4  FM quick reads on HVAC

1. Energy Model Can Improve HVAC System Energy Efficiency

Today's tip from Building Operating Management: Energy models are valuable in achieving high performance HVAC designs.

How efficient can a building's HVAC system be? To a very large extent, the answer depends on other factors in the building. The type of windows, the amount of insulation, the lighting system, the reflectivity of the roof — these factors and others like them can constrain the performance of the HVAC system by requiring it to work harder to heat and cool the building.

Today, it is possible to evaluate the HVAC impact of these other elements while the building is being designed. Powerful energy modeling software, available from a range of sources, enables the design team to estimate just how efficient a given set of design choices is, and then to compare other designs to identify the one that best meets the building owner's requirements.

For example, Option A may involve code-minimum insulation, ordinary insulated glass windows and a non-reflective roof. Option B, with more insulation, low-emissivity windows and a reflective roof, may initially cost more, but pay for itself in energy savings. What's more, savings associated with a smaller HVAC system can free up funds to cover the cost of those added efficiency measures. In some cases, the energy model may identify options that actually reduce the first cost of the project.

The use of an energy model is required to obtain federal tax deductions under Section 179D of the Internal Revenue Code. These are also known as EPAct tax deductions for the Energy Policy Act of 1995. To qualify for a deduction, an HVAC project must reduce energy costs at least 16.67 percent below the costs for a building designed to meet ASHRAE 90.1-2001. Energy modeling has to show the energy cost savings.

It's important to keep in mind that the energy model, as important as it can be at the design stage, is only an estimate. The actual energy efficiency of a building will depend on how the building systems are operated. A well-designed building can't overcome poor operation.

High-Performance HVAC System Requires an Integrated Design

Today's tip from Building Operating Management comes from Jeffrey Heiken, engineering design principal with Kling Stubbins: A high-performance HVAC system requires an integrated design.

Designing a high-performance HVAC system starts with understanding its end goals. It effectively serves the functional needs of the building and its occupants. It minimizes the use of resources by accurately "right-sizing" components and configurations. It is flexible in response to changes in use. And it employs design elements to capture waste heat, reduce material or energy use, or reuse materials wherever possible.

Across the spectrum of building types, high-performance HVAC systems provide more pleasant and satisfying work environments, and efficiencies which translate into lower owning and operating costs.

But a high-performance HVAC system is impossible without a truly integrated design team fully engaged and focused on project goals from the start. That's because so many aspects of design are interrelated and have to be considered simultaneously to achieve the goal of a high-performance HVAC system. For example, the HVAC design is affected by sustainability elements like daylight projection into the building, which helps drive building footprint and building aspect ratio (length to width dimensions) as well as solar orientation on a site. Daylighting also brings consideration of external shading devices and internal reflective light shelves to prevent glare and heat gain while bringing natural light to the occupied spaces. Internal shading (often mechanized and automated) in concert with computerized lighting control systems are also common energy conservation measures. With all of those factors affecting the HVAC design — not to mention the exterior wall construction, glazing, occupancy and utilization — it's clear that an integrated design approach is essential. From building siting to building envelope composition, the performance of all elements is enhanced.

HVAC can't be an afterthought once the shell of the building has been designed. Compared to the overall building life, the design process is brief and often fast-paced. Attention to HVAC performance at the earliest steps will be felt for decades. So will a lack of attention.

When Upgrading Building Automation, Review Capabilities of Existing Systems

Today's tip from Building Operating Management: Before upgrading an existing building automation system, be sure to review the capabilities of the existing automation and HVAC systems.

When facility managers are considering upgrades to existing building automation systems, they are likely to be wowed by the capabilities available. But those capabilities will be useful only if they are implemented.

One of the most important factors to consider when reviewing the capabilities of the new system is that most existing systems are not used to their full potential. Some functions included in the original system may not have been needed when it was first installed. Management may have decided that some functions required too much effort or the collection of too much data to be of value. Still other functions may have been used initially, but dropped due to the lack of sufficient manpower or simply because they were too difficult to use.

Before making a decision to invest in a new system to gain additional system capabilities, make certain that they are not already available with the current system. If they are available, then the facility manager should evaluate whether anything about the new system makes it more likely that those capabilities will be used.

A review of existing capabilities must extend beyond the system itself to the building systems and components they will be interfacing with. Having the ability to control the operation of all building HVAC equipment is a feature needed if managing facility energy use is one of the primary goals of the system. If the HVAC systems themselves do not have the controls of the type and level of sophistication needed, then those HVAC systems will need to be upgraded or the energy savings impact of the new system will not reach its full potential. It may well be worthwhile to upgrade the existing HVAC system, but the option should be carefully evaluated before a decision is made to move ahead with a new building automation system.


HVAC , green buildings , high-performance design , integrated design , daylighting , energy conservation , energy modes

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