Road noise using window boards instead of thin plastic cills?

Hi

In our bay window which is double glazed it is so noisy from road noise

I have checked the silicon around the windows and are fine along with any gaps have been foamed

The only thing I think it could be is there is an air brick just below the window, and the noise is travelling through this up the cavity which is unfilled and through the thin plastic cills, so would it be better to replace the cill with 25mm window board/polyboard which is denser thus reducing to sound waves

Or would it be better to cover the gap in the cavity with acoustic mineral wool then with the window board? Problem with that is you are reducing / blocking air flow in the cavity

If you want to keep the cavity open then fit wood window boards - MDF primed ones - I think painted wood looks better than plastic.

Nige F said:

I think painted wood looks better than plastic.

Click to expand...

Same is true for the window

So why has your house got an air vent under the bay window? Is there something dodgy about its construction? Is it Victorian with a failed damp course? easiest thing to do is to remove the air brick, punch in glassfibre insulation around the cavity and put the airbrick back. Its only venting 3' height of wall any way. It should be venting under the floor to keep your joists dry. If its a Victorian house you might still have your sash boxes buried in the wall with a wonderful air leakage path all round the windows with an effective single skin wall for 4" at the sides of the window.
Frank.

Hi
The house is from the 1950's/60's with a suspended floor so the vent under the bay is venting under the floor. Is it not advisable to fill the cavity in the bay with acoustic mineral wool as in effect you would be blocking up the air vent?

I am hoping that replacing the thin plastic cills with 25mm window boards will make some difference to heat and more importantly reduce noise as it's a denser material

You could try putting books or newspapers on the window cill
to see if it improves things before doing anything.