Indoor Environment · North London
Indoor Air Quality Assessments in North London
Measured assessments of indoor air quality, humidity, ventilation rates and pollutant build-up — protecting occupant health and the building fabric. Specialist building-performance diagnostics across North London — N1-N22 · NW (NW1, NW3, NW5, NW11) · EN (Enfield).
Indoor Air Quality Assessments in North London
What we typically diagnose across North London.
North London's heavyweight Victorian and Edwardian housing stock — from the bay-windowed terraces of Holloway and Finsbury Park through the substantial detached homes of Highgate and Hampstead Garden Suburb to the inter-war semis of Finchley and Barnet — is well-known for cold floors, single-skin extensions and condensation in north-facing rooms. We use FLIR thermal imaging, blower door testing and moisture diagnostics to identify the actual problem before any insulation or remedial work is specified.
- Victorian solid-wall terraces in Islington, Holloway, Archway and Finsbury Park with high heat loss through original brickwork
- Single-storey rear-extension flat roofs in 1930s semis (Finchley, Barnet) with compressed or absent insulation
- North-facing bedrooms and bathrooms in N1, N5, N7 Victorian terraces with chronic winter mould
- Camden conversion flats with inadequate kitchen extract and bathroom ventilation
- Suspended floor perimeters in Holloway, Finsbury Park and Wood Green Victorian terraces
What this service is
Indoor Air Quality Assessments — in plain English.
An Indoor Air Quality (IAQ) assessment measures the air you actually breathe — CO₂, humidity, VOCs, formaldehyde, PM2.5, radon and temperature — over a representative period. Most homes have never been measured. Once you see the data, the right ventilation, filtration and source-control strategy becomes obvious.
Common problems we solve
The symptoms that bring people to this service.
- 01Headaches, fatigue, brain fog or poor sleep with no obvious cause
- 02Asthma, hayfever or eczema symptoms worse indoors than outdoors
- 03Condensation, mould and high humidity rooms
- 04Newly-renovated homes with strong off-gassing smells (paint, MDF, glues)
- 05Properties near major roads, railways or industrial sources
- 06Schools, offices and HMOs needing IAQ evidence for occupant welfare
How we investigate
Our diagnostic approach
- 01Continuous IAQ logging (CO₂, RH, T, PM2.5, VOCs) for 7–14 days
- 02Spot measurements of formaldehyde, NO₂ and radon where indicated
- 03Source-by-source pollutant inventory (cooking, candles, MDF, cleaners, biomass)
- 04Ventilation rate verification (anemometer / blower door + tracer-gas)
- 05Prioritised IAQ improvement plan: source control → ventilation → filtration
Diagnostic equipment used
What we bring on site
- Multi-parameter IAQ logger (CO₂ NDIR, RH, T, PM2.5 laser, VOC PID)
- Formaldehyde / NO₂ passive samplers (where indicated)
- Radon detector (long-duration where geology requires)
- Anemometer + balometer for ventilation verification
- Particle counter for filtration-strategy testing
Building physics — why this works
The science behind the diagnosis.
Indoor air is typically 2–5× more polluted than outdoor air. Pollutants enter from outside (PM2.5, NO₂, pollen), are generated inside (cooking, cleaning, off-gassing, breathing) and are diluted (or trapped) by ventilation. Without measurement you're guessing. With measurement you know exactly which lever — source control, ventilation or filtration — to pull.
What you get
Measured benefits — not vague promises.
- Measured CO₂, humidity, PM2.5, VOC and formaldehyde data — not assumptions
- Prioritised, evidence-based IAQ improvement plan
- Better sleep, fewer headaches, clearer thinking — documented
- Asthma and allergy triggers identified and removed
- A re-measured IAQ report after improvements as verification
What we measure
What we measure
- Carbon dioxide (CO₂) build-up as a proxy for ventilation effectiveness
- Relative humidity, dewpoint and condensation risk
- Extract and supply airflow rates per room
- Particulate matter (PM2.5 / PM10) where required
- Volatile organic compound (VOC) screening
- Mould risk areas via surface temperature and moisture mapping
Why it matters
Why it matters
- Modern, airtight homes need controlled ventilation to stay healthy
- Poor IAQ contributes to asthma, allergies and sleep disturbance
- Persistent high humidity drives condensation, mould and fabric decay
- Targeted, measured solutions outperform off-the-shelf fans
Typical findings
What we commonly discover during indoor air quality assessments investigations
- 01Bedroom CO₂ levels >2000 ppm overnight (fatigue, poor sleep)
- 02Indoor humidity above 70% RH driving condensation and mould
- 03VOC and formaldehyde from new finishes elevated for weeks after works
- 04PM2.5 spikes from cooking, candles and unflued appliances
Findings reflect patterns observed across completed RetrofitIQ projects — every survey is interpreted in the building’s specific context.
FAQs
Indoor Air Quality Assessments — common questions
What is an Indoor Air Quality (IAQ) assessment?+
An IAQ assessment is a measured evaluation of the air you actually breathe inside your home or workplace. We log temperature, relative humidity, CO₂, particulates (PM2.5 / PM10), volatile organic compounds (VOCs), formaldehyde and (where relevant) radon over a representative 7-14 day period; correlate it against occupancy patterns, ventilation rates and external pollution; and produce a written report with prioritised improvement recommendations. The output is data — not opinion.Why does indoor air quality matter for health?+
We spend 80-90% of our lives indoors, and indoor air is typically 2-5x more polluted than outdoor air. Chronic exposure to elevated CO₂ impairs cognitive function and sleep; PM2.5 is a class 1 carcinogen with measurable cardiovascular and respiratory impact; high humidity drives dust-mite and mould allergens; formaldehyde and VOCs from furniture, finishes and cleaning products are respiratory irritants. IAQ measurement quantifies these so you know what you are dealing with.How do you measure CO₂, humidity and pollutants?+
We deploy calibrated multi-channel data-loggers in the main living and sleeping spaces, recording CO₂ (NDIR sensor), temperature, relative humidity, PM2.5 (laser particle counter) and VOC index continuously over the assessment period. For formaldehyde and radon we use passive-diffusion sampling cards / detectors over the same window. The data is then downloaded, processed and benchmarked against WHO, CIBSE and Passive House guidance values.What CO₂ level is acceptable indoors?+
Outdoor air is around 420 ppm. CIBSE TM40 indicates 'good' bedroom CO₂ is below 1,000 ppm overnight; readings consistently above 1,500 ppm indicate inadequate ventilation and are linked to impaired sleep and morning headaches. We routinely log bedrooms in retrofitted London flats spiking to 2,500-3,500 ppm overnight — well above the threshold at which the data clearly shows cognitive and sleep impairment.What humidity range is healthy indoors?+
45-55% relative humidity (RH) is the optimum range — high enough to suppress dust mites and respiratory irritation, low enough to prevent condensation and mould. Below 35% RH is uncomfortably dry (winter dehydration headaches, static, respiratory irritation). Above 65% RH supports mould growth and dust-mite populations. Indoor RH is one of the most controllable and most undermeasured indoor-environment parameters.What are VOCs and where do they come from?+
Volatile Organic Compounds — a broad category of carbon-based gases released from paints, varnishes, new furniture (especially MDF and engineered wood), carpets, glues, candles, air-fresheners, cleaning products and combustion appliances. Some are mild (limonene from citrus cleaners), some are respiratory irritants (formaldehyde, benzene). New-build and recently-renovated homes often have elevated VOCs for the first 6-12 months — measurable, and reducible by source control + ventilation.What is formaldehyde and why does it matter?+
Formaldehyde is a specific VOC released by composite wood products (MDF, particle board, plywood with urea-formaldehyde glue), some insulation foams, fabrics and cosmetics. WHO classifies it as a known human carcinogen. Indoor concentrations should ideally be below 0.1 mg/m³ (100 µg/m³); levels above 0.3 mg/m³ are common in new-builds and need addressing. We test for formaldehyde routinely on IAQ assessments where new fitted joinery or insulation is involved.What is PM2.5 and how does it get inside?+
PM2.5 is fine particulate matter under 2.5 micrometres — small enough to penetrate the lungs and bloodstream. Indoor sources: cooking (especially frying and gas hobs), candles, biomass burners and smoking. Outdoor sources: traffic, brake dust, construction. In London PM2.5 levels are routinely 2-4x WHO guidance. Closing windows on traffic-side façades and filtering supply air (F7 / ePM₁ 50% on MVHR) brings indoor PM2.5 down 70-90%.Can ventilation alone solve indoor air quality problems?+
Partly. Continuous balanced ventilation (MVHR) with good filtration dramatically reduces CO₂, humidity, formaldehyde and VOC accumulation, and filtered supply reduces particulates. But ventilation cannot remove the source itself — if you are burning a lot of candles, frying daily with a gas hob, or living next to a building site, source-reduction is also needed. Our IAQ reports always identify source-control opportunities as well as ventilation upgrades.Do you test for radon in London?+
Yes — though Greater London is largely a low-radon area (per the UK Health Security Agency / UKHSA radon affected area maps), there are localised pockets and basements where radon testing is worth doing. We use UKHSA-approved passive detectors over 3-month exposure periods and provide the certified result and remediation guidance if action is needed.Can poor IAQ make asthma worse?+
Yes — substantially. High humidity supports dust-mite populations (one of the most common asthma triggers); mould releases respiratory irritants and allergens; high PM2.5 directly irritates airways; high CO₂ correlates with worse sleep and morning symptoms; some VOCs are direct bronchial irritants. We have seen measured asthma-symptom improvement in clients within weeks of an IAQ-led upgrade (controlled humidity 45-55%, PM2.5 filtration, mould remediation, source control).Can RetrofitIQ assess IAQ for landlords and HMOs?+
Yes — including evidence-grade reporting suitable for Awaab's Law / Homes (Fitness for Human Habitation) Act compliance. Mould complaints from tenants typically have a measurable IAQ dimension (high humidity, low ventilation rate, condensation-risk surfaces) that our reports document with logged data. Many social landlords and managing agents now commission IAQ assessments proactively to demonstrate compliance.Can poor IAQ be linked to a cold or damp house?+
Yes — closely. Cold internal surfaces drop below dewpoint, condensation forms, mould develops, RH stays high, ventilation gets blocked off to keep the heating in, CO₂ rises, the air feels stale. The IAQ story and the building-fabric story are inseparable. We routinely assess them together because the diagnosis and the remediation are connected.How is an IAQ report different from a damp survey?+
A damp survey identifies where moisture is entering, accumulating or condensing in the building fabric. An IAQ assessment measures what is in the air the occupants breathe. They are complementary — many of our projects start as a damp survey and end with an IAQ assessment, or vice versa. Together they give a complete picture of the building's effect on occupant health.What can be done to improve indoor air quality?+
In rough order of cost-effectiveness: (1) Source control — remove or substitute high-VOC products, switch to induction cooking, eliminate scented candles and air fresheners. (2) Ventilation — upgrade to continuous MVHR with filtered supply. (3) Humidity control — bring RH into the 45-55% band via ventilation + dewpoint management. (4) Filtration — F7 / ePM₁ 50% on the supply air, HEPA standalone units in single problem rooms. (5) Building-fabric upgrades — raise cold-surface temperatures to suppress condensation and mould. Every IAQ report we issue prioritises these for your specific property.Do you provide ongoing IAQ monitoring?+
Yes — for clients who want long-term verification we can install permanent IAQ monitors (CO₂, RH, T, PM2.5, VOC) feeding a dashboard, and review the data quarterly. This is particularly useful for new-build owners verifying that the design intent of the MVHR system is being delivered in real occupied conditions, and for landlords demonstrating ongoing compliance.
Next step
One company. One process. One point of responsibility.
We don’t simply identify problems. We investigate, diagnose, design solutions, carry out the work and verify the results. Book a Home Health Diagnostic Survey and we’ll tell you exactly which remedial works (if any) are actually needed.