cold floor

[JohnD]

under a floor, if you have a gap, you can stuff mineral wool to fill it. It will prevent air movement as well as adding insulation, and will muffle noise a little. Unlike polystryrene or Celotex, it does not burn or give off poisonous gases in a fire.

It can be pressed to tightly fill irregular gaps, with no precision cutting needed.

Not much heat is lost through a floor, except for cold draughts. There is obviously no convection; little conduction if there is an air gap, next to no radiation.

Block any gaps you find, preferably with pink fire foam or mortar.

I also have a room over an unheated garage. Easy peasy.

 

[Lower]

I live in a 1920's built house with suspended floors. Its a 'Z' shaped house and most rooms have 3 external, solid walls. When its windy, our lounge feels cold and even when the room feels warm the floor always feels cold which makes the room feel cold.

The lounge floor had a woodworm and rot problem so in the autumn we had the whole floor replaced and 50mm of celotex put in between the joists. I was hoping for a significant improvement in the warmth of the floor and the room. Disappointingly, there was hardly any change.

By comparison, my son's playroom is the same design with 3 outside walls and a suspended floor. We put down a high tog underlay and a wool carpet. That feels like it was of more benefit that the underfloor insulation and was much cheaper.

 

[JohnD]

When its windy, our lounge feels cold... celotex put in between the joists...hardly any change.

use a joss stick to search for draughts, especially round the edges of the room and under the skirtings.

go round the windows and door, too.

 

[Lower]

use a joss stick to search for draughts, especially round the edges of the room and under the skirtings.

go round the windows and door, too.

Its not draughts that makes the rooms cold, i can only assume its the wind sucking the heat from the solid walls. The room is well sealed now the floors been insulated (including foaming all the gaps) and we have decent UPVC windows. However, on a cold windy day the walls are very cold to the touch.

 

[JohnD]

But you said a carpet and underlay had done more good.

 

[Lower]

But you said a carpet and underlay had done more good.

The wool carpet and high tog underlay made that floor feel warmer than the fully insulated floor with normal underlay and carpet, though to be fair the difference is marginal.

The point i was trying to make was that insulating the floor gives little benefit to how warm the room feels. Both rooms still feel cold when its windy. I suspect that we'd need to insulate the walls get a significant benefit and that would mean destroying the appearance of the externals of the house or losing all the original features and moving doorways if we insulated internally.

 

[joeturbo]

I have taken a look under the kitchen cupboards and the is still one square when the pipe work is that I can see/feel beneath. Looks empty, will see if can borrow neighbors endoscope to feed under for a better look

 

[John D v2.0]

Not much heat is lost through a floor, except for cold draughts. There is obviously no convection; little conduction if there is an air gap, next to no radiation.

That's true, but in terms of feeling cold, having a pool of cooler air and a cool surface affects the comfort much more significantly then heat loss elsewhere.
This is because you don't really stay close to the ceiling or walls but your feet are close to the floor often.
Poor loft insulation affects your bills mostly, poor floor installation affects your comfort mostly.

 

[JohnD]

What I mean is, stuffing the gap with mineral wool will block the cold draughts, and provide all the insulation you need (which is not much for a floor as other losses are so small)

 

[joeturbo]

I have ordered a 5meter endoscope so can get a good look under the flooring before taking it all up

 

[joeturbo]

Still waiting for the endoscope to arrive. I have a chippy due to visit later this week who I will ask to take up some of the floor boarding just so can get an idea of what’s under there then potentially fill with mineral wool? I know there is what looks like white polystyrene in some areas but I doubt all of filled.

would it be worth insulating the carport ceiling? As mentioned there is ceiling board (I believe fire rated) then a 50mm void, then concrete.

 

[JohnD]

IMO stuffing the gap under the floor is all you need.

It will block draughts, and other heat loss through a floor, which is very small.

 

[Deleted member 174758]

... I will ask to take up some of the floor boarding just so can get an idea of what’s under there then potentially fill with mineral wool? I know there is what looks like white polystyrene in some areas but I doubt all of filled.

if as I suspect, the "white polystyrene" is Jablite, then you should be aware that it has a higher R value than mineral wool (it is almost twice as effective as an insulator). It would be interesting to know whether or not you have any cold spots in the kitchen floor caused by gaps in insulation or missing insulation, but that would require an infra red (FLIR) camera or a phone attachment (unfortunately the cheapest clip on FLIR I've seen for Android phones is just under £200 - my Androifd phone endoscope in comparison was under £50). As far as insulating beneath the concrete. TBH, having thought about it, I'm unsure that you'd get a huge benefit from insulating the ceiling below the floor because you are insulating a concrete slab which should already be insulated above, so before going ahead with it I think I'd want to see what a thermal imager made of the floor. Incidentally, is the car parking below you enclovsed and if not is it very windy?

 

[joeturbo]

IMO stuffing the gap under the floor is all you need.

It will block draughts, and other heat loss through a floor, which is very small.

okay, will concentrate on under the flooring.

if as I suspect, the "white polystyrene" is Jablite, then you should be aware that it has a higher R value than mineral wool (it is almost twice as effective as an insulator). It would be interesting to know whether or not you have any cold spots in the kitchen floor caused by gaps in insulation or missing insulation, but that would require an infra red (FLIR) camera or a phone attachment (unfortunately the cheapest clip on FLIR I've seen for Android phones is just under £200 - my Androifd phone endoscope in comparison was under £50). As far as insulating beneath the concrete. TBH, having thought about it, I'm unsure that you'd get a huge benefit from insulating the ceiling below the floor because you are insulating a concrete slab which should already be insulated above, so before going ahead with it I think I'd want to see what a thermal imager made of the floor. Incidentally, is the car parking below you enclovsed and if not is it very windy?

is there anyway to tell the difference between white polystyrene and jablite? (There is no silver foil or anything else attached as far as I can feel at the moment). I really think it’s unlikely that the polystyrene goes all through the flat as the floor is far to cold.

so if there is nothing under the floorboards I should use jablite to insulate the bulk of area? do you have a link? Would it be fire resistant?

the car port is completely open on 3 sides attached

 

[Deleted member 174758]

Jablite is very consistent and the foam "grains" are fairly large. Unlike Cellotex or Kingspan it has no silver foil covering. If it is a biggish sheet then it is unlikely to be repurposed packaging material - there would be no point in trying to cut corners that way. Jablite and almost all standard PIR insulations (e.g. Kindgspan, Cellotex, etc) are not fire resistant, but they offer higher insulation values than mineral wool. TBH if you have a fire it would have to b urn through the chipoboard flooring to get to the Jablite, so I wouldn't worry too much about that happening.

the car port is completely open on 3 sides attached

Wow! That car port looks like a wind tunnel (I originally wondered if it was an enclosed garage space), so yes I do now think there would potentially be some benefit from insulating the ceiling void with mineral wool batting (which is fire proof).