Research Hub · How buildings handle heat and cold

Air blowing is not air conditioning

Many people inside believe their unit is air-conditioned because air comes out of the vents. Often it isn't. This cutaway shows how air moves through a housing unit under three setups, where it reaches and where it doesn't, and how that changes what a body has to cope with in the dayroom and in the cells.

Illustration  It shows how these systems work in general, using published engineering numbers. It is not a measurement of any one prison. Every assumption is listed below.

Scroll through a whole July day inside →

Season
Cooling
95°F
15%
Building
Try a day
Air color = temperaturecoolhot

What the cutaway shows

Three ways to move air, one building

Fans & vents only

Moving air, not cooling it

  • An air handler pulls air in and pushes it through the vents. Nothing takes the heat out, so the air is as hot as outside or hotter.
  • Moving air feels good on skin up to a point, but it can't bring the room below the outside temperature.
Swamp cooler

Cools by adding water

  • Outside air is pulled through wet pads. Water evaporates and the air cools, but it also gets more humid. DOE
  • It needs fresh air in and warm, damp air out. Without an exit, humidity builds and cooling falls off. DOE
  • It works worse as humidity rises: about 73°F out of 100°F dry air, but only about 84°F out of 95°F air at 50% humidity. PNNL
Air conditioning

Takes heat and water out

  • A refrigerant loop carries heat outside, and moisture condenses on the cold coil, so the air gets cooler and drier. Archtoolbox
  • It works on humid days, and it can run on recirculated air.
  • In Colorado prisons that have AC, it is often switched on by calendar date, not by the heat. CPR
Dayroom vs. cell

Where the air stops

  • Cooled air delivered to the dayroom reaches a closed cell only through the gaps around the door. Turn on "Vents inside the cells" to see the difference.
  • Heat rises. Upper-tier cells and cells on the sun side run hotter. A 2023 account from Fremont Correctional Facility described south-tier cells usually above 90°F with swamp coolers. Prison Journalism Project
Colorado's own standard

61°F to 86°F

  • Colorado's health rules for penal institutions require indoor temperatures of at least 61°F in the coldest months and below 86°F in the warmest. 6 CCR 1010-13 §9.4
  • The readouts flag any space that falls outside that range.
Winter

Heat has the same problem

  • When heat comes through the same vents, the dayroom warms first. Cells behind closed doors, along cold outside walls, lag behind.
  • Being confirmed: security rules that limit layering clothes for warmth in Colorado prisons.

Being confirmed with people who know these buildings

  1. Do Colorado's newer prisons (such as Limon and Sterling) have real air conditioning, swamp coolers, or air handlers that heat in winter and only move air in summer?
  2. Does conditioned air reach the cells, or only the dayroom?
  3. How much of the air is fresh from outside, and how much is recirculated?

Older and newer facilities likely differ. Facility-specific versions will be added from community research and public records.

Assumptions behind the numbers

WhatValue usedWhere it comes from
Swamp cooler outputCloses 80% of the gap between air temperature and wet-bulb temperature (45% when warm air can't get out)Standard evaporative cooling method; matches the PNNL examples above within a few degrees
Air conditioningHolds the dayroom near 76°F at about 50% humidityTypical comfort setting; illustrative
Heat from people and lights+4°F in the dayroomIllustrative
Cell with door gaps onlyLower cell +3°F, upper cell +6°F over the dayroom (summer)Illustrative: heat rises and the roof and sun-side wall add heat
Cell with its own ventLower +1°F, upper +2°FIllustrative
Winter heatDayroom held near 68°F; cells lose heat to outside walls as it gets colderIllustrative
"Feels like"Heat index from temperature and humidityNational Weather Service formula
Standard61°F floor, 86°F ceiling6 CCR 1010-13 §9.4