Project Description

This is an energy efficient house that was built by the University of Ubonratchathani in 2005 as part of a research project funded by the Ministry of Energy. The house is a product stemmed from a housing design competition that had a condition to build a real house in order to collect data on thermal comfort. Passive design using radiation cooling, natural ventilation, solar shading, and roof insulation was used effectively

Butterfly house 1
2000px thailand ubon ratchathani locator map.svg
Btf house map
Btf house bird eye view 2

Building Details

Single House

New building project


150 m²

120 m²

80 m²


USD 43,000

USD 290



Project Team

Chulalongkorn University

Stonehengh Co., Ltd.

Dr.Atch Sreshthaputra


Stonehengh Co., Ltd.

Dr.Atch Sreshthaputra

Dr.Atch Sreshthaputra

Dr.Atch Sreshthaputra

Climate Analysis

Ubonratchathani has a Tropical Savanna Climate. The climate is arid with little rain in winter, relatively high temperatures in summer, cool in winter, and rain from May to October, about 70-90 days. The average annual temperature is 28-29 degrees Celsius. Maximum temperatures average 33-34 degrees Celsius and minimum temperature averages 23-24 degrees Celsius. April is the hottest month of the year, while winters are cool in January.

Udon thani climate graph

Design Approach

Located on a large open space area with prevailing wind most from the south

Stack ventilation. Natural Ventilation, Radiative Cooling. Solar Shading.


Special Feature

Daylight from north façade.

Low-flow, low-flush bathroom fixtures

Stack Ventilation and Venturi Effect

Local materials within 500 kM

Large trees on west and south side

Building Material

Reinforced Concrete

Autoclaved Aerated Lightweight concrete block with 1" Polyurethane Foam and Gymsum Board

Glazing percentage of walls - 0.2 U-value of windows - 5.8 W/m2.K Solar Heat Gain Coefficient (SHGC) of windows - 0.68 Visual Transmittance of windows - 0.72


Double roof with ventilated cavity, Metal sheet and 6" Fiberglass Insulation

Energy systems

T-5 Fluorescent lamps


Electric ceiling fan in living room

Split-type air-conditioners

High-efficient air-conditioners (EER > 12)


Lessons Learned

Natural ventilation works effectively all year round especially at night. Daylight is not really necessary as the occupants are not inside during the daytime. Stack ventilation is difficult to control and predict at times.