Indoor Air Quality (IAQ)

Detailed Explanation

Indoor air quality (IAQ) is a multi-parameter concept measuring the impact of breathed air in an enclosed space on health, cognitive performance, comfort and productivity. Per WHO, ASHRAE, EPA and EU data, people spend 85-90% of their lives indoors; making IAQ far more critical than outdoor air quality.

IAQ assessment uses 6 main parameters:

1. Thermal comfort — temperature (T), relative humidity (RH), air velocity (v), surface temperature (Tr), clothing insulation (clo), activity level (met). Calculated via PMV-PPD indices (TS EN ISO 7730).

2. CO2 — by-product of human metabolism, indicator of inadequate ventilation. ASHRAE limit 1,000 ppm (quality target <800 ppm), cognitive performance drops 20% above 1,500 ppm (Harvard COGfx study).

3. Particulate matter (PM) — PM10 (≤10 μm, upper respiratory), PM2.5 (≤2.5 μm, alveolar penetration), PM1.0 (≤1.0 μm, enters bloodstream). WHO 24-h limit PM2.5 15 μg/m³, PM10 45 μg/m³.

4. VOCs (Volatile Organic Compounds) — from paint, furniture, carpet, cleaning products, photocopiers; formaldehyde, benzene, toluene etc. Total VOC (TVOC) <500 μg/m³ as quality target.

5. Microbiological load — bacteria, mould, virus, allergens. Legionella (water system), Aspergillus (HVAC scale), SARS-CoV-2 (inadequate ventilation).

6. Relative humidity — the hidden regulator of IAQ; below 30% RH respiratory drying, static; above 60% RH mould, mites, allergy risk. Optimum 40-60%.

These six parameters interact: high RH + low ventilation = mould; low RH + static = electronic damage + increased virus spread (SARS-CoV-2 stays viable 60% longer at low RH — China Public Health 2021).

Why It Matters

IAQ impact is measured across health, productivity, financial and regulatory dimensions:

1. Health impact — Sick Building Syndrome (SBS) symptoms (headache, eye irritation, mucosal dryness, fatigue) appear in 30-40% of indoor workers; especially in low humidity (25-35% RH), high CO2 (>1,000 ppm) + VOC combinations. WHO reports 20% of respiratory infections are IAQ-driven.

2. Cognitive performance — Harvard COGfx study (2015): office decision-making performance drops 50% as CO2 rises 600 → 1,400 ppm. At 30% RH mucosal dryness + virus spread + distraction; productivity drops 15-25% (Allen et al. 2019).

3. Financial impact — for a mid-sized 500-person office with average annual payroll of 25 M USD; a 5% productivity gain = 1.25 M USD/year. IAQ improvement investment is typically 100,000-300,000 USD; ROI <6 months.

4. Regulatory compliance — TS EN 16798-1 (2019) mandatory in EU buildings; ASHRAE Std 62.1 reference; LEED v4.1 + WELL Building Standard high-credit category. Turkish OHS regulation has required IAQ measurement since 2018.

5. Post-pandemic transformation — SARS-CoV-2 reset IAQ perception; ASHRAE Epidemic Task Force 2020 report recommended RH 40-60% + MERV-13 filtration. WELL Building IAQ category raises rental value by 3-7% (JLL 2022 research).

NKT engineering treats IAQ not just as HVAC capacity calculation but as multi-parameter system design: NKT - Climate Track T/RH/CO2/PM/VOC monitoring, control strategy, seasonal optimisation, reporting. Design consulting on WELL and LEED projects.

Practical Example

An 18,000 m² office tower built in 2019 in Levent, Istanbul. 1,200 staff, finance + consultancy tenants. Post-pandemic IAQ assessment in 2022.

Baseline assessment: • Temperature: 22-24°C ✓ ASHRAE • Relative humidity: winter 22-28%, summer 58-65% ✗ (winter <30%, summer >60%) • CO2: average 950 ppm, peak 1,400 ppm ✗ (>1,000 ppm sustained) • PM2.5: 18-25 μg/m³ ✗ (above WHO 15 μg/m³) • VOCs: TVOC 720 μg/m³ ✗ (above 500 μg/m³) • Complaint rate: 42% of staff with SBS symptoms

Occupancy data: lease occupancy 85%; real occupancy 62% (post hybrid work). 2 floors did not renew their leases (-2.4 M USD/year revenue loss).

NKT IAQ improvement package:

1. Humidification — 8 × Neptronic SKE4 80 kg/h (640 kg/h total), winter 45% RH ± 5 guaranteed. RO water system, in-duct SAM-e distribution. Capex: 280,000 USD

2. Dehumidification — 4 × Microwell condensation units integrated into AHUs for summer, 50% RH ± 5 guaranteed. Capex: 95,000 USD

3. Filtration upgrade — F7 → MERV-13 + HEPA prefilter, PM2.5 < 10 μg/m³ target. Capex: 65,000 USD

4. CO2-sensor DCV — dynamic ventilation across 36 zones, OA modulation. Capex: 45,000 USD

5. NKT - Climate Track IAQ Pro — 48-point T/RH/CO2/PM/VOC monitoring, mobile dashboard, tenant reporting. Capex: 35,000 USD

Total capex: 520,000 USD. Financial result (12 months later): • Occupancy 62% → 88% (vacant floors re-leased) • Annual rent increase: 1,800,000 USD • ROI: 4 months • Staff complaint rate: 42% → 8% • WELL Building Gold certification

This example shows IAQ is not just a health concern but a financial-strategic tool.

Engineering Note

Engineering criteria in IAQ design and system optimisation:

• Multi-parameter approach — not only temperature and RH but CO2, PM, VOCs and microbiological load must be evaluated jointly. Single-parameter optimisation (e.g. cooling only) worsens other parameters. • Dew-point-based control — RH readings drift with temperature; dew point is more reliable. The NKT - Climate Track engineering tool by NKT makes this standard. • Seasonal optimisation — winter humidification + summer dehumidification + shoulder-season economizer + year-round ventilation; each season needs a different control strategy. • Ventilation vs filtration balance — high OA (ventilation) dilutes CO2 + VOCs but increases particulate ingress; MERV-13 + HEPA filtration must be combined with high OA. • Demand-Controlled Ventilation (DCV) — CO2-sensor-driven dynamic OA modulation, 25-40% energy savings + IAQ quality preservation; fixed OA wastes energy and overdries indoor air during low-occupancy hours. • Microbiological control — UV-C lamps integrated into HVAC inactivate moulds and viruses up to 99%; DI water + UV-C standard for Legionella control in water systems. • Condensation risk — high RH causes condensation + mould on cold surfaces (windows, exterior walls, chilled-water pipes); the control strategy must include surface-temperature monitoring + time-delayed RH adjustment. • Sensor placement and calibration — not the shop/office average but the occupant breathing zone (1.4-1.7 m height); 12-32-point multi-sensor network; calibration twice a year. • Reporting and transparency — tenant/occupant dashboard with daily IAQ report; used in WELL Building, LEED and ESG reporting.

NKT Application Link

With its modern IAQ-driven approach, NKT delivers comprehensive indoor air quality solutions, not only humidification and dehumidification:

1. Multi-parameter IAQ assessment — pre-project 4-week T/RH/CO2/PM/VOC measurement, baseline report, optimisation proposals. 2. Humidification package — Neptronic SKE4 (resistive, hygienic, ±1% RH), SKG4 (adiabatic, low energy), SAM-e distribution, RO water preparation. 3. Dehumidification package — NKT Microwell, CD/CDP condensation-type, AD silica gel rotor (for dry rooms and special applications). 4. Ventilation integration — DCV (CO2-sensor), economizer, ERV heat recovery, NKT engineering design. 5. NKT - Climate Track IAQ Pro — 12-48 point T/RH/dewpoint/CO2/PM/VOC monitoring, web + mobile dashboard, BMS/SCADA Modbus integration, reporting (WELL, LEED, ESG compatible). 6. UV-C and microbiological control — UV-C integration inside HVAC, Legionella prevention in water systems. 7. WELL Building + LEED consulting — certification process support, IAQ category score optimisation, documentation.

Sample configuration: 18,000 m² office tower: 8 × SKE4 80 + 4 × Microwell + DCV 36 zones + NKT - Climate Track 48 points + WELL Building consulting. Capex 520,000 USD, ROI 4 months (rent increase + productivity). NKT IAQ report guarantees WELL Gold certification within 12 months.