Energy Efficient Building Design Questions and Answers

Answer: A

Correct answer: east or west

The morning and afternoon sun on those elevations is low and comes from the side, so an overhang would have to be enormous to intercept it. Vertical fins block a low sun approaching obliquely, and on the west in particular they address the worst combination in the building - strong radiation arriving when the fabric is already warm.

Answer: B

A blind inside absorbs the energy within the conditioned volume and re-radiates it there, so the plant still has to remove it. Keeping the sun off the glass is the only measure that removes the gain rather than relocating it.

Answer: C

Correct answer: less dense than the outside air and rises

Warm air is lighter, so it rises and leaves through high openings, drawing cooler air in low down. The driving pressure is the density difference multiplied by the height between the openings, which is why the effect is small in a single storey and substantial in an atrium.

Answer: D

Correct answer: the indoor to outdoor temperature difference and the height are both large

The driving pressure is proportional to both, so the effect is strongest on a cold day in a tall building. That is also its limitation as a cooling strategy: it works least well in hot weather, when the temperature difference is small and the cooling is most wanted.

Answer: A

Wind pressure is positive on the windward face and negative on the leeward, and openings on both let that difference drive a flow through the space. A single-sided room ventilates far less effectively however large the opening.

Answer: B

Correct answer: catching air at height and directing it down into the building

A wind catcher rises above the roof into faster, cleaner and cooler air and directs it down a shaft into the rooms below. In many traditional examples the incoming air passes over water or through a damp cellar first, so evaporation cools it further on the way - which is why the type belongs to hot dry regions.

Answer: C

The cooling comes from water evaporating into unsaturated air, so a large wet bulb depression is what makes it work. In humid air there is little capacity to absorb moisture and the method fails while making conditions worse.

Answer: D

At three or four metres the annual swing has almost disappeared, so air drawn through a buried duct is cooled in summer and warmed in winter. The tunnel must be long enough for the exchange and dry enough to avoid mould.

Answer: A

The sun heats the mass through the glass and the wall releases the heat into the room over the following hours, giving a time lag that suits an evening occupancy. Vents at top and bottom let it work by convection as well as conduction.

Answer: B

Correct answer: into the occupied space, where mass absorbs it

Direct gain is the simplest passive arrangement: south glazing admits the sun into the room itself, and exposed floor or wall mass absorbs it and releases it after dark. The cost of that simplicity is glare and a swing in temperature, which indirect systems such as a Trombe wall moderate at the expense of some efficiency.