Florescent (and incandescent) lightbulbs are typically discarded and their residue is added to landfill waste, or illegally discarded, but in their original form, the vacuum (space) they contain is a highly valuable insulating component available to improve the insulation of existing buildings and of new buildings. The thermal conductivity of a perfect vacuum is many times less than the thermal conductivity of fiberglass insulation or rockwool or foam panels conventionally used to insulate homes and commercial buildings.

By re-use of discarded florescent tube light bulbs, we are able to inexpensively approximate a "Vaccuum insulated panel" (VIP)

The thermal resistance of VIPs per unit thickness compares very favourably to conventional insulation. Commercially available VIPs achieve a thermal conductivity of 0.004 W/(m·K) across the center of the panel, or an overall value of 0.006-0.008 W/(m·K) after allowing for thermal bridging (heat conduction across the panel edges) For instance, standard mineral wool has a thermal conductivity of 0.044 W/(m·K),[4] and rigid polyurethane foam panels about 0.024 W/(m·K). This means that conventional VIPs have about one-fifth the thermal conductivity of conventional insulation, and therefore about five times the thermal resistance per unit thickness. Based on a typical k-value of 0.007 W/(m·K), the thermal resistance of a typical 25 mm-thick (one-inch thick) VIP would be 3.5 m2·K/W (20 h·ft²·°F/BTU). To provide the same thermal resistance, 154 mm (six inches) of rockwool or 84 mm (three inches) of rigid polyurethane foam panel would be required.

Fiberglass offers an R-value of 2.2 to 2.7 per inch, while rock wool has an R-value of 3.0 to 3.3 per inch, making it a slightly better insulator than fiberglass. Rock wool rated at R-15 and designed to fit a 4-inch wall costs $0.62 per square foot as of 2013. In 2012, Kingspan Insulation launched OPTIM-R™ which offers an R-value as high was R-56 for a 2 inch panel thickness.

Vacuum insulated panels were first seen in commercial applications such as refrigerators, freezers and cold shipping boxes. The outstanding thermal performance of VIPs is able to provide the thinnest possible solutions to a number of temperature-controlled applications. VIPs have, more recently, been seen in building applications as more stringent regulations have come into place.

However, the price per unit of thermal resistance of conventional VIPs is much higher than that of conventional materials. A conventional VIP is typically filled with a rigid, highly-porous material, such as fumed silica, aerogel, pearlite or glass fiber, to support the membrane walls against atmospheric pressure once the air is evacuated. An adhesive is typically used to seal the thin envelope, but the adhesive can fail and allow air to enter the vacuum of the VIP and degrade its thermal performance. The cost of conventional VIPs has generally kept VIPs out of traditional housing situations but their very low thermal conductivity makes them useful in situations where either strict insulation requirements or space constraints make traditional insulation impractical.

The Department of Energy recommends an R-value of 13 to 15 for walls in Zone 3, with an R-value of 30 to 60 in the attic. These new tube-based VIPs can help achieve these high R values within existing dimensional constraints. The US Department of Housing and Urban Development began research to evaluate the market potential for the use of vacuum insulated panels in residential buildings. The research concluded that VIPs have become a ‘feasible and important’ means for designing energy efficient buildings.

What it does

The present invention uses the inherent strength of the cylinder form of glass (e.g., inexpensively available from discarded post-consumer florescent lamp tubes) to provide an all-glass vacuum tube, multiples of which can be combined in an linear array to provide a VIP that has low thermal conductivity and that is well-proven to be inherently resistant to air infiltration.

A linear array of post-consumer florescent tubes (PCFTs) according to an embodiment of the invention is also translucent to ambient light (sunlight) which provides an opportunity to leave the interior and exterior wall translucent so that natural sun light can illuminate interior spaces through the wall. (A protective shell (e.g., glass plate) on the exterior and plastic or glass light-diffusing interior plate is presumed).

How I built it

Assembled post-consumer florescent tubes (PCFTs) in a plane forming a panel (or double-layer, triple-layer stacked arrays) within the dimensional constraints of an existing building wall space.

Challenges I ran into

Most post-consumer florescent tubes are nominally "four feet" long. But, wall cavities are often less than or more than 8 (2 x 4) feet. However, post-consumer florescent tubes are available in many lengths, such as 1 foot, 2 foot,3 foot, 4 feet and 8 feet long, and can be installed to reasonably fill the existing dimensions.

Pre-installation removal of the minute quantities of mercury in post-consumer florescent tubes can be achieved during conventional recycling procedures, such as by heat "distilling" of the intact tubes, or chemical injection washing, through one end, before vacuum restoration and resealing.

The recycling of post-consumer florescent tubes can provide LOCAL JOBS for unskilled laborers, and simultaneously provide a reduction of the fossil fuel (heating and air-conditioning) energy consumption of residential and commercial buildings.

Accomplishments here that I'm proud of

Finding ways to save energy, and reduce fossil fuel consumption is very satisfying.

Turning trash into treasure is always satisfying.

What I learned

One man's trash is another man's treasure.

What's next for Spacebased insulation and translucent walls.

Further, modifications of conventional recycling practices can allow for the MODIFICATION of post-consumer florescent tubes (PCFTs) to provide additional functional features of wall-installed PCFTs. The recycling process offers opportunities to add value to PCFTs. For examples:

1) The PCFTs can be cleaned out (phosphor coating removed by gentle sand-shaking), then vacuum restored, and then resealed, to become fully-transparent to natural (sun) light.

2) The in-side of PCFTs can be chemically "mirrored" (e.g., zinc-ed, silvered, after the interior phosphor coating removed), then resealed, and/or relective foil-covered on the in-side and/or out-side of the linear array, to become opaque to natural light and even less transmissive of radiative heat energy.

3) The PCFTs can be modified (mirrored, foiled, inside and outside) to function as "Lyden Jars" for electrical energy (charge, voltage) storage (e.g., reusing the existing through-glass electrodes).

4) The vacuum inside the PCFT can be exploited to provide a zero-humidity "reference" (e.g., calibrating a humidity-dependent dielectric) for an external humidity sensor (e.g., reusing the existing through-glass electrodes). IN-WALL STATUS (e.g., humidity, barometrics) can be monitored (e.g., with umbilical). Modified tubes can operate as barometers, humidistats, thermometers. The data obtained from such modified tubes can be analyzed and used to operate fans and other environmental modifiers.

5) The vacuum inside one or more of the installed PCFT tubes can be accessed by tubules and harnessed as a barometric reference, and therefore employed as a component of an ambient air-pressure sensor.

6) Even "dead" florescent tubes are capable of continuously providing light if a sufficiently-high voltage is applied across their length (or width). Therefore, by wiring unmodified PCFTs to supply a high-voltage power source (e.g., derived from transformer output of a solar PhotoVoltaic DC battery) (or from AC (unrectified) outputs of windmills or microhydro generators), the PCFT can forever provide illumination even after in-wall or in-ceiling installation).

7) Modified PCFT in-wall panels can radiate naturally-obtained ambient light even after sundown (by interior coating of inexpensive conventional glow-in-the-dark materials. Illumination can also be obtained by installing post-consumer recycled "one-hour glow in the dark" lamp tube disclosed at )

8) New structures, such as a "greenhouse" or a "hotbed" for the production of food crops can be constructed from assemblies of PCFTs. The PCFTs are translucent (and potentially transparent) to natural light. The translucent PCFT assemblies can even generate visible light (e.g., using high-voltage power supplied from batteries, or from AC (unrectified) outputs of windmills for extending the natural growing seasons.

8) PCFTs are a "waterproof" insulation material (they do not loose their thermal resistance while or after being submerged in flood water) and they can be installed circumferentially around hot pipes to reduce heat loss. The efficiency and reliability of steam-power transmission lines can be increased by use of circumferential assemblies of PCFTs, such as by reducing heat loss and thus avoiding condensate-related problems (see

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