In our town, the majority of houses are made out of concrete, and almost every building has a corrugated galvanized steel roof. If you've ever visited the tropics, that sentence should have made you start sweating. When the sun comes out, our house is like an oven - the roof soaking up the heat and radiating it down into the concrete box. When it rains, forget conversation. The drumming of the drops on the roof is deafening. And the concrete fosters mildew as it limits airflow. But there's another option!
Climate control
To encourage good flow of rain off the roof, thatch roofs must be steep. This leaves a vaulted ceiling on the inside of the building, which allows hot air to flow up and out of the living area, gradually working it's way through the leaves. Metal roofs do not allow upward airflow. Thatch does not quickly transmit heat from the sun through to the living space. Metal does. Thatch allows airflow that helps keep the humidity down. If you want a mildew-free mattress or couch, this is a GOOD thing.
Cost
The cost breakdown between thatch and metal is pretty close. In Nepal we learned that thatch is relatively expensive because it has to be replaced more often than metal. That doesn't seem to be the case in Ecuador (see next section). The initial cost seems to be about the same between thatch and metal. A 2.4 meter by 1.2 meter sheet of metal roofing costs about $7, whereas a bundle of high quality thatch that should cover approximately the same area is $5-10. Compared to concrete, they're both pretty cheap.
Longevity
Thatch comes in all kinds of different varieties, and each has its strengths and weaknesses. The best type we've learned about can last up to 60 years if well cared for. Maintenance of thatch consists of lighting a wood fire in the building to smoke the thatch. This inhibits mold and repels insects, both of which break down thatch. This process was never inconvenient in the past - cooking was done over wood and a fire was always kept lit in the hut. Since smoke was constantly being generated, the thatch was kept dry and smoky. But if you don't want your house to be smoky all the time, how often do you have to smoke your house? Well, let's say you're really into low-maintenance and do it once at construction. If you use a good species of thatch material, you can probably get 10 years out of your roof. In the constant rain, metal roofs usually last less than that, so they have to be replaced regularly.
Miscellaneous
I love the woven design of the underside of a thatch roof. Rusty galvanized metal...not so much. Thatch is renewable (it grows on plants) and recyclable through composting. Metal must be mined and is technically recyclable, but the amount of rust on metal roofing by the time it is worn out makes recycling very expensive for the amount of usable material. Thatch roofs are difficult and time consuming to build. Metal roofs can be stuck on in a day once the framing is in place.
Ok, let's do a summary comparison of thatch versus metal.
The indigenous people groups of the Amazon region have developed amazing technology that allows them to live comfortably in a challenging environment. I don't think that "modern" technology has been able to improve on it.
I'd love to hear about your experiences with zero-energy climate control systems from your local area. Post a comment below!
..Isaac..
 | |
| A thatched outbuilding, recently remodeled. Note dead tire put to a useful function holding the cap of leaves in place. |
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| The roof that used to be on the same building. |
Climate control
To encourage good flow of rain off the roof, thatch roofs must be steep. This leaves a vaulted ceiling on the inside of the building, which allows hot air to flow up and out of the living area, gradually working it's way through the leaves. Metal roofs do not allow upward airflow. Thatch does not quickly transmit heat from the sun through to the living space. Metal does. Thatch allows airflow that helps keep the humidity down. If you want a mildew-free mattress or couch, this is a GOOD thing.
Cost
The cost breakdown between thatch and metal is pretty close. In Nepal we learned that thatch is relatively expensive because it has to be replaced more often than metal. That doesn't seem to be the case in Ecuador (see next section). The initial cost seems to be about the same between thatch and metal. A 2.4 meter by 1.2 meter sheet of metal roofing costs about $7, whereas a bundle of high quality thatch that should cover approximately the same area is $5-10. Compared to concrete, they're both pretty cheap.
 |
| Interior of a thatched roof in a restaurant in Tena. |
Longevity
Thatch comes in all kinds of different varieties, and each has its strengths and weaknesses. The best type we've learned about can last up to 60 years if well cared for. Maintenance of thatch consists of lighting a wood fire in the building to smoke the thatch. This inhibits mold and repels insects, both of which break down thatch. This process was never inconvenient in the past - cooking was done over wood and a fire was always kept lit in the hut. Since smoke was constantly being generated, the thatch was kept dry and smoky. But if you don't want your house to be smoky all the time, how often do you have to smoke your house? Well, let's say you're really into low-maintenance and do it once at construction. If you use a good species of thatch material, you can probably get 10 years out of your roof. In the constant rain, metal roofs usually last less than that, so they have to be replaced regularly.
 |
| The bathroom at a school in town, with a roof that will need to be replaced soon. |
Miscellaneous
Ok, let's do a summary comparison of thatch versus metal.
| Thatch | Metal | |
| Climate Control | + | - |
| Cost | + | + |
| Longevity | + | - |
| Maintenance | - | - |
| Aesthetics | + | - |
| Renewable | + | - |
| Ease of Construction | - | + |
The indigenous people groups of the Amazon region have developed amazing technology that allows them to live comfortably in a challenging environment. I don't think that "modern" technology has been able to improve on it.
I'd love to hear about your experiences with zero-energy climate control systems from your local area. Post a comment below!
..Isaac..
| This post is part of the Rethinking High Tech series. |
Well, I haven't lived in a thatch-roofed house yet, so I can't give personal experience about pests and thatch. With our tin roof, we still have plenty of cockroaches, flying ants, etc. and have seen rat poop in places where it falls from roof beams...
ReplyDeleteI have heard that there are some insect critters that prefer to live in thatch, but regularly smoking the roof keeps them from moving in.
You may be aware that in Flagstaff, there is a "home" on the south side of downtown which is made completely from metal railroad containers. I pass it frequently and it looks very much like the outside is corrugated metal similar to what you describe. I can imagine how hot it must get in the tropics and if you had a winter down there how cold it would get as well. Is there any access to "insulating" type materials such as polystyrene foam board? Would it make a difference if you could just get it cool inside your place? What did folks do back in the time before A/C? They used a fan blowing over ice or an evaporative cooler perhaps. So I assume no electricity is the norm there. Yes? So what technique do you use to maintain body temperature? Lots of questions I know but not many answers. Cheers and regards!
ReplyDeleteGreat questions, Phil! I apologize for the slow response. "Winter" is an interesting topic in Ecuador. Stay tuned for a blog post soon about that...
ReplyDeleteLack of insulation is definitely a problem, for both temperature and noise. A well insulated house could be closed up during the day and opened at night to maintain more comfortable temperatures.
Electricity is pretty commonplace even in quite small communities in Ecuador, but as far as I know there is no one who owns an air conditioner in our town. Evaporative coolers have limited usefulness in very humid environments. The best strategy I've seen for the humid tropics is to design the house to catch breezes, combined with well insulated walls and roof, regardless of what the outer skin is made from. A thatch roof gives you a head start, as it is a much better insulator than metal roofing.