Building Services Engineering 5th Edition Handbook

258 Condensation in buildings
4. Evaporated water within the building meets surfaces at below dew-point temperature.
5. Cyclic variation of indoor surface temperatures always produces below dew-point
locations.
23. What always combats condensation problems within occupied buildings?
1. Thermal insulation.
2. Impervious building materials.
3. Removing open water surfaces.
4. Air conditioning.
5. Heating and ventilation.
24. From where does water vapour originate within a building?
1. Atmospheric rain.
2. Wind-driven atmospheric humidity.
3. Occupants and their activities.
4. Lack of sufficient natural and mechanical ventilation.
5. Refrigeration systems and food storage.
25. What is the relationship of building materials to moisture mass transfer?
1. There is none, building materials do not leak water.
2. Good design and construction removes all moisture issues.
3. Modern building materials have zero permeability.
4. Porous structural materials absorb and pass moisture.
5. Vapour barriers isolate brick, concrete and thermal insulation materials from moisture
generated within a building.
26. What drives moisture flow through a structure?
1. Vapour pressure difference in Pascals.
2. Air temperature difference in ◦ C d.b.
3. Percentage saturation difference.
4. Air moisture content difference in kg H 2 O/kg dry air.
5. Wet-bulb air temperature difference in ◦ C w.b.
27. Which is correct about condensation and mould growth?
1. Always occurs in buildings over 20 years old.
2. Cannot happen with current design standards.
3. Readily forms in the UK in room corners, on window sills, in cupboards on external walls
and within structures having an overall thermal transmittance of over 1.4 W/m 2 K.
4. Must be removed, the surface gloss painted and outdoor air ventilation minimized.
5. Impervious external surface materials need to be matched with an outdoor vapour
barrier to stop moisture flowing into the wall, floor or roof structure.
28. Vapour diffusion into a structure that then condenses is called what type?
1. Adiabatic.
2. Complex.
3. Leakage.
4. Interstitial.
5. Intermediate.