Cascading temperature demand: The limits of thermal nesting in naturally ventilated buildings

19th-century thermosiphon ventilation and its potential for heat recovery in buildings today

“…Consider the sequence of three rooms shown in Figure 5 A, where heating in the middle space, , causes the ventilation, , to flow in one direction. 53 , 54 Now consider “folding” this room sequence, as shown in Figure 5 B, so the last room in the stream (Space 3) conducts heat to the first room (Space 1) through a shared partition wall. In this case, the partition wall is the heat exchanger, with conductance ].…”

“…Each Space has a relative temperature in excess of the exterior, given by where and are the interior and ambient exterior air temperatures, respectively. Neglecting radiant transfer from surfaces, and assuming good thermal mixing of the air in each room, the relative temperatures follow the cascade and are defined using simple energy balances 53 , 54 as where is the volumetric heat capacity of the ventilation stream and is the exterior envelope conductance of space . The term represents heat carried by the ventilation stream from space to space +1.…”

“…Reducing temperature demand refers to integrating adaptive strategies into building designs and operation, so that occupants accept and even desire some degree of spatial or seasonal variation in temperature. 54 The vast body of work on adaptive thermal comfort has shown that occupants’ thermal expectations are influenced by both short 65 , 66 , 67 and long-term 68 , 69 exposure to their indoor climate, which may be “nudged” toward wider thermal variation. 70 For example, occupants in naturally ventilated buildings, which have interior temperatures that vary closely with the exterior from day-to-day and season-to-season, have expressed thermal satisfaction over far wider temperature ranges than occupants in mechanically ventilated ones with narrow setpoint bands.…”

“…Architects would need to embrace the flow logic of the temperature cascade, as would the building’s users. 54 For example, consider Figure 9 B as a place for eating and socializing. Space 1 is an indoor garden, Space 2 is a dining area, and Space 3 contains the service rooms.…”

“…Note the separate ventilation terms for each space here. For effective mixing ventilation, each room is given a separate chimney vent, 54 and has its own ventilation terms. The total flow rate per person is divided in the same way as the internal heat gains and total envelope conductance, such that .…”