Is indoor air worse than outdoor?

In urban London frequently yes — indoor air contains all outdoor pollutants (ingress through ventilation) plus indoor sources (cooking, off-gassing, candles, cleaning, occupant biology). Without active ventilation, CO2 + VOCs + PM2.5 accumulate. With MVHR + filtered supply (F7 filter), indoor air can be measurably cleaner than outdoor — IQAir filtration reduces PM2.5 80%+.

How much does IAQ monitoring + improvement cost?

Monitoring only: 1–3 monitors £150–£550 install. Improvement: MVHR retrofit £4,800–£12,500; portable HEPA units £250–£950 each; low-VOC paint premium £25–£65/m²; induction hob £450–£1,200; ventilation upgrades £350–£1,800. Total premium for IAQ-optimised renovation: £8,500–£18,500 above standard.

What about radon in London?

Most of London below 1% probability of radon above 200 Bq/m³ (UKHSA radon map). Exceptions: pockets of north-west London (Hillingdon, Harrow), south-east boroughs near Kent/Surrey chalk. Basement conversions in any borough: test radon during construction (£60–£185 passive detector 3-month exposure). If >100 Bq/m³ install positive-pressure ventilation or sub-slab radon extraction.

Indoor Air Quality Monitoring London 2026 | Builderr

How Should Indoor Air Quality Be Monitored in a London Home?

London indoor air quality monitoring targets: CO2 below 800 ppm (1,000 ppm acceptable), PM2.5 below 10 µg/m³, VOCs low (specific TVOC <500 µg/m³), humidity 40–60% RH, radon below 100 Bq/m³ if at-risk postcode. Monitors £75–£385 (Airthings View Plus, IQAir AirVisual Pro). MVHR enables IAQ optimisation; without active monitoring + ventilation, urban London IAQ frequently worse than outdoor. Critical for asthma, allergies, children.

Pollutants and sources

CO2: human respiration; high levels (>1,200 ppm) cause drowsiness, cognitive impairment. Indicator for overall ventilation adequacy. PM2.5 (fine particulates <2.5µm): cooking (gas, frying), traffic ingress, candles, woodburners. Penetrates lung tissue; linked to cardiovascular disease, cancer. London Mayor's policy target ambient PM2.5 10 µg/m³; many inner London streets exceed annually. VOCs (Volatile Organic Compounds): off-gassing from paints, adhesives, MDF furniture, cleaning products, fragrances. Health impacts vary by compound — formaldehyde Group 1 carcinogen (WHO). Radon: naturally occurring radioactive gas from granite/uranium-rich subsoil; concentrated in basements and ground floor. UK Health Security Agency action level 200 Bq/m³ (target <100). Cornwall, Devon, Northamptonshire highest. NO2: gas hobs, vehicle exhaust, woodburners. Triggers asthma.

Monitoring devices

Budget £75–£185: Airthings Wave Plus (CO2, VOC, humidity, temperature), Eve Room (HomeKit), Awair Element. Cloud-app data, alerts when thresholds exceeded. Mid £185–£385: Airthings View Plus (adds PM2.5, radon), Awair Omni, Aranet4 (medical-grade CO2). High £385–£950: IQAir AirVisual Pro (PM2.5 medical-grade, AQI dashboard), Foobot Home, multi-pollutant scientific-grade. Whole-house: 3–5 monitors (kitchen, bedroom, living, bathroom, child's room) provide IAQ heatmap. Smart home integration (Home Assistant, Apple HomeKit, Google Home) automates ventilation response — e.g. MVHR boost when CO2 > 1,000 ppm. Builderr installs MVHR with IAQ-linked controls (Zehnder ComfoControl + Aranet sensors) on premium retrofits.

Solutions and lifestyle

Sources control: low-VOC paints (Earthborn, Edward Bulmer), formaldehyde-free MDF (CARB Phase 2, E1 EU), avoid candles + plug-in fragrances, ban smoking indoors (PM2.5 spike 100× normal), induction hob over gas (eliminates NO2). Ventilation: MVHR delivers 0.4–0.6 ACH continuous fresh air filtered (G4 or F7 filter at supply); achieves CO2 600–800 ppm typical. Without MVHR: opening windows during low-pollution periods (off-peak hours, away from main roads) helps but limited in inner London. Filtration: portable HEPA air purifier (Dyson Pure Hot+Cool, Blueair, IQAir HealthPro) reduces PM2.5 in bedroom 80–90% within 30 minutes; £250–£950 per unit. Schools and child bedrooms: highest priority for IAQ optimisation; demonstrable cognitive + health benefits with PM2.5 <10 µg/m³ + CO2 <800 ppm. London Plan and Mayor's policies increasingly require IAQ assessment in development applications.