Energy Efficient Building Design Questions and Answers

Answer: C

Correct answer: simultaneous outdoor illuminance under an unobstructed sky

The daylight factor is a ratio taken at the same moment, so it is a property of the room’s geometry and glazing rather than of the weather. That is what makes it usable in design: it can be computed once and applied to any sky condition, and a figure of two per cent is a common minimum for a working space.

Answer: D

A horizontal surface in the upper part of the window bounces light onto the ceiling and thence to the back of the room, while shading the area near the window that had too much. It improves the uniformity as much as the level.

Answer: A

Raising the window head is therefore worth more than widening the window, and a room deeper than about twice that height needs top lighting or electric light at the back. It is the rule that governs plan depth in a daylit building.

Answer: B

The first requires each component to meet a limit, the second allows one to be worse if another is better, and the third simulates the whole building against a reference. The third gives the designer most freedom and demands most analysis.

Answer: C

A heavily glazed facade may comply if the glass is better than required or the roof is insulated beyond the minimum, the whole envelope being assessed together. It suits a design whose architecture demands one departure.

Answer: D

Correct answer: compare alternatives before anything is built

Simulation is a design tool, and its value is comparative: it shows whether a deeper overhang or better glazing does more for the same money, at a stage when both are still choices. Its absolute predictions are less reliable, since occupancy and weather will differ from the assumptions.

Answer: A

Real occupants keep different hours and different set points from any assumption, and the weather file is a past average. The same assumptions applied to two options make the difference between them far more trustworthy than either absolute figure.

Answer: B

The definition is an annual balance rather than an instantaneous one, so the building draws from the grid at night and exports by day. Reaching it requires the demand to be cut first, since generating enough to cover a wasteful building is rarely possible on the site.

Answer: C

Correct answer: the roof area available for generation is limited

A building has only so much roof and facade to put panels on, so the generation it can carry is capped. If the demand is not reduced first, that ceiling is reached before the balance is struck - and demand measures are usually cheaper per unit than generation besides.

Answer: D

Occupants of a naturally ventilated building in a warm month accept and prefer higher temperatures than the same people in winter, so a fixed set point over-cools in summer. Allowing the set point to drift with the season is a large and free saving.