Development of passive houses for tropical dryzone of Sri lanka

Abstract

Sri Lanka has diverse climate conditions that can be broadly divided into tropical wet zone, dry zone and tropical uplands. The designing of passive houses for tropical dry zones would be a challenging task since quite harsh climate conditions would prevail everyday at least for few hours. Therefore, it needs detailed studies to plan thermally comfortable passive houses for dry zone of Sri Lanka.

The main aim of this project is to determine the ways and means possible to create a thermally comfortable environment in the house located in dry zone with the use of passive elements. Initially, a literature survey was conducted to determine passive techniques desirable for dry zone. The thermal effect of the various design options was established by using computer simulations carried out with the aid of DEROB-LTH.

The outdoor climatic conditions were obtained from Meteorological Department of Sri Lanka. The required climate data were maximum and minimum temperatures, sun shine hours and relative humidity.

As an outcome of this detailed study, a set of rules were developed for the designers since they can use them during preliminary design stage. Some of the main finding are shown below: 1. Light colours for roofs and walls should be used. Light colour paints like white, light cream, off white for roof and walls are recommended 2. For dry zone opening windows or the natural ventilation will not help to give thermally comfortable environment. 3. Trees in north-south direction should be provided in order to reduce the indoor temperatures. Hence cultivation of the large and tall trees like Jack, Teak or Nuga is promoted. 4. When ever possible, bricks should be used for construction. 5. Roof insulation material such as Aluminum foil or Aluminum foil along with asbestos roof and ceiling should be constructed.

Whenever possible, reflective insulation material should be used and dark colours should be avoided. If insulation is used, maximum effort should be taken to minimise the infiltration into the house. Shadings with the insulation should be provided in order to control the solar gains in to the house. Large trees and window sunshades are most beneficial.