Question 1

Using a Psychrometric chart or a sketch of one, without calculation or use of tabulated data, which air condition do you expect to have a higher vapour pressure than the air in the room you are in now?

A)35^oC d.b., 32^oC w.b.
B)20^oC d.b., 50% Percentage Saturation
C)10^oC d.b., 80% Percentage Saturation
D)-5^oC d.b., 100% Relative humidity
E)40^oC d.b., 10% Percentage Saturation

Accepted Answer

The air condition with a dry bulb temperature of 35°C and a wet bulb temperature of 32°C (Option A) is expected to have a higher vapor pressure than typical room air because the closer the wet bulb temperature is to the dry bulb temperature, the higher the moisture content and thus the higher the vapor pressure.

Question 2

Why does condensation occur within a building?&#10;A)Users leave taps running, baths full, water evaporates and deposits onto room surfaces, making air moist&#10;B)Evaporated water within the building meets surfaces at below dew point temperature&#10;C)Kettles, cooking, fish tanks and open bowls of water evaporate more water vapour into room than ventilation can remove&#10;D)Porous building materials provide pathways for cold moisture to ingress a warm building and make indoor surfaces damp&#10;E)Cyclic variation of indoor surface temperatures always produces below dew point locations

Accepted Answer

Condensation occurs when evaporated water within the building meets surfaces that are at a temperature below the dew point, causing the water vapor to condense into liquid form on those surfaces.

Question 3

What is air, in terms of condensation risk?&#10;A)Dry gas needed to ventilate humidity out of buildings&#10;B)Mixture of oxygen, nitrogen and carbon dioxide&#10;C)Mixture of dry gases and water vapour&#10;D)That which causes the problem&#10;E)Humans and animals breathe out humid air

Accepted Answer

Air is a mixture of dry gases and water vapor, which means there is always a risk of condensation when humid air comes in contact with a surface that is colder than the dew point temperature of the air. It is important to control the indoor humidity level and use proper ventilation to reduce the condensation risk.

Question 4

What is the movement of humidity through a building called?&#10;A)Mass transfer&#10;B)Ventilation&#10;C)Natural or mechanical ventilation&#10;D)Condensation&#10;E)Evaporation

Accepted Answer

The movement of humidity through a building is a form of mass transfer, which refers to the movement of mass from one place to another. Humidity can travel through a building by diffusion, convection, and other means.

Question 5

What drives moisture flow through a structure? A)Percentage saturation difference B)Air temperature difference in ^oC d.b. C)Vapour pressure difference in Pascal's D)Air moisture content difference in kg H₂O/kg dry air E)Wet bulb air temperature difference in ^oC w.b.

Accepted Answer

Moisture flow is driven by the vapour pressure difference in Pascal's, which is the driving force behind water vapour movement from an area of high vapour pressure to an area of low vapour pressure.

Question 6

In the context of condensation in building, what does Rv stand for?&#10;A)Volumetric resistance of a material&#10;B)Resistance value&#10;C)Resistance volume&#10;D)Vapour resistivity&#10;E)Total vapour resistance

Accepted Answer

The answer of In the context of condensation in building,...

Question 7

How can a porous wall or roof have its' vapour resistance improved?&#10;A)Replace with new materials&#10;B)Wallpaper internal surfaces&#10;C)Drill ventilation holes to ventilate structure&#10;D)Add a layer of polythene film&#10;E)Cannot be done so increase heating within building

Accepted Answer

Adding a layer of polythene film can increase the vapour resistance of a porous wall or roof. This can be done by adding the film to the inside or outside surface of the wall or roof. This will help to reduce the amount of moisture that can pass through the wall or roof and into the building, which can help to improve the indoor air quality and reduce the risk of mold and mildew growth.

Question 8

Which is true? A)MN s/g m = GN s/kg m B)10³ kN s/g m = GN s/kg m C)10³ N s/g =MN s/g D)10⁶ N s/kg = MN s/g E)kN s/kg = MN s/g

Accepted Answer

The answer of Which is true?&#10;A)MN s/g m = GN...

Question 9

Why are thermal and dew point temperature gradients for a structure calculated and drawn?&#10;A)Calculate thermal admittance of the structure&#10;B)Decide where additional thermal insulation or vapour barrier improves performance&#10;C)Discover dynamic behaviour of the structure&#10;D)No need to do it anymore as computers do all design&#10;E)Calculate optimum thickness of thermal insulation

Accepted Answer

Thermal and dew point temperature gradients are calculated and drawn to determine where additional thermal insulation or vapour barrier is needed to improve the performance of a structure. This helps identify areas where there may be heat loss or moisture buildup, which can lead to structural damage or reduced energy efficiency.

Question 10

Which are the units of moisture mass flow rate through a building structure used to calculate condensation risk? A)kg/s B)kg/m² s C)grammes/hour D)kPa/m² E)N s/kg

Accepted Answer

Moisture mass flow rate through a building structure is typically measured in kg/m² s, which represents the mass of moisture passing through a unit area per unit time.

Deck 11: Condensation in Buildings