Meeb Chapter 2 - Climate, Comfort & Design Strategies

Front 1

Metabolism

Back 1

The rate at which we generate heat. It changes with level of activity, when and what we eat, and where we are in our daily cycle.

Measured in met = 18.4 Btu/h ft^2.

1 met of energy per unit of surface area (of a seated person) = 360 Btu/h or 106 watts.

Heat dissipates into the environment to keep us health and comfortable.

Age, weight, gender impact metabolic rate

Hint 1

2.1 The Body

Front 2

What is hypothalamus?

Back 2

Our internal thermostats.

Touch, blood, and water are signals for a change in heat regulation.

It causes a change in our blood distribution system in response to signals from our skin to core temparatures

Front 3

Hypothalamus:
Vasoconstriction

Back 3

Occurs in COLD CONDITIONS

A decrease in blood flow to the skin.

Caused by cold signals.

The sweat glands produce and send less water to the skin, thus causing a reduction in evaporation and heat loss.

The farther away from our central body mass the greater the surface area; the faster that body part gets cold.

Front 4

Hypothalamus:
Skin Surface

Back 4

Is the most variable thermal zone.

Front 5

Hypothalamus:
Vasodilatation

Back 5

Occurs in HOT CONDITIONS.

An increase in blood flow to the skin.

Caused by warm signals.

More water is generated by the sweat glands, thus causing increased evaporation and heat loss

Front 6

From MEEB (10th)
The three phases of the design process are generally known as

Back 6

A. Concept design, schematic design, and design development
B. Scheming, conceptual design, and benchmarking
C. Value scaling, stability benchmarking, and design development.
D. Conceptual design, value scaling, and regenerative design

Answer: A

Front 7

Although plans can and do change during all phases of the design process, to ensure a smooth process, fundamental decisions about the building should be made during the:

Back 7

A. Design development phase
B. Construction phase
C. Conceptual design phase
D. Occupancy phase

Answer: C

Front 8

Which of the following is an example of design intent?

Back 8

A. The building will score a 0 on Malcom Wells' Architectural Value Scale.
B. The lighting system power density will be no greater than 0.9W/ft^2.
C. The building will be green, with a focus on indoor environmental quality.
D. The building will achieve a Platinum KEED rating

Answer: C

Front 9

Which of the following is an example of design criteria?

Back 9

A. No building space will experience more than 1,000 ppm CO2.
B. The building will use primarily passive systems.
C. The building will provide outstanding comfort for its occupants.
D. The building will be aesthetically pleasing.

Answer: A

Front 10

Which of the following building requirements are written in prescriptive language?

Back 10

A. A public building must maintain a temperature of at least 68 degree F (20 degrees C) during all seasons.
B. A building shall be able to resist wind speeds of up to 100 mph (161 km/h).
C. A building shall be able to safely drain rain falling at a rate of 2 in./h (50.8 mm/h).
D. Pipe in a roof drainage system shall measure no less than 3 in. (7.63 cm) in diameter.

Answer: D

Front 11

Which of the following entities is most likely to generate building design standards?

Back 11

A. The City of San Francisco.
B. The American Federation of Labor - Congress of Industrial Organizations.
C. The American Society of Heating, Refrigeration and Air-Conditioning Engineers.
D. The International Code Council.

Answer: C

Front 12

The term "energy efficiency" in architecture can best be described as:

Back 12

A. Conserving energy as well as balancing outputs and inputs.
B. Minimizing depletion of renewable energy resources.
C. The degree to which a building project complies with codes.
D. The ratio of HVAC system outpur to HVAC system input.

Answer: D (no, A)

Front 13

Which of the following maxims reflect an overall design philosophy that encompasses the concept of sustainability?

Back 13

A. Consider nature as both model and context.
B. Use only the finest materials for building longetivy.
C. Use only structural insulated panels (SIPs) for insulation and enclosure.
D. Maintain a constant temperature of 72 degrees F (22.2 degrees C) within the building envelope.

Answer: B (no, A)

Front 14

Which of the following building features embody the design philosophy "manage storage"?

Back 14

A. Ample closet space.
B. Cisterns that capture rainwater for re-use within the building.
C. A separate conditioned space for heat-producing computers.
D. A large, multi-vehicle garage.

Answer: B

Front 15

Which of the following characteristics best exemplify a passive climate control system?

Back 15

A. The system uses no energy.
B. The system uses built-in electric space heaters.
C. The system/building components play multiple roles.
D. Mechanical cooling is used with solar heating.

Answer: C

Front 16

PSYCHOMETRIC CHART
What are the three basic definitions used to describe various air conditions?

Back 16

1. Atmospheric Air

2. Dry Air

3. Moist Air

Front 17

What is Atmmospheric Air?

Back 17

Air that contains nitrogen, oxygen, carbon dioxide, water vapor, dust, pollen, smoke, etc. Bascially, the air we breath and use for ventialtion.

Front 18

What is Dry Air?

Back 18

Air when contaminants (smoke, pollen, dust) and water vapor has been removed from Atmospheric Air.

It contains 78% nitrogen, 21% oxygen, and 1% other gases.

It is used as a reference in Psychrometrics.

Front 19

What is Moist Air?

Back 19

Air that is a mixture of Dry Air and water vapor.

Front 20

The Psychrometric Chart

Back 20

The relationship between Dry Bulb (enthalphy), Wet Bulb, Relative Humidity, and Humidity Ratio

Front 21

What is Dry Bulb Temperature?

Back 21

1. It is the temperature determined by a thermometer.

2. The temperature given in weather reports.

3. Dry bulb temperature scale is located at the base of the chart by vertical lines. The vertical lines indicate constant dry bulb temperature.

Front 22

What is Wet Bulb Temperature?

Back 22

It indicates the cooling effect of evaporating water.

It is determined by passing air over a thermometer that has been wrapped with a moist cloth. The evaporating water causes a cooling effect and lowers the temperature compared to the dry bulb air temperature.

Wet bulb temperature scale is located along the curved upper part of the chart; it's lines slope from left to right and denote equal wet bulb temperature.

Front 23

What is Dew Point Temperature?

Back 23

It is the temperature below where moisture will condense out of air.

The temperature at which the water vapor in the air becomes saturated and condensation begins.

Front 24

How does Dew Point Temperature effect human comfort?

Back 24

Humans tend to react with discomfort to a high dew point (i.e. greater than 59 °F), as it interferes with the body's normal process of perspiring (producing sweat) to cool down. High relative humidity (which results in a high dew point) impedes the evaporation of sweat and reduces the effectiveness of evaporative cooling. As a result the body may overheat, resulting in discomfort.

Lower dew points, less than 10 °C (50 °F), correlate with lower ambient temperatures and the body requires less cooling. A lower dew point can go along with a high temperature only at extremely low relative humidity, allowing for relative effective cooling

Front 25

What is Relative Humidity?

Back 25

A measure of how much moisture (relationship with Dew Point) is present in regard to how much moisture the air COULD hold at that temperature.

Relative humidity is given in weather reports.

It is stated as a percentage. The 100% relative humidity (saturation) line parallels to the wet bulb and the dew point temperature scale line. The 0% relative humidity line falls along the dry bulb temperature scale line.

Front 26

How do you read the psychometric chart?

Back 26

Other values can be determined on the psychometric chart if two properties of moist air are known.

Front 27

Determine the temperature of walls to prevent condensation given an air dry bulb temperature of 80 degrees and a relative humidity of 70 degrees.

Back 27

Example 2

Front 28

What is the lowest temperature that can be obtained from air coming off a cooling pad given an air dry bulb temperature of 90 degree and a relative humidity of 35%?

Back 28

Example 3

Front 29

How can one check relative humidity in order to adjust a humidifier?

Back 29

Example 4

Front 30

Explain the sling psychrometer?

Back 30

Sling Psychrometer image.

Front 31

Determine the wall temperature required to prevent condensation given an air dry bulb temperature of 80 degrees and relative humidity of 70%

Back 31

Example 2

Front 32

What is the lowest temperature that can be obtained from air coming off a cooling pad given outside air temperature of 90 degrees and relative humidity of 35%?

Back 32

Example 3

Front 33

How can relative humidity be checked in order to adjust a humidifier?

Back 33

Example 4

Front 34

Explain the sling psychrometer

Back 34

Sling Psychrometer figure

Front 35

Heat Flow:
What is Heat Flow?

Back 35

Heat energy that moves from high concentration to low concentration.

Measured in Btu which is the energy required to raise 1 lb. of water to 1 degree (152 cal).

Front 36

Heat Flow:
What is CONDUCTION?

Back 36

1. The kinetic energy exchange of heat through touch.

2. Air is not a good conductor of heat energy. Energy is transferred through physical contact.

3. The molecular agitation within a material without any motion of the material as a whole.

4. Conduction is most effective in solids-but it can happen in fluids

Front 37

Heat Flow:
For heat transfer between two plane surfaces, such as heat loss through the wall of a house, what is the rate of Conduction Heat Transfer?

Back 37

Q = U x A x ∆T
Btus = u-value x area x temp. change

This is the material's ability to conduct heat.

Front 38

Heat Flow:
What is CONVECTION?

Back 38

1. Heat transfer within a fluid medium: air, water

Front 39

Heat Flow:
What is HEAT FLOW?

Back 39

Heat energy that moves from high concentration to low concentration in Btus.

The energy required to raise 1 pound of water to 1 degree F (152 cal).

Front 40

Heat Flow:
What is CONVECTION?

Back 40

Heat transfer within a fluid medium such as air or water.

Air movement - hot air rises and could air falls.

Wall Surface Example:
A film of air exchanges energy with air that gets caught on thw wall surface. Moving air can never get to the wall. Heat transfer happens slow because of the air film.

The temperature of air and surface change (Δt)

Front 41

Heat Flow:
What is RADIATION?

Back 41

The transfer of heat thru ELECTROMAGNETIC WAVES (no molecules needed)

- Emittance: the ability of ajn object to emit radiation.

- Absorbants: ability of an object to receive radiation.

- Δt: temperature change.

Relative size:????

Front 42

Heat Flow:
What is EVAPORATION?

Back 42

A change of state of a substance

- LATENT HEAT: the energy embodied in water vapor.

- As temperature reaches our body temp. (98.6 degress), conduction, convection, and radiation stop being heat transfer options and evaporation is the alternative; thus dry moving air is essential. When the temperature falls, evaporation lessens and conduction, convenction, and radiation start becoming heat transfer options and they increase.

Front 43

Clothing:
What is CLO?

Back 43

-The insulative value of clothing.

- Total clo of typical clothing is 0.15 clo per pound of clothing's weight. This number is higher in the winter and lower in the summer.

Front 44

Comfort:
What are the three comfort factors?

Back 44

1. Personal
2. Measureable environmental
3. Psychological

Designer has the primary objective of heating and cooling people, and the building is the means to the end.

Front 45

Comfort:
Describe the Personal comfort factor.

Back 45

It's what you control: Metabolism, clothing, adaptation to environment such as migration to a comfortable place, drinking or eating warm or cold foods.

Front 46

Comfort:
Describe the Measureable Environmental comfort factor.

Back 46

It is the primary aim of the building and controlled by the designer.

1. Air temperature: range of temps for a given activity

2. Surface temperature: radiation

3. Air motion: increases convection/conduction and rate of heat transfer

4. Humidity: controls the rate of evaporation

Front 47

Comfort:
Describe the Psychological comfort factor.

Back 47

Controlled by the designer:

1. Color
2. Texture
3. Sound
4. Light
5. Movement
6. Aroma

Front 48

Comfort:
Heat tranferred by Conduction (touch)

Back 48

Depends on surface temperature.

The opposite of Radiation.

Front 49

Comfort:
Heat transferred by Convection (molecules):

Back 49

Depends on air temperature, then air movement, then humidity.

The opposite of Evaporation.

Front 50

Comfort:
Heat transferred by Radiation (touch and orientation):

Back 50

Depends on surface temperature (and orientation to the body).

The opposite of Conduction.

Front 51

Comfort:
Heat transferred by Evaporation (humidity):

Back 51

Depends on humidity, then air motion, then air temperature.

The opposite of Convection.

Front 52

Comfort:
What is Mean Radiant Temperature (MRT)?

Back 52

The average surface temperature of a space's surfaces.

Front 53

Comfort:
What is the "Comfort Zone"?

Back 53

The combinations of air temperature and relative humidity, with a clo of 0.6.

This zone can be expanded by adding more sun or more wind.

In very dry climates, add more moisture to the air.

Figure 2.4, pp. 42

Front 54

Comfort:
What is Operative Temperature?

Back 54

The average temperature of a space's temperature and the MRT.

Front 55

Comfort:
What is Acclimatizating?

Back 55

Modifying the body and mind to become more resistant to cold or heat stress. pp. 47

Front 56

Comfort:
The body is thermally sensitive in the following places:

Back 56

Heat receptors: Finger tips, nose, elbows

Cold receptors: Upper lip, nose, chin, chest, and fingers

Front 57

Comfort:
What is Radiant Asymmetry?

Back 57

It is the difference between two opposite surfaces' temperatures.

Front 58

Climate s:
What are the four climate zones?

Back 58

1. Cool (northern most USA and Canada)
2. Temperate (Central US, Mexico)
3. Hot-arid (Southwestern US)
4. Hot-humid (Southeastern US)

Front 59

Cooling Design Strategy:
What is Natural Ventilation Cooling?

Back 59

When higher air temperatures are offset by more air motion.

Typically used in humid, hot climates were day and night temperature changes are minimal.

Design buildings to be open to winds and closed to direct sunlight.

Buildings should be thermally lightweight since night air is not cool enough to remove built-up daytime heat.

Front 60

Cooling Design Strategy:
What are the two variations of Natural Ventilation?

Back 60

1. Cross ventilation: accomplished by using windows.

Design relies on narrow plan with large opening at either end.

2. Stack ventilation: utilizes low windows for intake and high windows for exhaust.

Based on the principle that hot air rises.

Stack ventilation is weaker than Cross ventilation.

Front 61

Cooling Design Strategy:
What is High-Mass Cooling?

Back 61

Used in warm-dry summer climates with hot days and still-cool nights.

Night temperature takes heat away from building mass.

Themal mass is located on floors, walls, or roof but requires a "sink" to reject its heat by night.

Two variations:
1. Roof ponds
2. Earth contact

Front 62

Cooling Design Strategy:
What are advantages to Roof Ponds?

Back 62

Roof ponds can radiate to the cold sky, but should be protect from direct sun during daytime.

They and be used for one or two story buildings.

A massive roof allows for design freedom below and in walls and fenestration.

Front 63

Cooling Design Strategy:
Describe Earth Contact.

Back 63

When the earth acts as a heat sink, keeping walls and floors cool.

Best to allow contact in summer and isolate the earth from building in winter.

Front 64

Cooling Design Strategy:
Describe High-Mass Cooling w/Night Ventilation

Back 64

Used in hot-dry summer climates.

Uses cool air at nighttime temparatures to flush away stored daytime heat.

Uses fans to ventilate quickly since nighttime hours are fewer than daytime.

Building transitions from thermally closed by day to thermally open at night.

Nighttime temperatures must be below the comfort zone for this stategy to work.

Front 65

Cooling Design Strategy:
What is Evaporative Cooling?

Back 65

When moisture is added to air, the air increases in relative humidity while decreasing in dry-bulb temperature.

Uses HVAC equipment.

Creates high indoor air velocities and noise.

Building smells of wet material.

Creates cool air at the inlet and warm air at the outlet.

Front 66

Heating Design Strategy:
Name the three solar heating strategies.

Back 66

1. Direct Gain (DG): allowing sunlight and heat into the space so it warms thermal masses.

2. Indirect gain (TW-Trombe Wall): sun hits thermal first, then passes as heat to the space behind.

3. Isolated gain (SS-sun space): when a sun space or green house is heated day and some of the heat is released into an adjacent space.

Front 67

Heating Design Strategy:
Direct Gain application.

Back 67

1. Requires mass to be minimum 4" thick.

2. Best used in building with southern glass facade.

3. Popular because of its simplicity, ample daylight and southern view.

4. Glare is a problem, causes overheating on sunny days, and large radiant heat losses thtuogh glass at night. This results in large diurnal diffenence in interior temperature.

5. Best for winter heating and is similar to night ventilation of mass.

Front 68

Heating Design Strategy:
Indirect Gain application.

Back 68

1. A Trombe wall in front of a window has made this the least used strategy.

2. Doesn't admit much daylight and the wall blocks views.

3. It allows less glare, less overheating on sunny days, and not fading of furniture in direct sunlight.

4. Provides large radiant heat in the evenings.

Front 69

Heating Design Strategy:
Isolated Gain application.

Back 69

1. More popular since it provides a sunny inhabitable space, has broad daily temperature variations which makes the adjacent space pleasant.