diff --git a/code/ATMOSPHERICS/datum_pipeline.dm b/code/ATMOSPHERICS/datum_pipeline.dm
index d2978e887a4..d72b8b2dbf7 100644
--- a/code/ATMOSPHERICS/datum_pipeline.dm
+++ b/code/ATMOSPHERICS/datum_pipeline.dm
@@ -210,7 +210,7 @@ datum/pipeline
 		
 		//if the h/e pipes radiate less than the AVERAGE_SOLAR_RADIATION, then they will heat up, otherwise they will cool down. It turns out the critical temperature is -26 C
 		// Only would happen if both sides (all 2 square meters of surface area) were exposed to sunlight.  We now assume it aligned edge on.
-		heat_gain += surface * STEFAN_BOLTZMANN_CONSTANT * thermal_conductivity * (air.temperature - COSMIC_RADIATION_TEMPERATURE) ** 4
+		heat_gain -= surface * STEFAN_BOLTZMANN_CONSTANT * thermal_conductivity * (air.temperature - COSMIC_RADIATION_TEMPERATURE) ** 4
 		
 		air.add_thermal_energy(heat_gain)
 		if(network)