Floor Insulation: Which one?

redabici

Our living room and hallway are currently carpeted. We have pets so want to rip up the carpet and have floorboard. We can restore the floorboards ourselves, we did it with the bedrooms, but have no idea how to do insulation.

I believe the floor is suspended timber (1930s house) and the floorboard are original (including those massive old-school nails. I've been reading about insulation but honestly don't understand half of it. I'm hoping someone could help me with some basic knowledge in simple English. This is what I have so far:

- The traditional type (garden net then rockwool/sheepwool?). Will need to pick up the whole floor. Is this the most effective way to insulate? Would it be an issue to lift such old floor? If not, do we restore the floor first (just sand not varnish) then do insulation or insulation then floor work?

- Something about the beads/balls? Apparently these are easier to install as you only need to lift a few board? Is it more efficient in terms of keeping heat? What do I need to look out for in terms of types of beads?

- What are the insulation boards? Are they just for concrete floor?

Thank you so very much

FreeBear

First, you do not want to use beads or any other loose fill insulation. The quantities required will be excessive and you will block off any air flow under the floor. The air flow is required to prevent the joists rotting.


Assuming your floor is the same as mine - Tongue & groove boards - There is a real risk of damaging the boards as you lift them. You'd also need to remove some/all skirting boards to get the floorboards up. Once the boards are lifted, staple netting to the bottom of the joists and fill the gap with mineral wool or fiberglass insulation batts. Replace the floorboards, and then sand/seal.


Solid Celotex/Kingspan PUR sheets could be used, but you would need to nail (or screw) battens close to the bottom of the joists to prevent the sheets from falling in to the void. If your joists are like mine (2"x3"), PUR sheets would provide a better level of insulation. But you do need to make sure that air flow is not compromised.

armchaireconomist

Presuming you have a suspended timber floor, I wouldn't use the blown-in insulation as you'll end up filling the entire cavity. Air must be able to circulate.


Can't comment on net/rockwool, personally can't see it working on a suspended timber floor.


Insulation 'boards" are rigid slabs, like what's use in roof rafter insulation. No harm in cutting them slightly larger than the openings and jamming them between the floor joists - no fixings needed. However you will need to lift the entire floor. These are the most expensive of the options however.


There's also the reflective blanket insulation, often used on underside of roof rafters. These don't hold mass as such but reflect the heat so would help stop heat escaping under floor, but effects minimal.


In all honesty draught proofing it is probably the most important aspect.

Slinky

Get someone in to help?


http://www.sapwells.co.uk/

redabici

Thank you. Looks like we'll go with net/wool. This will be a messy job!
Yes I will get someone in to help but want to know what we're doing first to make sure we get the right one for the job.

System

look for underfloor insulation installers in your area - I got mine done for less than I could buy the materials for and I didn't have to squeeze under the floor wearing a mask to do it! double bonus