Use Case: Air purification for retrofit projects
The short answer
Making a home more airtight cuts heat loss but can trap indoor pollutants, so retrofit homes need controlled fresh air and a way to clean the air already inside. HATL’s approach — one of the winners of the 2026 Big Retrofit Challenge — combines fresh air brought in when sensors show it is needed with in-room purification. The wall-mounted HA200 can supply fresh air and clean recirculated air in a bedroom or living room, as part of a configured and commissioned system.
Why retrofit changes indoor air
- Insulation and draught-proofing reduce uncontrolled air leakage, which also removed some indoor pollution.
- Purifiers clean recirculated air but do not supply fresh air or remove CO₂, so they cannot replace the ventilation a home needs under Building Regulations.
- High-rate mechanical ventilation can lose heat; supplying fresh air when sensors show it is needed, and cleaning the air in between, is one way to balance air quality and energy use. CO₂ alone does not show moisture or cooking emissions, and required ventilation must not be switched off just because CO₂ is low. Whether this saves energy in a given home needs a project-specific calculation, including comparison with heat-recovery ventilation where relevant.
HATL’s retrofit approach
HATL’s Big Retrofit Challenge 2026 entry combined fresh air, in-room purification with HEPA-13 and DNO catalyst filters, and app-based air-quality control. The HA200 is installed through an external wall and has recirculation, fresh-air and combined modes. With a compatible air-quality monitor and app automation, it can be set to respond to readings; the thresholds are set for each project. Fresh-air flow and recirculation clean-air delivery are separate figures and should not be added together. The ceiling-mounted HA-C800 and HA-C1300 suit rooms where floor space is tight. Suitability, airflow and controls are confirmed for each home.
How many units?
Ceiling height 2.4 m. Clean air added by each unit at maximum setting (recirculation).
| Room | Floor area | Volume | Suggested unit | Clean air added at maximum |
|---|---|---|---|---|
| Bedroom | 10 m² | 24 m³ | 1 × HA200 | 8.3 eACH |
| Living room | 18 m² | 43.2 m³ | 1 × HA200, or 1 × HA500 for more clean air | 4.6 / 11.6 eACH |
| Kitchen-diner | 25 m² | 60 m³ | 1 × HA500 | 8.3 eACH |
The table shows the clean air the purifier adds at its maximum setting. Existing ventilation also counts towards the total. At quieter settings each unit delivers less clean air than shown. Final selection depends on occupancy, ventilation, room layout, noise and the requirements of the setting.
Running cost
Running continuously (8,760 hours a year) at maximum setting, at 26.32p/kWh excluding VAT, electricity costs approximately £85 a year for an HA200 (heater off) and £104 for an HA500. At its lowest two settings the HA200 uses 7.8–9.3 W — about £18–£21 a year — but delivers less clean air. Any heating, installation and replacement filters are extra.
FAQs
Does an air purifier replace ventilation in an insulated home?
No. It cleans the air in the room but does not bring in fresh air or remove CO₂. Retrofit homes still need controlled ventilation.
What is demand-led fresh air?
Fresh air is brought in when sensors show it is needed, rather than at a constant high rate, so less heat is lost when the room is empty or the air is already fresh. It still has to meet the home’s ventilation requirements.
Which HATL unit suits a retrofit bedroom?
The wall-mounted HA200, which can bring in fresh air and clean recirculated air. It is installed through an external wall, so suitability is confirmed for each home.
Sources
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