Door insulation redux

[Garald]

I have two metal doors, one leading to a common corridor, the other one leading to a courtyard. Since they were installed by a previous owner, I have no information on whether there is any insulation inside, but there can't be much. I want to know how to improve insulation by attaching fabric or other materials to the door.

 

If I understand correctly, there are basically two effective things one can do (since one needs much more thickness for effective insulation of a more conventional kind):

a) convection barriers,

b) reflective material (basically, "space blankets")

 

What I have so far:

1) door seals/gaskets (work rather well - before, one could clearly feel a draft by wetting the back of one's hand and putting it on the door's edges on a cold day),

2) a Moondream thermal curtain, beige and ugly as sin,

3) on the corridor door, a William Morris curtain, with lining pocket still empty.

 

Notes:

- I used to think that 2) was just an overpriced curtain, but now I realize it must have a space blanket inside (since it is 99.99% polyester and 0.01% aluminium)

- My parents and my girlfriend dislike both curtains, but 2) in particular, for non-identical reasons: my parents associate curtains on doors with extreme poverty, whereas the gf associates it with windows in Amsterdam brothels. Go figure.

 - My parents suggest https://www.amazon.fr/magnétique-thermique-Phonique-Isolation-extérieure/dp/B0BJ2XZDKR/ref=pd_lutyp_ci_mcx_mr_typ_d_d_sccl_1_2/258-6865142-2480719?pd_rd_w=7ub4t&content-id=amzn1.sym.7c1a512f-46a9-459c-9fcb-1c7b8864b865%3Aamzn1.symc.0e04ee4a-2b8c-44d8-b829-f6d01bf2800a&pf_rd_p=7c1a512f-46a9-459c-9fcb-1c7b8864b865&pf_rd_r=N33HFZP7ZADRK8GC1NFX&pd_rd_wg=XQmgG&pd_rd_r=54d45237-debc-459e-99e3-f2e1671ffab7&pd_rd_i=B0BJ2Z21VL&th=1&fbclid=IwAR2FUPTW2ARERdP9w81MtLRnG52fcKpLXomTXWRJzkMZSfYTYcW1Ro1bROE (which looks like a (heavy?) cotton curtain made for doors, nothing more)

 

As I see it, I can do two things:

- cover up the Moondream thermal curtain with that thing from Amazon

- line the William Morris curtain with a space blanket, getting a local sewing shop to sew it into place (can space blankets be washed?).

 

Comments?

 

 

 

[Russell griffiths]

My neighbour has just done something similar 

ugly steel security door, drilled it full of 10mm holes and pumped in 3-4 cans of expanding foam, he then screwed oak tongue and groove boards to the face, it now looks like an old farm door, he had to add timber to the frame and pad out the architrave. 

It looks better than I probably described it. 

[SteamyTea]

Basically, reflecting thermal energy is not going to be very good, so that only leaves you with the option to add some sort of sheet insulation material.

Or maybe fused silicone (aerogel).

If you have the option to add thickness to the door, even 20mm of phenolic is going to help.

Post up a picture and see what the creative minds can come up with.

14 hours ago, Garald said:

parents associate curtains on doors with extreme poverty

When I was a kid back in the 1960s, we lived in Holland, many of the houses/flats has rugs on the wall.  This was a response to the Hongerwinter 20 years before.

If I see rugs on walls now I see it as an act of defiance rather than poverty.

 

14 hours ago, Garald said:

the gf associates it with windows in Amsterdam brothels.

 

Never seen an Amsterdam one, but passed by a lot of Den Haag ones.  There was a brothel at the end of our street.  When my parents needed a babysitter, that is where the girls came from.

[Garald]

2 hours ago, SteamyTea said:

Basically, reflecting thermal energy is not going to be very good,
 so that only leaves you with the option to add some sort of sheet insulation material.

Or maybe fused silicone (aerogel).

If you have the option to add thickness to the door, even 20mm of phenolic is going to help.

 

I thought reflecting thermal energy and stopping convection were the only thing one could do with trivial thickness. Is 2cm of anything (that is, anything other than a vacuum) really going to help more? (I thought phenolic should be used only on the outside, due to potential toxic emissions? Of course for all that I know there may already be phenolic inside the door.)

 

2 hours ago, SteamyTea said:

Post up a picture and see what the creative minds can come up with.

 

Here's the beige curtain that most likely has a space blanket within it, as part of the lining.

 

 

OK, OK, if I keep this ugly beige curtain, I'll have its bottom part hemmed. Behind it:

 

 

OK, this second picture is so out of focus that you can barely see the new seals on the side and on the bottom. They help.

 

The same kind of door is hidden behind this nicer-looking curtain:

 

 

 

 

2 hours ago, SteamyTea said:

When I was a kid back in the 1960s, we lived in Holland, many of the houses/flats has rugs on the wall.  This was a response to the Hongerwinter 20 years before.

If I see rugs on walls now I see it as an act of defiance rather than poverty.

 

I think my parents are thinking not of "improvised supplementary insulation" but of "the landlords are too cheap to pay for doors, so they put curtains instead".

 

2 hours ago, SteamyTea said:

Never seen an Amsterdam one, but passed by a lot of Den Haag ones.  There was a brothel at the end of our street.  When my parents needed a babysitter, that is where the girls came from.

 

That sounds like the beginning of many an interesting story.

 

Edited January 1 by Garald

[SteamyTea]

So basically you have a flat panel door, can you stick a sheet of insulation on it without making it look silly?  May need some hinge/frame/trim modification to help the looks.

 

37 minutes ago, Garald said:

an interesting story

Are they brothel creepers.

[Garald]

1 minute ago, SteamyTea said:

So basically you have a flat panel door, can you stick a sheet of insulation on it without making it look silly? 

 

That's the challenge, isn't it? You'd think that would be standard by now. I wonder why one can't just get it on IKEA or Amazon.

[SteamyTea]

8 minutes ago, Garald said:

Amazon

This one has a U-Value of 1.3 .m^-2.K^-1

 

https://www.amazon.co.uk/VidaXL-Anthracite-Front-Door-Anti-Burglar/dp/B0CQWR99ZP

 

Or for a tenth of the price, the padded cell look.

 

Edited January 1 by SteamyTea

[Garald]

5 minutes ago, SteamyTea said:

This one has a U-Value of 1.3 .m^-2.K^-1

 

https://www.amazon.co.uk/VidaXL-Anthracite-Front-Door-Anti-Burglar/dp/B0CQWR99ZP

 

I meant insulation that can be added to an existing door without making it look silly, not a new door.

 

I think I've seen (non-obviously-silly) insulation padding on the inside of front doors in Moscow, so it exists.

Edited January 1 by Garald

[Russell griffiths]

What about the look of a gentleman’s library 

dark maroon leather in a diamond or hexagonal pattern. 

[Ferdinand]

If it is a rented property, are there limitations on what and how you can attach things to the door?

 

Can you use something like Aerogel blanket (ie Spacetherm or similar) for your layer on the door face and then one of the suggestion above as a cover? Aerogel blanket is available in self-adhesive form, I believe - if you look around.

[Garald]

3 hours ago, Russell griffiths said:

What about the look of a gentleman’s library 

dark maroon leather in a diamond or hexagonal pattern. 

 

Sure, would be nice, but where to get it?

[Russell griffiths]

 

 

how about this. 

[SteamyTea]

52 minutes ago, Russell griffiths said:

 

 

how about this. 

I was going to google 'tufting', but thought better of it.

[Garald]

5 hours ago, Ferdinand said:

If it is a rented property, are there limitations on what and how you can attach things to the door?

 

Ah, I see, someone here I haven't yet bored to death with my neverending renovation stories. No, it ia not a rented place :).

 

5 hours ago, Ferdinand said:

 

Can you use something like Aerogel blanket (ie Spacetherm or similar) for your layer on the door face and then one of the suggestion above as a cover? Aerogel blanket is available in self-adhesive form, I believe - if you look around.

 

Is Aerogel safe and flexible enough that it can be used as a curtain lining (where it might be partially exposed, unless it comes already hermetically enclosed in something)? I thought silica could be a bit problematic over time. I've just read that aerogel fabrics are now a thing, but it's unclear to me whether they are already in the market.

 

But yes, I guess aerogel blankets could make sense behind sealed tufting. Should I wear a mask while cutting them? Is that enough?

[Garald]

1 hour ago, Russell griffiths said:

 

 

how about this. 

 

Right  - where can one get this sort of thing?

[Garald]

(... for a reasonable, clearly stated price?)

[SteamyTea]

12 hours ago, Garald said:

Aerogel

Forget Aerogel, it is not the product for here.

Space Shuttle tiles and nuclear reactors maybe, in the domestic setting, no.

[Garald]

17 minutes ago, SteamyTea said:

Forget Aerogel, it is not the product for here.

Space Shuttle tiles and nuclear reactors maybe, in the domestic setting, no.

 

Tufting gives one enough space for (much cheaper) polyurethane mousse. Of course the price of aerogel seems to be itself less than labor costs.

 

Here is a DIY kit - not of the right dimensions for me (I have a taller door), and quite frustratingly no technical specifications are given for those 5cm of mousse:

https://www.swaldeco.com/fr/boutique/kit-design-porte-capitonnee-blanc?fbclid=IwAR2BTgRM-87kHG1D3LFfetr2b_RnEaU9JQRPqhglEF40n6mPzwoNqGpmHTM

(Price of kit: 413 eur)

 

Apparently, having this sort of thing done by a decorator costs in the order of 1400-1700eur - not much less than a new door.

https://rideaux-stores-tapissier-decorateur.over-blog.com/isolation-phonique-etude-notariale-sevres.html

 

I'll shop around. This sort of thing seems to be advertised mainly for sound insulation - itself a very good thing, since the heat pump external unit is on the other side (though it's audible only when working at full steam). OTOH the kind of insulation that people have in mind may be mainly in the other direction, viz., privacy - notice how the clients mentioned in the blog above are psychiatrists and lawyers.

 

https://www.isol-bruit.net/portes

 

From a purely technical perspective, what should I insist on, then - fireproof polyurethane foam surrounded by reflective material "space blankets") on both sides?

Edited January 2 by Garald

[Adrian Walker]

13 hours ago, Garald said:

 

Ah, I see, someone here I haven't yet bored to death with my neverending renovation stories. No, it ia not a rented place :).

 

 

Is Aerogel safe and flexible enough that it can be used as a curtain lining (where it might be partially exposed, unless it comes already hermetically enclosed in something)? I thought silica could be a bit problematic over time. I've just read that aerogel fabrics are now a thing, but it's unclear to me whether they are already in the market.

 

But yes, I guess aerogel blankets could make sense behind sealed tufting. Should I wear a mask while cutting them? Is that enough?

Aerogel is not flexible or affordable for this application. 

[SteamyTea]

There are a couple of ways to think about insulation.

 

It stops thermal transmittance by physically stopping warm material moving to colder material.  This is often called convection.  This is why windows are not very good, you want light to pass though but not thermal energy.

The key to that part is the size of voids in the material, the smaller the voids (bubbles) the less movement is possible, but you get a greater ratio of solid material that may, or may not, have a higher thermal conductivity and a different heat capacity.

 

The other way to think about it is at the sub atomic level.

When a material is heated, the electrons become 'loose' and can eventually instantaneously jump up to the next electron orbital shell.  If there is a space there for the electron, then there is no change in temperature, if there isn't a space, then, because of the exclusion law, the electron has to loose energy so that it can drop back down to the original orbit.  When an electron does this, it instantaneously changes to a photon, then back to an electron, at the lower energy level.  The excess energy that it had is released as radiation, which flies off following the sum of all possible paths until it interacts with the next electron, and the process starts all over again.

 

So apart from physically stopping 'hot' material moving, all thermal conductance is actually a radiative forcing.  This is why, in isolation, reflective materials can act as insulators, except the photoelectric affect allows some energy though the material and re-radiate somewhere else.

 

In the case of 'normal' insulation, the key points are the void to material ratio, and their heat capacities (air is 1 J.gm^-1.K^-1, Polyurethane is 1.6 J.gm^-1.K^-1 and Phenolic 1.5 J.gm^-1.K^-1) and conductivities (Air is ,0.022 W.m^-1.K^-1 Polyurethane is 1.6 W.m^-1.K^-1, Polyurethane is 2.9 W.m^-1.K^-1, Phenolic is 1.45 W.m^-1.K^-1).

The above numbers would imply that just an air gap is pretty good, but the problem with that is that air can move because of thermal expansion, which causes density changes, which causes movement.

 

The above is not the whole story, and there is a lot more to it that I have tried to explain (if it was simple to explain, we would all know it).

 

Have you got an infrared thermometer to see what the temperature difference is across the door.  You may find it is not as great as you think.

I have just looked at my temperature differences, it is 13.4°C outside and 18°C inside.  That part of the door is 44mm of pine.  The larger recessed panel is at 12.5°C outside and 15.7°C inside and is 20mm thick.  The glass is at 10.7°C outside and 13.6°C inside, overall the double glazed unit is 24mm thick.

If I have got my arithmetic right (very likely it is wrong), that works out at:

 

At the current temperature differences (12 K)

Thicker timber Losses 4.9 W.m^-2.K^-1.

Thinner Panel Losses 15.6 W.m^-2.K^-1.

Glazing Losses 14.4 W.m^-2.K^-1.

 

Working out the areas, thicker frame is 0.625m², Thinner Panel 0.335m² and the Glazing 0.62m².

Work that lot out and it comes to 17.2 W

That makes my door have an overall U-Value of 1.44 W.m^-2.K^-1.  If the temperature stays about the same all day, that is 0.035 kWh/day.  10p/day at current electricity rates, so about £10/year extra on my bill.

Not brilliant in todays terms, but it is 37 years old.

 

 

Edited January 2 by SteamyTea

[Garald]

On 02/01/2024 at 10:09, SteamyTea said:

 

 

Have you got an infrared thermometer to see what the temperature difference is across the door.  You may find it is not as great as you think.

 

 

 

 

Just measured the temperature differences with a new infrared thermometer. (I've tried calibrating it against the inside of my fridge, but it still seems to lean towards the cold side; when applied to my skin, it gives me readings around 28.5C, which would imply I am dead.)

First reading:

The temperature on the outside of the door curtain is exactly the same as that on the wall next to it: 15.5C

The temperature on the inside of the metal door (behind the curtain) is 7.5C.

The temperature on the other side of the metal door is -2.5C.

 

Second reading (just went back downstairs):

Temperature on door curtain = temperature on wall = 18C

Temperature on the inside of metal door = 10.5C

Temperature on the outside of metal door = -0.5C

 

According to the weather report, the current outside temperature in the area is -2C.

 

Not sure what one can deduce from these figures alone - other than that the R value of the curtain (a fairly thick but not magical polyester curtain with a space blanket inside, from what I can deduce) is between 70 and 80% of the R value of the metal door. 

Edited January 9 by Garald

[Garald]

On 02/01/2024 at 10:09, SteamyTea said:

 

 

Have you got an infrared thermometer to see what the temperature difference is across the door.  You may find it is not as great as you think.

I have just looked at my temperature differences, it is 13.4°C outside and 18°C inside.  That part of the door is 44mm of pine.  The larger recessed panel is at 12.5°C outside and 15.7°C inside and is 20mm thick.  The glass is at 10.7°C outside and 13.6°C inside, overall the double glazed unit is 24mm thick.

If I have got my arithmetic right (very likely it is wrong), that works out at:

 

At the current temperature differences (12 K)

Thicker timber Losses 4.9 W.m^-2.K^-1.

Thinner Panel Losses 15.6 W.m^-2.K^-1.

Glazing Losses 14.4 W.m^-2.K^-1.

 

 

 

Actually, how do you find the losses given just the two temperatures? Or do you need to know the conductivity of the material beforehand?

[SteamyTea]

8 minutes ago, Garald said:

 

Actually, how do you find the losses given just the two temperatures? Or do you need to know the conductivity of the material beforehand?

You know the thickness and surface area as well, so starting with the thermal conductivity, k = W.m^-1.K, and resistivity R = L / k (where L is thickness in metres) you can rearrange to make W the subject.  Once R is known, U-Value can be calculated U = 1/R, losses then calculated by incorporating the area A.

 

Marks will be deducted for failure to show your workings.

 

(and I did say, as I always do, that I may have made an error)

Edited January 9 by SteamyTea

[Garald]

16 minutes ago, SteamyTea said:

You know the thickness and surface area as well, so starting with the thermal conductivity, k = W.m^-1.K, and resistivity R = L / k (where L is thickness in metres) you can rearrange to make W the subject.  Once R is known, U-Value can be calculated U = 1/R, losses then calculated by incorporating the area A.

 

Marks will be deducted for failure to show your workings.

 

(and I did say, as I always do, that I may have made an error)

 

Right, then it's easy. The problem is that I have no idea of what is inside the metal door - a void, insulation, what exactly? (It was installed by the owners before the previous owners.) Surely there has to be a way to figure out k or R from empirical data alone - what data do we need to collect?

[SteamyTea]

1 minute ago, Garald said:

The problem is that I have no idea of what is inside the metal door

You can look at a list of k values and take a guess.  See how well it fits.

https://www.engineeringtoolbox.com/thermal-conductivity-d_429.html