2-Story (Cob) House in hot-humid climate built on rice terraces ?

Hello permies,

I'm interested in building sustainably in my new home of Lombok, Indonesia !
I've been dreaming/reading up on of living sustainable for a while but nothing beats asking some more experienced Guys.
Some info about location and climate :
To our front we are facing the sea (20km) and behind us is the beginnings of Mt. Rinjani (Volcano). We are nestled on top of a hill and our land stretches down rice terraces that lead down to a valley. The climate is hot year round ~30° /90F and humidity at around +70%
My Question(s) would be :
Do we have suitable conditions to build a cob house ? ( or should we try other types of earthen building?) Can we achieve passive cooling with these conditions ? And also: Is a 2-Storey house worth trying ?

Thanks so much for having a look at my post, hope to learn from it as much as i can !
Take care , padraig

I really don't know much about cob housing, but I do know that the amount of rainfall you get would be pretty important during the build; here's an question/answer to someone building in Florida's panhandle area: "If you get very frequent rain you may want to put up a big tarp over the site during construction, or build the roof first. As long as it is carefully designed and built (good high foundation, adequate roof overhangs, protective plaster if necessary) it should last a very long time. However, that doesn't necessarily mean that cob is the most suitable building material for that area. High mass materials like cob can be great at passive cooling, but only if there is some way to cool them down[…] In a dry climate like the high desert, even when daytime temperatures are very hot it still gets cold at night and the heat absorbed by the cob during the day can be discharged. In a hot moist climate where nights are warm, high mass materials lose their passive cooling abilities. You may need to augment with mechanical cooling."

I would only consider the build the roof first option. After you have a completely finished roof with all drainage issues worked out you could begin using the cob.

To avoid issues of rain splatter, consider using concrete block for the first 18 inches.

Rather than pure cob, some sort of woven bamboo treated with Borax, would give a substrate to build on and some reinforcement.

I had some luck with evaporative cooling in Cebu Philippines. We averaged 80% humidity , so you are likely to have better results.

Marie Repara wrote:If you get very frequent rain you may want to put up a big tarp over the site during construction, or build the roof first. As long as it is carefully designed and built (good high foundation, adequate roof overhangs, protective plaster if necessary) it should last a very long time.

However, that doesn't necessarily mean that cob is the most suitable building material for that area. High mass materials like cob can be great at passive cooling, but only if there is some way to cool them down[…] In a dry climate like the high desert, even when daytime temperatures are very hot it still gets cold at night and the heat absorbed by the cob during the day can be discharged. In a hot moist climate where nights are warm, high mass materials lose their passive cooling abilities. You may need to augment with mechanical cooling."[/i]

Thank you Marie !
We do get alot of monsoon rain, but we want to try and finish the house during dry season which lasts around ~5 months. I would have no problem with finishing the roof first though either, so better safe than sorry.

Also we are 600m/2000f above sea level so temperatures do tend to cool down to below 20°/70F at night. Would that be suitable for high mass ? What can we expect during the day ?

Dale Hodgins wrote:  
Rather than pure cob, some sort of woven bamboo treated with Borax, would give a substrate to build on and some reinforcement.

I had some luck with evaporative cooling in Cebu Philippines. We averaged 80% humidity , so you are likely to have better results.

Thanks Dale, alot of old structures use these technique ive heard i will try and learn the exact reasons why !

I suggest you first search out the New Zealand and/or Japanese Building Codes for structures in earthquake zones.

Apparently cob structures are okay, but heavily dependent on design characteristics.

We share a similar climate, so ventilation will be paramount. The roof should shed water well away from the foundations and walls e.g. Verandahs all around.

Two storey pole and timber structures are traditionally effective. Coupled with a few modern tweaks they would work well and be relatively cheap.

F Agricola wrote:Also we are 600m/2000f above sea level so temperatures do tend to cool down to below 20°/70F at night. Would that be suitable for high mass ? What can we expect during the day ?

From what I've read, when it comes to hot/humid climates, cob works great if you utilize passive solar design. I'm not sure what night-time temperature would be ideal, but for warmer/moister areas professionals say that shade is key:
"In a hot humid climate where the air temperature stays high all night, you won't get as much cooling advantage from cob's thermal mass[…] In that case I'd recommend large roof overhangs (covered porches are great for keeping the sun off your walls), lots of insulation in the roof, and plenty of opening windows for ventilation [...] Definitely porches and deep roof overhangs for shade."

(I don't know what online resources you've found, but the "Ask the Experts" section on www.greenhomebuilding.com has a lot of question-and-answer posts from people all over the world that is pretty helpful. Here's the question/answer from the cob section: http://www.greenhomebuilding.com/QandA/cobQandA.htm )

I would also use the permies search bar to locate posts using the keywords, "cob" and "humid climate". There's a number of them that received a lot of good replies.

F Agricola wrote:I suggest you first search out the New Zealand and/or Japanese Building Codes for structures in earthquake zones.

Apparently cob structures are okay, but heavily dependent on design characteristics.

We share a similar climate, so ventilation will be paramount. The roof should shed water well away from the foundations and walls e.g. Verandahs all around.

Two storey pole and timber structures are traditionally effective. Coupled with a few modern tweaks they would work well and be relatively cheap.

Thanks agricola !
Thats great input since lombok has had strong eartquakes before...
I wonder if it would be possible to build a bamboo framework (string bamboo together if neccesary) and build cob structures around it ? Would it harm the safety of the house facing earthquakes ?
We are also building against a slope so the ground floor would be built against the hill on one side with no possiblities for windows etc on that side. I was thinking of building sort of vents through the earth side with a fresh breeze coming up through the side facing the valley. Would that be enough to guarantee enough ventilation ?

Having real fun trying to figure out the designs of a sustainable house so far, I would love to have a structure that wouldnt require an AC. Im gonna try out some cob structures soon to get a feel for the building process and share some infos when i get some results