This $120 Thermal Flywheel Wall Holds Heat 72 Hours — The Soviet Secret Banned in USA

Added: 2026-05-09

[00:00:00]By the time this video ends, you will know exactly how to build a wall inside your home that absorbs heat during the day and releases it slowly for 72 full hours with no furnace running, no firewood burning, and no electricity consumed. Not 6 hours, not 12 hours, 72 hours. I will give you every material, every measurement, every layer, and every calculation step-by-step.

[00:00:24]Soviet engineers in Novosibirsk perfected this system in 1959 for housing in regions where temperatures dropped to -58° Fahrenheit, -50° Celsius. Their test buildings held interior temperatures above 62° Fahrenheit, 16.7° Celsius, for 3 full days after all active heating was cut off completely. The US Department of Energy published a translation of that Soviet research in 1977.

[00:00:50]14 months later, that translated document was reclassified and pulled from public circulation. The original Soviet designation was NIIZhF report 41-C.

[00:01:01]It has never been reissued.

[00:01:03]What you are about to learn is exactly what was in it. Stay until the end. The final 2 minutes explain why this never appeared in a single American building code and who made sure of that. This system is called a thermal flywheel wall. Every material has a specific heat capacity, the energy it stores per kilogram per degree of temperature rise.

[00:01:22]Dense concrete holds 880 joules per kilogram per degree Celsius. Standard brick holds 840 joules. Rammed earth holds roughly 1,000 joules. A wall built from dense brick, 12 in 305 mm thick, 8 ft 2.4 m tall, 10 ft 3.05 m wide, contains approximately 1,800 kg of thermal mass. Heated from 50° Fahrenheit to 80° Fahrenheit, 10° Celsius to 26.7° Celsius, that wall stores around 53 million joules, 14.7 kWh of heat. Enough to warm a 400 square foot, 37.2 square meter, room for 60 to 72 hours in mild winter conditions with no additional heat input. That is not a claim, that is arithmetic. The Soviet design added one sheet of tempered glass mounted 3 in 76 mm in front of the mass wall creating an air gap that acts as a solar collector during daylight and a buffer at night.

[00:02:22]Heat moves slowly through 12 in 305 mm of brick arriving at the room facing surface 36 to 60 hours after the sun went down. That time delay is the flywheel effect.

[00:02:34]Materials list, total cost $95 to $130.

[00:02:38]Dense reclaimed brick, 60 to 70 standard bricks, cost $35 to $55. Always choose reclaimed over new, denser, higher thermal mass, and free of air entrainment additives that reduce heat storage. Two 60 lb 27.2 kg bags of type S mortar, cost $14 to $18. One tempered glass panel, 34 in by 80 in 864 mm by 2032 mm. Standard door replacement glass, cost $28 to $40. 8 ft 2.4 m of 2 by 4 lumber with four 90° metal corner brackets, cost $9 to $14.

[00:03:20]One quart of flat black exterior masonry paint, cost $8 to $12. This is not decorative. It is the system's solar engine. Two standard 4 in x 10 in 102 mm by 254 mm register grills with damper blades, cost $6 to $10. Total $100 to $149 at reclaimed pricing. You will also need a trowel, spirit level, circular saw, drill, silicone sealant, rigid foam offcuts, and L brackets. Step one, wall location.

[00:03:54]The thermal flywheel wall must face south on the interior side of your southernmost exterior wall. The winter sun tracks low in the southern sky with peak solar exposure between 10:00 a.m.

[00:04:04]and 3:00 p.m.

[00:04:05]Every degree away from true south reduces collection efficiency by roughly 2%. Up to 20° east or west is acceptable. The exterior wall behind your mass wall must have a window or you must cut one. Sunlight must reach the dark mass wall surface through the glass layer during daylight hours. No direct sunlight access means no thermal charging and no 72-hour heat delivery.

[00:04:28]Mark your build footprint. 10 ft 3 m wide, 8 ft 2.4 m tall, 12 in 305 mm deep. Load check. The mass wall weighs approximately 1,800 lb 816 kg. On a concrete slab, no concern. On a wood floor above a basement, install a support beam directly beneath the footprint before laying a single brick.

[00:04:52]Step two, laying the mass wall.

[00:04:56]Mix type S mortar to peanut butter consistency. Holds a peak when you pull the trowel. Too wet and it compresses under brick weight. Too dry and it will not bond. Lay a 3/8 in 9.5 mm mortar bed along your 10-ft 3.05 m floor line. Set your first course in soldier orientation, bricks standing on their long edge, widest face toward you. This maximizes thermal mass depth per course.

[00:05:23]Check plumb every third course. A wall out of plumb develops cracks within two heating seasons. A cracked wall loses 15 to 25% of thermal storage capacity through internal air infiltration.

[00:05:35]Butter each vertical head joint fully, no gaps. Air pockets inside the wall act as insulation, which sounds useful but prevents heat from penetrating the full mass depth. You want a solid monolithic thermal block. Let each course set 45 minutes before laying the next. Below 50° F, 10° C, tent the wall with plastic sheeting for 24 hours to prevent mortar freezing before full cure. Built to 8 ft, 2.4 m, approximately 14 soldier courses. Allow 48 hours full cure before proceeding.

[00:06:07]Step three, painting the mass.

[00:06:11]Apply two coats of flat black masonry repaint to the entire south-facing surface. A flat black surface has solar absorptance of 0.95 to 0.97, capturing 95 to 97% of incoming solar radiation and converting it to stored heat.

[00:06:27]Unpainted red brick absorbs only 60 to 70%. That gap determines whether your wall delivers 48 or 72 hours of heat from one day of sunlight. Allow 24 hours between coats.

[00:06:41]Step four, vent holes.

[00:06:44]Cut two vent openings in the mass wall.

[00:06:46]One at floor level, 4 in by 10 in, 102 mm by 254 mm, centered horizontally.

[00:06:54]One identical opening at ceiling level, also centered. During daylight, solar radiation heats the air in the 3-in 76-mm gap. Hot air rises and exits through the upper vent. Cooler room air enters through the lower vent. This convective loop delivers 85° F to 100° F, 29.4° C to 37.8° C air into the room at zero operating cost while the sun is up.

[00:07:22]At sunset, close both damper grills.

[00:07:25]This stops reverse thermosiphoning. The cooler overnight air gap would otherwise pull room heat back out through the glass. Closed vents force stored heat to move slowly through the wall into the room. That is your 72-hour delivery mechanism. Install grills with dampers facing you so you can operate them by hand. Step five, glass frame and installation.

[00:07:46]Build a rectangular 2 by 4 lumber frame to hold your tempered glass panel. Use 90° metal brackets at each corner secured with 2.5-in 63-mm wood screws.

[00:07:57]Interior frame dimensions must match the glass panel exactly. Mount the glass using clear silicone sealant along all four edges, no mechanical fasteners.

[00:08:06]Tempered glass fractures under point stress. Silicone distributes load across the full edge. Stand the framed panel 3-in 76-mm in front of the painted mass wall.

[00:08:16]Anchor the base to the floor with two L brackets and the top to a ceiling joist or stud with two more.

[00:08:22]Seal the 3-in 76-mm gap perimeter, top, bottom, and both sides with rigid foam board cut to fit, silicone sealed in place. Leave only the two vent openings unblocked. Sealing the perimeter stops cool room air from short-circuiting the convective loop. Step six, charging and testing.

[00:08:42]On your first clear sunny day, open both vents at 9:00 a.m. and leave them open until 4:00 p.m.

[00:08:48]A probe thermometer in the air gap should read between 90° Fahrenheit and 130° Fahrenheit, 32.2° C and 54.4° C, even when outdoor temperature is as low as 20° Fahrenheit, -6.7° C.

[00:09:05]At 4:00 p.m., close both vents. The wall is charged. The room-facing surface will begin to feel warm between 36 and 40 hours later. Peak heat delivery occurs between 36 and 60 hours after charging.

[00:09:17]That is the flywheel effect operating exactly as the Soviet engineers documented. If air gap temperature stays below 75° Fahrenheit, 23.9° C, on a clear day, you have a perimeter leak. Reseal all four foam strips with fresh silicone and retest.