Video summary

I tested the effectiveness of cooling gel, EightSleep, BedJet and other cooling beds

Main summary

Key takeaways

Science and Nature

Scientific concepts / nature phenomena presented

  • Heat transfer & thermal insulation

    • Memory foam and foam layers behave as insulators, affecting how quickly heat is dissipated.

  • Thermometry / experimental measurement

    • Use of digital temperature sensors and a Raspberry Pi to collect temperature vs. time data.
    • The experiment tracks the drum water temperature change rate as a proxy for how well each cooling system removes heat.

  • Energy input simulation of body heat

    • A ~100 W cartridge heater is used to mimic the approximate power of human body heat production.

  • Thermoelectric cooling (Peltier modules)

    • “Mattress Cooler USA” uses Peltier modules, described as thermoelectric devices that create a hot and cold side when current is applied.

  • Phase / evaporative cooling (concept)

    • One water-cooled approach mentioned involves blowing air through water so evaporation carries heat away.
    • This is criticized as potentially unsanitary due to dust/mold buildup.

  • Fluid circulation and thermal buffering

    • Water-cooled designs use pumps and water reservoirs to absorb and transport heat.
    • The reservoir’s warm-up over time changes cooling effectiveness.

  • Practical physiology framing (not directly tested)

    • Discussion of how real humans change heat output based on stress, food, exercise, and movement—leading to the choice to reduce human variability.

Key discoveries / conclusions claimed

  • Foam toppers with “cooling gel”

    • Provided only small improvement in the drum temperature rise rate compared with non-cooling foam (within the margin of error).

  • “Cooling mattress” (Temperpedic with cooling gel)

    • Underperformed relative to other options tested.

  • Gel-grid mattress (Purple)

    • Performed best among non-water/other foam systems tested so far (lowest reported drum temperature rise rate).

  • Water-cooled systems vary widely

    • Eight Sleep: showed minimal net cooling under test conditions (drum temperature increased slightly).
    • Chili Sleep: reduced drum temperature more than Eight Sleep (about a quarter-degree per hour stated).
    • Mattress Cooler USA (Peltier + PVC water pad): reported as strongly effective in drum cooling (over 1°C per hour stated).

  • Critical design detail

    • Comfort/temperature perception depends on whether there is foam or a cover layer, not just raw cooling performance.

  • Fans (BedJet / standard fan)

    • Remove heat but are limited by comfort:
      • They blow room-temperature air; drum cooling was reported around ~1°C per hour for BedJet.
      • In real comfort testing, direct airflow to feet reduced perceived comfort.

  • Fan cooling vs heating

    • BedJet is positioned as excellent for heating in winter and for sweat management (drying via airflow/evaporation), even if it is not primarily a cooling solution.

Experimental / methodology outline

  • Problem with simple bed sensors

    • Initial plan: put temperature sensors on the bed and sleep with them.
    • Result: data was “not useful enough” due to human variability (stress, diet, exercise, movement).

  • Heat-simulation setup

    • A large plastic water drum (~15 gallons) acts as a human-torso-scale thermal mass.
    • A ~100 W cartridge heater inside the drum simulates body heat input (claimed ~100 W).
    • An aquarium pump circulates water to reduce internal temperature gradients.
    • Digital temperature sensors monitor:
      • temperature inside the drum (and sometimes room temperature).

  • Preheating

    • Drum is preheated to about body temperature using an SV cooker so the test starts without a long warm-up phase.

  • Comparative testing approach

    • The drum is placed on each mattress/product for hours.
    • The key metric is how the drum temperature changes over time:
      • whether it increases (poor dissipation) or decreases (good dissipation),
      • compared by rate of change across products.

  • Water-cooled comparisons

    • In addition to mattress-integrated systems, a final water-cooled baseline is built:
      • A ~5-gallon plastic bucket pumped through a PVC cooling cover.
      • Designed so the reservoir temperature rises naturally during the night, improving cooling over time.

Researchers / sources featured

  • No specific researchers or academic sources are named.
  • Brands/products referenced (as sources of technology, not researchers):
    • Eight Sleep
    • Chili Sleep
    • Temperpedic
    • Mattress Cooler USA
    • Purple
    • Beautyrest (sleep tracking mention)
    • BedJet
    • Hybrid Premiere / Restore Hybrid / Chili Pad Doc Pro / Pod 4 / Pale (mentioned as rebranding/model updates, not named researchers)

Original video