Paul Filters

Paul heat recovery units are divided into several series – Climos, Novus, Focus and others – each with several airflow-capacity variants (e.g. Climos 200, Novus 300, Novus 450, Focus 200, Focus 250). The exact model is shown by a longer letter-and-number code on the front panel of the unit, not just the series name.

Since units within the same series name can have differently sized filter compartments depending on airflow capacity, you need to know the full model code or measure the current filter – that's the only way to guarantee an exact match when ordering.

Paul units standardly use an M5 class filter for the extract/intake air and an F7 (ePM1) class filter for the supply air – this combination meets the requirements of passive house construction, where all fresh air enters solely through the ventilation system. Some models (e.g. Climos 200) also offer a simpler M5+M5 set without fine filtration.

An F7 filter captures pollen and fine particles better than an M5, so in passive houses, where windows are rarely opened, its effect on indoor air quality is especially noticeable.

The Paul ISO Filterbox is a separate, duct-mounted filter box (usually DN160 in diameter) used for additional air filtration before or after the main heat recovery unit, rather than being an internal component of the unit itself. It's often installed in the supply air line when a higher class of filtration is needed – for example activated carbon or F9 level – that the main unit doesn't support.

The filter's size depends on the box's DN diameter, so when ordering you need to specify that diameter, not the heat recovery unit's model.

Yes, as long as the filter is made to the same ISO 16890 standards and matches the original's dimensions exactly. Our equivalent Paul filters:

• are manufactured in the EU from the same quality filtering fibre
• are cut to the same tolerances as the original filter
• fit without any modification to the housing

Since filters need to be replaced several times a year, and in a passive house they play a particularly important role in air quality, an equivalent lets you save money without reducing either filtration efficiency or the unit's operating reliability.

The standard interval is 3–6 months, but in passive houses, where the recovery unit is the sole source of fresh air, it's recommended to check the filters more often – every 2–3 months, especially the F7 filter on the supply air side. A clogged filter not only worsens indoor air quality but also increases the load on the fan and energy consumption, since the unit has to work against greater resistance.

During pollen season (April–June), it's worth checking the filter every month.