Consulting Specifying Engineer April 2015-CSE : Page 64

Integration: Lighting and HVAC systems angularly selective set of louvers can be adjustable and motorized, they might be able to adjust at various times of day to block both the high-angle sun for heat con-cerns, and the low-angle sun for glare con-cerns at other times, while rarely blocking as much daylight as a non-angular shading system would block. Aside from selective shading of solar radiation, non-selective general shading such as fritting and mesh shade screens is another option. While blanket-coverage shading on the outside of a façade can reduce solar heat gain, it likely reduces potentially useful visible light to the same degree, and limits this useful light at all hours, including when there is no glare or heat gain concern. In some cases, such as frit or diffusing interlay-ers, these approaches may even reduce visible radia-tion more so than infrared, which may help glare or excess illumination expo-sure but may not have as notable a double-duty ben-efit as infrared protection at the same time. There is one more key consideration in optimal and smart design and planning of glazing: striving toward glass of the size and speci-fication for useful coverage Figure 5: In Abu Dhabi, the customized grid shell fritted and transmission without glass panels at Yas Island Marina Hotel provide a first line excess. While admitting of defense for solar shading, with continuous balconies radiation in the form of serving as overhangs as a secondary shading benefit. useful light and infrared Custom-made color changing LED luminaires are fitted to heat gain, glass is also com-each node of the grid shell to transform the appearance of monly a chink in the armor the fritted glass at night, as photographed by Bjorn Moer-of the building envelope’s man Photography. insulation. So excess glass The most productive angular selection might allow excess heat into the building tends to be a horizontally biased louver or during the day beyond useful illumination shading grid to cut out the highest and hot-and views, while also allowing excess heat test sun angles. On the east and west, one to leave the building at night and possi-often reiterated but problematic thought bly adding to heating energy expenditure. might be to implement vertical louver-like Glazing panels are always limited in their systems. The low-angle sun can probably insulating ability compared to the potential only be shaded for limited times of the insulation of other portions of the building year by such a system, while a horizontal envelope, making excess glass at least a shading system can block some mid-day three-fold problem in glare, infrared heat, sun throughout the year. However, if an and insulation impacts. Selecting angles of radiation to admit can be done even without automation, by using fixed louvers, cellular panel-ized modules, overhangs, and so on. In traditional architecture, this could take the form of window shutters and jalousie systems, eaves and overhangs, colonnades and porticos, mashrabiya, and more. While architectural styles evolve over time, and these traditional shading forms may be reserved for historical revivals, the cur-rent necessity for cautious use of energy brings notably visible shading systems back to the forefront of architecture. It is only with notable shading systems that any degree of expansive glazing design can be responsibly enjoyed. 64 Consulting-Specifying Engineer • APRIL 2015 Electric light Once the planning of glass and day-light for a building has been consid-ered—with the balance of solar gains, useful light, and insulation require-ments—the electric lighting fixtures and their visible and infrared radiation should be considered. What are the key factors in coordinating or integrating HVAC and internal electric lighting sys-tems? It is important to acknowledge the changing technology of electric lighting and its impacts on the way its heat is radiated, to judge the future potential for the next generation of buildings. In original incandescent lighting, metallic (tungsten) filaments within light bulbs are heated by electricity running through them, and creating heat and light due to the resistivity of those filaments. The typical glass bulb-shaped enclosures trap heated air around the filament, while infrared (and some UV) radiation is largely emitted in the same directions as the illumination. With the advent of halogen lighting, the trapped air temperature is used with halogen gas fill within the bulb, to power a cycle by which small traces of evaporated fila-ment are deposited back to the filament for extended life and efficiency. Howev-er, the waste heat is still primarily radi-ated to the same places of the building as the visible light. Only a tiny portion of waste heat is conducted back through a standard light socket, and some heat convected away from the glass bulb of the incandescent or halogen lamp. Fluorescent and discharge lamps repre-sent an entire generation (or multiple gen-erations) of lighting technology based on running electricity through element-filled chambers to produce a glowing arc, rather than a glowing hot filament. Whether using low-pressure mercury in a large fluores-cent tube with phosphorescent coatings, or high-pressure mercury, metal halides, and/ or sodium in a tiny chamber within a bulb, the electrical arcs through these elements radiate more visible and UV wavelengths and less infrared waste than incandescent lamps. The electrodes used in such prod-ucts still conduct electricity and generate heat through their resistance, but with the

Previous Page  Next Page

Publication List
Using a screen reader? Click Here