Analysis II Façade Redesign: Architectural Precast Panels

Analysis II Façade Redesign: Architectural Precast Panels

Analysis II Façade Redesign: Architectural Precast Panels Overview: This analysis covers the comparison of the current EIFS façade and my proposed change to architectural precast panels. It compares several important factors and shows the results of a structural analysis showing that the existing building can support the heavier façade. The precast is a higher quality and more durable system that will last the life of the building. It has a greater cost associated with it, but is well worth having confidence in the performance of the façade when it needs to last for the life of the building. Background: The façade of a building is the main barrier between the outside weather, and the interior of the building. It is crucial that the façade can keep water and moisture out of the building, and that it can handle the type of weather it is going to be exposed to. In the case of the Goizueta Foundation Center, the façade chosen was an exterior insulating finish system, which I will refer to as EIFS from here on. This system consists of several layers, shown in Figures 5 and 6 below. A. Substrate/Sheathing B. Adhesive C. EPS Insulation Board D. Reinforcing Mesh E. Base Coat F. Finish Coat Figure 5: Layers of the EIFS system used on the Foundation Center Figure 6: Isometric section of EIFS layers 21

EIFS has several benefits, but also many drawbacks. Mainly, it is not a good system to install in an area that receives a moderate amount of rainfall. This is the case with Atlanta. The average annual rainfall in Atlanta is 51. For a system that can have problems in wet areas, Atlanta does not seem to be a good place to be installing it. Not to say that EIFS may perform well in its initial testing for moisture penetration, but over the life of the building it will certainly need maintenance and/or repair. Moisture damage to a building with an EIFS façade can be extremely expensive to repair and replace. In some cases, the remediation costs more than the initial construction itself. The drawbacks of EIFS certainly validate a redesign of the façade. The foundation center is an educational building on a university campus. Universities build buildings that are going to be in use for 100 years or more. With this in mind, the building must then be exposed to 100 years of weather and storms. EIFS was first used in the United States in 1969. It is barely more than 35 years old. There is no guarantee that it can withstand 100 years of weather and storms because it hasn t been around even half that time for it to be tested. A university wants a building with a high quality façade, and that is why I chose architectural precast panels. I have compiled a list of factors that I feel are important when choosing a façade (see Table 4 below). Cost Weight Insulation Value Ease of Installation Water Tightness Factors EIFS Precast Panels EIFS is very cost effective, at about $10/sf. Second advantage, EIFS is a very light façade system The insulating board in the EIFS system has an R-value of 3.8 per inch thickness. Labor intensive, requires scaffolding and all work is done from the exterior. Entirely dependent on the quality of the installation. More expensive, Architectural Panels costing roughly $40/sf Architectural Panels weight 62.5lb/sf Concrete suffers here with an R-value of only.1 per inch thickness. Panels are placed by crane, and insulation is done from the inside. Water tightness can be achieved through sealants and is very effective. 22

Time of Installation Maintenance Durability Fire Resistance Quality Control In this case, 115 days, and requires steel construction to be completed before it can begin. Can be very costly, and is also labor intensive. EIFS has only been around for 35 years, no guarantee it can last for the typical life of a university building. Also only comes with a 5 year warranty, 10 year was purchased for this project. Tested for fire resistance, but materials are still combustible. Left up to field installation. Must be installed 100% per specifications or water penetration becomes a serious issue. Can be placed at a rate of 12 panels per day. Does not require steel structure to be complete to hang panels on lower levels. Little to no maintenance required. Extremely durable, can easily last 100 years under normal weather conditions. Concrete is noncombustible. All Panels are made in the factory in a quality-controlled environment. Table 4: Comparison between EIFS and Precast Panels Proposed Solution: Through the use of a precast panel façade, I hope to show that it would be a higher quality building that will last as long as the building will be expected to. Precast concrete is an extremely durable material, withstands all types of weather, and will be able to protect a building for 100 years. There are many other advantages that precast has over EIFS. EIFS is a labor intensive system to install. It requires scaffolding which increases the time it takes to install. Not only does the scaffolding make the installation time longer, but the fact that the steel erection must be completed before the EIFS can be installed. The foundation center was erected in two sequences. After sequence A was complete, the EIFS started installation there while the crane erected sequence B (see Figure 7 on the following page). 23

Figure 7: Steel erection and building skin sequence The entire steel sequence was approximately 85 days, 40 for the first sequence, and 45 for the second. The entire EIFS installation took a total of 115 days. This is 115 days after the first steel sequence was completed (see Figure 8 on the next page). Please refer to the schedule on the next page. The exterior skin installation lasted from October through March, so the building was exposed for the entire winter. If precast were being installed, there is no need for the steel structure to be complete for panels to be hung. There are a few opportunities to save schedule time here. First, a smaller crane could be used to hang panels on the lower levels of the building until it is out of reach, at which time the tower crane could take over placing panels. Second, the tower crane could set steel in the morning and panels in the evening. Either way, the building would be enclosed much sooner than in the case of the EIFS. It would likely be enclosed by the end of the year, being that there is no wait for the structure to be complete, and the precast would be insulated from the inside (see Table 5). EIFS Precast Panels 115 Days 60 Days 35, 25 10/11/2004 3/18/2005 Sequence A: 9/6/2004 10/22/2005 Sequence B: 10/25/2004 11/26/2004 Table 5: EIFS and Precast Panel schedule comparison 24

Figure 8: Detailed schedule of structural steel and EIFS construction sequences 25

Cost: Now to speak of the downsides of precast; its cost, weight, and insulation value. For the cost comparison, Table 6 shows the difference between the systems: Material Quantity Unit Unit Cost Total Cost EIFS façade 57000 sf $9.73 $554,610.00 Architectural Preacast 57000 sf $40.00 $2,280,000.00 Table 6: EIFS and Precast Panel cost comparison This is a substantial increase in cost. Not only does the material itself cost more than the EIFS, but precast also requires additional framing and insulation. I have added the rough cost of the framing and insulation into the per square foot cost of the precast panels. Insulation: For insulation, the precast system will use R-19 batt insulation. This will have a U-value around 0.05 vs. 0.04 for the EIFS system. To increase the efficiency of the precast system, a thicker insulation could be used, such as R-22. This is an important aspect of the façade because of its direct affect on heating and cooling costs. Structural Analysis: Lastly, I will discuss the weight issue. The architectural precast panels I have proposed to use are a solid 5 panel, made of normal weight concrete, and weighing 62.5 lb/sf. I analyzed a column on the NW (rear) elevation (see highlighted section in Figure 9 below). Figure 9: NW (Rear) Elevation with the analyzed column and surrounding precast panels highlighted 26

The panel connections are column bearing, so the spandrel beams do not require testing. I calculated the loads from the floor deck, beams and girders, façade, and roof that are carried by that column. The specifications state that the combined dead and live load carried to the columns from the floor deck is 225lb/sf. The composite deck is 3 18 gage with 6-¼ lightweight structural concrete and wwf 6x6 w1.4xw1.4. Using this information, I drew a model in the structural program RAM Advanse, and applied the loads I calculated at each floor level (see Table 7). I drew the column, defined the steel type and section sizes, and then analyzed it. After analyzing, I ran the check for code compliance, and the column was labeled OK under the applied load scenario. Screenshots from this analysis, as well as analysis reports can be found in the appendix of this document. Figure 10 (on the following page) shows the column, beams, and girders that were involved. Note that the column was spliced between the 3 rd and 4 th levels, as the drawing is not clear in showing this. Floor Level Lower Roof Level 5 Level 4 Level 3 Level 2 Load Type Loads Unit Total Load Roof 17.5 Façade 17.0 kip 19.4 Members 1.9 Slab 105.0 Façade 15.7 kip 17.8 Members 2.1 Slab 105.0 Façade 19.0 kip 1.9 Members 1.9 Slab 105.0 Façade 21.8 kip 24.2 Members 2.4 Slab 105.0 Façade 0.0 kip Members 1.9 1.9 Table 7: Summary of loads from each level of the building transferred to the analyzed column 27

Lower Roof W18x35 W18x35 14 W24x55 W14x61 Level 5 Level 4 13 W24x55 W14x61 16 W14x99 Level 3 W21x68 18-6 W24x55 W14x99 Level 2 15-6 W24x68 W14x99 Figure 10: Diagram of the analyzed column, with beams, girders, and floor heights shown The column I selected to analyze was the smallest in the rear elevation that was under the typical load I determined. Being that it was successful under the additional load of the precast, the remainder of the exterior columns would be as well. Conclusions: This analysis has brought to light the shortcomings of an EIFS façade and the benefits of using precast panels. After comparing all the important factors that are a part of façade selection, I feel that the precast panels would be a much smarter choice for this building. The main reasons being that it is a university building that will be standing and in use for the next 100 years, and precast is more than capable of protecting a building for this amount of time. The additional cost is a substantial increase, but to avoid repair and maintenance costs that will come in due time with EIFS, it will be a very wise decision to pay the greater initial cost. 28