The life-cycle costs of white roofs are less than those of black roofs. Green roofs are more expensive over their life-cycle than white or black roofs. Dark roofs should be phased out in warm climates for black is the new white pdf health purposes. Despite lasting at least twice as long as white or black roofs, green roofs cannot compensate for their installation cost premium.

This annual difference is sufficiently small that the choice between a white and green roof should be based on preferences of the building owner. Owners concerned with global warming should choose white roofs, which are three times more effective than green roofs at cooling the globe. We strongly recommend building code policies that phase out dark-colored roofs in warm climates to protect against their adverse public health externalities. Check if you have access through your login credentials or your institution. The drupes are cooked briefly in hot water, both to clean them and to prepare them for drying. The drupes dry in the sun or by machine for several days, during which the pepper around the seed shrinks and darkens into a thin, wrinkled black layer. Once dry, the spice is called black peppercorn.

On some estates, the berries are separated from the stem by hand and then sun-dried without the boiling process. Once the peppercorns are dried, pepper spirit and oil can be extracted from the berries by crushing them. Pepper spirit is used in many medicinal and beauty products. White pepper consists solely of the seed of the pepper plant, with the darker-coloured skin of the pepper fruit removed. Rubbing then removes what remains of the fruit, and the naked seed is dried. Sometimes alternative processes are used for removing the outer pepper from the seed, including removing the outer layer through mechanical, chemical, or biological methods. Green pepper, like black, is made from the unripe drupes.