Most people witnessing the devastation in Haiti have felt ­powerless to help, but not architects. Since the earthquake on 12 January, some 350 British architects have volunteered their services to ­Article 25, the UK's leading architectural aid charity. There has been a ­similar ­response in the US: design ­charity ­Architecture For Humanity (AFH) had 600 enquiries a day in the week after the disaster. Obviously, there is a­ ­colossal job of reconstruction to be done. Roughly one third of the capital, Port-au-Prince, has been ­destroyed, and some 2 million people have been made homeless.  For now, there are more immediate concerns: treating the wounded, getting in supplies, restoring sanitation, and grieving for the dead. "Now would be exactly the wrong time to pitch up in Haiti," Robin Cross, ­Article 25's director of projects, tells me. "You would simply be another burden on a very strained ­infrastructure." Kate Stohr, co-founder of AFH, agrees. "You don't go in and talk about building new schools when people are grieving. The first reconstruction doesn't typically start for six to nine months, and there will be a period of three to five years where we'll be ­actively working and need volunteers. "  In the broader sense, though, there is plenty that architects can and are ­doing. Natural and man-made disasters have created similar circumstances around the world, where homes, schools, hospitals, and other structures are needed quickly and cheaply. In addition, according to the UN, one in seven people now live in slum ­conditions. One of its millennium ­development goals is to improve the lives of 100 million slum dwellers by 2015. These are real, urgent problems for architects to solve.  As an example of what could be done in Haiti, Cross points to Article 25's work in northern Pakistan. After the 2005 earthquake destroyed the homes of some 3.5 million people, the charity, in partnership with Muslim Aid, has been building seismic-resistant homes there for those not able to do so themselves. These houses are a variation on a local design, except with a new lightweight structural frame made up of small lengths of timber. They don't look very different from the outside – low, single-storey dwellings rendered in mud and stone – but in the event of another earthquake, they will flex rather than collapse entirely. The houses are also secured to concrete plinths with steel straps, so they are less likely to be shaken off the hillsides, as happened in 2005. It's simple, low-tech stuff, and necessarily so, says Cross. "There is a place for ­innovation, but it's often best to adopt the materials and skills found locally. We've built about 100 houses there so far, but we've also used each one of them as an exercise in training people. It's ­important that when we leave we haven't just left buildings behind – we've also left a community with an increased capacity to rebuild itself."  Much of this architecture has a no-nonsense honesty and stripped down-functionalism that would please the less-is-more forefathers of the modern movement. It also makes much of what we do in the west look frivolous and ­extravagant by comparison. AFH published a book of such projects four years ago, Design Like You Give A Damn; there is now so much of this sort of humanitarian design going on, they are ­working on a sequel. (The same year, AFH also formed openarchitecturenetwork.org, a website where architects can publish their designs for peer review and free use by anyone who sees fit. On its homepage, they have adapted Le Corbusier's famous maxim ­"architecture or revolution": "We don't need to choose between ­architecture or revolution. What we need is an ­architectural revolution."  If this is a revolution, it is one that could only have happened in the information age. AFH was founded in 1999 by Stohr and Cameron Sinclair, two San Francisco-based architects. Witnessing returning refugees in Kosovo, they ­decided to hold an open online design competition for temporary housing and received hundreds of entries from around the world. From there, they spread into work in sub-Saharan Africa, and disaster zones including the aftermath of Hurricane Katrina and the Indian Ocean tsunami. The organisation now has 80 chapters in 25 countries, and a network of 40,000 professionals. "It's very life-affirming for architects," says Stohr. "On these projects, when you finish, you get a hug from the client."  Another consequence of the ­information age is the emergence of the celebrity-driven development project. In Haiti alone, AFH is now working with Ben Stiller's charity Stiller Strong (motto: "Stealing great ideas from other people's charities to build a school in Haiti"). Stiller founded his ­organisation before the earthquake, and is now roping in friends such as Robert de Niro and Owen Wilson to raise funds. AFH are also working with singer Shakira, whose Barefoot Foundation plans to build schools in Haiti. Haitian-born rapper Wyclef Jean, meanwhile, has his Yéle Foundation, which has been involved in a number of projects, including the construction of a new music studio in Cité Soleil.  The pioneer of the celebrity development field would probably be Brad Pitt and his Make It Right Foundation. The actor, an architecture enthusiast, visited New Orleans two years after Hurricane Katrina and – frustrated by the slow pace of reconstruction – ­recruited 21 architects to design new houses for the devastated Lower 9th ward, including Frank Gehry, David Adjaye, Thom Mayne and Shigeru Ban. This has resulted in an assortment of funky housing types that are affordable, storm-resistant (they are raised on stilts) and green, with features such as solar panels and rainwater harvesting. Pitt's charity has been criticised, though, for transplanting alien architecture into a context where it wasn't called for. One non-Make It Right resident, of a standard single-storey house, ­complained of feeling "like a Mini Cooper boxed in by SUVs". 54 houses have been completed so far, ­although 150 are under construction.  Similar concerns have been raised about the reconstruction of Haiti. "It would be easy to regard this catastrophe as some kind of blank slate on which an architect can come along and define a new masterplan, but you need to treat the subject with much more ­caution," says Cross. "Although the physical infrastructure has been badly destroyed, there are remaining social and economic infrastructures. You need to pick up those threads and build a new Haiti around them."  Architect John McAslan agrees. He returned from Haiti recently, ­having been involved in development work there before the earthquake, particularly on architectural conservation projects. One thing that rarely gets mentioned is Haiti's outstanding ­historic architecture, including its US Victorian-influenced "gingerbread" houses – tall, ornate constructions decked with towers, turrets, balconies. "One of my great fears is that some of the damaged historical buildings that survived will be demolished," says McAslan. "You can't be too concerned about the heritage when there are lives to be saved, but I think one needs to hold onto the past."  Like many practices, McAslan's puts a portion of its resources towards pro bono work around the world. Alongside projects like London's new King's Cross station, the firm has won acclaim for low-tech work such as prototype schools in Malawi, in cooperation with Bill Clinton's development charity. Made of local brick and timber, these smart, simple buildings are designed to optimise natural cooling, harvest rainwater and do without electric lighting – perfect for Malawi's remote villages. McAslan could well be doing similar work in Haiti soon; Clinton's initiative has again enlisted him to help with the ­rebuilding effort.  "What's needed most urgently in Haiti is coordination," says McAslan. "If there isn't any, there's a real danger a lot of effort and good intentions will be wasted." The rainy season is fast approaching, and with it the threat of sanitation-related diseases, not to mention hurricanes. In 2008 alone, Haiti was hit by four hurricanes, and the temporary shelters in which many Haitians now live will not stand up to another one. "We need coordination, we need short-term preparedness for the rainy season, and we need a long-term commitment to reconstruction."  With such pressing survival issues, is it appropriate to be thinking about architectural revolutions or questions of aesthetics? Yes, says Stohr. "Aesthetics are terribly important. Imagine you're a child and you've lost everything and lived in tents for five years. That's half your life. It is actually really important after a disaster to build back beautifully. It brings back a sense of normalcy. When all those beloved landmarks are gone, if you replace them with things that don't have cultural meaning and aren't, frankly, beautiful, you're not ­rebuilding that community."  • This article was amended on 30 March 2010. The original said that the Make It Right project had completed 15 homes in New Orleans. This has been corrected.
Last month's earthquake in Haiti left two million people homeless. As the colossal reconstruction effort begins, Steve Rose talks to the architects who are transforming disaster zones around the world