3 - Cooling With Thermal Mass And Natural Ventilation

Question 1

What are the 5 passive design systems?

Answer 1

1. Orientation
2. Glazing and shading
3. Day lighting
4. Natural air currents and convection systems
5. Thermal mass and structure

Question 2

What are the factors that determine thermal mass? (3)

Answer 2

1. Specific heat capacity (materials ability to store heat for every kg of mass)
2. Density
3. Thermal conductivity (measure of ease with which heat can travel through a material). Should be moderate for high thermal mass so the absorption and release of heat synchronises with the buildings heating and cooling cycle

Question 3

What is critical mass?

Answer 3

Dense materials dont get any more useful after ~50mm in reducing daily temp cycles

Question 4

What does critical mass depend on?

Answer 4

1. Material
2. Structure
3. Climate
4. Air movement
5. Insulation

Question 5

Why does thermal mass need to be evenly distributed in a space? (2)

Answer 5

1. Mass needs to be coupled to a space so that heat transfer from mass to air can be carried out over a large area
2. Cooling perception of a cool mass

Question 6

What are the 3 advantages of natural ventilation and 1 disadvantage? (4)

Answer 6

1. Alternative to air-conditioning
2. Does not consume energy or contribute to CO2 emissions
3. Provides reasonable standards of air quality

Disadvantage: doesnt maintain constant environmental conditions

Question 7

Natural ventilation can meet cooling demands if…? (3)

Answer 7

Theres:

1. Good solar control
2. Low levels of internal gains
3. Acceptance that temps will reach over 25 degrees sometimes

Question 8

What are the 2 forces that drive natural ventilation in a building?

Answer 8

1. Difference in pressure due to positive on windward and negative on leeward
2. Difference in pressure due to vertical temperature

Question 9

What are 4 types of windows

Answer 9

1. Sliding sash
2. Top hung
3. Vertical and horizontal pivot
4. Louvres

Question 10

What are 3 forms of vertical ventilation?

Answer 10

1. Stack
2. Chimney
3. Atrium

Question 11

What size should roof lights be?

Answer 11

5-10% of floor area, protected from direct sunlight