Low energy Design and Thermal Comfort: Climate analysis

The Analysis [5], which is a pre-design tool was used for climatic examination. A well — defined warm-humid tropical climate, with two defined seasons: the rainy season from May to August and the dry season for the rest of the year. Discomfort is found most of the time due to high temperatures and humidity levels. The only possible passive cooling strategy is promotion of air movement (by cross ventilation or induced by fans — physiological cooling). This can minimize discomfort for most periods of the year.

The adaptive model developed by De Dear et al [6] based on extensive research field with tropical inhabitants had demonstrated the different acclimatization levels for people living in such conditions and was used for this project. A comfort zone based on De Dear’s model was set with January neutrality zone set for Salvador-BA, Brazil, as 23.5-28.5C and for July: 23.1-28.1 C.

Energy conscious site planning A planning which maximizes the use of natural resources on the site. For this case, an open plan, appropriate solar orientation (S/N axix) protected the glazing areas from the East/West sun and directed the opening areas to the prevailing breezes (NE-SE). The rooms are located on the northeast side of the site (summer breezes are predominantly NE). This is also the location of the roof integrated Photovoltaic system (PV) and the solar water heating system.

Passive cooling: natural ventilation

Maximize cross ventilation by orienting towards the prevailing breezes — NE and SE. Interaction with the outdoors and treatment of petential barriers to the path of breeze through the house. Use of adequate window openings to allow maximum airflow. Incorporating suppelementary means of promoting air movement (fans). These were the strategies for maximum comfort ventilation. Discomfort was noticed during the 3 hottest months of the year. The use of fans and cross ventilation could not obscure the effects of heat and humidity through physiological cooling. The simulations undertaken using ESP-r demonstrated that when no control was used (either by shaidng or ventilation — using the airflow network model), temperature reached up to 40C in the lower level (Office and kitchen). The bedroom zone achieved the best performance dut to its orientation, minimal exposed surfaces, insulation and provision of solar shading and ventilation. During the wors summer months (December — January) the airlow network modelling confirmed the NE/E most

frequent wind flow through simulations of the Master Bedroom (Fig. 3)

as related by many studies by Parker [8] and other authors, it’s a powerful way of improving performance. These results were confirmed through TAS, ESP-r and DOE 2.1-E simulations. White zincalume coated curved roof was used for the central roof, with radiant barrier system and R1.5 bulk insulation lined internally with plasterboard. Even if the improvement due to the insulation (reflective and resistive) is not significant as it would be without the low solar absorptance values in the roof, it still contributed to reduction in thermal discomfort and cooling loads.

Western walls had also been painted on light color (0.2 absorptance) and combined with bulk and radiant barrier system. Lightweight materials were used elsewhere. Thermal mass had been used only on living areas, where daytime was the period of use for the house so some load shifting could be provided. The office (located on the NW side) runs as a dual mode operation [4]

(daytime A/C — 9am-6pm) and through simulations, it has been determined significant savings compared to a conventional A/C basecase house (62%). During nighttime, the bedrooms were also operated on a dual mode basis (A/C from 10pm-7am), reducing cooling loads compared to a base case up to 80%.

Energy efficient appliances & equipment After construction costs, a building’s greatest expense is the cost of operation. Operation costs can even exceed construction costs over a building’s lifetime. Careful selection of high efficient appliances and lighting further minimized the Guarajuba Ecohouse’s electrical load. The smaller appliance, lighting loads resulted in less PV capacity required to meet the home’s total electrical load. These were based on the PROCEl (Brazilian governmental regulation program for reduction of energy consumption through appliances and equipment). High efficient compact fluorescent lighting and high-efficient appliances were used.

Renewable Energy Use: Solar PV grid connected system and solar water heating system

A utility grid connected PV roof system is used at this project and a solar hot water system. It was basically sized to provide power that would offset as much of the household load as possible.

For the summer period, the air conditioning equipment was to be used, for daytime only periods (office), so part of the PV roof was optimized to maximize the annual yield, and part to meet the peak load requirements for A/C in summer. A 2.5kW PV system was defined on the roof of the Guarajuba Ecohouse in a split array arrangement with 1.8kW facing north and 0.7kW facing N/NW (Figs 5-6). The N/NW facing array was included in the project to augment the afternoon peak demand period during summer (for the A/C office loads) [7]. Based on the simulations run with ESP-r and PV Design Pro-G 4.0. The low energy design
features combined with the PV grid connected system, reduced total electrical consumption by more than 60%, when compared to the basecase simulated (traditional housing in Brazil). The PV component had demonstrated the feasibility of eliminating the peak load posed by the cooling system on the utility during its coincident peak demand period.