or sulphur. They are present in solids or liquids and are either volatile or occur in a gaseous state at room temperature, which means they move quickly around indoor spaces. Some of them modify the chemical composition of their local environment and are harmful to our health.

Formaldehyde, a colourless, volatile, and toxic gas (classified as carcinogenic by the EU), and other VOCs, are often found in paints, paint strippers, wood preservatives, wood products, binders, glues, waxes, plastics, pesticides, aerosols, synthetic carpets, cleaning products, disinfection products and degreasers. Health effects include asthma, eye, nose and throat irritation, headaches, loss of coordination, nausea, liver, kidney and central nervous system damage. VOCs can be endocrine disruptors and cause respiratory and hormonal diseases, prolonged sleep and behavioural disorders, reproductive disorders and foetal development, cancer, and multiple chemical sensitivity (MCS).

Another harmful component to pay close attention to is particulate matter (PM)- fine particles and fibres with a diameter of 10 micrometres (PM10) or less (PM2.5 and PM 1). PM2.5 particles can reach the lungs, and PM1 can reach the bloodstream. Short and long-term exposure to these particles is associated with cardiovascular and respiratory diseases, including lung cancer. These diseases become more evident when the fibres come from highly toxic materials such as asbestos.

Which are the best materials and products to use in our home?

To avoid and minimize harmful substances inside the home, it’s best to look for products that have been modified or processed as little as possible, made with low-emission paints, varnishes, and glues, formaldehyde free, and if possible, certification for low emissions. Three such certification systems are mentioned below, which classify materials and products and quantify their harmful emissions.

Linoleum or solid wood floors are recommended because they usually contain few adhesives and generally have low emissions. Anything that has been varnished or coated in a controlled factory environment (rather than on-site) will lead to lower emissions in the home. If you use laminated timber flooring, look for one that is free of formaldehyde.

Carpets are in generally not advisable, as they end up collecting all kinds of particles, and in some cases, contain volatile coal ash or polyurethane laminates. Natural fibre carpets are recommended.

Furniture and wood composite products can be a significant source of emissions because they are often made with urea-formaldehyde adhesives. Look for solid wood or plywood furniture, free of formaldehydes. 

As far as kitchen counters go, natural rock is a good option, such as quartz. Alternatively, look for Corian (a synthetic material for solid surfaces composed of acrylic resin and aluminium hydroxide).

As for thermal insulation, exposure to sprayed foam insulation containing isocyanates can cause asthma. If you use fiberglass or mineral wool insulation, make sure it’s formaldehyde free. In general, bio-based or mineral insulation are the healthiest options.

Be careful: products are sometimes sold as “ecological” due to their recycled content, but they can be harmful to your health. For example, some ceramic tiles are made with recycled glass from cathode ray tubes from old TVs, which are considered hazardous waste due to their high lead content.

Emissions & materials: certification systems

1. French certification for indoor air emissions

Emisiones Dans l’air intérieur
Figure 2: Example of the indoor air emissions certification, with A+ product rating

The label “Émissions dans l’air interieur” classifies building materials, furniture and finishing products marketed in France, being mandatory for all products sold there. The certification classifies products according to VOC emissions, from A+ to C (A+ being lowest emissions), according to the ISO 16000 standard. If a product exceeds the limits, it cannot be sold (admittedly “C” class is not very demanding…). The following emissions are evaluated:

  • Formaldehyde
  • Acetaldehydes
  • Toluene
  • Trichloroethylene
  • Xylenes
  • 1, 2, 4 Trimethylbenzene
  • 1, 4 Dichlorobenzene
  • Ethylbenzene
  • 2 Butoxyethanol
  • Estriol

2. Baubiologie Rosenheim Institute certification

Geprüft und empfohlen
Figure 3: IBR Certificate Seal

The IBR, Institute for Biologically Sound Construction, is a German institution that certifies healthy and environmentally sustainable consumer construction products, and includes a series of tests that measure the emissions of a product, including:

  • Radioactivity
  • Biocides
  • Polychlorinated biphenyls
  • Heavy metals
  • VOC
  • Formaldehydes
  • Biological compatibility
  • Electrostatics

3. Eurofins Indoor Air Comfort certification


This certification systems classifies construction products into two categories: Standard level “Indoor Air Comfort – certified product”, which shows compliance with product emissions criteria established by EU authorities, and Higher level “Indoor Air Comfort GOLD – certified product”, which shows additional compliance for product emissions with the criteria set by the most relevant ecolabels and sustainable building organisations in the EU.

MICA Wall indoor air quality sensor
Figure 5: MICA Wall indoor air quality sensor

What you don’t measure you can’t improve

There are several testing laboratories in Spain for the measurement and certification of materials and their VOC emissions, such as Tecnalia, and SGS. What if I want to measure the indoor air quality of my home without spending a fortune? There’s affordable equipment with reasonable accuracy, such as the range of MICA sensors, manufactured by Inbiot. They measure VOC’s, formaldehydes, ozone, suspended particles, radon gas, CO2, temperature and relative humidity.

The following figure shows measured data from a MICA sensor of formaldehyde concentration in a bedroom over the course of a week.

According to the technical standard of measurement in Baubiologie SBM2015 for rest areas, values above 100 μg/m3 are already extremely significant. “The search for emission sources is a bit like looking for a needle in haystack, based on the data and measurements. But you can gradually discard sources until you find the culprit” says Maria Figols, Project Manager at InBiot.

Figure 6: Formaldehyde concentration measured in a bedroom for one week in December 2019

Better living with less emissions

Creating healthy indoor environments is clearly on the agenda, with the construction sector on centre stage. Choosing the right low-emission materials will improve indoor air quality and can help reduce illness for occupants, in the short, medium, and long term. Using products with some of the certification systems shown above is a good place to start. Alongside emissions, these kind of certification systems also assess the environmental impact of a product, making sure they don’t pose a significant hazard during manufacturing, deconstruction, recycling or waste treatment phases. Reducing the source of indoor contaminants should always be the first step. The second step- and equally important- is controlled and efficient ventilation.


To Maria Figols and Xabi Alaez from InBiot for their contributions.


[1] Guía Edificios y Salud, Siete Llaves para un edificio saludable. García de Frutos, Daniel et al. Consejo General de la Arquitectura Técnica de España, Consejo General de Colegios de Médicos. Enero 2020.

[2] Monitorización de vivienda de alta eficiencia, 30 Marzo 2020. InBiot.