The document discusses environmental factors that affect human comfort, including air temperature, relative humidity, air movement, surface temperatures, air quality, lighting, acoustics, and security. It specifically focuses on air temperature, relative humidity, and their combined effects as depicted on a psychrometric chart. The psychrometric chart shows the conditions needed for condensation and how indoor conditions would change with cooling or heating of indoor air without adding or removing moisture.

2. Air temperature Relative humidity Air movement
Surface
temperatures
Air quality (IAQ)
Lighting
•quality
•quantity
Acoustics
Security
Building Envelop -The Third Skin
The 3rd
. skin moderates the differences between the
75 degrees
65 degrees
+100
- 5

3. The combined affects of
environmental
conditions on
comfort
•Air temperature
•Relative humidity
•Air movement
•Surface radiation

4. Dry Bulb Temperature Reading
Changeinquantityofwaterintheair
Changeinquantityofwaterintheair
The
psychrometric
chart
Charts the combined affects of air
temperature and moisture content

5. 50% RH
Psychrometric Chart
Definition of Relative Humidity
The amount of moisture in the air
expressed as a percentage of the
maximum amount of moisture the air can
hold at the given temperature.
Example: at dry bulb temp. of 77 and wet
bulb temp. of 63, the air is holding 50% of
it’s maximum capacity at 77 degrees.
Enter dry bulb reading
Enter wet bulb reading

6. warmingcooling
drying
Adding
moisture

7. warmingcooling
drying
Adding
moisture
Warm &
Dry
Cool &
Humid
Winter
Summer
Energy efficient zones
Winter: higher humidity off-sets
lower furnace thermostat setting
Summer: lower humidity off-sets
higher AC thermostat setting

8. 50% RH
Air is 100% saturated
with moisture and
condensation begins
The saturation curve

9. 50% RH
Air is 100% saturated
with moisture and
continues to cool
Moisture removed
by condensation
What if cooling
continues ?

10. 50% RH
Air is 100% saturated
with moisture and
continues to cool
Moisture removed
by condensation
Same air is reheated to 70 degrees
and no moisture added – RH of the
room goes down (dryer)

11. Dry Bulb Temperature Reading
Changeinquantityofwaterintheair
Changeinquantityofwaterintheair
Chart Exercises
What is the RH in the classroom?
Dry bulb ________
Wet bulb _________
RH = _________

12. Dry Bulb Temperature Reading
Changeinquantityofwaterintheair
Changeinquantityofwaterintheair
Chart Exercises
Based on the current room RH, how
cool would the walls need to get to
start noticing condensation ?
Dry bulb ________
Wet bulb _________
RH = _________

13. Chart Exercises
Assume the room is at pt. “A” when class
begin and we are comfortable, which
direction would room condition tend to
move toward as a response to our presents
?
Mechanically: (Summer)
we need to (add or remove heat)
we need to (add or remove moisture)
A - Room starts out
here
B
C
D
E