1、Author A is a professor in the Department of Mechanical Engineering, Accredited State University, City, State. Author B is a research fellow at Commercial Company, City, State. High Performance Buildings using Whole Building Integrated Design Approach Mohamed Abaza ASHRAE Member HIGH PERFORMANCE BUI
2、LDING PROGRAMS High Performance Building (HPB) programs have become a model for greater resource and energy-efficient practices for selected renovations and new construction projects. The goal of the HPB program is to produce a permanent improvement in standard design practices among building design
3、ers and owners that result in higher efficiency and lower utility costs and incorporate many of the sustainable building practices being recognized by the US Green Building Council. ENERGY MODELING AND LIFE CYCLE COST ANALYSIS Energy conservation is central to long term economic and ecological susta
4、inability. Energy efficiency is not only directly tied to occupancy and program use, but also specific to the design of the building. Design teams can use Energy Modeling to determine the estimated energy consumption of a facility before the first brick is placed. Energy modeling is the common term
5、used for an integrated whole building hourly energy simulation. It can be simply explained as a tool used to predict annual energy consumption in a building. The model is developed using computer software programs such as Trane Trace or Visual DOE and input parameters such as building design, orient
6、ation, climate zone, utility rates and heating and cooling loads. While the Engineer of Record (EOR) will perform energy analysis to determine the proper selection of equipment to meet building loads, this Whole Building Energy Model is different; rather than selecting equipment, this model will dem
7、onstrate the performance of equipment in the operation of the facility. Creating the model and then analyzing the outputs requires a specialized skill set, which includes working closely with the design and operations team. The first model that is run is always that of the base case building; what w
8、ould the consumption be if the building was designed only to code? Next, the building is modeled as designed where, individual Energy Conservation Measures (ECMs) are entered and their effect on consumption analyzed. These ECMs are essentially upgrades to the systems, and can include any potential m
9、odification to design, including envelope, insulation, equipment, window, systems or other suggestions. Results of each ECM impact are presented in the energy modeling reports. Based on the value engineering results the most cost effective ECMs are selected and the Whole Building Design is modeled i
10、ncorporating all the chosen ECMs. This can be very helpful in understanding the effect on energy consumption and costs that can result in removing ECMs during the value engineering process. The energy model is built in early design and updated throughout. Reports are submitted beginning in the schem
11、atic design phase, with the most cost effective impact coming no later than the Design Development. The energy model is also updated, as required, and re-submitted at the Construction Document Phase. It is important to perform the modeling as early as possible so that any Energy Conservation Measure
12、s (ECM) can be value engineered early The maximum number of points under LEED Energy and Atmosphere Credit 1 can only be earned by performing an energy model, which will demonstrate the percentage improvement in the proposed building performance rating compared to LV-11-C029240 ASHRAE Transactions20
13、11. American Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc. (www.ashrae.org). Published in ASHRAE Transactions, Volume 117, Part 1. For personal use only. Additional reproduction, distribution, or transmission in either print or digital form is not permitted without ASHRAES p
14、rior written permission.the baseline performance rating per ASHRAE 90.1 requirements. Modeling can also be used to determine on-site renewable energy and green power as a percentage of the base case energy consumption. Additionally, energy models are also required for certain government, utility or
15、other energy efficiency grants and incentives. Life Cycle Cost Analysis (LCCA) is a practical method and a guideline for evaluating the economic performance of building service systems. By using LCCA, the most cost effective design decision can be made, which has the lowest life cycle cost during th
16、e project study period among the various design alternatives and ECMs; maximizing return on investment. Life Cycle Cost Analysis balances the long term operations and maintenance with the first cost budgetary concerns of the project. Several factors are considered when calculating LCC, which require
17、s information from several key team members. Estimators and contractors can provide the first cost of the equipment, including materials, installation, delivery, etc. The manufacturer can provide maintenance and utility consumption requirements which can then be applied to local rates and tariffs; h
18、owever, the latter is best obtained by performing a Whole Building Energy Model. Finally, replacement costs and overhaul information is also factored to understand the full financial implications of a given system. Each building system can be analyzed as such to calculate the cost of ownership. The
19、hourly based LCC results indicate that as efficiency increases, the lifetime operating cost has greater impact on the LCC than the total installed cost. In other words, the increase in total installed cost that occurs when equipment efficiency is increased is offset by the decrease in lifetime opera
20、ting costs. ENERGY EFFICIENCY OF LEED Here is where the problem lies; to date no one has been able to put a dollar value on the cost of environmental impact, or environmental impact avoidance. Yes we all know that LEED takes into account environmental impact, however it does not spell out the exact
21、dollar value of the environmental impact, and no one can. The only measurable impact is energy, and that is why the emphasis has always been on energy. In fact when LEED first began they championed themselves on being able to conserve energy through their system. Maybe they should have been more car
22、eful with the way they marketed the program. The truth is if they had not marketed it that way, there would have been very little buy in. Owners are more concerned about energy cost savings than they are about the cost of environmental impact avoidance. The fact is the cost savings associated with e
23、nvironmental impact avoidance is higher than the energy cost savings. In an effort to maximize LEED points energy modelers have been pushing the envelope, lowering the Energy Use Intensity (EUI) sometimes unrealistically, using unrealistic occupancy and equipment schedules that do not accurately dep
24、ict actual schedules. Energy modeling is only a prediction and an engineering tool, not the solution; the modeling results are subject to who is using the software. Ultimately the greatest energy savings will be reflected through the occupants/tenants and the correct commissioning and ongoing measur
25、ement and verification after occupancy. The final whole building design model should take into account the buildings performance in its entirety. That is why the modeling process should be integrated right from the design charette all the way to and after commissioning. The process should be an iter
26、ative process. This process will ensure that the whole building design will take into account the buildings performance in its entirety once systems are installed and operational. Increased energy consumption during the initial months of occupancy due to incompletely installed or commissioned system
27、s can be avoided if the commissioning process is integrated right from the design charrette and integrated with the energy modeling and design process. Energy efficiency has to be monitored, mainly through sub-metering or utilizing smarter building systems, where Information Technology (IT) and Buil
28、ding Automation Systems (BAS) are all merged onto one Internet Protocol (IP) platform. In the future this monitoring will be done wirelessly using Quantum Technology which is currently being researched by Defense Advanced Research Projects Agency (DARPA). Continuous commissioning and monitoring are
29、essential in maintaining energy performance. 2011 ASHRAE 241Figure 1: LEED Cost by level vs. $350/ft2 ($32.5/m2) traditional construction. Contrary to popular belief, incremental costs associated with construction of LEED buildings is only marginally more than “traditional” cost of construction. PLA
30、NNING AND ACHIEVING HIGH PERFORMANCE BUILDINGS (HPB) The HPB Program includes several ways to access available incentives, which are based upon the complexity of the project and the schedule. Pre-Qualified Equipment, Custom Measure (system-based) and Whole Building incentives are offered. These thre
31、e opportunities allow flexibility for the HPB Program to help as many building owners as possible to participate. A building must sufficiently reduce the electric demand and electricity use (with emphasis on demand) to satisfy the HPB Program requirements. Design-team communication is equally as imp
32、ortant to successful building performance as efficient mechanical systems are. The 2030 Challenge proposed by ASHRAE/IESNA and USGBC 189, Standard for the design of High Performance Green Buildings except Low-Rise Residential Buildings, has made High performance buildings increasingly popular. Creat
33、ing buildings that respond to increased demands for energy efficiency and carbon accounting while balancing efficiency goals with economic constraints is extremely difficult to achieve. The meter for High Performance Buildings is Kbtu/SF/YRkWh/m2/YR which is the automobile equivalent of mpg. High pe
34、rformance buildings behave in the opposite manner to a high performance vehicles. The benchmark to which a high performance building is compared to is the Commercial Buildings Energy Consumption Survey or the ASHRAE 90.1 energy standards. To be sustainable High Performance Buildings must be economic
35、al, taking into account first costs, life-cycle costs and return on investments. Economy can be achieved on a system level and then on a component level. The system level for example will be building orientation and the component level could be variable frequency drives on pumps and air handling uni
36、ts. High performance buildings will use less material more effectively, are more durable and require less maintenance. Requirements for High-Performance Design x Entire design team to be part of design process from the start. x Building to meet OPR (Owners Project Requirements). x VE (Value Engineer
37、ing) changes are tracked back to the BOD (Basis of Design) and OPR to ensure energy efficiency measures were not eliminated. x Whole building is approached as one system. x Use of Energy Modeling to predict energy consumption. x Economic decisions must include life-cycle costs. x Energy, resources a
38、nd materials to be used efficiently. x Use durable material that require less maintenance and are recyclable. x Incorporate QA process of commissioning into the design and delivery process. 242 ASHRAE TransactionsRequirements for Efficient HVAC Design x Examine heat flow though the building via comp
39、uter economic analysis to ensure reduction in HVAC equipment size. x Capture Natural-energy flows, such as passive solar heating, daylighting, natural ventilation, and occupant generated heat. x Reduce internal loads by implementing daylighting and using Energy Star-labeled equipment. x Divide the b
40、uilding into thermal zones resulting in higher system controllability and greater occupant satisfaction. x Use multiple-zone control within larger units. x Reduce system losses in ducts and piping. x Use low pressure duct work. x Employ premium efficiency motors. x Use variable-load fan systems and
41、consider part-load performance in equipment selection, since the peak load is only needed 1% of the time. x Employ occupancy based controls, time of use and demand based. x Use Energy recovery for ventilation air. x Curtail electric loads during peak demand period, could be achieved by using ice sto
42、rage systems. x Only use High-efficiency mechanical systems. x Establish an operations and maintenance manual x Make provisions for proper performance monitoring and verification CASE STUDY We are currently serving as the Program Manager for the City of New Haven Public Schools Construction Program,
43、 which includes construction or renovation of 47 facilities totaling over 3.9 million square feet362,310 m2. The $1.47 billion program now stands as a national model for its massive scope, innovative financing, high degree of community support, construction standards and outstanding design. The City
44、 needed to update its aging schools while trying to reduce energy costs, which were rising at a rate of nearly 8% per year since 1988. We helped the City identify high performance goals and met with the entire project team including City officials, architects, engineers, consultants, construction ma
45、nagers, maintenance and end users to go through them. The Citys high performance goals were to: x Provide an immediate and ongoing cost avoidance to the school system x Ensure new buildings are designed and constructed to meet high performance efficiency and green building guidelines x Improve therm
46、al comfort of building spaces and increase system reliability x Commit specialized technical resources to assist with technical challenges related to energy x Create an opportunity for students and staff to learn about energy efficiency and participate in the program We developed standards concernin
47、g materials, design, construction and energy efficiency. All of the schools are now designed to high performance standards and meet Energy Star efficiency levels. Within the first year of the high performance initiative, New Haven achieved $1.1 million in cost avoidance without capital investment. T
48、o date, over the 5 year period, the City has saved over $10 million from a reduction in average overall building operating efficiency of over 65%. At the core of the program is our High Performance Program, a comprehensive, value added integrated design process. 2011 ASHRAE 243Early in Schematic Des
49、ign, the entire project team, including design professionals, consultants, our Program Management Staff, Construction Managers, commissioning agents, operations enhanced collaboration and team commitment is paramount. Experience is valuable in teams designing high performance projects. Energy modeling should be used to inform the design, commission the project, and monitor post occupancy. Measurable goals should be established early and accomplished throughout the duration of the project. One of the fundamental measures of every good design
