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# variable thermal conductivity building material

 (+7) [vote for, against]

Properly insulating a house is essential to achieve adequate comfort and efficiency. However sometimes the insulation prevents the desired outside temperature from entering the house (for example if you want the warm afternoon sun to heat your cold house).

So I propose a building block with a thermal conductivity that can be varied.

This block would have three layers: two conductive layers sandwiching an insulating layer. The core of the block would have a hole extending through it (the axis of the hole co-planar with the layers). A cylindrical component would loosely fit in the hole. This cylindrical component would also be made of longitudinally extending layers: two insulating layers sandwiching a conductive layer.

The idea is the cylindrical component can be rotated from an insulating configuration (with layers of the block and the cylinder co-planar) to a conducting configuration (the layers of the cylinder are perpendicular to the block such that the conducting layer of the cylinder forms a conductive path between the conductive layers of the block).

The blocks would be stacked together like bricks (sans the mortar) with the cylinders linking together. The blocks at the ends/corners of the walls would contain a small motor to rotate the cylinders.

The blocks would run on a simple algorithm such as:
Heat mode: IF outside>21 THEN conductive ELSE insulating.

The blocks could also be used in the floor utilising the fact the the ground is about 14 year round.

I'm posting this from my phone in a remote location (Thredbo) so unfortunately I can't provide illustrations.

 — xaviergisz, Dec 16 2009

Trombe walls http://en.wikipedia.org/wiki/Trombe_wall
[DavideAndrea, Dec 16 2009]

Solar collector http://www.motherea...s-Heat-Grabber.aspx
Apparently you can grab your mothers' heat... [bdag, Dec 22 2009]

 Hello, Something like that: a trombe wall with shades (I have seen one here in town).

Wikipedia article on trombe walls: "Fixed or movable shades, which can reduce nighttime heat losses."
 — DavideAndrea, Dec 16 2009

 [+] but, 1. If a cylinder or motor breaks, than what?

2. Also, if these are 10X more expensive then bricks than they would be about \$200/sq ft.
 — leinypoo13, Dec 16 2009

 Your idea is more immediate than a trombe wall which is about thermal storage at certain times and release at other [later] times.

A passive solar designed house would be much cheaper; couldn't you just open a window?
 — scootie, Dec 16 2009

I worry about moving parts. Could one achieve this with pipes? Pipes full of air: insulating. Pipes full of water, conductive, sort of.
 — bungston, Dec 16 2009

 Thermal conductivity of air: 0.025 W/m K

Thermal conductivity of mercury: 8.3 W/m K
 — Wrongfellow, Dec 17 2009

 7 votes for structural English Ivy.

 Hear that Monsanto? There's a virtual goldmine here.

 I personally think a chemical / physics solution to this might prevail.

Galileo thermometers!
 — Zimmy, Dec 22 2009

 [bungston] perhaps pipes full of argon or krypton or perhaps vacated altogether.

Sounds preposterously overcomplicated. Bun for that. Try one of these chaps in the link.
 — bdag, Dec 22 2009

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