Insulating a (presumably hollow) metal door from within

[Garald]

As some of you may remember, I insulated a hollow external metal door some time ago by pasting 3cm-thick cork on it. I just removed an ugly curtain rod that had been attached to the door some time ago (long story). I was about to cover the bit that just got uncovered with more cork, but I thought: why not drill a hole in the metal and fill the cork with tiny polystyrene balls (say) and then cover the hole with cork?

 

Is this the sort of thing that an individual with essentially no DIY skills (and a regular Bosch drill) can do? How would I get the tiny polystyrene balls in? (And can one just walk to a store and ask "please give me a bag of tiny polystyrene balls for insulation"?) Also, is there much of a point in doing that? How much good would it do, given that the polystyrene would still be surrounded by conducting material?

 

(Ignore the bit of moth-eaten alpaca sweater on the handle - I'll find a neater way of cutting off that thermal bridge.)

 

Suggestions of things less dangerous than polystyrene in case of fire are also welcome.

Edited November 13 by Garald

[Gone West]

8 hours ago, Garald said:

Suggestions of things less dangerous than polystyrene in case of fire are also welcome.

https://www.mikewye.co.uk/product/foam-glass-bubbles/

 

Presumably something like that is also available in France.

[Thorfun]

10 minutes ago, Gone West said:

https://www.mikewye.co.uk/product/foam-glass-bubbles/

 

Presumably something like that is also available in France.

not a great lambda value though, but better than nothing!

 

Thermal Conductivity – 0.07 W/mK.

 

i believe cellulose is around 0.040W/mK?

[Redbeard]

11 hours ago, Garald said:

why not drill a hole in the metal and fill the cork with tiny polystyrene balls

 

I got confused re this, but assume that in this sentence 'cork' should actually be 'core'??

[Conor]

get a new door.

[Garald]

2 hours ago, Redbeard said:

 

I got confused re this, but assume that in this sentence 'cork' should actually be 'core'??

Yes, « core» or « door ». Sorry.

[Garald]

2 hours ago, Conor said:

get a new door.

A well-insulated outside security door costs 4K eur over here.

[Garald]

4 hours ago, Thorfun said:

not a great lambda value though, but better than nothing!

 

Thermal Conductivity – 0.07 W/mK.

 

i believe cellulose is around 0.040W/mK?

4 hours ago, Thorfun said:

not a great lambda value though, but better than nothing!

 

Thermal Conductivity – 0.07 W/mK.

 

i believe cellulose is around 0.040W/mK?

Right - wouldn’t I be better off filling the door with wood shavings or cat litter?

[Thorfun]

1 hour ago, Garald said:

 

Tbh, I like @Conor’s suggestion the best. 
 

3 hours ago, Conor said:

get a new door.

 

[Garald]

32 minutes ago, Thorfun said:

Tbh, I like @Conor’s suggestion the best. 
 

 

Wait. Are well-insulated exterior doors affordable elsewhere? Are 4k eur doors a France-only thing?

[Thorfun]

7 minutes ago, Garald said:

Wait. Are well-insulated exterior doors affordable elsewhere? Are 4k eur doors a France-only thing?

4k seems a little excessive. i actually need one as our firedoor to the garage from the house is just a standard internal FD30 door. so i've been thinking about sticking some celotex to it and putting a piece of ply over the top!

 

but i will research "proper" doors but if they're even half of what you say then i will just go with a similar solution to yours.

[Garald]

3cm-thick cork is already not bad, but my girlfriend hates it. What I’m proposing is meant to complement that, though, not replace it.

[Thorfun]

cork seems to have a thermal conductivity of 0.036-0.38 W/mK which isn't too bad. i'd probably still want to put 6mm/9mm ply over the top so i can screw the handle to it so if i'm doing that i might as well stick 25mm PIR which has a thermal conductivity of around 0.023W/mK.

 

that is my current plan unless i can find a reasonably priced proper insulated fire door.

 

 

[Garald]

22 minutes ago, Thorfun said:

cork seems to have a thermal conductivity of 0.036-0.38 W/mK which isn't too bad. i'd probably still want to put 6mm/9mm ply over the top so i can screw the handle to it so if i'm doing that i might as well stick 25mm PIR which has a thermal conductivity of around 0.023W/mK.

 

that is my current plan unless i can find a reasonably priced proper insulated fire door.

 

 

Right, if I knew any carpentry, I might have considered PIR, except putting in PIR is unkind to the fireman who comes to drag out one’s charred remains.

 

Also, bare cork does not look that bad if you are not my girlfriend. Bare anything else is not really an option.

Edited November 13 by Garald

[Thorfun]

24 minutes ago, Garald said:

unkind to the fireman who comes to drag out one’s charred remains

if they're coming in through the garage and then in to the house rather than the multiple other entrances then there's something much worse happening!

[SteamyTea]

18 hours ago, Garald said:

How would I get the tiny polystyrene balls in

With difficulty as they probably have a different electrical charge to the door.

Have been told that graphite coated PS balls 'flow' better, but I have no personal experience.

Edited November 13 by SteamyTea

[Iceverge]

1 hour ago, Garald said:

Also, bare cork does not look that bad if you are not my girlfriend. Bare anything else is not really an option.

 

 

This sentence feels likes it's only a slight spelling mistake from @Pocster levels of innuendo. 

 

Back to the door. The simplest thing I can think of is to buy some more adhesive backed cork tiles and fit them as neatly as you can. 

 

Or a far greater concern would be and draughts so make sure it seals excellently. 

[Pocster]

32 minutes ago, Iceverge said:

 

 

This sentence feels likes it's only a slight spelling mistake from @Pocster levels of innuendo. 

 

Back to the door. The simplest thing I can think of is to buy some more adhesive backed cork tiles and fit them as neatly as you can. 

 

Or a far greater concern would be and draughts so make sure it seals excellently. 

Ah yes ! I’ve plucked a few corks in my time .

Always smell them to check they’re fresh .

If good ; ram the bugger in 👍🍾🥳🤠😝

[Garald]

2 hours ago, Thorfun said:

if they're coming in through the garage and then in to the house rather than the multiple other entrances then there's something much worse happening!

 

Oh, this is a metal door leading directly to the (now rather cold) courtyard. That's why I am so obsessed with insulating it well! The room used to be a laundry - now it's my parents' studio when they visit.

 

1 hour ago, Iceverge said:

Back to the door. The simplest thing I can think of is to buy some more adhesive backed cork tiles and fit them as neatly as you can.

 

Oh, I've got plenty of adhesive-backed cork. As I said, there's a 2cm-thick layer and then a 1cm-thick layer on the door by now. I'm not sure I can put on any more without making the door even odder-looking and hard to close. That's why I'm wondering what to put inside the door.

 

1 hour ago, Iceverge said:

Or a far greater concern would be and draughts so make sure it seals excellently. 

 

Yes. Someone came with a fan door last week and pointed out some weak spots in the weather-stripping - just fixed it I think. I've also had to pare down the cork a bit with a utility knife to make sure the door closes well and the cork doesn't come off.

 

[Thorfun]

Had a thought (which I’m now considering) can you use expanding foam injected in through a hole or two? 

[Garald]

2 hours ago, SteamyTea said:

With difficulty as they probably have a different electrical charge to the door.

Have been told that graphite coated PS balls 'flow' better, but I have no personal experience.

Here are some examples of graphite- and non-graphite-coated balls:

https://www.leroymerlin.fr/produits/materiaux/isolation/plaque-polystyrene/polystyrene-expanse/250-litres-billes-de-polystyrene-m1-anti-feu-isolation-poly-xpansion-85633522.html

https://www.materiaux-naturels.fr/produit-decl/5798-billes-isolantes-polystyrene-graphitees-200-litres

The problem of graphite-coated balls is that they catch fire quickly (within a metal door, would that be a non-issue or a death trap?)

 

The other issue is that one apparently needs some sort of gun to blow them in, though that doesn't seem to be necessarily all that every expensive:

 

https://www.materiaux-naturels.fr/produit/1238-pistolet-propulseur-de-billes-isolantes

 

I guess the manically consistent choice would be to blow in cork bits. The cork bits from materiaux-naturels seem too large (the "pistolet" works only with spheres up diameter up to 2mm), and even those from here may be:

https://www.natureliege.fr/granulat/6-granulat-de-liege-naturel-en-vrac-pour-l-isolation-thermique-et-acoustique.html#/268-epaisseur-2_a_5mm/696-conditionnement-sac_de_100l

 

Of course cork gives only 3/4 the insulation of polystyrene, but it's probably wiser to have a bag of cork rather than a bag of polystyrene in the garage.

[Garald]

29 minutes ago, Thorfun said:

Had a thought (which I’m now considering) can you use expanding foam injected in through a hole or two? 

 

This is going to be awkward: I don't think it's going to work unless I either remove the cork panels first (no thanks) or drill holes at the top of the door (and take the door off its hinges, which I also don't want to do).