Valentina Nelin has a revelation that will likely shock the hundreds of thousands of Jerusalemites readying their air-conditioning systems and fans on the eve of the summer solstice. "You don't need air-conditioning in Jerusalem," believes the green architecture consultant. "Jerusalem is a special place; it has virtually the perfect temperature for houses. If your house is oriented correctly, you don't have the greenhouse effect in the summer [causing houses to absorb excess heat and warm up]," she explains. The trouble is that the vast majority of homes and offices in the city aren't built with the climate in mind. Jerusalemites might blame the electricity company when their energy bills peak in the summer and winter when appliances go into overdrive to cool and warm their homes - tasks that account for 75 percent of energy consumption - but they could just as easily point the finger at architects and town planners. A new 40-unit development in Katamon is due to combine what Nelin describes as "a high standard of living with a low environmental impact." The project on Sderot Shai Agnon, due to get under way shortly, aims to be the first residential building constructed according to the Israeli "Green Building" Standard 5281, which encourages more environmentally sustainable building practices (as reported by In Jerusalem, "A REAL viable solution," June 6). Russian-born Nelin, who holds a master's degree in environmental and bioclimatic architecture from Madrid, is currently preparing an application to the Standards Institute of Israel for the standard that covers energy, water, land and other environmental issues including air quality and the building process. If the development scores 55 or more out of 100 points specified by the conditions in the standard, then it will be able to call itself the first officially "green" home in Israel. The project, supervised by property developer Gideon Neumann and architects Carlos Pruce and Dafna Alexandrony, will cover 2.4 dunams consisting of low-rise cottages alongside a 13-story tower designed to reduce the energy consumption of the residents by "tens of percents" by using correct orientation to the sun, good insulation and passive solar-heating devices. The building has been designed in accordance with precise calculations of the local climate and movement of the sun, without which such systems would be a "catastrophe," says Nelin. Apartments can also be extended, reducing the need for new building elsewhere. "What is important is that it is a regular building," says Nelin. "Green building should be high quality. If something is high quality, you don't have to make repairs, which means using natural resources." Three floors of parking and storage will be located underground to make an economical use of the space, but one visibly "green" feature will be roofs covered with vegetation in order to improve thermal insulation. The building process is accounted for too, incorporating "landscape rehabilitation" to make constructive use of the debris that will be dug up at the site. "We can't use all of the soil at the site, so the extra will go to other building works in the area, not to the rubbish tip," says Nelin. She points out that Neumann is the first developer to preserve wildflowers on the site, transferring them temporarily to the Jerusalem Wildflower Sanctuary in Neveh Ya'acov until construction is complete. Digging is expected to commence at the site in the coming weeks, representing a gap of over a quarter of a century since one of Jerusalem's first modern green buildings was constructed. Completed in 1981, the Hegedus's family home lies on a quiet side road in Kiryat Menahem, to the west of the Malha Mall. Aside from the lush garden whose vines creeping up the large stone walls give it a distinctly tropical feel, there's little else to set apart the large detached house from others in the area. Two doors away, a new house is being built, still hollow while the neighbors give their air-conditioning system a workout as the summer comes into full swing, but Alexander Hegedus sits in his living room enjoying the cool atmosphere without a fan in sight. "All winter I dress like this too," says Hegedus with a smile, pointing to his T-shirt and shorts. "It's very hot here in the summer, but the house doesn't heat up." The house's unseasonably cool temperature in the summer, and virtually free heating during the winter, owes itself to the range of both "passive" and "active" elements in its design. The former include 70-cm. thick stone walls that contribute to powerful insulation. By taking a long time to heat up, the walls keep the interior cool in the summer afternoons, while retaining heat during the night. The house is warmed by solar heating in the shape of unassuming gray plastic tiles on the exterior, not to be confused with expensive photovoltaic panels which convert the sun's heat into electricity. For example, thermosymphonic air collectors, a triangular prism at the house's rear that heats up cold air as it enters, warm the floors below and circulate it within the house. Climbing the spiral staircase, Hegedus leads In Jerusalem to a bedroom. "This room is always warm," he says, explaining the trombe wall system that uses a plastic external wall set back 20 cm. from the brick wall to heat the layer of air in between, which then circulates around the bedroom via two rectangular holes in the wall. The room doesn't overheat in the summer because the windows' orientation protects them from the sun's higher altitude at this time of year. "We receive our heating virtually free," he says, adding that their heating bills for the entire winter amount to no more than NIS 1,500, mainly for wood that fuels a large stove downstairs. The building's architects, Tony Rigg and Ruth Lahav, also designed the nearby Nofim residential home, which was built three years later according to similar principles of "bioclimatic" architecture, reaping electricity savings estimated at around 75%. "We save electricity, but we do waste water," acknowledges Hegedus's wife Amia, as she relaxes in the shade of the well-watered plants. "When we built the house, we could have improved the water collection system but the cost of construction was very high," reflects Alexander Hegedus. "We built the house with our own hands; it was a tremendous effort. We built it from our salary and didn't have the expenses for a water collection system, but it is possible." The new development in Katamon hopes to make more efficient use of water by capturing rainwater and using it for gardening. Nelin insists, however, that this expertise is not something modern and that many of Jerusalem's older Arab houses and buildings in the Old City with their thick, insulating walls, were designed with the thermal comfort of their residents in mind, long before electricity-hungry air-conditioning came on the scene. But the notion of combining ecology and architecture has been slow to take off in modern Jerusalem. "I set myself the goal that in 10 years all new buildings in Israel will be built according to green architectural principles," says Nelin. "I hope it [Shai Agnon] will be an example to others."