Passive design guidelines for Philippine housing based on the bahay kubo

Abstract

Philippine low-income housing is uncomfortable since it is not built to deal with the hot and humid climate in a passive way. Since local vernacular architecture is known to have a good climatic responsive performance, the aim of this research is to learn how Philippine vernacular design strategies can improve thermal comfort for low-lying, sub-urban and rural, low-income housing. The strategies studied are openings, eaves, stilts, orientation, roof insulation and roof angle.
 Two-day in-situ thermal measurements are used to study the comfort performance of the housing typology. To study the influence of the strategies or combinations of them on comfort, numerical predictions are used consisting of energy and CFD, wind-driven simulations. The numerical models are validated before the strategies are varied on a general case or a case study. The average exceeding temperature (AET) in Kelvin is used to assess comfort. It is calculated by accumulating for every hour of the year the exceeding temperature in Kelvin and divide this by the amount of hours that could be uncomfortable. A conceptual implementation study is performed to take disaster resilient and practical considerations into account. The impact of varying the strategies on the case study resulted in a reduction in AET of about 5 K for openings, 0.7 K for orientation, 0.6 K for eaves, 0.5 K for stilts and 0.1 K for roof insulation. On this basis, it can concluded that applying the guidelines as stated below, comfort increases significantly. More impact can be obtained if the strategies are implemented and combined as described by the passive design guidelines below. • To increase wind driven ventilation in wind direction, openings should be made on the wind- and leeward facade until ground floor, have an opening height (O_h) based on the facade height (F_h) by the rule of thumb: O_h[m]=0.85·F_h[m], include a leeward roof opening and include openings on the remaining facades. • Dependent on the wind direction, the openings should be opened accordingly. If no wind is present, all roof openings should be opened. During typhoons, they should be closed. • As much open area on facades in the main monsoon wind direction is advised. The openings on the other facades should be placed in the middle of the width to increase the performance with wind coming from the other directions. • Hinged eaves with a 15° angle and length calculated by the rule of thumb:  E_l,15°[m]=0.6·F_h[m] should be used. During typhoons they should be folded in to decrease the related pressures.
• Increasing stilts height increases comfort by an exponential decay. To determine the height, a comfort increase of about 0.17 K for 1 meter, 0.30 K for 2 meter and 0.40 K for 3 meter in AET reduction are obtained. Braced, wooden stilts are advised to protect against floods and increase earthquake resilient behaviour. • A roof insulation with an Rc-value of 1 m²K/W is advised to gain about 0.2 K AET. Further research is needed on buoyancy driven ventilation to improve the provided design guidelines.