UKC

Since it seems to be insulation / energy-efficiency month on UKC... we've recently bought a Victorian terraced house. It has typical Victorian suspended floors (over a cellar at the front and a sort of filled-in-with-rubble cellar at the back) with exposed floorboards. The exposed floorboards are full of period charm and we genuinely like the look of them, but as might be expected they're cold and draughty as all heck so we're looking at putting suspended floor insulation under them.

I've had a quick buzz through the government's best practices document and I think our setup is suitable for some sort of vapour-permeable insulation between the joists.

Two questions:

1) In general, are there any particular caveats or things we should be looking out for (given that we're getting someone professional in to do it and not just bodging it ourselves with old rollmats or something)?

2) In particular, can anyone recommend a floor insulation service in Sheffield?

Thanks!

Make sure you keep enough ventilation around the joist ends otherwise they'll rot. 

The floors in such properties pretty much relied on air being drawn through the air bricks under the floor and up the chimney by a fire. Without this circulation it can be problematic.

Thanks! Yeah, I've been looking though the information here:
https://www.gov.uk/government/publications/insulating-suspended-timber-floo...

(which afaict is describing the practices that a reputable installer should be following anyway, rather than being a decision-making guide for punters, but the more you know...)

and I think the recommendation is to use a vapour-open insulating material like rock wool in older buildings like ours, for roughly that reason.

It is also worth checking the size and condition of existing air bricks, which can often become blocked up or covered.  The bottom of each brick needs it be at least 75mm above external floor level.  They rely on cross flow so any internal walls within your cellar should have corresponding air bricks (or open doorways etc) so they don’t stop the flow. You can find the correct amount of free flow in the building regs or though a Google search. 
 

Have you considered wood fibre? It’ll likely work out as slightly more expensive than mineral wool or glass wool but manages moisture better.