Gap Filling Floorboards, Ventilation vs Draughtproofing

[cjm]

I know there've been various threads on this subject but I've still got a few questions so any help much appreciated. We're having the floorboards of our Victorian house sanded and finished and are wondering whether gap filling the downstairs floorboards is a wise idea. The boards are in good condition, however the survey noted that while the sub floor ventilation is okay, it's not particularly good and recommends making some improvements to it. That said it's clearly not at all an urgent matter and there are no signs of damp or infestation and boards have been treated with a DPC. Question is do we gap fill and potentially cut down on the room's ventilation or be more energy efficient and gap-fill to draughtproof? Another option is to see what it's like during winter, and gap-fill or insulate later on, although since we're having the work done soon it's why this is a consideration now.

Many thanks for any advice on this!

 

[MdB]

You want as much air as possible going from outside the house, under the floor and then out the other side so as to keep the underfloor area dry. You also want some air from outside to reach your living space to ventilate it and to supply oxygen to your fire if you have one. Gaps in floorboards is one way to do this but you don't want a howling gale either.

 

[Roger H]

If you can get access to the undersides of the floorboards it would be a good idea to fix insulation underneath. Either rigid foam or maybe something more eco sandwiched between your joists (maybe securely held in place by some noggins or battens), or rockwool suspended in netting stapled to the joists or suspended on small noggins/battens would be options. Alternately, lift the boards to do the same (hard, messy).

And if you need more underfloor ventilation, some airbricks for crossflow.

 

[cjm]

Thank you both! Very helpful.