Mechanical subfloor ventilation

[musicaltoot]

I've recently bought an Edwardian mid-terrace house with a suspended timber floor and a modern extension. There has been no subfloor ventilation installed in the concrete slab, despite it passing building compliance. I don't want to disturb the concrete slab because of the subsidence risk, but the lack of ventilation is causing a damp issue. I've installed more air bricks at the front of the property, with little improvement. There is only scope to install air bricks at the front of the property, which is roughly rectangular in shape. Can a PIV unit be installed to ventilate the subfloor?

I've added a rudimentary drawing of the layout of the property, showing the position of air bricks at the front

 

[freddiemercurystwin]

It's quite similar to this thread: https://www.diynot.com/diy/threads/airbricks-end-inside-extension.625439/

 

[musicaltoot]

Thank you, I'll have a look

 

[Harry Bloomfield]

I've added a rudimentary drawing of the layout of the property, showing the position of air bricks at the front

I would suggest reposting the diagram, with a better explanation of what is in the drawing.

 

[musicaltoot]

Thanks for the suggestion. It's a floorplan of the ground floor of the property. Living room at the front where the air bricks are located (in blue), extended kitchen diner at the back. I added the island in yellow. It is flanked by adjoining properties on either side (black)

It is not to scale...I'm clearly not a CAD designer

 

[Harry Bloomfield]

There is only scope to install air bricks at the front of the property, which is roughly rectangular in shape. Can a PIV unit be installed to ventilate the subfloor?

Normally, underfloor ventilation, relies on the natural higher pressure of the wind on one side of a property, versus that on the lee side, to create an air flow. A way in, and a way out. Your problem is that it is single sided, all the same pressure, and so no, or minimal air flow.

Therefore, your only solution is mechanical ventilation. I would add a duct and fan, drawing air from the front, centre, and discharging it at the rear, centre, close to the new slab. Beyond that, I have no idea..

 

[musicaltoot]

In theory, would it work to have an air input and an air output fan on the front wall in an attempt to circulate the air in the subfloor void?

I'm not sure how builders can tell inspectors that there's ventilation in the concrete and it just gets passed. I would never have bought a property without adequate subfloor ventilation

 

[Harry Bloomfield]

In theory, would it work to have an air input and an air output fan on the front wall in an attempt to circulate the air in the subfloor void?

It would work, but ducting it all the way to the rear, ensures there is more air movement throughout the underfloor, for lower power consumption.