Quite nervous doing this...

[paulca]

So my house has loads of underfloor "ventilation".  The meter cupboard had bare floor and was allowing cold air in.  Literally it was like 5*C in there at night time and cold air pouring in so much that if you open a window the meter cupboard door would blow open.

So I decided to put thermal underlay down to cover all the cracks and holes.

Thing is... it has a conductive upper layer!  No point turning the power off either.  Just had to nervously make sure it didn't hit anything.  I don't think there is any exposed live, but it was still a bit daunting.

Of course I did bump the trip test button and it's got such a heavy spring on it, it went CRACK! and darkness.  Scared the living sh1t out of me.

Done now though, phew!

[andy3055]

That looks pretty dangerous and could be against the local code!

You could line the floor with plywood instead and seal off all the edges with silicone sealant - the kind used for sealing bathroom sinks. For better insulation, line up foam sheets under the plywood.

Just my thoughts.

[thinkfat]

What on earth is THAT? Your house mains wiring??

[dmills]

Yup, older style UK incomer, meter, RCD and breaker box, not the neatest job I have seen but fairly typical of what you find in older housing stock, and FAR from the worst job you will see.

Current rules would need non flammable materials and a metal cased breaker box, but you only got to make those changes if doing major work.

Regards, Dan.

[Ed.Kloonk]

What on earth is THAT? Your house mains wiring??

Nice timber backboard. Classy. 

[TerraHertz]

So that's just some lightweight foam with a foil layer, sitting there unattached?
Won't make any difference. If air draft came up through gaps in the floorboards before, it still will. And lift that foam up like a piston.

I'm guessing that 'solution' was chosen because you don't have any means of cutting to shape something solid, like plywood?

How about this instead: Some old heavy felt carpet underlay, with a layer of something like linoleum or rubber floor matting on top. Those are all things that can be cut with scissors. Then seal any gaps around the edges with silastic. But if you cut the underfelt a bit oversize that won't be necessary.

End result: a relatively non-flamable, electrically insulating layer, heavy enough to hold down against draught pressure.

Or, just seal all the floorboard gaps with gap-filler.

[paulca]

So that's just some lightweight foam with a foil layer, sitting there unattached?
Won't make any difference. If air draft came up through gaps in the floorboards before, it still will. And lift that foam up like a piston.

Yes, it's regulation compliant foam underlay for putting under hardwood flooring.  I believe it's fire retardant.  The upper layer is mica or something, probably not actually conductive on it's surface as it's laminated in plastic.

I weighted it down with stuff.  But, yes the air still gets round it and I can still feel a draft under the door. 

I might just seal the door surround.

On my meter box.  This is a late 1960s house.  Looks like the meter box has been updated maybe 10 years ago.  Not sure if house has been rewired, but it is using black/red twin and earth and has way too many double plugs for a 1960s house.  However it's still out of date, if it was rewired it was 10 or 20 years ago.

A rewire is on the long finger, but at approximately £3000 it will need to wait for other work first.

[BillyD]

I imagine it should at least reduce air flow through the floor of that compartment which should be some help.
Just wondering about the boards that the electrics are mounted on, could there also be draughts coming through the gaps in these boards and around the edges, etc.
Assuming that the door the cupboard doesn't get opened very often, it might be more effective to tackle the cupboard door - put a good seal around it, a latch to ensure it doesn't spring open, maybe even insulate it.

[janoc]

Hum, if anything goes wrong in that closet, you have at least a well prepared electrocution chamber now. You feeling nervous about doing this is a pretty good indication that it is a terrible idea.

Sealing the holes and cracks with either silicone or foam is a much better (and safer) way.

[ebastler]

Looking at your original post, I had not realized that you meant that to be the complete job!?!    As you state, this stuff is meant to go underneath hardwood floor. Please do yourself a favor and put something on top of it — pine board, cheap laminate, whatever.

[paulca]

Yes, I'm currently considering laying heavy underfelt over it and putting a draft strip around the door.  It doesn't have to be pretty, it's an under stairs cupboard.

Also I think the "foil" is just metalized plastic sheet, it's probably only 1 or 2 atoms of aluinium thick to create the thermal mirroring.

[TK]

Yes, I'm currently considering laying heavy underfelt over it and putting a draft strip around the door.  It doesn't have to be pretty, it's an under stairs cupboard.

Also I think the "foil" is just metalized plastic sheet, it's probably only 1 or 2 atoms of aluinium thick to create the thermal mirroring.

[paulca]

Yes, I'm currently considering laying heavy underfelt over it and putting a draft strip around the door.  It doesn't have to be pretty, it's an under stairs cupboard.

Also I think the "foil" is just metalized plastic sheet, it's probably only 1 or 2 atoms of aluinium thick to create the thermal mirroring.

You know how mirroring of surfaces works in the modern world and how they can use silver to coat mirrors and not have it cost thousands?  They vapourise the metal (or metal compound) and allow it to condense onto the electrically charged surface forming a layer with is literally only a few atoms thick but creates a perfect mirror effect.

Even electroplating can be done to produce extremely thin layers.  Food packaging with "foil" is quite often actually plastic with an extremely thin layer of metal to make it look like foil. Crisp packets for example.

[Monkeh]

That looks pretty dangerous and could be against the local code!

?!

Double insulated cabling, what's the problem?

[Twoflower]

A telescope mirror has a coating about 100nm a diameter of an Al atom is about 125pm. So I think that's a bit more than 1 or two atoms.

An Al is cheap, so even a 1mm layer wouldn't cost a fortune compared to the whole thing.

If interested spend some time watching this (Recoating a Giant VLT Mirror):

[NivagSwerdna]

An isolation switch just after the meter.  That's quite novel?

[andy3055]

That looks pretty dangerous and could be against the local code!

?!

Double insulated cabling, what's the problem?

The problem is what he has done. We are not addressing the cables in this post.

[paulca]

An isolation switch just after the meter.  That's quite novel?

As I understand it, this is common.  It is also a requirement in some houses depending on the type of earthing.

If you are replacing a consumer unit/breaker board in a house you need to disconnect the mains, however the main inlet in the UK is usually sealed with metal seals and you are not allowed to break the seals.  Breaking the seals is considered "tampering with ultility equipment" and a criminal offense, since you could have been installing a meter bypass loop, yes that's a thing! Some areas it's just a matter of calling up the distributor and getting authorisation to cut the seals and pull the main fuse, in others it requires the distributor send out an engineer to do it.  Either way the distributor has to come back out to replace the seals later.  All this costs money and time.

So in a lot of places a sensible spark will install some form of 80/100A isolator between the meter and the consumer unit making it easier in future to isolate the board to do work on it.

[paulca]

That looks pretty dangerous and could be against the local code!

?!

Double insulated cabling, what's the problem?

The problem is what he has done. We are not addressing the cables in this post.

His point is, there is no exposed mains.  As discussed elsewhere, (a) the flooring is not actually conductive in it's current state (I can test that) and (b) it should/will be covered with something else.

[NivagSwerdna]

So in a lot of places a sensible spark will install some form of 80/100A isolator between the meter and the consumer unit making it easier in future to isolate the board to do work on it.

Indeed. I'm a bit jealous. I'm pretty sure my consumer unit cannot be isolated without pulling out the company fuse.

[Monkeh]

That looks pretty dangerous and could be against the local code!

?!

Double insulated cabling, what's the problem?

The problem is what he has done. We are not addressing the cables in this post.

... and what is it he's done? Placed an object next to a cable?

[paulca]

That looks pretty dangerous and could be against the local code!

?!

Double insulated cabling, what's the problem?

The problem is what he has done. We are not addressing the cables in this post.

... and what is it he's done? Placed an object next to a cable?

It's a lot more funny if you think about all the things that you would normally find in the understairs cupboards.  Examples:

The hoover.
Your wellie boots.
The kids wellie boots.
The tent.
Camping gear.
The boxes of biscuits from Christmas that nobody likes.
Your sons first bike that he's well outgrown but you still keep in case you have another kid.
The ironing board.
The spare car battery.
Engine oil / washer fluid.
Shovel for the drive and car window scraper.
Your old HiFi the wife hated.

Usually it's piled so high that to read the meter you need to pull a load of junk out first.

It used to be a favourite place to play hide and seek when I was a kid.

[Bud]

Your sons first bike that he's well outgrown but you still keep in case you have another kid.

Usually that goes along with your sons carseat that was hoarded before the bike 

[coppice]

That looks pretty dangerous and could be against the local code!

?!

Double insulated cabling, what's the problem?

The problem is what he has done. We are not addressing the cables in this post.

... and what is it he's done? Placed an object next to a cable?

It's a lot more funny if you think about all the things that you would normally find in the understairs cupboards.  Examples:

The hoover.
Your wellie boots.
The kids wellie boots.
The tent.
Camping gear.
The boxes of biscuits from Christmas that nobody likes.
Your sons first bike that he's well outgrown but you still keep in case you have another kid.
The ironing board.
The spare car battery.
Engine oil / washer fluid.
Shovel for the drive and car window scraper.
Your old HiFi the wife hated.

Usually it's piled so high that to read the meter you need to pull a load of junk out first.

It used to be a favourite place to play hide and seek when I was a kid.

It amazes me people get away with this kind of thing as much as they do. The terminals on most meters, and some of the other items used for consumer wiring, are not well shielded, and its very easy for some piece of metal amongst the junk in a cupboard to poke into one of those recesses.

[jogri]

You know how mirroring of surfaces works in the modern world and how they can use silver to coat mirrors and not have it cost thousands?  They vapourise the metal (or metal compound) and allow it to condense onto the electrically charged surface forming a layer with is literally only a few atoms thick but creates a perfect mirror effect.

High-end mirrors are treated this way (or any mirror that shouldn't suffer from thin film interference), but normal household mirrors are created using chemical deposition: The metal you want to use as a coating is dissolved, if you add something that has spare electrons your metal will get reduced and you get a layer of pure metal on everything the metal will stick too. If you want to coat a mirror, you just dip the warm, clean glass surface into a pool containg the solution of your dissolved metal and the reducing agent (some form of sugar) and wait a few minutes. This process is way faster, cheaper and less complex than vapour deposition, but the surface finish won't be nearly as good.

Today, mostly aluminum is used (it is cheaper than silver), but even a silver coating is rather inexpensive: The silver is going to cost you roughly 500 bucks per kilo, and since you can use a 0.1 molar solution (~15g of silver per liter) you are looking at roughly 10 bucks per liter.

Btw, a "mirror" with a 2 atom thick coat would be completely black. The metallic character necessary to get a reflection starts to kick in at a few hundred layers.

But btt: I would suggest using a vapour barrier (basically just a fancy PE foil) and vapour barrier tape and making sure to get an airtight seal. If you can stop the air movement, the air between the floor and the door should provide a rather decent insulation.