Construction Of Efficient Buildings Research Articles

Effect of Air Space Thickness within the External Walls on the Dynamic Thermal Behaviour of Building Envelopes for Energy Efficient Building Construction

This paper presents the comprehensive investigation of the effect divided air space thickness within the wall on unsteady heat transfer characteristics such as thermal transmittance, thermal admittance, decrement factor and time lag of five building material walls for energy efficient building enclosure design. The five building material composite walls such as laterite stone, mud brick, cellular concrete, dense concrete and cinder concrete with total thirty configurations were studied. A computer simulation program was developed to compute unsteady heat transfer characteristics using the cyclic admittance procedure. From the results, it is observed that the decrement factor decreases with the increase in the divided air space thickness within the composite wall for all building materials. Dense concrete was observed to be the energy efficient from the lowest decrement factor point of view among five studied building materials. Dense concrete decrement factor decreases by 23.65% for 0.02 m air space thickness compared to the conventional composite wall without air space. It is also noticed that the time lag increases with the increase in the divided air space thickness within the composite wall for all building materials. Cellular concrete was observed to be the energy efficient from highest time lag perspective among five studied building materials. Cellular concrete time lag increases by 6.23% for 0.02 m air space thickness compared to the conventional composite wall without air space. The results of the study help in designing energy efficient building enclosures.

Evaluation Method for Energy Saving Effect of Reflective Thermal Insulation Coatings

According to the climate and energy saving characteristics in the hot summer and cold winter zone, especially in view of requirements for thermal insulation in summer, reflective thermal insulation coatings (RTIc) are gradually applied in building energy efficiency of exterior envelope. A feasible evaluation method for energy saving effect is very important for acceptance of energy efficient building construction. In this paper, thermal resistance has been used as the evaluation index. The energy efficiency of the reflective thermal insulation coatings was investigated. Four hot boxes were applied contrast test. Based on the qualitative and quantitative analysis of electricity consumption within 36 hours and comparative analysis of heating process simulating sunlight environment, thermal resistance of RTIc can be calculated on the basis of the correlation between power saving rate and thermal resistance so that energy saving effect of RTIc can be quantitatively characterized.

Modeling Thermal Comfort and Optimizing Local Renewal Strategies—A Case Study of Dazhimen Neighborhood in Wuhan City

Modeling thermal comfort provides quantitative evidence and parameters for effective and efficient urban planning, design, and building construction particularly in a dense and narrow inner city, which has become one of many concerns for sustainable urban development. This paper aims to develop geometric and mathematical models of wind and thermal comfort and use them to examine the impacts of six small-scale renewal strategies on the wind and thermal environment at pedestrian level in Dazhimen neighborhood, Wuhan, which is a typical case study of urban renewal project in a mega-city. The key parameters such as the solar radiation, natural convection, relative humidity, ambient crosswind have been incorporated into the mathematical models by using user-defined-function (UDF) method. Detailed temperature and velocity distributions under different strategies have been compared for the optimization of local renewal strategies. It is concluded that five rules generated from the simulation results can provide guidance for building demolition and reconstruction in a neighborhood and there is no need of large-scale demolition. Particularly, combining the local demolition and city virescence can both improve the air ventilation and decrease the temperature level in the study area.

Summary on the Evaluation Indicator for Thermal Insulation Performance of Reflective Thermal Insulation Coatings

Reflective thermal insulation coatings (RTIc) are applied widely in Hot Summer and Cold Winter Zone and in Hot Summer and Warm Winter Zone. A feasible evaluation method for energy saving effect is very important for acceptance of energy efficient building construction. Combining with the research on RTIc at home and aboard, series of evaluation indicators of thermal insulation performance and energy saving effect of RTIc such as solar reflectance, hemispherical emittance, temperature, thermal resistance, energy efficiency and thermal inertia were summarized and the existing problems and several suggestions were also proposed.

Nano-scale hydrogen-bond network improves the durability of greener cements

More than ever before, the world's increasing need for new infrastructure demands the construction of efficient, sustainable and durable buildings, requiring minimal climate-changing gas-generation in their production. Maintenance-free “greener” building materials made from blended cements have advantages over ordinary Portland cements, as they are cheaper, generate less carbon dioxide and are more durable. The key for the improved performance of blends (which substitute fine amorphous silicates for cement) is related to their resistance to water penetration. The mechanism of this water resistance is of great environmental and economical impact but is not yet understood due to the complexity of the cement's hydration reactions. Using neutron spectroscopy, we studied a blend where cement was replaced by ash from sugar cane residuals originating from agricultural waste. Our findings demonstrate that the development of a distinctive hydrogen bond network at the nano-scale is the key to the performance of these greener materials.

Construction Site Waste Generation—The Influence of Design and Procurement

This paper seeks to define critical influences which are of practical use to New Zealand builders and that can lead to more resource efficient building construction, through the reduced generation of waste material. To explore these critical influences, surveys were carried out based on a survey conducted in a similar construction environment (Australia). Three construction groups were targeted for the survey—architects, quantity surveyors and sub-contractors. The resulting critical determining factors from the surveys are discussed, and conclusions drawn. The information gained will be fed into a variety of formal and informal waste minimisation plans and projects.

Energy performance and energy conservation in health care buildings in hellas

Energy performance data for 30 health care buildings have been collected during an extensive energy audit of buildings in Hellas, within the frame of a National Energy Programme sponsored by the CEC VALOREN Programme for energy conservation in buildings. This short monitoring campaign was performed with on-site visits of a trained panel of engineers to each building, in order to register all information relevant to the buildings' construction, heating, cooling, lighting, systems and all other mechanical and electrical systems. The technical results of these audits, the role of the cooling and heating systems on the energy consumed in health care buildings, are discussed. The annual average total energy consumption in hospitals is 407 kWh/m 2 and in clinics is 275 kWh/m 2, the majority of which is consumed for space heating (73.4% in hospitals and 65.3% in clinics). Several scenarios for possible interventions to the outer envelope of the buildings and to the heating, cooling and lighting systems, are proposed and evaluated, in order to assess the effectiveness of various energy conservation techniques. Based on the results from several simulations, it is concluded that it is possible to reach an overall 20% energy conservation. The energy consumption for heating can be reduced by 15% in hospitals and 11% in clinics by using more efficient heat production and distribution systems. Proper insulation of the buildings can conserve 173 kWh/m 2 in hospitals and 103 kWh/m 2 in clinics. Cooling can be reduced by 68% (in hospitals) and 56% (in clinics) by using night ventilation and by 80 and 97%, respectively, by using ceiling fans. Natural cooling techniques, under certain conditions, can also provide an important reduction of the cooling load. The use of high efficacy lamps can reduce the electric energy consumed for lighting by up to 50%. This information provides a representative picture of the existing conditions on energy consumption in health care buildings and can be used as guidelines for future energy efficient building construction.