The MVHR filters are currently on a 4-month cycle, i.e. they get replaced 3 times a year. I had been thinking that was a little excessive and maybe they could stretch to 6-months but based on the condition of the intake filter I’m going to stick to a 4-month cycle.
The last set were installed at the start of May. There was a lot of dust kicked up by the cereal harvest in the adjacent fields which must have contributed to some of the surface debris and I guess it’s been fairly dry which probably meant there was more dust in the air than in winter.
The replacement filters are a slightly different design, with the F7 filter for the intake looking much more like the G4 used for the extract, without the longitudinal support ribs. It will be interesting to see how that looks next time they get replaced (1st January).
Note that the main job of the G4 filter is to protect the heat exchanger from dust extracted from within the house. That’s getting cleaner every time it gets changed as there’s now less bare plaster to create dust and less sawdust and other debris being created within the house.