Z E M C H 2 0 1 2 I n t e r n a t i o n a l C o n f e r e n c e
766
and can provide more flexibility to the layout organization. These aspects are not
discussed here.
2.1.1. Leeward sawtooth roof
The leeward sawtooth roof is a building component that can increase natural ventilation
by combining wind driving and convective ventilation (Allard & Santamouris 1998) and
when the outlet opening is greater than 20% of the house cross section, it is more
efficient than the wind catcher sawtooth roof (Gandemer & Barnaud 1989). The leeward
sawtooth roof geometry parameters can be optimized in order to increase the pressure
coefficient at the leeward outlet opening surface. If we consider the inclination angle of a
tropical house, the 15° pitched roof can intensify the negative pressure more than other
angles (Holmes 1994). The negative pressure coefficient module of three different
leeward sawtooth roof geometries were analysed and its performance with an on-floor
air diffuser by a naturally pressurised plenum was observed.
2.1.2. On-floor air diffuser by a naturally pressurised plenum
The on-floor air diffuser is a variant of the one used by Architect João Filgueiras Lima,
Lele in the Sarah Hospital Network. Under-floor reflector-diffusers, aided by a
mechanical ventilation system, were used for leading air stream flow to the internal
ambient of the hospital located at the upper level (Fig. 9). In the current research the
potential of the on-floor air diffuser which works as a complement to the natural cross
ventilation is analysed by CFD simulation. Both on-floor air diffuser and cross ventilation
can be described as an upward natural cross ventilation system in which the on-floor air
diffuser should take the air stream flow through occupancy zones or air stagnated areas.
The on-floor air diffuser could be located along the main axis of the houses as shown the
figure 7. The on-floor diffuser geometry was not discussed in this paper as it was not
considered in the simulation. Further research should consider it, as it has a specific
pressure drop.
Figure 9. Ventilation system by on-wall air diffusers (a) and Sawtooth roof (b) - Fortaleza Sara
Network of Rehabilitation Hospital (Fortaleza, Brazil).
Figure 7. Program Organization
Concept
Figure 8. Leeward sawtooth roof models analysed (A1,
C1 and D1). The two cases, both A and B are shown.
