in the news

Back to Guest Features


Ad: American Hydrotech







October 2008
guest feature article

Relaxing Villa Santai, the First Greenroof in Bali ~
the eco-friendly greenroof project in Bali, Indonesia, incorporating water retention, recycling and conservation methods

Photo Courtesy Victor Sinclair

Eco-friendly and gorgeous in Lovina, North Bali.

By Victor Sinclair
October 3, 2008

Photos Courtesy Victor Sinclair

Bali, the famous tourist destination of southeastern Asia, is suffering from a lack of sufficient electricity and water deficiency. Electricity cuts for the local populace are the order of the day. The government of Bali, together with PLN, the state electricity company, focus on supplying electricity to areas frequented by tourists, or regions with an increasing expatriate populace.

Villa Santai is situated in the hills behind Lovina, North Bali, in a region that is notorious for the scarcity of its water in the dry season, beginning in May/June until October/November. Lake Berantan, one of three lakes in the mountains, is the source of the water for the springs in this region. The lake’s water table is steadily sinking (3 m in the past years) and already over 60% of the natural springs are now dry. Along the coastal areas the water is pumped up from the ground water table.

The concept for Villa Santai

Two factors are the driving force behind the design of Villa Santai: an insufficient supply of electricity and dwindling water resources compounded by the fact that the economy of Bali is geared to and dependant upon the income from tourists and the growing population of expatriates looking for a slice of ‘that tropical island’ where to retire. Projects to introduce changes in the usage of energy, water resources and waste management, etc. are dependent on private initiatives.

The concept for Villa Santai (santai = relax in Indonesian) was to build an environmentally friendly villa reducing the need for electricity using green lawn roofs, as well as to conserve and retain water. I am the self-taught architect and designer for the villa complex, having worked in Indonesia since 1993 and lived in the north of Bali since 2005. The villa is specifically designed for the generation of expatriate ‘baby boomers’ that the economy is increasingly dependent upon - those who are aware of the global climate crisis and are willing to set examples for environmentally friendly building concepts.

The land

The land, approximately 3.600 m2, was chosen for two main reasons, firstly it borders 70 meters on a river - although in the dry season it carries no water, in the wet season it is a source of abundant water - and secondly, is just far enough from the main road (120 meters) to insure peace and quiet. In early 2007 before construction work could begin, an application was made to the land department for permission to build on the plot because of its 50° gradient. The plot was terraced into 14 separate levels leading down to the banks of the river, with an even steeper gradient of 80° with a depth of approximately 10 meters.

Left: Fourteen separate levels lead down to the banks of the river; Right: Beginning construction.

The application was granted and the earth was “redistributed” into four main levels. The steep bank of the river was “reshaped” to incorporate a Water Recycling Biotope of approximately 50 meters in length and between 2-5 meters wide to process 85 m3 of water. The riverbed and the banks on either side were “sleeved” to a depth of between 2.5 and 3.0 meters and a width of between 2.0 and 3.5 meters. Both ends of the river were then dammed, resulting in approximately 420 m3 of retained water. Together with the Water Recycling Biotope, we then had water catchments totaling 525 m3.

Water is a key element in the design of Villa Santai.

The Water Recycling Biotope and close-up of Lotus Pond.

The actual villa buildings are designed with pitched greenroofs totaling 615 m2 of grass at angles of 35° and these are the green lungs of the villa complex. Designed around the theme of water, the villa complex is divided into three separate buildings, and four distinct levels; the parking area leads to an apparently flat building (16 meters long x 8 meters wide – the main building on two levels totaling 320 m2), which upon entering has as an open, raised gallery to one side and a central stairway leading down to a terrace and three guest rooms.

The green lungs of Villa Santai.

The third level, accessed from the terrace by a broad stairway leading down between two lotus ponds, is central to the design of the villa complex. The third level encompasses the two further buildings, the Master Bedroom and the Kitchen/Dining Room, a Lap Pool measuring 18 x 4 meters with endless run off and a wide terrace surround on three sides set between the two structures. Separated by the Lap Pool, two stairways at the end of the terrace surround lead down to the fourth level, the garden.

Construction of the greenroofs

Bali, or for that matter Indonesia, is to date devoid of building materials concerning the construction and implementation of greenroofs. Should these materials become available, there would still be the question of affordability because they would necessarily be imported. The idea of a wooden roof construction to support an organic greenroof in the tropics is not a realistic option because of all the beetles and bugs that just love to feast on wood. Wood, of course, can be treated to avoid being eaten, but this then becomes a question of environmentally friendly chemicals that are available and the duration of their affectability. So for the construction of our greenroofs, the only real option was to use poured re-enforced concrete (12 cm thick).

Construction supports.

Not only was the idea of pouring a pitched concrete roof something unheard of by the local population and our construction workers, but the thought of piling earth on top of it and planting grass was enough to cause laughter and ridicule for this British foreigner, at the mere mention of it! Unfortunately the reaction of many expatriates living here on Bali or on Java, where I used to live, was not that different when they heard of my project. And although the Dutch and Germans seemed to hold back, they were skeptical to say the least.

All this only re-enforced my determination to continue and to prove that greenroofs were not only energy saving, but at the same time would enhance the overall picture of a new villa in the landscape and have positive effects for our environment.

It almost took a village to construct Villa Santai.

Before the rainy season begins in Bali it is very hot and dry, not ideal for pouring concrete, especially with rationed water supplies.  To make the calculations and pour a roof in concrete was not so difficult after ordering the relevant books on (see References below) and the process began to slowly take shape. A fond memory was when we actually poured the roofs by May 2007 at the end of the rainy season - first of all the Kitchen/Dining Room and then the Master Bedroom. All concrete pouring is done by ‘special’ teams on the construction site and these teams normally comprise 5 – 6 men on the cement mixer and the same number to do the pouring, but with the roofs the equation was rather different as 30 men and women were actually necessary on the roofs to do the pouring. With the pitch of the roof and the human bucket chains crawling over them, the work was tedious but successful, the resulting photos having historical as well as sentimental value.

Concrete roofs a success!

After 14 days the concrete had settled enough and the bamboo supports and the hardboard moulds were removed and my construction workers were eager to throw on the earth. The disappointment was tangible when they were told that the roofs would first have to really settle in order to look for any leaks or cracks that might occur after the dry season.

The pitched greenroofs of the Master Bedroom and the Kitchen/Dining Room are also an integral part of the rainwater retention system. Not only is the rainwater that flows off the greenroofs retained in three separate retaining tanks that are hidden under the terrace surround of the Lap Pool - two of which retain 50 m3 of water each and one that retains 200 m3 of water - they also supply the water the greenroofs needed to survive the dry season.

When the rainy season began again, extremely late last season in January of 2008, the few leaks that appeared were quickly taken care of and the roof was treated with water sealant cement used for swimming pools. Finally the question that was on everybody’s mind, "How to get the earth or substrate to ‘stick’ to the pitched roof?", was answered.

Local lava as an aggregate

Indonesia does have one ideal material in abundance to offer for greenroofs and that is lava stone, the ideal material to use as a mix with the earth and to stop the substrate from slipping. Small blocks of lava, each 5/7 – 8/10 cm in size were cemented to the roof at 25/30 cm distances from each other. In addition, substrate retention walls of 10 cm height and 2 cm width were cut from lava stone and cemented 1.5 meters apart horizontally along the roof, also regulating the rainwater drainage. The depth of the substrate that was put on the roof has an average of 11/12 cm before the planting of the grass. Running vertically, each roof has three ‘walkways’ placed a few meters apart (30 cm wide and 14 cm high), made of lava stone for the gardener to use when trimming the grass and to funnel rainwater faster into the retaining tanks.

Small blocks of lava, each 5/7 – 8/10 cm in size were cemented to the roof at 25/30 cm distances from each other.

Grass squares from Java

The decision of what sort of grass to use was not easy; there are many sorts of grasses that can be used, short rooted and not too thirsty etc., but in the end the classic slow growing golf course lawn seemed the best bet. Considering the skepticism and the jokes made about the roof, a neat and trim lawn seemed the best option, rather than something wild and natural.

Left: Covering up the growing media before the grass arrives; Right: Installing the sod under slippery conditions.

Tarpaulin steadying the substrate for another less rainy day.

The day came when the grass lawn ordered from Java finally arrived. For two days beforehand the ‘human chains’ had managed to put all the substrate on the two roofs and the grass lawn squares were piled high ready to be placed - then the sky darkened and the rains came pouring down. The roofs were covered with tarpaulin to stop the earth from getting too soggy and running away while the grass squares were put in place, but tropical rains are tropical rains.

Slowly but surely the roof is getting sodded.

A quick look at the weather forecast told us that the rains were to last for another three days, so the decision was made to continue and spite the elements, but when sections occasionally took off on their own and hit the deck, skepticism about the success of project greenroof was rekindled. On the third day the grass lawn was up at last and as a sign of welcome, the sun came out and the picture was complete.

A beautiful day in Bali.

Greenroofs give back to nature

The result? Astonished compliments and amazement at the real cooling effect under the greenroofs, naturally some still thought that with all the rains the greenroof would go swimming. The greenroof ‘skin’ has held and with it we have given back, as the leading architect for greenroofs in the 1960’s – 80’s, Friedenreich Hundertwasser, so tellingly said and I quote,

“The nature that we have on the roof, is that piece of nature that we murdered, when put the house there.”

This, I also believe to be true.

Greenroofs mingling in with nature and giving back a little, too.

At present, two roofs are finished; the main building with the largest roof remains to be poured which will begin as soon as the rainy season begins again this season in October – November, depending on climate change factors. We have a climate crisis, and it is possible to discuss, debate and procrastinate and to look for solutions far and wide. But if only every building built gave back to nature the footprint it took on its roof, the crisis would be a problem that could be managed, and not an impending disaster. For Bali and for Indonesia this Villa Santai project is a beginning, and I believe that it would be fantastic if greenroofs as future sustainable building elements become a true trend.

Computer animated pic of the main building at Villa Santai.

The project can be viewed at:


The books I ordered from were:

1) GUIDE TO MASONRY & CONCRETE by Creative Homeowner Press. This is a simple basic book.

2) Birkhäuser – Concrete Construction Manual. This book is for professionals, originally from Germany authored by:

Friedbert Kind-Barkauskas Dr. Ing., Architect and Jörg Brandt, Dr. sc. agr. Both from Bundesverband der Deutschen Zementindustrie e.V.; Bruno Kauhsen Prof. Dr. –Ing., Architect of the Department of Architecture, North-East Lower Saxony; Stefan Polónyi, Emer. Prof. Dr. –Ing. E.h. Dr. h.c. Dr. Ing. E.h. and Claudia Austermann Dipl. –Ing. Both from Faculty of Building, Dortmund University.

Publisher's Note:  See more details of the Villa Santai in The Greenroof Projects Database.

Born in Singapore and educated in England, Victor Sinclair traveled extensively throughout Europe and settled in Germany in the ‘1980s. Through a personal acquaintance, he became involved with the re-development plans of the old harbor area in Düsseldorf and they successfully initiated the process to put under heritage some of the old warehouses. It was during this period that Victor taught himself the basics of architecture.

Traveling extensively throughout Asia and China in the ‘90s, Victor began exporting furniture from Indonesia and Chinese antiques to Europe. After the Asian monetary crisis resulted in an emerging democracy in Indonesia, he decided to move to Indonesia permanently. The combination of the love of architecture and the need to assist in finding methods to conserve the dwindling water resources in the North of Bali lead to the idea of developing environmentally friendly building concepts incorporating greenroofs.

Contact Victor at: and + 62 811278110.

Also for October 2008 see the Guest Feature Article "Sustainable Head-Quarters: The West Midlands Fire and Rescue Authority" by Frances Carroll.

Past Guest Feature Articles

The opinions expressed by our Guest Feature writers and editors may not necessarily reflect the beliefs of, and are offered to our readers to simply present individual views and experiences and open a dialogue of further discussion, debate and research.  Enjoy, and if you have a particular comment, please contact the author or send us an email to:


Back to Top