Round table at Southern California Edison

Fashion or trend? | Convincing the client | Critical needs

Critical Needs

Premise

With more complex integrated façade systems, design and engineering requires the involvement and expertise of multiple disciplines to optimize whole building performance. This diverse design team needs to have various critical tools and information sources at their disposal to quickly narrow down the range of acceptable solutions. We posed the question of what are the critical needs of this design team? What are the short-term and long-term needs and what is their relative importance?

Please click HERE to view questionnaire (MS Word - 79 KB)

Survey results

A single-page survey form was given to attendees to fill out after the discus-sion of this topic. The form listed various products and services that may be developed (or further developed) to facilitate use of advanced façade systems at each phase of the design.  The survey asked respondents to 1) check the box if they would like such material available for use, and 2) circle the single most desired product or service.

Several options were given for each design phase (see Figure). Of the total responses (n=15), the following was determined:

• 60% (n=9) thought that guidelines explaining the pros and cons of various systems for different climate zones were the single most desired product, while 87% said they would like this material available for use in the conceptual design phase.
• 53% (n=8) thought that simplified tools to estimate equivalent thermal and optical indices of advanced facades was the single most desired product, while 100% said they would like this material available for use in the schematic design phase.
• 40% (n=6) thought that design guidelines was the single most desired product, while 100% said they would like this material available for use in the schematic design phase.
• 47% (n=7) thought that tools that integrate thermal and daylighting impact of facades with whole building systems was the single most desired product, while 87% (n=13) said they would like this material available for use in the design development phase. ·
• 33% (n=5) thought that tools to construct control algorithm specifications or sequence of operations code was the single most desired product, while 53% (n=8) said they would like this material available for use in the construction documents phase. ·
• 47% (n=7) thought that life-cycle tools to document intent and refine operations throughout the building’s life was the single most desired product, while 87% (n=13) said they would like this material available for use in the bid, commissioning, and troubleshooting phase.

In the early phases of design (conceptual and schematic), most respondents desired explanatory products and services (guidelines, well-established references, building case studies (to better understand the application, uses, and pros and cons of advanced façade systems. In the latter phases of design (design development and construction documents), most respondents desired tools, simulation models, and mock-up facilities to better quantify the impacts of the design on whole building performance or to implement such designs properly (e.g., control algorithm specifications). Other tools needed for compliance were also desired (thermal-optical indices, NFRC rating procedures). For the bid and post-occupancy phases, diagnostic and commissioning tools were also strongly desired to ensure proper operations throughout the life of the building.

Note: Please click on the picture for a printable version of this graph

Individual Responses

Individual responses focused on the need for easy-to-use simulation tools. Full-scale, on-site, outdoor mock-ups of the façade and their adjacent building zone also played into the discussion, possibly because the use of mock-ups in Europe differs so substantially from the U.S. The use of simulation tools to assist with building diagnostics was also discussed.

It was evident from both individual responses and from private discussions that architects and even engineers were unsure of the value of applying these advanced façade concepts to their specific building or to regions within the U.S. This confusion surrounded primarily double-skin façades.

“The advantage in Germany, with double-skin facades, is that you can eliminate the air- conditioning and heating duct work and just have ventilation air, because people will accept ventilation air coming through the outside wall. This does not work in some regions of the US because there is too much humidity and condensation. There are a lot of issues that are specific to our climate zones that are not applicable to Germany, so we really don’t know how these things operate here in a lot of cases.” – Architect

“I don’t think that we have done a good enough job of really looking at these different [performance] metrics for these types of structures in the different regions. Because they are not all applicable. I think that it has created a lot of confusion among clients and architects alike.” — Engineer

“I am kind of on the other extreme [from European design solutions]. In Phoenix, you are not trying to grab a little piece of light, you are dealing with massive amounts of it. I think that a lot of it comes down to “Where is the best place to do these different systems?” One hundred percent outside air is very, very important. Is the façade the appropriate place to do that? I really question that I can have a building in Phoenix that will survive without a mechanical system.” — Architect

With a whole building systems approach to analysis, engineers are finding that rules of thumb must be discarded for a performance-based approach to gain compliance with the energy codes and to understand and optimize the design. Because of the time involved to understand which façade systems are applicable and how various building systems work together, respondents wanted tools that were very easy to use (good user interface), sufficiently accurate, and gave reliable guidance in the very early stages of design. Several mentioned the need for a 3D interface between CAD and simulation tools to reduce costs and time.

“I think that one of the key things for reducing the cost of design for innovative buildings and innovative facades is again that the tools need to get better for us. As the tools increase their usability, accuracy and precision, we will have a better opportunity to sell these ideas to our clients. Reduce our time and energy spent in improving the somewhat unproveable and that will lead to better integrated buildings.” — Engineer

“When we are diving into sustainability and integrated buildings, we essentially have to abandon the rules-of-thumb approach to design. With our practice, we deal with projects all over the country and all over the world, so each job is essentially a new learning experience for that particular application. Whole building performance simulation tools like DOE-2 and EnergyPlus are really useful to us in quantifying the benefit we get from each system. It is going to require a substantial amount of learning and work on the part of the designers to put these tools to use on particular projects. Many of our colleagues at this round table event know this from experience: applying these advance facade technologies takes a lot of upfront effort. With one of our projects, it took 110 permutations of DOE-2 analysis for us to really understand what was happening dynamically with the building. We were able to quantify the results and provide the data to our client, and this gave us a leg to stand on as far as the life-cycle costs. I think that developing the whole building approach is really going to be the key here in the future, especially with compliance, because these advanced technologies and buildings that we are designing do not fit the prescriptive requirements of energy codes. We are always on the boundaries and we are always required to demonstrate essentially by performance. We should be developing the tools in those directions to aid us in doing this quickly, more efficiently and cheaper so that we can be good-quality architects and designers as well as profitable.” – Engineer

"Additional tools (software programs) need to be developed for use during the schematic design phase, that enable the architect or engineer to analyze quickly three or four design alternates providing a level of assurance that one is going in the right direction from an energy standpoint." - Architect

“When you are looking at a fairly complex problem in schematics and you use a simplified tool, do you have the confidence that the simplified tool captures the complexity of performance that real systems have? What you don’t want is to be pointed in a direction by a simplified tool and then six months later, as you get further into design, find out with detailed analysis, that it won’t work and you start all over again.” – Researcher

“The bottom line of what we are looking for is typically dollars. What are my energy savings? What is my increased first cost? What is my payback and what is my life-cycle cost? We are talking about energy tools with the precision of billions of BTUs. Our final result is hundreds of thousands of dollars or a million dollars in energy costs in the end. You have to ask yourself, “What is the accuracy required for this project?“ Some projects require full accuracy. We try to measure it with as much precision as we can get, but there are other projects where it is simply not required. A general understanding of the energy use of the building, a simplified model may be sufficient.” – Engineer

“I think the advantages in energy engineering is that we don’t necessarily have to have a complete set of documents in order to have a more accurate picture of what the building is doing. We have a lot of bases of knowledge. We can model very accurately with less information today. I think that the key would be to have a sophisticated, accurate precise tool with a very simple interface. We don’t necessarily need to simplify the assumptions or to simplify the quality of the information that we get from our computer tools, because the technology is already there. We need to simplify the application of the tool. When that is done I will be out of business, but I think that is the direction we need to go.” – Engineer

“Most engineers don’t mind the complexity associated with putting in a control sequence. But if it is complex to get 3D-geometries into the building, that feels like a waste of time. That is why the links with CAD are of particular importance to us.“ – Engineer

“It would be great if 3D information could be downloaded into some other analysis software, especially given the amount of changes that our designers like to make.” – Architect

Fiber-optic array, Technology Museum, Berlin

Automated louvers on a skylight system, Technology Museum,  Berlin

For those involved in dynamic system tuning, open code was also desired.

“Controls is a critical part of both the simulation tools and making advanced façade systems work in reality. What we have found so far is that with DOE-2 and EnergyPlus, there is not quite enough openness in the code to put in unique control sequences. The control sequences you have built into your simulations need to reflect that complexity of modes. Especially as we go to mixed-mode buildings, the software needs to be open enough and sophisticated. If the modeling tools don’t allow you to do that, you do the 101 different snapshots, take all your snapshots and link them together, then make some predictions about how the controls perform.” – Engineer

The discussion on full-scale, outdoor mock-ups of the façade and their adjacent building zone began with their purpose in Europe: a) to verify overall performance (structural, weatherproofing, operations, energy) of the conceptual design over a period of a year at the building site, and b) to allow clients to view and fully experience the façade solution. Manufacturers will typically do mock-ups of the façade in the U.S. after the bid process, to work out physical details not verify performance. Mock-ups are also occasionally done to gain NFRC compliance in the U.S.

“Mock-ups are a serious added cost. In Europe, there is an awful lot of design time put in to developing software simulations of the building’s performance, but ultimately there is at least two floors that are mocked up and tested for as much as a year in order to verify energy, structural, and weather perfor-mance.” — Engineer

“In Europe, mock-ups are usually started during design development or in schematic design. This is a main point with these advanced facade systems: you had better invest this time in the design process rather than afterwards in the post-occupancy phase. In Europe, mock-ups are not done by the manufacturers. They are done by the design team or by test institutions, so it is more of an anonymous design solution not a specific product. It is more concept related rather than product related.” — Engineer

“You build a mock-up on site so that the client can visit it weekly to get an impression of its performance. It is a fully equipped office with all the mechanical systems, so you get a feeling about this double façade, such as how it looks from the inside during different weather conditions.” – Engineer

“In the US, we find that there is typically not enough time allowed in the construction process to do an accurate study of the mock-up. We are generally asked to compress the time to design a custom system, produce it, put it in a test chamber. Sometimes the building is even going up as we are still testing this exterior façade. I think we really ought to expand that time in order to get a better view of what’s going on with this entire system. If we can consult with the architect ahead of time, generally we can get a decent schedule, but generally it is in the bid phase when we are presented with a set of construction documents, and if we are successful, then we go for the mock-up.” — Manufacturer

"We would prefer selecting a curtainwall contractor very early in the project design phase and developing the double wall (airflow) façade in collaboration with the designers rather than independently, which may result in the bidding of these types of façades to contractors lacking the experience to implement them." - Architect

"With respect to NFRC (National Fenestration Rating Council) and current computer modeling available in the U.S., I do not believe the influence of airflow in a double wall façades can be modeled or tested." - Architect

In Europe, comparing simulated performance to measured performance is a fundamen-tal issue to gaining client approval. Simulation tools rely on many fundamental simplifying assumptions and incomplete data. Therefore, prior to investing on the order of millions of dollars in a complex building system, mock-ups are also used to validate simulation data.

“When you talk about mock-ups of specific components in the building, we must remember that we are looking at an integrated building at this point. You would essentially have to build a building to mock up a building. So I think that computer simulation is the key because you have all the components at your fingertips. You are able to look at the interactions between the systems and most often than not, the advantages and disadvantages in the building are counterintuitive. When you look at the building and how it interacts with the HVAC and lighting system it is often times counterintuitive.” – Engineer

“Typically we evaluate the concept by simulation and then most clients are relatively skeptical. There are nice pictures and colors if you show CFD simulations, for example, but who believes it? If you are constructing large building projects, the investors are quite critical. Often they come in and say, “Couldn’t we prove this with a test?” Then it is easy in Europe to convince them to invest around $50,000 to $100,000 dollars for such a test.” – Engineer

The difficulty of applying such data from either mock-ups and simulations to generalized guidelines in other climates and situations was discussed, emphasizing the need to combine the benefits of simulation tools with measured data.

“In one project, we established a protocol for testing and measuring the performance of daylighting systems in test rooms and I think five or six countries built test rooms and tested various systems in each room in each country. That was the good news, that you actually have some real perfor-mance data. The difficulty is say, the Norwegians tested an interesting light shelf at their latitude for six months one year and now I am in Berkeley trying to figure out whether the Norwegian data can be transposed in some way between climates or latitude and so on. The answer, of course, is not without great difficulty. Which is where the tools come in. I think that there are tools for characterizing instantaneously the performance of the system. I think that some combination of those tools plus a snapshot of measured data is where we are heading.” – Researcher

“A lot of these solutions are not static solutions. They are dynamic solutions. There are whole issues of operations in control sensors. Are they automatic or manual? How do you maintain performance over time? If you have a system that is dependent on something, such as louvers blocking direct sunlight, how do you get it installed right, commissioned and insure that over time it really works? History in the US is that there is great skepticism on the part of owners that it really works. Dynamic operation and user occupant interaction with controls are huge issues from my point of view with all these advanced systems. The tools need to be able to capture, in part, the dynamics of that performance and, if it is an occupant-operated system, how the occupants will use the system.” – Researcher

Finally, the discussion focused on post-occupancy performance . The following questions were raised but not fully answered: a) do we want to know how the building is actually performing (exposing oneself to potential liability) and b) can simulation programs actually applied in all practicality to on-site commissioning, diagnostics, and tuning of the system?

“One thing to remember with LEED is that it is a certification of the design, not the product. It is a tool for us as designers to take ourselves to the next level, not necessarily as a control quality assurance issue for the building as a product. What happens when you find out that your façade isn’t performing properly? What do you do? Who’s liability is it? Do you want to find out?” – Researcher

“For the last question, the answer is clearly “yes”, because you are either wasting energy and money or you are making people uncomfortable and less productive. The answer to liability and what do you do isn’t quite so simple.” – Researcher

“There is some movement to take some of the design tools, and make it into an on-line emulator that could be part of operations. You have spent all this time and energy into modeling and doing design optimizations, so why not put that knowledge into the operations of the building? With online diagnostics, it collects data, compares it to what it should do, and when it sees a discrepancy it can try and figure out what to do.” – Researcher

“If you specify the control system, there is the general contractor and then the first sub, second sub or third sub who will finally translate this into a controls program. This is horrible! What you get back has nothing to do with the specifications. At this point, we are in the stone age, transferring from a kind of scientific design into a real control system.” – Engineer

“There has been some research recently that has shown that while all the energy simulations programs have good agreement between each other, they don’t necessarily have good agreement with reality. My question has always been, “Should we be benchmarking against our simulations or should we be validating our simulations against what’s happening in real life?” In either case, having enough complexity in the programs is necessary to do it in either direction. What kind of commissioning process should there be for a naturally ventilated building or a building that spends some of it time in a naturally-ventilated mode? Certainly there is no international standard for that.” – Engineer

“It is the whole argument between precision and accuracy. Our tools can be very, very precise and horribly inaccurate. I agree with what you said exactly. That we should be configuring our tools to match reality rather than necessarily achieving some ideal operation.” – Engineer

“I see two problems generally with these sort of things. First, it usually costs money to find out what the performance really was and that is often lacking, and the second is that invariably, especially when you are a leader and trying to do something new, usually things don’t always go the way you thought or hoped. It is a question of “Is there a way of bringing that out in the open and discussing it in a proactive positive way as opposed to some how feeling that it is exposing any possible flaws?” It seems to me that the history in some of the large façade problems that we have seen in the states in the last 20 or 30 years is that they get settled in law courts. Understanding what went wrong is sealed in some kind of settlement and the rest of the profession does not have the opportunity to learn. There should be a feedback loop where we would all get to learn from each other. That is a challenge.” — Researcher

Question/Information: eslee@lbl.gov