Healthy Materials

Volatile organic compounds (VOCs) are carbon-based chemicals that evaporate readily at room temperature - which is precisely why we can smell them and, more importantly, breathe them. They come from a long list of common building products: solvent-based paints and varnishes, adhesives and sealants, the resins in engineered wood, carpets and their backings, vinyl flooring, foams in furniture, and many cleaning products. Once installed, these materials off-gas - release their volatile content into the indoor air.

The health stakes are real. Short-term, elevated VOCs cause the classic 'sick building' symptoms: headaches, dizziness, eye, nose and throat irritation, fatigue. Long-term or high exposure to specific compounds is more serious - formaldehyde, common in the urea-formaldehyde resins that bind MDF, particleboard and some plywood, is a recognised human carcinogen and respiratory irritant; benzene and others carry their own hazards. Because we spend ~90% of our time indoors (Lesson 6.1), even low concentrations add up to a significant chronic exposure.

The critical design insight is timing. Off-gassing is not constant: it is highest when a material is new and decays over time - but at very different rates. Solvents in paint may largely dissipate in days to weeks with good ventilation; formaldehyde from wood products can continue off-gassing for months to years, and heat and humidity accelerate it. This is why the three-move logic of Lesson 6.1 matters so much here: you can dilute with ventilation and remove with filtration, but the most powerful move by far is to cut the source - to specify materials that never contained the harmful chemicals in the first place. You cannot ventilate your way out of a bad material specification.

Beyond the VOCs you can smell, building products can contain a wider cast of hazardous substances - persistent, bioaccumulative or toxic chemicals that harm occupants, workers who make and install them, and the environment across the product's life. The most influential response is the Red List maintained by the International Living Future Institute as part of the Living Building Challenge (Module 8): a roster of the 'worst in class' chemicals and materials a truly healthy building should avoid entirely.

Recurring names on such lists include formaldehyde; phthalates (plasticisers common in flexible PVC/vinyl, linked to endocrine disruption); halogenated flame retardants (in foams and electronics); PFAS, the 'forever chemicals' used for stain and water resistance; PVC (polyvinyl chloride) itself, problematic across its life-cycle from feedstock to disposal; formaldehyde-based binders; certain heavy metals (lead, cadmium, mercury, hexavalent chromium); and older hazards like asbestos. You do not need to memorise the chemistry, but you do need to know the categories and the usual culprit products - flexible vinyl, conventional engineered wood, some paints and sealants, stain-resistant textiles and carpets.

The honest complication is that avoidance often involves trade-offs and substitution risk. Removing one hazard can introduce another if the replacement is poorly understood ('regrettable substitution'), and some red-list chemicals do a genuine job - flame retardants meet fire codes, PVC is cheap and durable. The regenerative approach is not blanket panic but informed avoidance: prefer materials that never needed the hazard (solid timber over formaldehyde-bonded board; linoleum, rubber or tile over vinyl; naturally durable or mechanically-treated textiles over PFAS coatings), demand evidence about substitutes, and reserve the hazardous option for where code genuinely requires it and no proven alternative exists.

None of this is actionable if you cannot find out what a product contains - and historically you could not. Ingredient lists were trade secrets; a specifier had to trust a marketing label. The single biggest advance in healthy materials over the last decade is the material transparency movement: a push to make manufacturers disclose contents and hazards in standardised, comparable formats, so designers can choose on evidence rather than faith. Think of it as a ladder, from no information at the bottom to fully verified health at the top.

The key tools, roughly in ascending order of what they tell you about health: third-party emissions certifications such as GREENGUARD Gold, GEV EMICODE or FloorScore test the finished product's VOC emissions into air (useful, but they test output, not full contents). A Health Product Declaration (HPD) is an open standard that lists a product's contents and their associated health hazards - a proper ingredient-and-hazard report. A Declare label, from the International Living Future Institute, is a 'nutrition label' for building products: it lists ingredients, states final assembly location and end-of-life options, and crucially declares whether the product is Red List Free, Red List Approved, or merely 'Declared'. At the top, Cradle to Cradle Certified assesses material health alongside circularity, renewable energy and water (linking to Module 4).

Note the important distinction from Environmental Product Declarations (EPDs), which you met in the carbon modules: an EPD reports a product's environmental life-cycle impacts (carbon, energy, water) - it is about the planet, not directly about occupant health. HPDs and Declare labels are about human health - what is in the product and whether it is hazardous. A complete healthy-and-low-carbon specification uses both. The practical skill is to write transparency into your specifications: ask for HPDs and Declare labels, prefer products that provide them, and treat a manufacturer's refusal to disclose as information in itself.

Turning all this into a real, buildable specification is the designer's craft, and it is very much interior-designer and architect territory because these are the materials occupants touch and breathe every day. A few practical strategies make it manageable rather than paralysing.

Focus effort where exposure is highest. The materials that matter most for indoor air are the ones with large surface area, indoors, that occupants are close to: paints and wall finishes, flooring and its adhesives, ceilings, and furniture and joinery - especially engineered-wood cabinetry and its edge banding. Prioritise getting these right over chasing every minor component. Specify low-VOC and no-added-formaldehyde products as a baseline: low-VOC paints and adhesives are now mainstream, well-performing and barely more expensive, and no-added-urea-formaldehyde (NAUF) or formaldehyde-free boards are widely available. Favour materials that are inherently healthy - solid and certified wood, clay and lime plasters, natural linoleum, stone, ceramic, natural-fibre textiles - which also tend to be the biophilic natural materials of Lesson 6.3, another example of one move serving several goals.

Manage the handover, not just the product. Even good materials off-gas most when new, so allow a flush-out period with heavy ventilation before occupancy where the programme permits, keep materials dry and well-stored on site (damp boards off-gas more), and sequence so wet, high-VOC trades finish before soft, absorptive materials go in (the 'dirty before clean' rule). Finally, coordinate with the other lessons: healthy materials support clean air (6.1), overlap with biophilic natural finishes (6.3), and interact with acoustic and thermal choices (6.2) - a soft absorptive acoustic material must also be low-emitting. And remember the whole-life view from Module 4: the healthiest materials are frequently the low-carbon, bio-based, circular ones too, so healthy-material selection is not a separate silo but part of the integrated, regenerative material strategy that a good building pursues as one system.

A crucial refinement to healthy-material thinking is that exposure is not felt equally by everyone. The 'average adult' assumed in many guidelines is not who occupies a nursery, a paediatric ward or a care home. Designing for the most vulnerable occupant, not the median one, is both the ethical and the rigorous approach - and it changes where you spend effort.

Children are the clearest case. They breathe more air per kilogram of body weight than adults, their organs and nervous systems are still developing, and they spend time close to floors where heavier compounds settle and where soft, off-gassing materials like carpets and foam mats accumulate. Schools, nurseries and children's bedrooms therefore deserve the strictest material scrutiny. Hospitals and clinics house people whose health is already compromised and who cannot leave, making low-emitting, cleanable, non-toxic surfaces a clinical issue, not a comfort one. The elderly and those with asthma, allergies or chemical sensitivities react to concentrations others tolerate. And do not forget the people who are exposed most intensely of all: the construction and manufacturing workers who cut, sand, glue and breathe these materials daily - a genuinely healthy material is healthy across its whole life, from factory to installer to occupant to disposal.

This maps onto a practical prioritisation. Apply your most demanding healthy-material standards - no-added-formaldehyde, verified low-emission, red-list screening, HPD/Declare transparency - hardest in schools, healthcare, childcare and homes, and to the materials with the largest indoor surface nearest people. In a warehouse or plant room the calculus differs. This is not a licence to be careless elsewhere; it is a way to direct finite effort and budget where the human return is greatest. It also links straight back to the equity dimension of sustainability: the burden of unhealthy buildings falls hardest on those with the least choice about where they live, learn and are treated - which is exactly why healthy materials belong at the heart of a regenerative, and just, practice.