Vacuum Insulated House (Not V.I.P.'s, instead like a vac flask)

#1

Is it possible to vacuum insulate a house in the same style of a vacuum insulated flask?

vacuum%20insulated%20flask

For example,

I’m not sure what thickness of metal would be necessary to hold a vacuum of that size… Maybe a fan could recreate the vacuum when it leaks eventually? The simplicity & effectiveness of the vacuum flask is fascinating to me.

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#2

Not sure how realizable that approach would be for an entire house, but Panasonic makes vacuum insulating panels that deliver R-60 per inch:

https://na.industrial.panasonic.com/products/hvacr-appliance-devices/vacuum-insulation/vacuum-insulation-panel

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#3

I was imagining a vacuum insulated tiny house. The walls would be two pieces of metal with a vacuum in-between and that’s it. The wall thickness I chose was 1.5" (it looks thicker because I added a layer for plumbing and electrical to flow through) with two 1/4" thick pieces of metal with a 1" vacuum in-between. I agree it’s possibly not realizable, but I think it’d be cool if we figured out a way…

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#4

When you remove the air inside the panels, the outside air pressure presses on them with 14.7 pounds per square inch (at sea level). This means that a 12" x 12" panel would need to support some 2,000 pounds to keep it from collapsing. If you add in supports, then the material making up the supports conducts the heat in or out of the system, decreasing the effectiveness of the vacuum. Pressurizing it with CO2 to offset the atmospheric pressure will provide about 30% better insulation than an air gap.

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#5

If I could have downloaded your model, I would have changed the standing guy to one crumpled on the floor. If the air had been sucked out, he would not be standing quite as confidently as he is.

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#6

I suspect that the common “vacuum insulated flask” has only a partial vacuum between the walls, else it would also collapse. Since Dewar bottles (the technical name for a vacuum insulated flask) have been used for a long time, I would suppose that someone sometime made a study of the insulation value vs the partial pressure (and maybe specific gas) used in the cavity.

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#7

read about http://www.double-glazing-info.com/Choosing-your-windows/Air-or-Argon-gap

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#8

And so do Kingspan (see here). I would like to know how such panels avoid collapsing inwards. My guess is that there is some kind of waffle like structure made of low conductivity material. This system has its uses when insulation thickness is at a premium but it also has some significant problems, including cost.

You obviously cannot fix through a VIP, so in sandwich construction, you must separate panels by another material that can be penetrated, creating an inevitable cold bridge. Also, there is no way of knowing if a panel has been breached (say by a tiny pinhole) and having something as delicate as a VIP on a building site means that a lot of specifiers would not trust it.

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#9

The power loss due to thermal conductivity is:

P = k * A * ΔT / d

where k is the thermal conductivity, A is the area of a panel or wall, ΔT is the inside/outside temperature difference (in °C or °K), and d is the thickness of the thermal barrier. To keep losses to a minimum, use a material with a low k value and make it (d) as thick as possible.

On the k side of things, here are some typical values for many materials (somewhere around 0.02 or less is desirable):

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

Note that some of the ones with the lowest values are unfortunately corrosive, flammable, and/or prohibitedly expensive.

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#10

Combining the most recent posts by @Bep and @jimhami42, you might conclude that it would be better to consider a gas filled void rather than a vacuum.

Kingspan’s VIPs have a declared R value of 0.007. Impressive but that may be for the panels themselves rather than a whole roof (say). That is because you cannot cover the whole area with butted VIPs.

Xenon has a R value of 0.005. This is a gas that is used in high spec glazing (not to mention headlights) and has one of the lowest R values of any material, barring perhaps the latest aerogels.

Whilst you could in theory conceive of a double skinned shell made of metal (say) with a gas-filled cavity, the challenge then would be getting sufficient rigidity, especially when fitting other components like windows and doors. Appliances like fridges and freezers are presumably made a bit like this but with something like a urethane foam insulation core.

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