Answer to Question 1
While students might jump to the answer of dark shingles in order to help the roof absorb sunlight and thus be warmer in the winter, when energy bills are likely to be higher, the key is to remember the persistent snow cover. In an area with persistent winter snow cover, most roofs have an albedo above 90 all winter long because they are covered with snow. This is particularly true of new construction that is completed with good insulation in the attic, preventing heat loss to the roof. Therefore, the shingle color is most likely to play a role in the energy balance of a home during the summer when it is actually visible and interacting with incoming solar radiation. In that case, the lighter shingle is the better choice, as its higher albedo will ensure that the roof reflects a greater percentage of incoming solar radiation and stays cooler as a result.
Answer to Question 2
They are so light that their fall speed is very slow. This would result in their evaporation before reaching the ground.
