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Some of the most exciting energy savings in new and retrofit construction today are found in passive systems. These systems are desirable because once installed, they perform with little or no need for maintenance or operation, creating economies, which are ongoing and significant.
In today’s performance-oriented building environment louvers and sunshades are more than accessories. When correctly specified and carefully selected, they can make a considerable contribution to a building’s overall energy performance.
Sunshades Improve Aesthetics and Create Energy Savings
Building location and orientation are the determining factors for sunshade usage and ultimately what benefits are possible. In moderate to warmer climates where cooling is a factor, strategically placed sunshades can be a first line of defense against the sun’s penetration throughout the day, creating opportunities for a variety of efficiencies.
The orientation considerations in the northern hemisphere for sunshades are west-, south- and east-facing windows and surfaces. The sun’s angle to the earth’s surface, or solar altitude, helps determine what affects sunshades may have on the structure.
The factors for sunshade placement include the building’s orientation in relation to southern exposure, the solar altitude when heating and cooling seasons alternate, i.e. April 15 and September 1; and the solar altitude during peak heating season, which is mid-January. While a structure’s southern, eastern and western exposures can each benefit from shading; the southern exposure is the easiest to shade and promises the most energy savings.
Sometimes shading is added on the northern exposure to provide aesthetic continuity only. In each application, the shelf location, blade spacings and projection dimensions need to be optimized according to the solar altitudes on each surface.
There is general agreement to the benefits of architectural sunshades. The most obvious benefit is related to HVAC systems and cooling costs. Building owners and architects have reported 15 to 50 percent savings on cooling costs and overall annualized energy costs in structures where shading solutions are optimally designed.
In addition to ongoing costs, smaller, less costly air conditioning units can sometimes be specified, reducing both initial construction expense and future cooling expense. Since sunshades reduce A/C unit usage, they can also reduce peak electrical demand. This can impact a building’s design for electrical, using smaller, less expensive components to handle smaller loads. These HVAC and electrical savings occur perpetually without additional cost.
Sunshades are also relatively maintenance free. Deland, Fla.-based Kingspan North America offers design options to help project teams create an aesthetic appearance that remains functional and is tailored to specific applications, as well as integrated with other building envelope components.
There are also benefits for the building occupants who use natural light when sunshades are installed. Interior window treatments can be eliminated, as well as expensive customized glass. With fewer artificial light requirements, occupants benefit from natural light, which is documented to increase comfort and productivity, along with many other positive results.
Louvers Create Ambient Air Flow Where it Otherwise Couldn’t Go
Louvers are another passive system that delivers long-term benefits. Their horizontal blades are specifically designed to facilitate air flow, while keeping other undesired elements out, such as water, dirt, debris, and in some cases wildlife or people.
Internal heat gain is frequently a problem in large commercial structures. If the need for cooling is determined by internal heat gain and not just outside temperature, there is opportunity for ventilation. Air flow in these applications is frequently created via louvers, allowing free air space for air to flow, while keeping out unwanted elements. Factors, such as what is behind the louver, as well as climate/storm probability, etc., will determine how easily the louvers prevent the egress of rain.
Louvers are all about reconciling the amount of free space available with the amount of obstruction created by the blade and frame. Typical louver free areas range from 35 to 60 percent of the wall opening, so 65 to 40 percent remains obstructed. It’s desirable to create a high percentage of free area that maximizes air flow. However, the prevention of rain or other debris entering determines how much of the free area must be obstructed.
Louvers create resistance to air flow based on its frame and blade shapes. Lower blade angles cause less resistance, higher angles more. Whether louvers will be used with fans, in open air, in hurricane zones, exposed to wind driven rain, etc., all determine how much resistance will be desired.
It’s the functional purpose of the air flow within a commercial structure which ultimately contributes to a building’s performance and energy efficiency. Air movement underneath a structure’s roof assembly can reduce heat buildup and lessen requirements on air conditioning units. When adequate ventilation is consistently created there may be opportunities to reduce the size of HVAC configurations. If the louvers are air intake for machines, HVAC or external cooling, there are specific calculations to ensure the louvers are adequately sized and machines will remain at desirable temps.
Kingspan North America markets architectural louvers made with high-performance extruded aluminum designed to satisfy a building’s specific HVAC needs without field cuts, flashings or exposed fasteners. For most manufacturers, their louver systems can be integrated with horizontal metal panels and coated to match the finished wall system.
The placement of louvers can help to optimize air flow within a structure. Ideally cross ventilation is created when louvers are placed at opposing ends of the structure. Designs that prevent cross ventilation may see louvers located adjacent to each other, which still allows for intake and exhaust.
A third possibility is a thermal chimney type of effect, which creates intake at a lower point and exhaust at a higher point or in a vertical component on the roof. In some applications louvers also control the entrance of sunlight into a structure, while still facilitating air flow.
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Paul R. Bertram Jr., FCSI, CDT, LEED AP, is the director, environment and sustainability for Kingspan Insulated Panels, Deland, Fla. To learn more, visit www.kingspanpanels.us.