Not a fan of installations done this badly
More new build woes unfortunately, this time relating to poor installation of extraction systems. Multivent installations are becoming increasingly popular in new build properties due to concerns relating to air tightness; they are an improvement on single room extraction fans and significantly cheaper to install than whole house MVHR systems.
This particular fan was continuous running and designed to be ultra quiet which is great because I generally find that fans get turned off wherever the noise levels are intrusive. I’ve been recommending and specifying continuous silent running centrifugal fans for quite a few years now.
Unfortunately there was clearly something wrong because I checked the ceiling mushroom outlets and they were not drawing any air whatsoever. I asked the client about this and they explained that they had turned the extract fan off about a week previously after noise levels were so high that it kept them up all night. In fact after a sleepless night the frustrated home owner went into the loft space in the very early hours of the morning and adjusted the motor speed control to its lowest setting to stop the noise. They complained about this to the developer the next day who claimed that not all their properties had fans installed but because they lived so close to the train tracks it had been installed especially to help deal with the noisy trains. I pointed out to my client that the developer was required to install an extraction system in all properties under the approved documents and the fan should be quiet.
A closer inspection of the installation was warranted because I know these systems are generally very quiet when correctly installed. On accessing the loft space I found that the developer had laid an old piece of wood across the bottom chords of the trussed rafter and simply sat the extraction unit on top of the loose piece of wood.
They can be mounted horizontally or vertically but in this case the extraction unit should have been fixed to a secure plinth with the special installation screws that come supplied with the unit. Motors are finely balanced in these units but they will move around under the centrifugal forces generated if not properly secured. Moreover the isolation screw installation is critical to prevent sound transmission through the building.
The other thing I really do not like to see is ducting secured with cable ties and in this case there was already a section of ducting disconnected due to this poor fixing method. The consequences of having an extractor fan pumping moist air into the loft space could have an extremely deleterious effect on the roof timbers and consequently end up being an extremely expensive latent defect for the developer.