Intermediate floor insulation - good idea or not?

[biffvernon]

You guys are talking about two quite separate phenomena. Hot air rises over cold air because it is less dense. Heat flows from a hot object to a cold object by conduction or by radiation. With convection it is the whole object (the piece of air) that moves.

 

[NT]

Quite so Biff. Need to review some physics here.

Heat is not interested in direction or gravity, and travels always from hotter to colder body. Whych is up or down has nowt to do with it.

Heat also changes density of air, resulting in stratification.

Air would only travel up the stairs into the top room from below if the bottom room were already warmer than upstairs. If this isnt so, downstairs has colder air than up, so no air swap will occur due to differing density. IOW there is one and only one way heat can flow, if upstairs is warmer than downstairs, and that is from upstairs to down.

Therefore interfloor insulation will be counterproductive. And this is why it is more or less never used.


NT

 

[Gervase]

And this is why it is more or less never used.


NT

Eh? I'ts been used on almost every building I've worked on, and has been used extensively in historic buildings.
In our own house we had bushels of bran and chaff laid down under the floorboards, as seen here:

In other buildings I've found husks and wool used similarly going back at least to the last part of the 18th century. It wasn't universal, but seems to have been particularly common under bedrooms and above entrance hallways.
The modern trend for every room, as specified by almost every architect, is for 80mm of rockwool in the void between the ceiling board and the floor above. I've had to fit enough batts of the filthy stuff in my time and done my share of cursing - if the joists aren't spaced suitably you have to use pins, long nails, bailer twine or pea-netting to hold the stuff up before the ceiling boards are fixed.
Admittedly the benefit is largely accoustic, but if it didn't provide a benefit it wouldn't be done.

 

[tony]

good photo,

Cables require some mechanical protection in the checked joists.

regards

tony

 

[middi]

Laymen terms.

If I have a one up one down cosy cottage, with an X amount of BTU/h being produced by my stove and the above floor being constructed in simple "gappy" floorboards, I will have to keep the fire going at full blast for as long as it takes to stabilise the temperature for the "comfort" living zone in the downstairs room.
Purely due to the fact that most of the heat, initially, has escaped to the upper floor.

With no means of "zone control" due to the "gappy" floorboards, a state of equilibrium in heat transfere has to be achieved before I can control the heat source and/or turn off the heat imput, to be replenished only when this has found its way out through the upstairs and downstairs external walls.

Now I ask you, presented with the same "heating problem" scenario, would I gain anything by installing a three feet thick heavy layer of insulation above or below those floorboards ?.

Of course a bl""dy would, I would only have to worry about loosing heat through the lower part of the house not worry about creating an oven upstairs, more heat to dislodge itself through the upstairs external wall or more heat to be pumped into the cottage in order to reach a state of heat transfere quilibrium.

Heat transfere ( or loss) is directly linked (pro rata) to the efficiency and/or thickness of insulation, be it internally or externally.

 

[Lime]

If we were talking about two sealed solid units, made of a good conductor of heat touching one upon the other, where the upper unit (bedroom) was warm and the lower unit (lounge) was cold then heat would eventually conduct from the warm to the cold unit.
However that is not the case in houses. Rooms are hollow leaky boxes full of a poor conductor (air) and if there is any temperature gradient at all within them the warmer area is always uppermost.
The dominant form of heat transfer within a house between rooms is one of convection not conduction nor radiation.
If air temperature readings are taken at differing heights within a room the upper air near the ceiling will always be warmer that that below it.
Where hot air meets a cooler surface heat is transfered quite readily and that primarily occurs at the ceiling.
Heat transfer from room air to floor is small in comparison.

A simple test is to switch off all downstairs heating leaving only the upstairs heated and leaving all interior doors wide open.
Within a few hours the lower part of the house has cooled considerably.

The reverse experiment, heating downstairs and not the upstairs with all doors open, results in both upstairs and downstairs being warm.

I regularly heat my house this way heating downstairs during the day and upstairs at night.
Upstairs is remains warm during the day but downstairs becomes cold during the night.

Hence convection plays a far greater role in heat transfer within a house than conduction or radiation.
What conduction there is within a house is primarily between hot air and cold surfaces with radiation playing an even smaller role in home comfort.

Obviously where a heating source is present radiation and conduction play an important part in heat transfer from the heat source to the room air.

 

[NT]

Admittedly the benefit is largely accoustic, but if it didn't provide a benefit it wouldn't be done.

exactly, materials are used specifically for soundproofing, rather than to avoid heat loss.

When individual room zoned CH becomes more common, inter-room thermal isulation will become more useful than today. But today, if you have some insulation, use it to insulate the exterior of the building.


NT

 

[NT]

Laymen terms.

If I have a one up one down cosy cottage, with an X amount of BTU/h being produced by my stove and the above floor being constructed in simple "gappy" floorboards, I will have to keep the fire going at full blast for as long as it takes to stabilise the temperature for the "comfort" living zone in the downstairs room.
Purely due to the fact that most of the heat, initially, has escaped to the upper floor.

With no means of "zone control" due to the "gappy" floorboards, a state of equilibrium in heat transfere has to be achieved before I can control the heat source and/or turn off the heat imput, to be replenished only when this has found its way out through the upstairs and downstairs external walls.

Now I ask you, presented with the same "heating problem" scenario, would I gain anything by installing a three feet thick heavy layer of insulation above or below those floorboards ?.

Of course a bl""dy would,

Yes, but with a standard CH system, which heats up and downstairs at the same time to very similar temps, you'd gain much more by putting that insulation between house and outside world.

Also bear in mind what youre describing is not comparable to the OPs situation.


NT

 

[Gervase]

Cables require some mechanical protection in the checked joists.

Agreed - that wiring (which came with the house and was a piece of DIY bodging) has long gone and been replaced by something which is no longer lethal and which meets Part P.

but with a standard CH system, which heats up and downstairs at the same time to very similar temps, you'd gain much more by putting that insulation between house and outside world.

But who has a CH system like that these days? Everyone I know who has installed radiators in the past five years or so uses thermostatic valves to zone their heating - the days of a single wall-mounted thermostat on a landing or stairwell are long gone. And with bedrooms some 5 degrees cooler than living rooms, then interfloor insulation is a must.
I really can't understand why you're so against the stuff! :shock:

 

[Penners]

Quite so Biff. Need to review some physics here.

Heat is not interested in direction or gravity, and travels always from hotter to colder body. Whych is up or down has nowt to do with it.

Heat also changes density of air, resulting in stratification.

Air would only travel up the stairs into the top room from below if the bottom room were already warmer than upstairs. If this isnt so, downstairs has colder air than up, so no air swap will occur due to differing density. IOW there is one and only one way heat can flow, if upstairs is warmer than downstairs, and that is from upstairs to down.

Therefore interfloor insulation will be counterproductive. And this is why it is more or less never used.

OK, NT, let's relate this to real life. I believe the OP has a heated living room, above which is a bedroom - possibly heated a bit less than the room below, possibly not. Between the two is a very leaky ceiling/floor.

The OP is complaining that the downstairs room is difficult to heat because the heat is rising through the floor into the room above.

In this case, surely you can simply ignore the ceiling/floor (because it presents virtually no thermal barrier), and imagine the entire structure as one tall room. The heat generated at floor level is rising up by convection and gathering at ceiling level, so the room becomes warmer at the top than at the bottom.

Are you saying that can't happen? If so, then I suspect I won't be alone is disageeing vehemently with you. What's more, we'd be joined by a number of companies who sell things called Heat Inverters to factories. These are basically vertical pipes with fans in them, that pump warm air from the top of the building down to floor level.

 

[tony]

Gervase,

although you need to comply with part p this has only recently introduced, it should comply with the iee wiring regulations,complying with the regs will mean you are complying with part p.

regards

tony

 

[Sal]

er... isn't it really simple... you know that old chestnut.. heat rises?

I was standing on a chair in my kitchen (changing light bulb) , my kitchen has a rayburn. It was noticably hotter nearer the ceiling than when I was not standing on a chair. er...thats cos heat rises....


insulation would hinder the heat in its continued journey through the gaps in the flooring and into the room above.

 

[Nemesis]

Nah, that's far too simple. It doesn't involve a load of blokes being full of pseudo science and airing it...


Am I showing a small amount of prejudice here?

 

[greenman]

Heat is not interested in direction or gravity, and travels always from hotter to colder body. Whych is up or down has nowt to do with it.
NT

Not quite, take this example. a 4 ft length of copper pipe, hold it vertically and heat the middle with a blowtorch. If your contention that heat is not interested in direction or gravity were true then both ends would get too hot to touch at the same time. As I think everyone knows this simply isn't true. I know this to be true, I've just done some plumbing

For fairness it has to be said that some heat does travel down the pipe, but in a totally disproportionate amount.

To fold this back into an real scenario, you are sat in your lounge downstairs, the radiator is on generating convetion currents of air in the room, the less dense hotter air will migrate to the ceiling where it will transfer its heat to the floor of the room upstairs. you can stop this in 2 ways, insulate the floor cavity or heat the room upstairs to match the hottest air of the room below.

 

[NT]

Sal:

>er... isn't it really simple... you know that old chestnut.. heat rises?

>I was standing on a chair in my kitchen (changing light bulb) , my kitchen has a rayburn. It was noticably hotter nearer the ceiling than when I was not standing on a chair. er...thats cos heat rises....


Like any rule of thumb, what you say here is somewhat simpler than real life.

If you're so sure heat rises, you may wish to ask yourself why new build houses always have insulation under the ground floor.



NT wrote:

>Heat is not interested in direction or gravity, and travels always from hotter to colder body. Whych is up or down has nowt to do with it.


greenman:

>Not quite, take this example. a 4 ft length of copper pipe, hold it vertically and heat the middle with a blowtorch. If your contention that heat is not interested in direction or gravity were true then both ends would get too hot to touch at the same time. As I think everyone knows this simply isn't true. I know this to be true, I've just done some plumbing

>For fairness it has to be said that some heat does travel down the pipe, but in a totally disproportionate amount.


Without wishing to state the obvious, had you considered that the flame itself produces a lot of hot air that rises, and that the pipe is therefore not heated evenly?


NT

 

[NT]

Penners:

> OK, NT, let's relate this to real life. I believe the OP has a heated living room, above which is a bedroom - possibly heated a bit less than the room below, possibly not.

That is unlikely, given that the upstairs room is hotter than downstairs. But not entirely impossible.


> Between the two is a very leaky ceiling/floor.

Is it really, or was this just the OP's initial perception of the problem?

If it really is very leaky, wouldnt replastering be a more logical first step?


> The OP is complaining that the downstairs room is difficult to heat because the heat is rising through the floor into the room above.

yes, incorrectly.


> In this case, surely you can simply ignore the ceiling/floor (because it presents virtually no thermal barrier),

2 layers of wood & plaster with a 6" cavity presents NO thermal barrier??


> and imagine the entire structure as one tall room.

So as well as presenting no thermal barrier, it also poses no resistance to air flow!!

Penners, I give up. You have lots of good stuff to say on many subjects, but I think on this it may be time to review some basic thermodynamics.

I guess this is a period property forum, and not a thermodynamics forum, nor an engineering forum.

If you want to discuss it with a whole bunch of experts, one of which I'm not on thermodynamics, I suggest asking the folk at news:alt.solar.thermal.


NT

 

[middi]

Let us try from another angle.


Assuming again having to heat our one up one down cottage with our gappy floorboards. We need to keep the downstairs room at 70 deg during the day and do not need any heat in this room during the night.

We wish ( for argument sake) the same temperature in the above room only during the night.

Regardless of the method of heat source or any sophisticated zone control mechanism used, the primary concern surely should be to concentrate the heat convectional currents and to confine the heat source within the required room and minimise as much as we can the heat transfere from one room to another trough the gappy floor.

Therefore to answer the original question, yes, as much insulation as possible in the floorboards will save us money, the better the insulation the more we save.

Of course there will be residual heat transfere from one room to another, but if this heat transfere is retarded for as long as possible from one room to another by good insulation and keeping the single upstairs door well closed, the rate at which heat is required within the particular room will also be prolonged. Less firings, less fuel, money saved.

If it were a 5 storey building built in the same manner as our one up one down and wished to heat only the lower floor during the day and the upper floor at night, I would fill with insulation all the other rooms.

 

[Sal]

If you're so sure heat rises, you may wish to ask yourself why new build houses always have insulation under the ground floor.

Without wishing to state the obvious, had you considered that the flame itself produces a lot of hot air that rises, and that the pipe is therefore not heated evenly?

here you contradict yourself. heat rises it seems (oh and my standing on chair in kitchen WAS real life, not forum life)


and even supposing it doesn't - does it matter? insulate between rooms and you will be able to stop heat moving from one to another (in any direction it cares to go). Just as Middi stated.

 

[GK]

insulate between rooms and you will be able to stop heat moving from one to another (in any direction it cares to go)

Correct - so if we take willcrick at his word when he says that upstairs is warmer than down, insulation will prevent the bedroom heat from moving to the sitting room

.......transfer its heat to the floor of the room upstairs. you can stop this in 2 ways, insulate the floor cavity or heat the room upstairs to match the hottest air of the room below.

Correct - if the room upstairs is the same temperature then insulating won't make any difference. But upstairs is already warmer so insulation will stop it moving down in this case

In the case of the heated pipe, without the heat from the convected air moving UP, conduction would heat the pipe evenly at both ends

GK (blokey sort of pseudo scientist)

 

[Lime]

In the case of the heated pipe, without the heat from the convected air moving UP, conduction would heat the pipe evenly at both ends

GK (blokey sort of pseudo scientist)

"blokey sort of pseudo scientist" :lol: :lol: :lol:


Am I correct in thinking that "without the heat from the convected air moving UP" is the nub of this thread's argument?

Perhaps some of this argument is more apropriate for building on the moon as that is the only area I know of that does not have the often over-riding effect of convection.

Truly a vacuous argument!