The Ventilation System

 Although I have talked before about the baffle boxes, and how they prevent noise from coming through the ventilation holes, I haven't yet explained how the entire ventilation system works, so I will do so now. Please note that pictures in this article were taken at varying stages during the project, but I thought it would be useful to put them all together in one section.

Essentially, the plan was to have a passive air intake, (a hole through the wall connected to a baffle box), and an active air outtake, using a powerful extractor fan. I have already gone through the calculations needed to spec the fan, so I will now describe the exact layout of all the components and how they interact together. To make this easier for myself, I drew diagrams of both intake and outtake to ensure I purchased all the correct parts. Let's start with the passive intake:

Passive Air Intake

Here you can see the side view of the exterior block wall, as well as the interior stud wall, with the ducting penetrating both walls. The baffle box is then fixed to the outer wall (the distance is exaggerated in the picture to show the connectors). You may notice that although I specced 6" ducting, we ended up with 5" holes through the blockwork: this was purely due to the lack of a 6" hole-saw. As they are fairly expensive, we decided not to purchase another one as a 5" saw was available, so we stuck with this, and used 5-6" ductwork connectors, reasoning that as the 5" segments were only short, they wouldn't restrict the flow of air too much. 

Eventually, once the interior wall was built,  I would then use some acoustic absorbing sticky-back foam in the duct to try and reduce sound transfer even more: 

And  finish off with a 6" inlet, to better distribute the air coming into the room:

Finally, on the outside of the studio wall, the baffle boxes is mounted as below (I will describe the mounting process in detail later on as it was fairly tricky):

Active Air Outtake

Moving onto the air outtake: this system was much more complex. Here is the diagram to begin with:

As you can see, the plan for the perforation of the outer wall was the same as for the intake, but there were additional parts needed both on the outside of the wall, and also upstream of the fan. For reference, the fan I used is the Envirovent SILMV500/150T - I chose this due to having sufficient flowrate of around 500m^3/hour, and also due to it's very low noise rating of 22dB. Here it is:

Beginning right-to-left on the "Ventilation connections" diagram above, I used the following parts:

• A backdraft-proof cowling on the outside to prevent rain from getting into the vent. Below you can see the backdraft preventer and cowling which I fitted to a piece of 2by8 in order to fix it to the exterior wall of the studio

• The ducting and connectors/adaptors through the wall (this picture was taken up in the rafters on the inside):
  
  
  

The fan itself, mounted on a piece of plywood board attached to the outer room rafters:

• The silver flexible ducting connection going from the fan to the baffle box:

• The baffle box itself: here we are looking up at the rafters from below. The connection to the fan is in red, the connection to the room is in green, and the box is in yellow. It was actually very difficult lifting this box into place, we had to use our plasterboard crane, and even so it felt quite unsafe as we had to manoeuvre it into position at height and it is extremely heavy!

• The connection between the box and the inner room coming down through the outer-room ceiling, and coming flush to the location of the future inner-room ceiling (this picture was taken much later on at the rockwool stage):

• And finally, on the inner room ceiling, the same ceiling vent as I used for the passive air intake:

The whole system was then wired up by our electrician to a switch, so that you can turn the ventilation on or off at will. Having used the studio for some time now, I find that I like to turn the air on every couple of hours or so if I'm in there by myself as it does get a bit stuffy eventually. It's crucial to be able to control the ventilation manually so that you can turn it off before recording, in order not to get any noise leaking into the microphones (especially relevant for condenser microphones). 

Overall, however, I was extremely pleased with how the ventilation system worked out. It's very satisfying to know all the components that are up out of view in the rafters, which allow you to have very little sound leakage, but a proper circulation of fresh air at the flick of a switch!

Next up - Assembling the Stud Walls