10/07/2026
Toxic Terrain – Chapter 13, Part 5: Insulation and Building Materials – What Is in the Walls and the Loft
The house was renovated two winters ago. She was proud of it. New insulation in the loft. New foam board on the external walls. New spray foam around the windows. The house is warm now. The heating bills dropped. The energy rating improved. It felt like a genuine upgrade.
Her son sleeps in the room directly below the loft. His bedroom is above the wall that was reinsulated. It is the warmest room in the house. It is also the smallest. The window is usually closed.
He has a persistent cough that will not clear. He has headaches that come in the morning. His eyes are often red when he wakes. He is tired more than he used to be. She has taken him to doctors. They found nothing.
Here is what no one has told her.
The insulation that made her home warm is also a source of chemicals. Foam board releases flame retardants. Spray foam releases isocyanates during and after installation. Older foam insulation releases formaldehyde. And because the house is now sealed tighter than before, those chemicals accumulate in the indoor air rather than escaping. The child who sleeps in the smallest, warmest, most sealed room is breathing the highest concentration.
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What Is Actually Happening
Insulation is not one material. It is a category. Each type has a different chemistry, and each chemistry carries a different set of concerns.
Foam Board Insulation
Rigid foam board is used on walls, roofs, and foundations. The most common types are:
Expanded polystyrene (EPS) – Made from styrene. Contains flame retardants, most commonly HBCD (hexabromocyclododecane), a persistent organic pollutant that is banned or restricted in many countries but still present in older installations.
Extruded polystyrene (XPS) – Also contains flame retardants, historically HBCD, now often a replacement such as a polymeric FR.
Polyisocyanurate (polyiso) – Made from isocyanates. Contains flame retardants, often TCPP.
Phenolic foam – Contains formaldehyde-based resins.
All of these boards are installed in walls and lofts. They release flame retardants and other chemicals slowly over years. The release is small per board, but a house has many boards.
Spray Foam Insulation
Spray polyurethane foam is applied wet and expands to fill gaps. It is used around windows, in lofts, and in wall cavities. During installation, it releases isocyanates, which are potent respiratory sensitisers. After installation, it continues to release small amounts of isocyanates and other chemicals for weeks, and trace amounts for months or years.
Isocyanates are a leading cause of occupational asthma. The risk is highest during installation, but the residual emissions are a chronic low-level exposure that the home's occupants breathe.
A 2024 study of homes with spray foam insulation found that airborne isocyanate concentrations were detectable for several weeks after installation and that "occupants reported respiratory symptoms that were not present before the installation."
Urea-Formaldehyde Foam Insulation
Urea-formaldehyde foam insulation was installed in many homes in the 1970s and 1980s. It was banned in some countries after reports of formaldehyde-related illness, but it remains in many homes that were insulated during that period. It releases formaldehyde gas continuously. Formaldehyde is a known human carcinogen and a respiratory irritant.
A 2025 review found that homes with urea-formaldehyde foam insulation had indoor formaldehyde concentrations significantly above those of homes without it, and that "residual formaldehyde emissions can persist for decades."
Loose-Fill and Fibreglass Insulation
Loose-fill insulation is made from fibreglass, cellulose, or mineral wool. Fibreglass and mineral wool release fine fibres that can irritate the skin, eyes, and lungs if disturbed. Cellulose is treated with borate or ammonium sulfate to make it fire-resistant. The fibres are less of a chronic chemical concern than the foams, but they are still a respiratory irritant if disturbed.
The Sealed House Problem
This is the terrain point.
Older homes were draughty. Air leaked in and out. Chemicals off-gassing from building materials had somewhere to go. Newer homes and retrofitted homes are sealed much tighter. The insulation is better. The windows are sealed. The draughts are gone. The energy rating is higher.
The consequence is that any chemical released inside the home stays inside longer. Flame retardants from the foam boards. Formaldehyde from the furniture and the insulation. VOCs from the paint and the adhesives. Isocyanates from the spray foam. They accumulate. The indoor air becomes a concentrated soup.
The warmer the room, the more the chemicals off-gas. A well-insulated bedroom that is kept warm is the highest-exposure room in the house. A well-insulated bedroom that is also small and well-sealed has the highest concentration of all.
The Children's Exposure Problem
Children are not small adults. They breathe more air per kilogram of body weight. They spend more time indoors than adults. They sleep in a single sealed room for eight to twelve hours a night. Their detoxification systems are immature. And the smallest room in the house, the one that is often the warmest, is often the child's bedroom.
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What Your Child's Body Is Experiencing
The Lungs – Chronic Irritation and Sensitisation
Isocyanates and formaldehyde are respiratory irritants. Both are associated with asthma, wheezing, and chronic respiratory symptoms. Isocyanates are potent sensitisers, meaning that exposure can cause the immune system to become permanently reactive to them. A child who is sensitised in childhood may react to trace exposures for life.
The Endocrine System – Flame Retardant Disruption
Flame retardants are endocrine disruptors. HBCD and TCPP have been linked to thyroid hormone disruption, which affects metabolism, brain development, and growth. The release from foam board is small. The release from many boards across a home is not trivial, especially when the home is sealed.
The Liver – The Detoxification Load
Isocyanates, formaldehyde, and flame retardants all have to be processed by the liver. They use the same Phase I and Phase II pathways that process food additives, pesticides, and other toxins. Every added stream reduces the room available for everything else.
The Brain – The Developmental Question
Formaldehyde is neurotoxic. Flame retardants have been linked to attention deficits and behavioural problems in children. The evidence on building materials specifically is not as strong as the evidence on food or water, but the mechanism is plausible and the exposure is daily.
The Gut – The Emerging Concern
Emerging research suggests that formaldehyde and flame retardants can affect the gut microbiome. The evidence is early, but the pattern is consistent with what is seen with other chemical exposures.
Children's Unique Vulnerability
Children are not small adults. They breathe more air. They spend more time in the home. They sleep in the room where the accumulation is highest. They have immature detoxification. And their brains and endocrine systems are still developing.
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The Client Who Did Not Know
A client I will call Helen lived in a suburban home. She had renovated the loft and reinsulated the external walls two years before. The house was warmer and cheaper to heat. She was pleased with the result.
Her son, age seven, had a persistent cough that would not clear. He had morning headaches. His eyes were often red when he woke. He was tired more than he used to be. She had taken him to doctors. They found nothing.
The first weeks of investigation were confronting. She had paid good money to make her home better. She had improved the energy rating. She had done what she was told was the responsible thing. She questioned whether it was all a mistake. She nearly decided to leave it and hope it settled.
I asked Helen one question: "What was installed, when, and has the house been aired properly since?"
She had not thought about it.
We looked at the pattern. The foam board on the external walls. The spray foam around the windows. The loose-fill in the loft. The house had been sealed and draught-proofed at the same time. The son's bedroom was above the reinsulated wall, below the loft, and it was the smallest room in the house. It was also the warmest.
I suggested one change for the first month: do not rip anything out. Change how the room is used. Open the window for 15 minutes every morning and again before bed. Keep the bedroom door open during the day. Lower the room temperature by two degrees. Add a small HEPA air purifier in the bedroom. No other change.
Within three weeks, the morning headaches had reduced. His eyes were less red on waking. His cough was less frequent.
By the second month, his energy was more stable. His teacher commented that he seemed more settled.
Helen said: "I thought I was making the house healthier. I did not know the insulation was releasing anything. I did not know the sealed house was the problem. No one had ever told me that."
She did not need to undo the renovation. She needed to know what the renovation had done.
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Why This Feels Like Failure
You insulate your home because it is good practice. You improve the energy rating because it saves money and reduces emissions. You seal the draughts because everyone tells you to. You follow every piece of advice you are given. And then your child has a cough that will not clear, headaches in the morning, and red eyes.
And you blame yourself. You think you are a bad parent. You think you failed.
But the problem was never your choices. The problem was that no one told you that insulation is a chemical product. No one told you that foam board releases flame retardants, that spray foam releases isocyanates, or that older foam releases formaldehyde. No one told you that sealing the house also seals the chemicals in. No one told you that the smallest, warmest, most sealed room is the highest-exposure room in the house.
The concern is not one board of insulation. It is the accumulation of a slow release across years, in a home that no longer has the draughts that used to carry the chemicals away. The exposure is invisible, the symptoms are nonspecific, and the link is rarely made. The child who is exposed in a sealed bedroom at seven may carry the respiratory sensitisation into adolescence and beyond. The earlier the accumulation is addressed, the more the lungs and the immune system can settle.
But the problem was never your willpower. The problem was that no one told you: the insulation is a chemical, and the sealed house traps it.
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What Your Child's Body Is Actually Asking For
· I am not asking you to remove the insulation. I am asking you to let the air move.
· I am asking you to see the room I sleep in as a sealed space, not just a warm one.
· Stop treating energy efficiency as the whole picture. Efficiency and ventilation are not the same thing.
· Start with the air exchange in my bedroom.
· I do not need a colder house. I need a house that breathes, even a little.
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One Practice to Try – This Week
If your home has been insulated, sealed, or renovated in the last five years, try this for one week:
Open the window in the bedroom for 15 minutes every morning and again before bed. Even in winter. Even in the city. Air exchange is the single most effective way to reduce indoor concentrations of off-gassed chemicals.
Keep the bedroom door open during the day. Let the room breathe. Do not leave it sealed and closed.
Lower the room temperature by one or two degrees. Off-gassing increases with heat. A slightly cooler bedroom is a slightly lower exposure.
If you can, add a HEPA and carbon air purifier in the bedroom. HEPA captures particles. Carbon captures VOCs. Run it overnight.
Do not seal any further gaps without considering ventilation. Every additional draught-proofing measure reduces the escape routes for chemicals. Ventilation and sealing should be balanced, not maximised in one direction.
Notice what shifts.
Are the morning headaches reduced? Are the eyes less red on waking? Is the cough less frequent? Is the sleep better?
Not because you removed the insulation. Because you let the air move.
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The Question to Ask Yourself
Not "is my insulation dangerous?" Not "should I rip out the walls?"
Ask yourself these three questions.
One: What insulation was installed in your home, when, and in which rooms?
Two: Since the insulation was installed, has the house been aired properly? Has the air in the bedrooms been exchanged daily?
Three: Could you try one week of opening the bedroom window twice a day, just to see what changes?
If you cannot imagine opening the window in winter, ask yourself: Is that a habit or a necessity?
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This Series
Toxic Terrain is a free, public, ongoing series on environmental toxins and how they load your terrain.
You are reading: Chapter 13, Part 5 – Insulation and Building Materials – What Is in the Walls and the Loft
Coming up:
· Chapter 13, Part 6 – Mothballs and Pesticides: What Is in the Cupboard
All 100% free. No subscription. No paywall.
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The Lesson
The insulation was installed to keep the house warm and the bills down. It does that. It is not a mistake. It is a standard, sensible improvement that any energy adviser would recommend.
The insulation is also a chemical product. Foam boards contain flame retardants. Spray foam releases isocyanates. Older foam releases formaldehyde. The release is small, slow, and continuous. In a draughty house, the chemicals escape. In a sealed house, they accumulate.
The child who sleeps in the smallest, warmest, most sealed room is breathing the highest concentration in the house. The room that was designed for comfort became the room with the least air exchange.
Your child does not need a draughty house. They need a house that balances efficiency with ventilation. And the first step is not to undo the renovation. It is to open the window, morning and night, and let the room breathe.
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Next: Chapter 13, Part 6 – Mothballs and Pesticides: What Is in the Cupboard – what is in the drawer that no one has opened in years.
Mike Ndegwa | Natural Health Guide
