There seems to be a lot of existing IEV fans being left in homes where fabric measures are being lodged with Trustmark as PAS2035 compliant, anecdotally without any air pressure test being completed to ascertain whether the air permeability of the building envelope is above or below 5 m3/m2h at 50 Pa after the installation. My understanding is that if the air permeability is not known, you must replace IEV with an alternative such as continuous MEV or PIV, as IEV “shall be assessed as inadequate” (C.2.4). This is also explicitly stated in C3.3 and C3.5. Please confirm if my understanding is correct? If so, what will Trustmark look to do with all of the previous non compliant measures? As a follow up to this, if an air pressure test is completed post installation and it can be evidence that the air permeability is above this threshold, does PAS2035 require all IEV fans to be tested using a calibrated anemometer and if so, does the tester need to hold a suitable qualification (NICEIC etc) to ensure that the extract rates meet those required in Approved Document F? Or is it acceptable to just assume that the fan is designed to extract at the required rate for the wet room it is in and that the in-situ extract performance is actually still delivering this minimum required rate? Presumably where an air pressure test has been completed, if brand new IEV fans are fitted with known extract rates that meet ADF, the RC can assume compliance without the need for any testing of the fans? (Assuming it is needed)

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