cold bay window

[str]

We libe in a stone built house with a bay window that seems to attract the cold weather.

The windows are replacement double glazed and seem fine, but the bottom 2ft is tongue and groove cladding (could be original to the 100 yr old house?) which has nothing behind it apart from an air space then the inside of the stone wall.

Can i replace the tongue and groove but fill the void with insulation? thee are air vents in the outside wall and I assume they provide air flow into the floor void as opposed to the wall void (the house is solid stone so no cavity - the bay has a "cavity" due to the space between the strapping and the wall).

If it is okay to do as I plan, should i include some form of moisture control (plastic sheeting?) (there is not any issues at present with moisture); what would be the best insulation material to use?; and should I leave a small air gap or just fill the void completey?

thanks

 

[wms]

fill the void using some thing like kings span foil backed insulation solid.
it would not hurt to use a vapor control barrier,or foil backed boards.

 

[str]

my other thought was to use expanding foam to get a proper airtight seal - whilst this would be expensive, the alternative would be to use a panel of kings span then foam round it to seal all edges/joins.

Would I end up with any issues in making this completely airtight?

 

[wms]

the kings span cut in between as tight as you can get it, will suffice it will allow a small amount of advantagess air to help in the void, expanding foam is a night mare and can have a pushing effect where you don't want it if you over apply. before fitting the king span,if you are working from out side as I understand. you could seal all the edges with a flexible sealant within the void to prevent internal draughts.