Energy Master Planning for Mechanical Systems in New and Existing Buildings and Facilities

by Grahame E. Maisey, P.E. and Beverly Milestone, LEED AP
Building Services Consultants, Inc.

Last updated: 08-12-2010

Introduction

Building mechanical systems and their associated heating, cooling and electrical generating systems play a large role in the US electrical and fossil fuel use and especially electrical demand during the summer months. At the building level, mechanical systems are a large part of the overall building energy efficiency, maintenance costs and occupant comfort and productivity. Within sustainable, high-performance buildings, these systems must perform much better than typical systems in every aspect: construction costs, energy, maintenance, and comfort. Sustainable, high-performance mechanical systems should have performance goals for carbon neutral energy consumption—or better—and must be designed to require the minimum of materials for life-cycle installation, maintenance, modifications, and alterations while providing optimum comfort to maximize occupant productivity. Buildings consume almost 50% of the US energy consumption and are the cause of peak electrical demand during the summer cooling months. EMPs can help transition facilities, buildings and their mechanical systems from energy users to energy generators while also eliminating peak cooling and heating electrical and fossil fuel loads. Planning facilities and buildings toward becoming energy generators requires that we minimize energy use and move to mechanical systems that are most adaptable to clean, renewable energy sources as well as systems that do not create a higher demand for electricity or fossil fuel during high and low outside design conditions.

Note that the performance of the building envelope is critical in assisting peak performance from the mechanical systems. The building envelope is the first defense against the outside environment and as such provides the tension between the outside temperature, humidity, wind and solar and black sky insolation. The performance of the building envelope can not only minimize the mechanical system requirements but also enhance the occupant comfort. There are a couple of high performance building envelope standards developed for the more temperate European climate: Passive Haus and Minergie. These envelope standards help minimize the energy use from the services for the buildings and also improve occupant comfort.

Sustainable, high-performance buildings and facilities require substantially more planning and design effort than conventional buildings. Energy Master Plans (EMPs) provide the necessary protocols and steps to plan for mechanical and associated energy systems within a ""whole building" context to achieve sustainable, high-performance buildings. EMPs are "whole building" life-cycle plans, generally spanning over 100 years, instead of typical life-cycle performance programs that span the life cycle of the system only—usually 20 to 40 years.

A majority of funds spent on buildings during their entire life cycle is on the occupants' wages (see WBDG Productive Branch for more information). As such, it could be said that comfort and productivity are THE key indicators of high performance. The primary reason mechanical systems are installed in buildings is to provide occupant comfort. Accordingly, EMPs stress the importance of systems maintenance throughout the building life cycle so that occupant comfort as well as energy performance are optimized and sustained. Maintenance requirements, therefore, also become a critical aspect of the design.

Description

A. EMP Goals and Objectives

EMP End Goals and Objectives are very different to most building design goals: carbon neutral energy, supplied by clean, renewable energy sources; optimum occupant comfort for maximum productivity throughout the whole building life cycle; minimum material for the whole building life cycle, including maintenance and remodeling; minimum first and whole life operating costs. Typical goals and objectives for a HVAC system could be: beat ASHRAE 90.1 by 30%, meet ASHRAE comfort criteria, and minimize installation cost. EMPs could have mechanical systems that are initially poorer in energy performance than ASHRAE 90.1 but nonetheless have detailed plans to become carbon neutral.

Note that the EMP refers to the whole building life cycle, not the mechanical system life cycle, so the planning is for the whole life of the building from initial design or major retrofit through to deconstruction. The End Goals and Objectives for comfort and maintenance shouldbe met immediately, but the energy use can be developed to become carbon neutral at some time in the future, when economics allow the introduction and expansion of clean, renewable energy (e.g., ground heat exchange, solar thermal, solar photovoltaic and wind systems).

The building or whole facility should be analyzed to determine how much clean, renewable energy will be available in the future. This energy includes all sources, some of which may not be allowed by local codes at present, such as windmills. The total available energy should be estimated to provide not only the energy for operation but also the energy for maintenance, the embedded energy of future construction and a proportion of the transport and food energy consumed by occupants in the facility. In short, the total future available clean, renewable energy should be the total future energy budget for the building or facility.

The initial energy use should be minimized and the mechanical systems selected to use low warming temperatures during the heating season and high cooling temperatures during the cooling season to make them most adaptable to clean, renewable energy sources. The systems should also be slected so that they can use clean, renewable energy sources to eliminate both heating and cooling peak demand for electricity and fossil fuel. This last requirement is a critical requirement usually overlooked but is essential for truly sustainable buildings.

B. A Framework for Sustainability

There are different platforms available that present sustainability pathways for various situations. One such is The Natural Step (TNS) platform, which is a science-based system that has gained global acceptance. TNS begins by considering 4 conditions for sustainability and develops goals and objectives from these conditions and moves from there. The primary method in the framework is back-casting, which establishes the end goals and objectives and then works back from them to the current planning situation. Essentially, what back-casting does is prevent the planning process from going down blind alleys, it maintains a focus toward true sustainability. The figures below summarize TNS concepts and how TNS is applied to Energy Master Planning.

C. Strategies for Sustainable, High-Performance Mechanical Systems within EMPs

Comfort and Productivity

Optimizing comfort for the building life cycle is the most challenging strategy. Thermal comfort conditions include radiant and ambient temperature control, both of which should be controlled. Humidity and clean outside air ventilation must be controlled year-round. It has been found that by providing individual comfort temperature control for the occupants increases comfort and productivity of the occupants, so individual control is an important consideration when designing systems, basically developing small zone controls. Ventilation should also be controlled and used to prevent the spread of viruses and disease by supplying 100% outside air, eliminating recirculated air and providing controlled flow throughout the building. This is particularly important in hospital environments but can make a considerable improvement in schools and offices.

Thermal Environmental Control

Human beings are more sensitive to the Mean Radiant Temperature than Ambient Temperature. As such, radiant temperature control is essential for excellent thermal environmental control. Fortunately, controlling the radiant temperature can lead to strategies for saving energy and maintenance. In most casesit is possible to use large areas for radiant cooling/heating to move the radiant system temperature closer to the room temperature, allowing an ambient temperature strategy to be initiated (using low temperature warming and high temperature cooling, 5°F to 15°F different to room temperature). See also WBDG High-Performance HVAC.

Humidity Control

Desiccant dehumidification control will be necessary to provide direct, energy efficient low humidity control in geographic areas where there is high humidity. Liquid desiccant systems are most promising and it appears there will be systems available in the near future that will be applicable to institutional, commercial, and residential as well as industrial situations. In geographic areas that have cold weather, desiccant humidification control will also be necessary to augment energy recovery systems.

Ventilation Control

As will be explained in the next paragraph, minimizing the amount of air distributed throughout the building is essential. One of the most efficient ventilation strategies is displacement ventilation. Most situations only require 0.05cfm/ft² ventilation air most of the time. Outside conditions of high humidity during the cooling season and low temperatures causing low humidity during the heating seasonwill most likely cause an increase in the air distribution requirement, up to 0.3cfm/ft², depending a great deal on the performance of the building envelope to resist the ingress and egress of moisture. Large fluctuations and increases in occupancy will also increase ventilation requirements. Ideally, two or three ventilation levels would optimize air distribution and ventilation supply, with the system(s) supplying 0.05cfm/ft², 0.15cfm/ft² or 0.3-cfm/ft. With careful planning and design, the multiple distribution levels can be performance by one ducted system.

Controlling viruses that can spread by airborne transports and cause diseases such as the common cold requires controlling the flow of air throughout the building. Controlling the flow of air through the building envelope is the first priority, which is done by good envelope systems (i.e., wall, window, entrance, and roof). Controlling the flow of air between floors is the next priority, and this can be done through sealing floors and minimizing thermally caused flow by balancing the airflow and carefully controlling the temperature differences between floors. High-rise buildings need special efforts to control air flow caused by thermal currents, hot air rising, and cold air falling. See also WBDG Air Barrier Systems in Buildings.

Controlling the spread of viruses will also be improved by supplying only cleaned and treated outside air and eliminating recirculated air that could be contaminated with and by anything inside the building. When supplying minimum ventilation air, it is easy to supply 100% outside air, but when 1cfm/ft² or more (which is the case in most all-air mechanical systems) is distributed throughout the building, it is usual to recirculate up to 90% of the air. In some cases, it is better to supply 100% outside air and use energy recovery systems than risk the health of the occupants. For example, schools, hospitals, and offices are notorious for spreading colds and flu, and a major culprit for this is the mechanical system. See also WBDG Air Decontamination

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Building Mechanical System Energy Use

EMPs focus on establishing the available clean, renewable energy sources and then moving the energy use to true carbon neutral as soon as practical for the building life cycle by minimizing mechanical system electrical and fossil fuel use and developing systems that can readily use clean, renewable energy sources. To achieve this objective requires planning and long-term strategies. Planning for the system to be carbon neutral for the current building layout is not the only challenge; the systems will also need to be flexible, adaptable, and expandable to cater to foreseeable future modifications and alterations while sustaining efficiency. Often, a modular approach to building floorplate design will allow different layouts and uses to operate with the same efficiency and minimum modifications.

Examining the energy use of the building mechanical system components and the longevity of the components is necessary. In a typical HVAC system, over 50% of the total energy use and over 50% of the total system cost is from the distribution systems, pumps and fans, ductwork and piping. Moreover, 75% of typical remodeling costs are for the distribution systems. Optimizing the distribution systems should be priority #1. Based on actual case studies by the authors of this Resource Page, an optimal, high-performance design has been shown to reduce the energy use by over 85% and reduce the materials use for the building life cycle.

Piping systems are 10 times more efficient for transporting thermal energy as compared to air distribution. Also, piping distribution requires only 10% of the space an air duct requires. Piping systems and radiant systems are complimentary, so it would seem logical to use radiant piping systems for heating and cooling. The reluctance to use radiant cooling panels in geographic areas east of the Mississippi is due to the high humidity levels potentially causing condensation. These potential problems can be avoided by using large areas of radiant system, 2/3 to 3/4 of the ceiling is an excellent solution. This way, the surface cooling temperature dewpoint remains high, while a lower humidity level maintained within the space also allows a strategy of higher air temperatures, saving energy and making condensation even less possible. Lowering the space humidity level from the customary 50% down to 40% also lowers the air dewpoint temperature, making condensation less possible. This is why an efficient and effective desiccant dehumidification system is so essential to sustainable, high-performance systems, because these systems can lower the humidity level during the summer by using heat, a commodity that is usually plentiful in the summer months. Minimizing the piping material use for the building life cycle and minimizing the energy use requires proper piping system selection.

An equal pressure or reverse return system is a solution for this design problem. Low load and high load pumps reduce the energy use by over 70% compared to flow and return systems with VFDs, and the system is also flexible, adaptable, expandable, and maintainable. Flow and return piping systems remain the dominant choice by designers, chiefly because connecting the dots is easier than planning out a distribution network. While common practice is to use constant pressure, variable speed pumping to two-way valving from a variable frequency drive (VFD) matched to a high efficiency pump, the authors of this Resource Page have found that this system requires a maintenance intensive pumping system that consumes 4 times more energy than a small pump on the equal pressure system, and is not as expandable, flexible, or adaptable. Within the EMP, eliminating fossil fueled systems is a major objective for a facility designed for environmental sustainability. Eliminating electricity and fossil fuel demand during low and high outside temperatures is also a requirement. In areas east of the Mississippi, refrigeration is needed more for humidity control than for cooling, and a desiccant humidity control system will accomplish humidity control without refrigeration, requiring only 120°F to 180°F hot water for dehumidification and 58°F to 65°F cooling water for the ventilation air and the radiant cooling. Examples of sustainable technologies—those that do not depend on fossil fuels—to provide the 120°F to 180°F hot water for dehumidification and 58°F to 65°F cooling water for the ventilation air and the radiant cooling. include solar hot water heating and ground source systems, respectively. For heating requirements, ground source for preheating combined with solar hot water can also be adequate in many situations and geographic areas. Where the ground temperature exceeds 65°F, absorption refrigeration can efficiently develop 60°F cooling water using solar thermal energy. Low temperatures in the winter months coincide with clear sunlit days that can take advantage of solar thermal systems to eliminate the heating demand. Note that while these systems are not applicable in all situations, the project team should consider options to achieving net zero energy use. Also, cooling and heating do not have to be dependent on the consumption of fossil fuels.

Developing existing systems toward sustainable, high performance solutions will often take several steps. For example, a current popular all-air system for medium and large institutional facilities is the fan-assisted VAV system. The following sequence shows how such a system can be developed to use ambient temperature systems and then be remodeled into sustainable, high performance systems.

These modifications move the system to utilize more ambient temperature cooling and warming water while reducing the electrical load by 60% and the maintenance requirement by 50%.

This diagram shows a typical mechanical system that provides all the characteristics required to be a sustainable, high performance mechanical system. All the maintenance is minimal and within plantrooms. The small radiant ceiling systems can have individual control. The ventilation is the most efficient and provides 100% filtered and treated outside air. The system can be remodeled easily and in sections. The system uses minimum amounts of ambient temperature water for warming and cooling.

Facility Energy Distribution for Building Mechanical Systems

Developing sustainable, high performance buildings is one part of an EMP for a facility. The generating plant and the distribution system to the buildings requires to be developed into sustainable, high performance systems.

An EMP for a facility starts by assessing the clean, renewable energy that will or can be available for the facility in the future. The generating systems are then planned, in steps, to develop into a sustainable, high performance generating and distribution system. Shown below are potential steps from a typical central plant chilled water and steam system to clean, renewable energy systems.

The TNS platform using the back-casting procedure that develops end goals before starting any project should be followed for both buildings and central plant. This saves enormous amounts of money by eliminating any false pathways or projects and will shorten the route to sustainability considerably.

Maintenance Optimization

Sustainable maintenance, which begins with minimizing maintenance requirements, is key to a sustainable building, particularly for its energy systems. At present, there are many facilities that have a "deferred maintenance program." Yet, based on the experiences of the authors of this Resource Page, maintenance deferment has been shown to cost the facility substantially more money in the long-term.

Sustainable maintenance requires substantial planning and effort early in the design process, and minimizing the maintenance requirement is one of the most challenging strategies to achieve. There are three conditions that must be fulfilled to achieve sustainable maintenance:

• All moving parts must be in plant rooms;
  • If the systems, equipment and components are not easy to maintain, they will not be; and
  • Typical maintenance programs will reduce maintenance effort through the building life cycle even though the maintenance requirements may rise as the systems age.

Materials Minimization

Whole building life-cycle material use assessment requires planning derived from experience and informed maintenance and use anticipation. The concept of "long life; loose fit" fails to meet expectations when it does not include "high performance" in its mantra, resulting in mediocre building performance from day one. However, "long life; loose fit; high performance" is a reasonable assessment of what we want to achieve with EMPs. Current building layout and use may change substantially, so a reasonable assessment of probable future modifications and alterations will allow the different scenarios to be taken account and the systems designed with these in mind. The systems must be flexible, adaptable, and expandable, but the magnitude and extent are the million dollar questions.

The distribution systems are key to success. The authors of this Resource Page recommend the piping system to be the equal pressure type with adequate capacity and modularity for the future. Also, radiant heating and cooling systems should be assessed and considered for their life-cycle performance and cost-effectiveness because they could last for 80 to 100 years with the new plastic technologies available. Lastly, ductwork distribution should be assessed for future modifications and designed to be flexible and adaptable. Systems similar to the piping systems, which are different to conventional systems, should be considered as well.

Individual Project Optimization

Each and every individual project must maintain the integrity of the whole EMP. As such, each project is required to provide its optimum performance from planning through to deconstruction. In order to achieve this goal, commissioning for whole life cycle performance is required. A method for this commissioning has been developed by the authors, known as Total Quality Commissioning (TQC). A key element in TQC is the provision of additional documentation. A Detailed Design Intent (DDI) document is required that combines the Clients Brief (CB) Design Intent (DI) and Basis Of Design (BOD) into one detailed document, written in a language that all concerned with the design, construction and operation of the building understand. This document explains in simple language the detailed reasons behind systems selection and sizing to provide the required life cycle performance. Another document required is the Sustainable Building Logbook (SBL), a document that is a diary and provenance of the design, construction, operation and whole life cycle of the project. The SBL contains a history from initial planning to deconstruction of the building performance, and records annual performance data and any modifications throughout the building whole life cycle. TQC combined with EMPs will help guarantee whole life cycle performance of both projects and plans.

D. Conclusions

Energy Master Planning represents the future model for both new and existing energy systems in sustainable buildings and facilities. EMPs should be used to develop design goals and objectives for new and future projects as well as existing facility modifications and upgrades. EMPs combine building and architectural science and engineering principles with the TNS platform to successfully develop sustainable, high performance building energy systems. The investment of effort and expertise necessary to develop EMPs is rewarded many times over by the improvements in facility performance, enhanced productivity, and operational cost savings.

Only by planning for sustainability can it really start to happen. This includes minimizing electricity and fossil fuel use so that all the energy required can be produced on site through clean, renewable sources. Planning also entails reducing maintenance by up to 75%, moving to total preventive maintenance, and optimizing occupant comfort and thus maximizing productivity.

EMPs also allow a multi-building campus or community to develop a distributed clean, renewable energy generation for heating, cooling and electrical supplies. EMPs lay out the processes, procedures, methods, protocols and strategies for moving from any present condition to a true, sustainable, high performance end.

Application

Energy Master Plans (EMPs) provide the necessary steps to plan for mechanical and energy systems within a "whole building" context to achieve high-performance buildings. EMPs can be developed for all building types and are especially useful for high occupancy buildings and/or complicated ones such as educational facilities, office buildings, health facilities, and research facilities. Ideally, EMPs would be developed when the building is being first designed. However, EMPs can also be developed for existing single buildings or multi-building complexes in anticipation of future expansion and modifications toward a sustainable future.

Relevant Codes and Standards

• Energy Policy Act of 2005 (PDF 1.9 MB, 550 pgs)
• ASHRAE Handbooks
• ASHRAE Energy-Efficient Design in New Buildings Series 90,
• ASHRAE Energy Conservation in Existing Buildings, Standard 100-2006
• CIBSE Guide F, Energy efficiency in buildings
• CIBSE Research Report 4, Engineering design calculations and margins—Free for members to download from Members Area

Additional Resources

WBDG

Building Types

Applicable and relevant to all building types

Design Objectives

Cost-Effective, Functional / Operational, Historic Preservation—Update Building Systems Appropriately, Productive—Assure Reliable Systems and Spaces, Productive—Promote Health and Well-Being, Productive—Provide Comfortable Environments, Sustainable—Optimize Energy Use, Sustainable—Enhance Indoor Environmental Quality, Sustainable—Optimize Operational and Maintenance Practice

Products and Systems

Section 23 05 93: Testing, Adjusting, and Balancing for HVAC, Building Envelope Design Guide
Federal Green Construction Guide for Specifiers:

• 23 70 00 (15700) Central HVAC Equipment
• 23 30 00 (15700) HVAC Air Distribution

Project Management

Building Commissioning, Project Delivery Teams, Project Planning and Development, Project Delivery and Controls

Organizations/Associations

• ASHRAE—A leading organization in the development of standardized commissioning guidelines.
• U.S. Green Building Council

Publications

• The Architecture of Building Services by Gordon Nelson. B.T. Batsford, 1995.
• Design With Climate by Victor Olgyay. Princeton University Press, 1963.
• Energy and Environment in Architecture. Baker and Steemers.
• The Energy Design Handbook by Ed. Donald Watson. Washington, DC: AIA Press, 1993.
• Fundamentals of Building Energy Dynamics by Ed. Bruce D. Hunn. The MIT Press, 1996.
• The Idea of Building by Steven Groak, E & FN Spon, 1992.
• Inside Out by Brown, Haglund, Loveland. New York, NY: John Wiley & Sons, Inc., 1982.
• Passive Low Energy Cooling of Buildings by B. Givoni. New York, NY: John Wiley & Sons, Inc., 1994.
• Passive Solar Commercial and Institutional Buildings by Ed. S.R. Hastings. New York, NY: John Wiley & Sons, Inc., 1994.
• Practical Thermal Design in Buildings by Peter Burberry. Batsford Press, 1983.
• Thermal Control of Buildings by D.J. Fisk. Applied Science Publishers, 1981.