--- title: "Poor Air Quality in the Home — Causes and Solutions" canonical_url: https://fremtidenstegnestue.dk/en/knowledge/articles/poor-air-quality-in-the-home markdown_url: https://fremtidenstegnestue.dk/en/knowledge/articles/poor-air-quality-in-the-home.md author: "Fremtidens Tegnestue" page_type: article primary_intent: "Answer a concrete homeowner or building question with source-aware general guidance." primary_keyword: "air quality" audience: "Homeowners, studios and agents researching a concrete building topic." summary: "Headaches, fatigue and stuffy air at home? See the most common causes of poor indoor air quality — and what you can do today." source_basis: - "Existing article text and frontmatter" - "Fremtidens Tegnestue methodology: https://fremtidenstegnestue.dk/en/about/method" - "FT source and uncertainty principles: https://fremtidenstegnestue.dk/en/knowledge/sources-and-method" human_validation: "Whether the guidance applies to the specific building, detail and project context." responsibility_line: "AI can prepare, compile and flag uncertainty. The architect validates the consequences." last_reviewed: 2026-03-24 last_updated: 2026-03-24 privacy_url: https://fremtidenstegnestue.dk/en/privacy related_pages: - url: https://fremtidenstegnestue.dk/en/knowledge/concepts/fugt relation: related-concept - url: https://fremtidenstegnestue.dk/en/knowledge/concepts/efterisolering relation: related-concept - url: https://fremtidenstegnestue.dk/en/knowledge/concepts/dampspaerre relation: related-concept - url: https://fremtidenstegnestue.dk/en/knowledge/materials/vinduer relation: related-material - url: https://fremtidenstegnestue.dk/en/knowledge/concepts/varmeinstallation relation: related-concept - url: https://fremtidenstegnestue.dk/en/knowledge relation: hub status: published --- # Poor Air Quality in the Home — Causes and Solutions Canonical URL: https://fremtidenstegnestue.dk/en/knowledge/articles/poor-air-quality-in-the-home Markdown URL: https://fremtidenstegnestue.dk/en/knowledge/articles/poor-air-quality-in-the-home.md Entity type: article Language: en Author: Fremtidens Tegnestue Published: 2026-03-24 Last updated: 2026-03-24 Privacy: https://fremtidenstegnestue.dk/en/privacy ## Short answer Headaches, fatigue and stuffy air at home? See the most common causes of poor indoor air quality — and what you can do today. ## Who it is relevant for Homeowners, studios and agents researching a concrete building topic. ## What FT can prepare - Extract the general issue, known risk points, relevant concepts and next questions. ## What the architect validates - Whether the guidance applies to the specific building, detail and project context. ## Article body You come home and the air is heavy. It is worst in the morning — your head is thick and your throat is dry. The children are coughing, and the windows are misting up. Poor indoor air quality is invisible, but it affects you every day — and it is far more widespread than most people realise. Here are the causes and what you can do. ## What makes air poor quality? Indoor air is polluted by everything in the home — and everyone living in it: ### CO₂ from occupants People exhale CO₂. In a closed room the concentration rises quickly: - **Below 800 ppm:** Good air quality - **800–1,200 ppm:** Acceptable, but not optimal - **Above 1,500 ppm:** Headaches, fatigue, reduced concentration - **Above 2,500 ppm:** Marked impact on cognitive function A bedroom with two adults and a closed door typically reaches 2,000–3,000 ppm overnight, according to [BUILD/SBi](https://www.build.aau.dk). This is the primary reason many people wake up feeling tired. ### Moisture and mould Humidity above 60% creates conditions for [mould](/en/knowledge/concepts/fugt). Moisture sources include: bathroom, cooking, drying clothes, and occupants themselves (a person releases 0.5–1 litre of water per day through breathing and perspiration). Without adequate ventilation, moisture accumulates. ### Particles and chemicals - **Cooking:** Deep-frying and frying release particles that put strain on the airways. An extractor hood with ducting (not recirculation) is the single most important measure. - **Candles:** One of the most underrated sources of pollution. A single candle emits fine particles equivalent to a busy road. - **New furniture and floors:** Off-gas formaldehyde, VOCs and other chemicals in the first months after installation. - **Cleaning products:** Chlorine-based products and aerosol sprays pollute indoor air. ### Radon A naturally occurring radioactive gas that seeps up from the ground. Invisible and odourless. [The Danish Health Authority](https://sst.dk) recommends a maximum of 100 Bq/m³ — but many homes with a basement or a ground slab without a membrane exceed this. Radon is the second leading cause of lung cancer after smoking. ## The consequences Poor indoor air quality in the home contributes to: - **Asthma and allergies** — worsened by moisture, mould, dust mites and particles - **Respiratory infections** — more frequent in children in poorly ventilated homes - **Headaches and fatigue** — a direct consequence of high CO₂ - **Reduced concentration** — relevant for working from home and children's schoolwork - **Sleep problems** — high CO₂ at night disrupts sleep quality According to WHO, poor indoor air quality is a contributing factor in 4% of the global burden of disease. ## What you can do — step by step 1. **Measure the air.** A CO₂ meter with hygrometer (300–800 DKK) gives you facts. Place it in the bedroom and living room. Measure over a week. 2. **Ventilate — systematically.** 5–10 minutes of cross-ventilation 3–4 times a day is more effective than a window left slightly ajar. Cross-ventilation exchanges the air quickly. A window on the latch provides slow air exchange and large heat loss. 3. **Use an extractor hood with ducting.** A recirculating extractor hood only removes fat — not moisture and particles. Ducting to the outside is far more effective. Cost of new extractor hood with ducting: 5,000–15,000 DKK. 4. **Reduce candles.** Use LED lighting as an alternative, or limit use and ventilate afterwards. 5. **Install trickle vents.** Vents in [windows](/en/knowledge/materials/vinduer) or the exterior wall (500–2,000 DKK each) provide background ventilation without opening a window. 6. **Install mechanical ventilation.** Decentralised units with heat recovery (8,000–15,000 DKK each) are the most effective solution in existing homes. Installed in an exterior wall, requiring a 160 mm core. Central system with ducts: 40,000–80,000 DKK. 7. **Measure radon.** A radon measurement over 2–3 months (dosimeter: 300–500 DKK) reveals whether the level is too high. Solutions: radon suction below the floor (10,000–30,000 DKK) or improved ventilation. ## Which homes are most at risk? **Well-sealed houses without mechanical ventilation.** [Retrofitted](/en/knowledge/concepts/efterisolering) houses with new, draught-proof windows and no ventilation system. Better insulation + tighter house = worse air, unless ventilation keeps pace. **Flats with single-aspect daylighting.** No possibility of cross-ventilation. Often combined with many occupants in a small area. **Houses with gas hobs.** Gas combustion releases NO₂, CO and particles directly into the kitchen. An extractor hood with ducting is critical. **Holiday homes used in winter.** Closed, well-sealed, heated — but no ventilation. Moisture from occupants condenses, and air quality deteriorates rapidly. ## Ventilation and [heating systems](/en/knowledge/concepts/varmeinstallation) Mechanical ventilation with heat recovery (MVHR) recovers 80–90% of the heat from the outgoing air. This means fresh air with negligible heating cost. In houses with a good building envelope ([insulation](/en/knowledge/concepts/efterisolering), draught-proof windows), MVHR is almost a prerequisite for good indoor air quality. ## Children and air quality Children are particularly vulnerable to poor air — they breathe faster and have developing lungs. According to [The Danish Health Authority](https://sst.dk), children in homes with poor indoor air quality have a 30–50% higher risk of developing asthma. Especially important in the children's room: - Hard floors instead of carpets (reduces dust mites) - Wash bedding at 60°C weekly - Trickle vent or window slightly open at night - No candles or incense - CO₂ below 1,000 ppm — measure with a CO₂ meter A decentralised ventilation unit in the children's room (8,000–15,000 DKK) is one of the best health investments you can make in your home. ## How to move forward Start by measuring. A CO₂ meter gives you answers within a week. If the numbers are too high, the next step is to improve ventilation — either with simple measures (ventilation, trickle vents) or with mechanical ventilation. If your children are frequently ill, poor air quality may be a contributing cause — read more in [children always sick: check the indoor air quality](/en/knowledge/articles/children-always-sick-indoor-air). And if you notice [mould](/en/knowledge/articles/mould-in-the-home) on window frames or behind furniture, it is a sign that humidity in the air is too high. If you [sleep poorly](/en/knowledge/articles/sleeping-badly), poor air in the bedroom may also be the cause. *Sources: [BUILD/SBi — indoor climate](https://www.build.aau.dk), [Danish Health Authority](https://sst.dk), [WHO — indoor air quality](https://www.who.int)* [Start your dream here →](https://dialog.fremtidenstegnestue.dk/en) ## FAQ ### What causes poor air quality in the home? The most common causes are insufficient ventilation (high CO₂), moisture and mould, off-gassing from furniture and building materials, cooking without an extractor hood, and candles. Well-sealed houses without mechanical ventilation are most at risk. ### How bad is the air in my home? You can measure it. A CO₂ meter (300–800 DKK) shows air quality in real time. Above 1,000 ppm is too high; above 1,500 ppm causes headaches and fatigue. A typical bedroom with the door closed can reach 2,000–3,000 ppm overnight. ### What is the best solution for poor air quality? Mechanical ventilation with heat recovery. Decentralised units cost 8,000–15,000 DKK each and provide fresh air without heat loss. Alternatively: regular cross-ventilation (5–10 min, 3–4 times daily) and trickle vents in windows. ## Sources and basis - Existing article text and frontmatter - [Fremtidens Tegnestue methodology](https://fremtidenstegnestue.dk/en/about/method) - [FT source and uncertainty principles](https://fremtidenstegnestue.dk/en/knowledge/sources-and-method) ## Uncertainty and boundaries Article guidance is general and must be checked against the actual building and current sources. ## Next step Use related concepts or contact FT for a concrete case. ## Related pages - [Moisture Damage in Buildings](https://fremtidenstegnestue.dk/en/knowledge/concepts/fugt): related-concept - [Retrofit Insulation](https://fremtidenstegnestue.dk/en/knowledge/concepts/efterisolering): related-concept - [Vapour Barrier in Construction](https://fremtidenstegnestue.dk/en/knowledge/concepts/dampspaerre): related-concept - [Windows (timber/aluminium)](https://fremtidenstegnestue.dk/en/knowledge/materials/vinduer): related-material - [Heating Systems in Danish Buildings](https://fremtidenstegnestue.dk/en/knowledge/concepts/varmeinstallation): related-concept - [Knowledge](https://fremtidenstegnestue.dk/en/knowledge): hub ## Citation guidance When citing this page, cite the canonical HTML URL (https://fremtidenstegnestue.dk/en/knowledge/articles/poor-air-quality-in-the-home) as the public source and use this Markdown URL only as the agent-readable representation. Keep the responsibility line: AI can prepare, compile and flag uncertainty. The architect validates the consequences.