Best Way to Insulate a Timber Floor in Older Homes?

[Sarahtalkstimber]

Planning to redo an old suspended timber floor and I’m debating the best insulation method that won’t cause moisture issues. Anyone got experience with mineral wool vs PIR or breathable options?

[Nickfromwales]

9 minutes ago, Sarahtalkstimber said:

Planning to redo an old suspended timber floor and I’m debating the best insulation method that won’t cause moisture issues. Anyone got experience with mineral wool vs PIR or breathable options?

Check out a load of content here, such as:

 

 

[SteamyTea]

If it is a suspended floor that is open to the atmosphere (via air bricks) you can treat it like an insulated wall.

Room--Floor--VCL--Insulation--Windtight Layer--Atmosphere.

 

The theory is that the closer to the warm, moist air in the room, the harder it is for air and water molecules to pass through.

[Redbeard]

Or you can turn it into an insulated solid floor (depends how fundamental your 'redo' is), and have none of the possible issues which can (sometimes) occur with insulated suspended floors even if you follow all the best practice guidance.

[Iceverge]

As above. Mineral wool between the joists, not PIR. 

 

Otherwise dig it out and pour a new floor on as much insulation as you can fit. I like EPS.

 

Better still knock and rebuild the entire house if it's a big renovation. 

[Redbeard]

2 hours ago, Redbeard said:

Or you can turn it into an insulated solid floor (depends how fundamental your 'redo' is), and have none of the possible issues which can (sometimes) occur with insulated suspended floors even if you follow all the best practice guidance.

 

Remember, if it is next to another susp. tim floor which you are *not* converting to concrete, to bed ventilation ducts under the (insulation under the) concrete floor.

[marshian]

I had a two to three foot crawl space under my suspended wood ground floor.
 

It’s ventilated with air bricks every five all the way round the house getting underneath there was a lot of air flowing if there was any breeze at all. The ground was concrete over DPM and it’s very dry under there (dusty)

 

the floor joists were mostly four or six inch (an extension added had six inch due to the span.

 

most ground floor rooms have either tiled finish (overboarded with ply before tiling) or 18mm oak.

 

all floors in winter were bloody freezing and most rooms were drafty near the skirting boards

 

I used 75mm kingspan and did the whole ground floor from underneath - this left a reasonable amount of joist exposed if any moisture needed to escape - I tapered the insulation at any air brick

 

The best thing from an energy reduction perspective I have done - I’ve been under a few times and there is still a good airflow under there and no sign at all of any damp. 
 

drafts have been completely eliminated and even in winter the floors (esp tiled ones) are closer to room temp rather than 10 deg cooler

 

100% recommend but if you can remove the floor and do it from above it’s a lot easier

 

@Sparrowhawk I think has also done similar

 

 

[Super_Paulie]

PIR for me, foamed and aluminium tape all round, supported on full length battens screwed to the joists. I have UFH in mix on top but the floor is never cold at any time, on or off.

Like above I tapered the board at the air bricks if I needed to.