Good afternoon. Welcome to PCI's webinar series. Today's presentation is Simplifying the Building Envelope with Precast Concrete. My name is Royce Covington, Manager of Member Services at PCI, and I'll be your moderator for this session. Before I turn the controls over to your presenters today, I have a few introductory items to note. If you need anything, please feel free to contact me by replying to your registration confirmation or send an email to marketing at pci.org. Earlier today, we sent an email containing handouts for today's presentation. The handouts are also available for you to download now, located in the handout pane near the bottom of the GoToWebinar toolbox. There, you will find a PDF of today's PowerPoint, detailed instructions to access your certificate, and a webinar attendance sign-in sheet, which is only for locations with more than one person viewing. If you cannot download any of the handouts, please email me immediately at marketing at pci.org. 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PCI has met the standards and requirements of the Registered Continuing Education Program, RCEP, of the National Council of Examiners for Engineers and Surveyors, NCEES, and we can offer one PDH for this course. PCI is a registered provider of AIA CES, but this presentation does not contain content that is endorsed by AIA. Any questions about the content of this webinar should be directed to PCI. This program content does not constitute approval by PCI, nor does it necessarily reflect the views or positions of PCI or those of their respective officers, directors, members, or employees. Questions related to specific products or publications will be addressed at the end of the presentation. Our presenters for today are Alex Wilfang, Account Manager at Wells Concrete. Alex has been with Wells Concrete since 2013, when she began her career in production control. In addition to maintaining the master production schedule, she learned the mechanics of custom mold building and plant logistics. From there, she moved into the drafting and engineering department, where she further developed her technical and spatial reasoning skills before being promoted to project estimator. In this role, she expanded her responsibilities from preparing cost estimates to include pre-construction assistance. Alex is a graduate of the University of Illinois, Champaign-Urbana, with a Bachelor of Science degree in architecture. Joining Alex is Dan Stindle, Facades Business Development Manager at Wells Concrete. Dan rejoined Wells Concrete pre-construction group in April of 2019. Prior to rejoining Wells, Dan worked as a project manager for a large general contractor construction management firm for five years. While working in the general contracting sector, Dan gained knowledge in a number of different construction software programs and certificates from LEED, Best Value Approach, OSHA 30, and SWPPP. Dan originally began his career at Wells Concrete in 2007, where he started out in the drafting and engineering department and quickly made his way into the pre-construction group. His technical experience, commitment to client relationships, attention to detail, precast efficiencies, project budgeting, and scheduling gives him a valuable understanding of how to best support their clients. Dan holds a Bachelor of Science degree in construction management, along with a minor in business administration from Minnesota State University, Mankato, and an AAS degree in architectural drafting from South Central College. Our learning objectives for today are describe different attributes of precast concrete envelope systems, explain thermal mass and how to use it to create more energy efficient buildings, understand the concept of resiliency and how precast pre-stressed concrete incorporates it to provide multi-hazard protection, describe aesthetic options for precast enclosure systems, and strategize to consider for prefabricated envelope systems. I'll now turn the controls over so that we can begin our presentation. Good afternoon, everyone, and thank you for that introduction. I'm glad to have everyone here. Thank you for joining us. And with that, let's get started. Today, Dan and I are here to talk about simplifying the building envelope with precast. So let's start out with what is the building envelope. Simply put, the building envelope is the physical separation between the conditioned and unconditioned environment of a building. It resists air, water, light, heat, fire, and noise transfer. Sticking to the basics here, what is precast? Precast concrete is produced off-site in a controlled environment. Plant-produced concrete eliminates outside variables such as weather and temperature, while also offering greater control over finishes and tolerances. Concrete members can either be designed as precast or pre-stressed. Precast concrete is designed with mild reinforcing, whereas pre-stressed concrete relies on tensioned steel cables. During pre-stressing, the steel cables are positioned along the length of the casting bed. One end is anchored to a fixed abutment, while the other end is attached to a hydraulic jack. The jack then tensions each cable to the designed force. After the concrete cures, the cables are cut, and the tension from the strand is transferred as a compressive force into the concrete. Okay, let's move into some advantages of precast concrete. One of the greatest benefits to precast structure is the speed of construction. Erection is not affected by seasons and can occur year-round without sacrificing quality. The production facility is a controlled environment, offering a high degree of quality control. Pre-stressed concrete is designed with mild reinforcing, offering a high degree of quality control. The pre-stressing process allows for long spans and shallow sections. It is a durable and inherently fire-resistant and sound-resistant material. Precast offers just about unlimited possibilities when it comes to form, color, and finish to achieve the desired look, and we'll talk about that more later. Okay, precast has a high thermal mass, which results in energy savings, and I believe Dan is going to touch on that also later. Concrete is an eco-friendly building material and is 100% recyclable. The steel inside is recyclable, and also a large portion of it is made from recycled material. All of these inherent attributes of precast concrete can be organized into three All of these inherent attributes of precast concrete can be organized into three higher level concepts, number one being versatility, which refers to versatility in aesthetics and design, as well as structure's use. Number two is efficiency in design, construction, and throughout operations. Finally, number three is resiliency in providing long-term durability and safety. High-performance materials like precast provide all three. Okay, so next we'll be moving into precast wall types. Precast is used for all types of buildings from low-rise to high-rise. This includes offices, retail and shopping centers, theaters and entertainment, public and institutional projects, and residential. Precast is also used in parking structures, bridges, and other applications, making it a very versatile material. Precast can come in many shapes, but one of the more common profiles is the spandrel, as seen on the office building to the left. These are typically rectangular sections that span column to column. Oftentimes they alternate with ribbon glass or are left open in the case of parking structures. Another common shape is the punched window wall, seen here on the right. These panels are typically one story tall and also span column to column, however in some cases they may span vertically over multiple stories instead. Punched window walls can be designed to fully encompass fenestration elements such as windows. Depending on the project, there is also an opportunity that the windows can be installed in the precast plant and shipped to the job site integral with the precast. This means fewer trades on site and is just one more way in which precast buildings brings efficiency to a project. Aside from punched window walls and spandrels, there are several smaller shapes such as column covers, again seen here on the left, mullions, and the list goes on. All of these elements can be combined to create interesting yet practical facades. Okay, let's start by looking at wall panels. These are the three primary types of precast walls. Number one is solid walls. These consist of one solid concrete wide and are usually six to ten inches thick. If the solid wall encloses a conditioned space, it will require some form of insulation and interior finish system like studs, furring, and drywall to be installed to complete the envelope. The second type is the insulated sandwich wall panel, which consists of an exterior and interior width of concrete, sandwiching a layer of rigid insulation. The thickness of each width can vary and is driven by design. With this system, the interior width of concrete is often used as the finished interior of the structure, reducing the need for furring, drywall, and so on. The third type is the thin shell, which consists of one exterior width of concrete, typically one and a half to three inches thick, supported by a structural frame. The frame is generally made from steel. Okay, here are a couple examples of solid precast walls. They can either be load-bearing or non-load-bearing, depending on the application. In this case, both projects are using solid precast members as non-load-bearing cladding. I'd also like to highlight that in many architectural applications, it is common to use a combination of facemix and backup mix. A facemix is generally colored concrete and may contain more expensive sands, aggregates, and pigments. The exterior of the panel is poured with the facemix, then a standard, less expensive gray backup mix is used for the rest of the panel. This helps to reduce costs. So, for example, the spandrels on the office building to the right were poured with about three to four inches of white facemix, then the remaining five to six inches was poured with a structural gray mix, where it would be hidden from view by interior finishes and drywall. Here are a couple more examples of solid walls, with the project on the right being a good example of solid load-bearing walls, probably supporting a steel roof and intermediate floor. Again, here you can see the variation in color from a combination of facemixes. Here is a good rendering to illustrate an example of insulated sandwich wall panels. Again, these consist of two wives of concrete sandwiching together a layer of rigid insulation and can be used in load-bearing and non-load-bearing applications. Here are a couple more examples of solid walls, with the project on the left being a solid wall and supporting a steel roof and intermediate floor. Again, here you can see the variation in color from a combination of facemixes. Insulated walls can be designed to work compositely or non-compositely, depending on the application. Composite panels use non-conductive Y-connectors so that both the interior and exterior sections of concrete work together to resist the load and provide full shear transfer between the Ys. This system allows you to reduce the overall wall thickness. Non-composite panels use connectors that allow each Y to work independently. Generally, the interior or structural Y is thicker and designed to resist the load. Panels can also be designed to be partially composite, which is somewhere in the middle between the two, providing partial shear transfer. Your pre-caster can help you determine which system makes the most sense for your project. Here is an example of an insulated cladding project with integral brick. It is important to note that any architectural finish that can be applied to a regular panel can also be applied to an insulated panel, including thin brick and CMU, colored concrete, form liners, and so on. Because the insulated panels do not require furring out, they can be produced so that the interior finish is paint-ready. I see this a lot in schools, gymnasiums, natatoriums, and rec centers where the pre-cast is serving as an extremely durable, exposed surface. Lastly, we have some examples of thin-shell wall panels. Again, these consist of a thin wall and a thin-shell wall. On the left is an exploded view of a system that is designed with a tube-steel frame. This provides great freedom in the possibilities of form and profile of the pre-cast façade. And, just like the solid and insulated pre-cast panels, the pre-cast panels can also be used as a form-and-profile system. the possibilities of form and profile of the pre-cast façade. And, just like the solid and insulated pre-cast panels, thin-shell panels can accommodate any architectural finish. In addition to being a lightweight alternative to traditional cladding, it is often possible to incorporate plant-installed insulation and windows into the thin-shell system. In some cases, the structural frame or backup system can even be used to attach drywall. In some cases, the structural frame or backup system can even be used to attach drywall. And with that, I'm going to hand it off to Dan to take us through the thermal performance in pre-cast. Alrighty, thank you all. Thank you, Alex, for that. In this section, I'll touch on the energy efficiency and thermal performance of pre-cast concrete. When we think of efficiency, we think of ways to reduce the amount of time or materials used. One simple example of efficient pre-cast is using a pre-cast wall panel for the building envelope properties, but also using that same wall panel as part of the structural system. This reduces additional materials such as beams, columns, saves time, increases the usable amount of square footage within the space, and ultimately reduces costs. You can also think about using a sandwich wall panel as the complete envelope by leaving the interior white of the concrete exposed to act as the interior wall finish. This eliminates the need for any additional wall furring, which is completely unnecessary when using pre-cast concrete. Pre-cast concrete is manufactured off-site, which means there's minimal site impact, no storage areas needed due to the just-in-time delivery. Pre-cast concrete is one of the fastest building systems available. Pre-cast concrete reduces complexity in wall assembly as compared to cavity wall systems. We'll touch more on some thermal performance in a little bit. Pre-cast concrete also reduces lifecycle costs by reducing the amount of maintenance required and the energy usage within the building. All of these benefits result in a better overall value for the owner and their occupants. Now let's get into thermal performance. Building envelopes are complex systems and are mostly affected by heat loss or heat gain from opaques and fenestration assemblies, the amount and quality of fenestration, and also air and moisture. Let's talk about some building envelope codes. There are two primary national energy codes in the United States. Projects typically adopt one or both of these versions of the code, and there also might be a unique local jurisdiction requirement to consider. First, you should be familiar with the various codes that govern these areas. Both ASHRAE 90.1 and IECC deal with thermal performance and energy usage. They both specify criteria for the different opaque assemblies based on the climate zone that your project is in. Then you would determine the requirements needed based on the envelope assembly. They also specify criteria for fenestration assemblies and address continuous air barriers, which is now a requirement of both and address continuous air barriers, which is now a requirement of both codes. One thing to note is that the reduction of thermal bridging is implied in both codes, but they do not quantify it. However, the National Institute of Building Sciences has been working on a possible thermal bridging guide which may help quantify it. Finally, moisture mitigation is not addressed by energy codes. It is handled by codes such as the IBC. So, how do we manage heat in precast concrete? There are four main components to heat flow management. First one is the use of proper insulation types and thicknesses, which ultimately block heat flow. We'll also eliminate thermal bridging within a precast wall assembly. We'll also eliminate air and moisture leaks through proper detailing and quality control. And we'll also utilize the thermal mass properties of precast concrete, which is a major benefit. U-factor is the measure of heat flow or thermal transmittance. The lower the U-factor, the less the material conducts heat, the better. Most people are familiar with U-factor when working with window assemblies. The people that are most familiar with U-factor are those that work with window assemblies, as they're typically rated by U-factor. Ultimately, a U-factor is the inverse of the R-value. So, a quick example of this is, let's say you have a window with a U-factor of 0.36. The R-value would be about an R2.8. Understanding the U-factor in building envelope assemblies is becoming more and more popular each day. We've actually ran into this on a recent project of ours and had to work through that process with the consultants. Again, the opposite of U-factor is R-value. The R-value is the resistance to heat flow. The higher the R-value, the better. The chart on the screen shows R-values of common materials used in construction. One thing to note is that the most common three materials used in building envelopes – steel, concrete, and glass – all have very low resistance to heat flow, which is why we use other materials as insulators. All climate zones require continuous insulation, or CI. ASHRAE 90.1 defines CI as insulation that is continuous across all structural members without thermal bridges other than fasteners and service openings. What is not clear here is the actual definition of thermal bridging as it relates to other fasteners and service openings. All building envelope systems have fasteners or connections to the structural system, but how many are actually allowed? This definition does not quantify thermal bridging, and it is an example of where the National Institute of Building Sciences may be trying to fill the gap. In the case of precast, precast actually has less connections than most other envelope systems. And in the case of a sandwich wall panel with integral insulation, all the connections are happening behind the continuous insulation layer, so there is no thermal bridging. The first step towards designing your building envelope is determining which climate zone your project is in. On the screen, you'll see that there are two climate zone maps available right now – IEDC map and the recently updated ASHRAE map. One thing to note here is that the two maps are not exactly the same. The ASHRAE map has moved boundaries up based upon new climate data. For example, Fargo, North Dakota is shown in zone 6 on the ASHRAE map, but is located in zone 7 on the IEDC map. When this happens, the best thing that you can do is to contact the local jurisdiction to confirm which climate zone they'll want you to design for. So, what is thermal bridging? Some materials conduct heat better than others, such as metal. Thermal bridging in a building envelope is where the materials penetrate the insulation barrier, creating short circuits in the assembly, which ultimately reduces the envelope's overall performance. As you can see in the thermal imaging on the right, these short circuits show up as warmer spots on the image. The actual performance of a wall system is based entirely on assembly, including thermal bridging. For example, a steel stud wall with an R-19 BATA insulation does not perform as a R-19 wall. And to be honest, it's actually closer to an R-9 due to thermal bridging. Another important attribute of precast concrete is thermal mass. Thermal mass refers to the heat capacity of a material. Precast concrete has high heat capacity, which means it slowly absorbs and gives heat. This can provide several benefits. Although it is hard to see on the screen here, the chart on the right shows a 24-hour, 24-hour, 24-hour, 24-hour, 24-hour, 24-hour, 24-hour, right shows a 24-hour thermal cycle for three different wall systems. Two stud cavity walls, one with wood, one with steel, and the third wall system being precast concrete sandwich wall panel system. All three wall systems have the same U factor, which means the only difference between them is their thermal mass effect. The thermal mass of the precast concrete creates a thermal lag, which shifts peaks of heating and cooling points relative to when they occur outside. You'll notice that the traditional walls occur shortly afterwards, whereas the precast wall occurs several hours later. In some areas of the country, these peaks occur when energy rates are less expensive. What's more important is the reduction in magnitude of these peaks. That means that we are using less energy to heat and cool the structure due to the thermal mass effect. Thermal mass also helps to maintain a more uniform temperature, reducing large fluctuations, and increasing occupant comfort. It is important to note that the benefits of thermal mass will vary based on your project location. Environments where the outside temperature fluctuates above and below the set dew points will have the greatest benefit. Thermal mass is recognized in ASHRAE 90.1 and is the reason why different requirements are provided based off of what type of wall construction is being used. For example, let's say that we have a project in Minneapolis, Minnesota. A wall mass only needs a single continuous insulation layer with an R-value of 13.3, whereas a steel subwall needs continuous insulation layer that has an R-value of 12.5 and requires an additional layer of an R-13 bad insulation within that same wall assembly. Moisture in buildings can cause several problems, including damage and mold. In general, mold requires a combination of the following conditions to grow. Fungal spores, which can be found on the surface of just about anything, clothing, furniture, walls, whatever it might be inside. Oxygen, which is also everywhere. Temperatures in the range of 40 to 70 degrees. Nutrients available, such as drywall and acoustical ceiling tile. And finally, moisture. And since the first four are almost present, that leaves us with determining how to control moisture. Moisture gets into buildings by one of four methods. Bulk water, for example, rain. So, we must prevent leaks through proper design and maintenance of flashing, joints, and roofing. Vapor diffusion, which is when water vapor moves through the materials of the envelope at a molecule level. This is driven by pressure and concentration differences and is addressed by vapor retarders and barriers. Air movement, which is about 100 times greater than vapor diffusion. And condensation, which is when moisture vapor condenses on the surface. So, how will you meet the continuous air barrier requirements of the IECC and ASHRAE 90.1? Well, good news for you. That is that precast concrete is an air barrier, meeting the sections of the ASHRAE code and requires no additional treatment. This is significant when compared to sub-cavity systems that typically have penetration through sheeting and insulation materials, which must be dealt with. Okay. Now, let's address condensation. We must understand the dew point analysis. Most of us are familiar with dew point from the nightly weather report or from holding a can of pop. The dew point or the dew point temperature is determined by the air temperature and its humidity or wetness and is the point when water is in its gas form, changes to liquid. Unlike nature, we can actually control where and when the dew point occurs in our building envelopes by carefully studying our internal temperature and humidity as it relates to the outside temperature and humidity. To summarize design requirements, high-performing building envelopes should include the use of continuous insulation, reduce or eliminate all thermal bridging, use the benefits of thermal mass where appropriate, use continuous air barrier to prevent air exfiltration and infiltration, use a vapor barrier to prevent moisture vapor diffusion, and reduce condensation potential by controlling the dew point locations and surface temperatures. Precast concrete is an efficient, high-performing envelope system that meets all the requirements that were previously talked about. Precast concrete sandwich wall systems can include continuous edge-to-edge insulation, eliminates thermal bridging through the use of coated or composite connectors, has thermal mass, and an interior white that can be left to expose to serve as the interior finish wall, reducing materials, cost, and time. Precast concrete is an air barrier and meets the specified cold requirements, and at three inches thick, precast concrete is also a vapor barrier. Precast concrete envelopes can combine all these systems into one efficient system. Now let's take a look at some hazard resiliency attributes of precast concrete. Precast concrete structures have the ability to increase the safety and security of its occupants. With the use of precast walls, floors, and roof assemblies, precast concrete is commonly used to protect occupants from fire, earthquakes, blasts, and impacts. There are multiple PCI design manuals available to address these topics in greater detail. Please reach out to your local PCI producer for more information. As noted on the previous slide, precast concrete has fire-resistant properties. Precast concrete is a natural fire inhibitor. Precast concrete is a non-combustible material, and it can achieve many different fire ratings while reducing the cost and keeping the structural integrity of the building intact for occupants to be able to exit the building. Precast concrete can be engineered to withstand the design requirements when designing for tornadoes, hurricanes, and man-made blasts. One thing to note is that the ICC 500 rating is becoming more and more popular in our region. And precast concrete is a great solution for this requirement. Here's a quick video showing you how the wall assemblies withstand impact. This video will show a two-by-four being projected at four different wall systems at the speed of 100 miles per hour. The first three wall systems are stud cavity walls, which are commonly used in residential light commercial construction. The first one has vinyl siding, and the other two have brick veneer. All three allow the two-by-four to penetrate, causing extensive damage. The fourth wall is a precast concrete sandwich wall, which turns the two-by-four into two-fix. This clearly shows the storm resistance of precast concrete. Okay, thank you for that, Dan. Now we're going to jump into the versatility of architectural finishes. Color in concrete comes from a combination of up to five components, the first being the color of the cement, which is either gray or white, depending on the desired mix. The color of the stone used also contributes to the final color. Coarse and fine aggregates are used in all concrete mixes and can change the appearance of the concrete depending on how much they are exposed. For example, each of the three samples above are the same mix design, however, you can see the difference between the right and left sides. The right side of the red and white panels have deeply exposed surfaces, so you see a lot of the natural variation in aggregates, whereas on the left side, the surface is only lightly etched. Pigments can also be added to the mix to give you a wider range of colors such as reds, browns, deep grays, or black. Finally, a coating such as a concrete stain may be applied to the surface. The most common surface treatments are broken into three types, acid etch, sandblast, and exposed aggregate. As you can see, acid etching the panel is the most mild and exposes just a little bit of the aggregate. Sandblasting exposes a little bit more, but the concrete matrix is still exposed. Then with the exposed aggregate finish, most of the concrete matrix at the surface is removed, displaying just the natural stones. Here we have a list of all of the available precast finishes, including acid etch, sandblast, water washed, form finish, polished, integral thin brick, stone, terracotta, or CMU, form liners, and graphic concrete. In this recent project completed in Fargo, North Dakota, the architectural team was looking for an aesthetic contrast on the exterior finish and was able to achieve this goal with one mixed design and three different treatments, including water wash, sandblast, and acid etch finishes. Another architectural feature included a wave pattern that was achieved by using a custom built station in our Albany location. This wave pattern was the sandblast and water wash to further explain the detail of the wall panel itself. This design was utilized throughout the exterior of the structure and was paired with a thin brick finish around the pool area. This project is located in Bloomington, Minnesota. The architectural features include four different colors, white, charcoal, buff, and a burnt orange, with sandblast and acid etch finishes used on all four colors. The combination offers eight different textures and colors. The exterior profile jumps in and out to create shadows that further showcase the building's unique design. In this project here, we utilized two different finishes with a single mixed design, water wash and sandblast. One unique thing to note about this project here is we were incorporating the dock doors as punched openings within a 12-foot wide wall panel. Another common finish for precast concrete wall panel systems is thin brick. We utilized the face of a clay tile, laid in a form liner, and cast concrete over the top of it to give you a masonry finish. In this project example, we used thin brick for the majority of the façade finish. And what you can see in the image there of the white in between the windows is actually a white polished concrete finish. This project was compromised with 100 percent thin brick façade. As you can see in the picture here, we took extra detail and created some additional forming to have the thin brick veneer project or be recessed every third coursing of the project. Another popular finish is polished concrete. We typically see polished concrete used at street levels or showcase finish areas on a building. In this project example here, we worked with the owner, the design team, and the contractor to best utilize polished concrete and protect their budget. We decided to use articulating bands of polished concrete with acidized finish and a sandblast finish to give it a multi-finish look utilizing the same matrix. In this project example here, we used a vertical form liner as you can see in the buff colored concrete. In front of that, we utilized a thin brick veneer for their office entry panels. This is an office building in Denver, Colorado. And what you're seeing here is a combination of acid etched spandrels with a white base mix, then the gray spandrels above with a geometric pattern created by pouring in a wooden form, and gray spandrels below with a linear form liner pattern. In this project example, Weld Concrete used a sandwich insulated wall panel with two different form liners and two different mix designs within one load-bearing vertical wall panel assembly. In this project example, we worked with the design team to basically showcase every color or finish feature that might be out there for precast concrete. We incorporated cornices at the top of the parapet walls, thin brick throughout two-thirds of the facade, sandblast accent areas, cast-in signage for the building address, projecting window sills, and the use of form liner for the base and banding throughout the project. As you can see here, this is a beautiful precast building envelope. As mentioned on the slide before, we were able to cast-in signage, whether it be building signage for the address of the building or images for a school mascot. There's two examples here on the screen for you to see. Graphic concrete is becoming more and more popular due to its ease of finish. Graphic concrete is a retarder that is printed onto a piece of paper, which is then laid into the concrete form, where concrete is cast over it. Once the concrete is cured, we'll strip the panel and wash the retarder off, which exposes the aggregates of the mixed design. As you can see, there's a number of different patterns available for graphic concrete, some that have dramatic contrast and some that have slight contrast. All right, so in closing, precast offers resiliency and long-term durability, versatility in aesthetics and design, and efficiency throughout design and construction, making it a high-performance material. And with that, I will turn it back over. Thank you, Alex and Dan, for your great presentation. Now we will start the question-and-answer portion of our presentation. And our first question is, our first question is, it appears the insulation in the sandwich panel wall is at the jam opening of the window opening. Is this correct? And if so, would this be typical at an exterior door opening? Yeah, that is correct. The insulation runs edge-to-edge of the panels, so even at openings, they'll run up to the edge. Yeah, one thing to add to that, a typical sandwich white configuration is a three-inch exterior concrete white, three inches of insulation, and a six-inch interior structural white. Okay, thank you. The next question is, do the ThinWall tube steel frame with exterior skin layer configuration still maintain fire-resistant rating? Yes, it does. The introduction with the ThinWall, or the new product that is in with ThinWall as compared to insulated sandwich wall panels, is the use of spray foam. And the use of spray foam triggers NFPA 285, which many producers have gone through the actual physical testing and have the proper documentation to prove its fire resistance. Excellent, thank you. The next question is, what are the relative costs of the – sorry, we're getting a whole bunch of questions in right now – what are the relative costs of the various surface finishes? So, I would say – sorry, go ahead. No, go ahead, Alice. It depends project to project. The colored concrete and exposed aggregates are probably about in the same range. The graphic concrete might be slightly more, and then form liners may be slightly more than that. But it really all just depends on, for form liners exactly, like what the relief is, how much extra concrete you need, how much rubber goes into the form liner, how much repetition there is. Same with graphic concrete. So, there's just so many variables project to project that it's really hard to say, and the best advice there is just reach out to your pre-caster for your project, and they would definitely be able to help you out with that and determine some – what's more efficient and within budget for you. All right, thank you very much. Next question is, is it possible to anchor a flagpole directly to the panel? I personally have not seen that. I'm guessing like maybe off the top of the building is what they're asking. We could possibly put like if there's an insulated panel, internal pilaster or something there. I think it's a matter of reaching out to your pre-casting engineer for that specific scenario so that they could run the wall section and determine that for you. Yeah, I would just add on to that a little bit that we would need the reactions and the loads that we need to design for from the structural engineering record, and we can provide a substrate that would be able to withstand those loads with it. It would be no different than signage on the exterior building or a canopy being mounted onto it. So, there's things that can be done to happen to that. Excellent. This next question is a two-part question. How well do these pre-cast buildings perform in high seismic areas, and especially with multi-story buildings? Dan, do you have any input on that? I'm in an extreme seismic area, so I just don't have much experience with that. There's not much seismic activity in Minneapolis, either, where I'm at, but obviously, we do have a number of producers that are in seismic zones, and they have successfully completed many, many projects, whether they're single-story or multi-story. I know on the PCI website, there's also videos that talk and show seismic testing and the additional connections and how design for those connections differ for them in a seismic zone. So, the best thing I would recommend is to contact a producer that is located in that zone, and they can specifically address that question for you further. Like Alex and I, we're not in that area, so we're not well-versed in that. Okay. The next question is, does use of hollow core wall panels improve the FTC and thermal resistance values, as opposed to solid panels? The data and the testing results that we have available to us does not show hollow core walls. I would question to see what tests that producer is able to provide, what insulation they're using, how are they calculating their R-value with it, and has it been tested? As I mentioned throughout, the term U-factor or U-value is becoming more and more popular. And that can also be a calculated U-factor, but there's also ways to do physical testing, whether you want to do a hot box test to determine and see what those results are. But I would go for the data and the hard-tested facts, but I wouldn't be able to comment on that, because I don't have that. All righty. Next question is, which one is better at performance for preventing thermal transfer, composite insulated precast walls or non-composite insulated precast? I think they would both perform – the composite and non-composite is really how the wall is handling the structural loads and not to do with the transfer of heat. What you need to be careful of is when you are going to composite, you want to work and understand with the producer how they are achieving that composite action, whether it's through the use of non-conductive ties or some other method. So, make sure you check on that if you're looking at a composite wall panel section and converting R-value. If they're using non-composite ties, there would be no difference between that and a non-composite panel. Okay. The next question is, what is different between medium, low, and high exposure aggregate finish, and how can we measure? The acid etch is the lightest finish, so just a small portion of the aggregates is exposed. And then, to create a medium etch, it really comes down to the length of time that somebody stands there and sprays the acid on the surface. That's how we get the acid etch light exposure finish. And then, the deeper finish, the exposed aggregate finish, where you really see a lot of the stone itself and not the concrete matrix, that is produced by laying a sheet down in the bed before the concrete is poured. And that sheet is covered in a retarder that stops the concrete matrix from binding with the aggregates. So, after it's cured and stripped and then washed, the concrete matrix at the surface just kind of is washed off. So, it's really, I mean, just by looking at it and looking at how much of the concrete matrix is there would, I guess, determine how far it's etched. All right. Our next question is, are tongue and groove connections between adjacent panels better than joints with an elastomeric joint sealant? All joints, whether it's tongue and groove or just a butt joint, definitely wants to have sealants and treat it both sealed on the exterior and on the interior. Where you start to see tongue and groove or shiplap joints is at a corner connection. And the use of that is to make sure that the insulation in the sandwich wall panel returns around the corner and stays continuous, and there's not a disruptor of solid concrete or no insulation being returned. So, I guess where I would typically see tongue and groove or shiplap is at the corners. Typical panel-to-panel joints on an elevation of a building is going to be a butt joint. And I would say on walls, on projects that we've looked at where they're calling out a shiplap corner, we generally suggest to do a mitered corner, and the insulation can be cut so that it is still continuous, and that makes it a bit easier for forming and stripping in the plant. It's a friendlier detail, but still offers continuous insulation. Thank you. All right, the next question is, is there a significant cost increase to using sandwich panels over solid walls of a similar concrete thickness? I would... Go ahead, Dan. Go ahead, Alex. No, you go ahead. You go first. Well, I would say not. So, it's basically transferring costs. So, if the insulation is now inside the precast, then you can eliminate the needs for stud and furring out and bat insulation on the inside of the structure. Also, time and less trades, because the precast can be manufactured, it shows up site, it's already there and installed and ready to go. Yeah, just Alex, you hit it perfectly there. The cost between the wall system, the precast itself is minimal. There might be some savings going to a solid wall, but not if you're going to go to the same overall thickness. And as Alex mentioned, your additional costs that you need to consider is from other trades, defer that wall out to have insulation and drywall added to that. Awesome. Thank you. Next question is, what range of blast resistance is provided and how are the panels joined? As far as blast resistance or impact resistance, there's a couple of ratings. You definitely want to understand from the structural engineer record what the building needs to be designed for. You want to understand the window openings and how windows are attaching to it. There's a lot of variables to that. If that person has a specific project or condition in mind, I would ask that they just submit the full question and we'll follow up with a phone call or an email and we can get some engineers involved as well. Next question is, what is the best way to treat external joints in precast walls and what is the best material that can be used to seal the joints in precast? The precast joints are caulked, typically, so you have one bead of caulk on the outside and then another on the inside. Is it possible to have a composite wall using only fiber type connector pins? Yes. Okay. That was very quick. I mean, there's a number of white connectors that are made of non-conductive materials. There's pins, there's mesh, there's a couple of things out there, but to be able to get a composite wall panel without a thermal conductive material, you would use one of those materials with it. Alex, anything else to add to that one? Yeah. You hit it. I was going to talk about the mesh versus the pins. Yep. All right. Next question is, are there bowing issues for composite insulated precast, especially for a big difference in inside and outside building temperature? I think the bowing has more to do with maybe the length of the panel and panels do sometimes bow, but during the erection process, we have connections from panel to panel that pulls the bowing out of them. Another thing that helps control that bowing is to have both the exterior and the interior white pre-stressed with strand. The engineers can calculate where that needs to be, what size it needs to be, and balance that loading out so that the bowing is removed. That's something that the engineers are definitely thinking about when they're designing. All right. It looks like we have time for one more question. What's the best method to improve precast panels for defense against climate changes? As far as building in different climate zones and picking the right insulation and thickness, I'm not sure I fully understand that question. All right. We'll go to a different question. Are welded connections to the structural frame better than bolted connections from inserts cast within the panel to the structural frame? As far as like precast to the structure, typically our connections are welded. On some cladding projects, we might do bolted connections, assuming that all the plates and that are installed in the right location, which is up to the contractor to make sure that happens. Bolting connections certainly allows us to go faster out in the field, but we can do either one depending on the project. All right. Well, thank you so much for answering all those questions. On behalf of PCI, I'd like to thank both Alex and Dan for their great presentation and all our attendees for their participation. As a reminder, certificates of continuing education will appear on your account at www.rcep.net within 10 days. A recording of today's webinar will be included, a link to view a recording of the webinar will be included in tomorrow's follow-up email, and also there will be a pop-up survey that appears after this program ends. If you have any further questions about today's webinar, please email marketing at pci.org with the title, Online Building Webinar. Thank you again and have a great day.

Simplifying the Building Envelope with Precast Concrete

webinar presentation

PCI

Royce Covington

Alex Wilfang

Dan Stindle

precast concrete benefits

applications of precast concrete

thermal performance

aesthetic options for finishes