Building Energy Resilience

In one of Cx Associates’ latest blog posts, Energy Metering Devices: What’s New, Katie Mason describes data loggers (aka energy metering devices) used in the industry to diagnose building system issues and calculate energy consumption. This data collection technology has come of age in that the loggers themselves are not outrageously expensive and modeling software has developed into a strong analysis tool. For a building owner, this means data loggers can clearly diagnose where equipment is operating poorly, triggering increased energy and maintenance costs. Data loggers are also instrumental to managers of local, state or regional energy efficiency programs in order to accurately calculate energy savings attributable to efficiency improvements. Let's look in more detail at these two applications of the new energy metering technologies.

Energy metering devices (also known as data logging meters) are improving rapidly. Data logging meters, such as power and light intensity loggers, are important tools for diagnosing building system issues and/or calculating how much energy certain equipment is using. They also allow you to see how individual equipment is performing over time, which is key for measurement and verification (M&V).

The toolbox of equipment we use for our building commissioning work changes as building science and standards evolve. As prices for technology continually fall, there often comes a time when equipment you didn’t think you really needed becomes affordable enough that you decide it’s time to take the plunge and invest in it. Having a digital camera 15 years ago was still quite expensive, but now you can get a decent camera for under $200, and most of us have them built right into our cellphones. It’s hard to imagine working as a Commissioning Authority now without such an essential tool as a digital camera. But building commissioning has been around longer than reasonably priced digital cameras, so it must have been possible to provide high quality Cx services without that capacity!

Introduction

The graphical interfaces that connect building operators to the HVAC, lighting, power management, security, and other systems are critical elements of a building control system (A.K.A. BMS, DDC, EMS, but for the purposes of this post, we will focus on the “graphics” portion of the controls server, independent of what the control server is called colloquially). The graphical interface provides the building operators quick access to many pieces of useful (and sometimes critical) information which supports building operation. These include, for example, system status readings, alarms, sensor readings, damper/valve positions, fan/pump speeds, and energy performance metrics. The graphics also provide a means for operators to change setpoints, adjust alarm limits, enable/disable equipment, and do many other functions throughout a potentially large building or campus, right from their desk or a control system workstation.

We are wrapping up the commissioning of a water source heat pump system for a 120+ room hotel. Our involvement began in the design stage when the initial concept was to use condensing boilers to heat both the domestic hot water (indirectly) and heat pump loop. While this is a fairly typical scenario, especially in the hospitality industry where first cost is typically given a very high priority, it leaves a lot of the boilers’ potential energy efficiency on the table.

Which energy systems should be included in a building commissioning process if you cannot do them all? Commissioning a building includes a lot of details, and often a lot of equipment. The overall process is generally standardized (see ASHRAE Guideline 0), but the scope of building commissioning can vary a great deal from project to project. LEED certified buildings require commissioning for all energy-related systems associated with HVAC, domestic hot water (DHW), lighting, and renewable energy. Non-LEED building projects may require only HVAC, or may include additional building systems such as the building envelope. But what energy systems can potentially benefit most from a building commissioning process? The precise answer to this question will depend upon the type and quantity of energy systems in a given building project; nevertheless, a reasonable answer to this question may be found in the 2011 Vermont Commercial Building Energy Standard (VCBES).

From building trades and commissioning work, I’ll occasionally notice something off-the-job about a particular building HVAC system, and it may become a distraction (though my wife may classify it as an obsession). I think we, as humans, are all prone to do this—examples include the English teacher that can’t stand the misapplication of “lay” vs “lie” by people outside of the classroom setting (my 95 year old former English teacher grandmother, for one), or the chef who may have trouble enjoying other people’s food without having to over-think the ingredients or preparation, and the like. Well, as you can imagine, this happens to HVAC engineers as well and today my “distraction” concerns commercial kitchen exhaust imbalance.

Outside air economizers are one of the most cost-effective, common, promising and troubled energy efficiency components you can find on a commercial air handling system. The concept is simple and beautiful – use outside air instead of expensive mechanical cooling when possible. When outside air is at the right temperature and humidity levels, turn off chillers, cooling towers and pumps, and bring in free air. In reality, however, while our firm has commissioned hundreds of outside air economizers (new construction and retrocommissioning projects), more than 50% of them have not functioned properly, causing significant energy penalties to the building operating costs.

Six months ago, I wrote a blog post that described the mobile applications, or “apps” that Cx Associates’ engineers have been finding useful for fieldwork or for deskside analysis support. These ranged in capability from the simple and relatively nontechnical--such as a PDF reader-- to the more technical--such as air property (psychrometric) calculator tools. In the fast evolving field of mobile applications, six months is a long time--and it’s no surprise that a bunch of new apps have appeared. This blog post supplements the last one, so if you have not read it, its worth checking out as well--the apps presented there are still extensively used by our engineers. (Please note that neither Cx Associates nor its engineers are affiliated or compensated by the app developers reviewed.)

Modern Building Automation Systems consist of three core conceptual components: information inputs (sensors, switches), controls outputs (actuators, VFD’s, relays), and a brain (controllers and a head-end). Traditionally, copper cabling of different kinds has connected all of these devices together in some manner. Each actuator and sensor may be connected directly back to a central controller, or often through local equipment controllers (such as a heat pump above a drop-ceiling) equipped with controls cards with a network interface. Regardless of the specific wiring scheme, the bottom line is that the building owner becomes the proud owner of a virtual spiderweb of controls cabling. In new construction, cabling can be installed before finished walls and ceilings are in place, so installation is not very disruptive and can be cost effective. For retrofit applications however, running new cabling can be very labor intensive and disruptive to surface finishes (drywall, woodwork), which can be ultimately very expensive.