Mech/Elec ALS Lesson Two - Comfort, Climate and Solar Design: Comfort Ranges and Zones

Human comfort ranges vary depending on recent exposure, culture, location, health and age.

Heat from humans must be allowed to dissipate.

Too much heat loss must be avoided.

Humidity in the air around us is a key factor to the bodies' process of cooling itself.

Psychrometric chart = graph which shows the air at different temperatures and different humidities. You can graph the total amount of energy stored in the air ( sensible heat + latent heat) on the same chart, see next definition.

Enthalpy = the term used for that combined heat energy stored in the air of sensible heat + latent heat. Lower enthalpy means lower stored heat of temp. & humidity.

Dry bulb temperature = The temperature measurement taken with a standard thermometer. Shown vertically on chart.

Wet bulb temperature = The temperature measurement taken with a wet sock over a standard thermometer allowing to take rate of evaporation into account.

Wet bulb depression = the difference between the dry and wet bulb temp's

psychrometer = thermometer with a wet sock over it.

sling psychrometer = thermometer with a wet sock over it when it's swung around the air manually.

(RH) Relative humidity = The percentage of complete saturation (how much water is in the air at a given temp. compared to how much the air could hold at that same temp.)

Air can hold more water when it is warm than when cold.

condensation = warm air when cooled releases liquid water since it's ability to hold moisture is decreased by the temp. drop. temperature differences on two sides of a material can cause condensation

Vapor barrier = put on warm side of insulation of a wall to prevent condensation within the wall

Comfort range = aka comfort zone, combinations of air temp. and relative humidity that is comfortable to most people which can be plotted on the psychrometric chart

IE. people doing sedentary work and lightly clothed, 65d-78d F and 25-75 RH is comfortable

Higher the RH the lower the temp. should be.

Effective temperature = Combination of ambient air temp (dry bulb) and the MRT (mean radiant temp.)

High MRT = lower ambient air / Low MRT = higher ambient air

local velocity = movement of the air, lets the comfort zone be slightly higher if air is moving which carries heat and moisture away more rapidly.