Navigant Research Blog

Decoupling H, V, and AC: DOAS and More

— April 14, 2014

Buildings have long been a target for energy efficiency improvements, as they consume a substantial portion of the world’s energy supply (about 40% in the United States).  More recently, the detrimental effects of poorly designed buildings have been established and buildings have been identified as an area to improve the health of occupants.  Though heating, ventilation, and air conditioning (HVAC) systems can be used to accomplish both of these goals, they typically cannot achieve both goals simultaneously.  Conventional approaches to improving indoor air quality (IAQ), such as increasing the ventilation rate or increasing filter efficiency, require using more energy, while increases to energy efficiency (such as improving a building’s seal to reduce infiltration) can have adverse impacts on IAQ.  However, addressing the requirements of heating, ventilation, and air conditioning separately have produced innovative approaches to improve health and reduce costs.

A Flawed Paradigm

Heating, ventilation, and air conditioning are generally lumped into a single system.  Why not?  For the most part, each task requires a box with fans and coils.  Using a single rooftop unit or air handling unit to provide ventilation, filter recirculated air, and produce comfortable temperatures is convenient.  Unfortunately, a single system can have a difficult time maintaining adequate control over disparate conditions.  In practice, adequately addressing IAQ takes a back seat to maintaining space temperature.

In fact, there is evidence that traditional HVAC designs systematically under-ventilate.  Thermostatically-controlled variable air volume (VAV) systems do a poor job of matching airflow to ventilation requirements, particularly in conference and meeting rooms when they are first occupied.  More people in a room increases the generation of both heat and carbon dioxide (CO2).  However, thermostats have a dead-band, an allowable deviation between the actual and desired temperature to avoid short-cycling and simultaneous heating and cooling. As a result, there is a time lag between when the space is occupied and when more than the minimum airflow is delivered.  Moreover, depending on the conditions, the 55°F supply air can offset the temperature rise quickly and return to the minimum position as the CO2 of the space continues to rise.  Theoretically, the minimum damper position should meet the ventilation requirements of a fully occupied room, but improper damper minimums or poor controls integration can lead to under-ventilation.

Separation of IAQ and Thermal Comfort

Decoupling ventilation requirements from thermal comfort through a dedicated outside air system (DOAS) is one way to address this ventilation issue and improve IAQ.  A DOAS provides 100% outside air to a building to meet the building’s ventilation needs.  Typically, it is equipped with some form of energy recovery to precool and dehumidify or preheat and humidify supply air from what is captured from exhaust air.  As a result, the system ensures adequate ventilation and prevents the spread of contaminants between spaces.  Including a DOAS in a building design improves a building’s IAQ by managing it separately from heating and cooling requirements.

However, improving IAQ does not have to be part of HVAC at all.  Introducing filters and outside air into a system that is already designed to move air is convenient, but the same effect can be accomplished by other means.  Adding plants into a space, for instance, can help reduce CO2 and ozone.

The future of IAQ might not be in HVAC, but in the building itself.  Lauzon, a North American flooring manufacturer, has developed a flooring-based solution, called Pure Genius coating, to manage volatile organic compounds (VOCs).  The coating uses photocatalytic titanium dioxide to break down VOCs into water and CO2.  Of course, when maintaining IAQ, converting VOCs to CO2 is a bit like robbing Peter to pay Paul.  However, it shows the advances that materials are making.  Solutions to the current limitations of HVAC equipment might come from outside the mechanical universe rather than from incremental engineering improvements.

 

Smart Building Apps Seek Relevance

— March 20, 2014

In a world where software applications are replacing bank tellersconcierges, and even opticians, what’s the impact on the role of building engineers?  As described in Navigant Research’s Commercial Building Automation Systems report, the convergence of information technology and building control networks is yielding vast amounts of data.  Moreover, the wider adoption of open standards and the decentralization of building networks make this data widely available.  Against this backdrop, the appification of building management seems inevitable.

Still, the universe of building management applications appears to be in its infancy.  A quick search of the iTunes App Store revealed several available choices.  Apps are available from developers as large as Siemens and as small as Lorenzo Manera (I don’t know who he is, either).  The low barrier to entry in app development means that new entrants are just as capable of bringing an app to market as veteran industry players.

Most of these apps appear to turn a mobile device into another building-level control panel, providing functionalities such as monitoring and controlling heating, ventilation, and air conditioning (HVAC) and lighting or providing some level of energy management.  With the proliferation of open protocols, these types of apps have become easy to develop.  However, they all seem to be equally unsuccessful; none of the apps identified have received enough overall ratings for an average rating to be displayed.

Worthy or Worthless?

Smartphones and tablets provide a slew of sensors and far greater mobility than laptops.  Successful apps take advantage of these features, whether it’s the ability to play games anywhere or to use the embedded camera to snap a quick Instagram selfie.  Residential building automation provides several compelling ways to leverage the properties of mobile devices: occupancy can be set using geolocation, outside air temperatures can be provided through the Internet, and devices can remotely monitor and control lighting, HVAC, and security.  Moreover, an app can obviate the need for a system console.

Apps for commercial buildings, however, are a different story.  Since they’re built on top of an existing building management system (BMS), they don’t replace any equipment.  They don’t provide any more functionality than the underlying system.  The sensors on the device do not provide any useful input.  Some building management apps may aid in commissioning, but the biggest feature appears to be providing another way to monitor the BMS.  The Facility Prime app from Siemens, for example, is described on iTunes as “an ideal interface for non-facilities employees that may need access to live system data.”  Until building management apps can provide more functionality for commercial buildings, they will remain a cool toy for home automation.

 

On Energy Efficiency, Congress Dithers

— February 17, 2014

The current congress’s first session was the least productive in recent history, and after the recent Politico Event, Energy and the 113th Congress, I’m not holding out much hope for the next one. During the event, Rep. Joe Barton (R-Texas), senior Republican on the House Energy and Commerce Committee, remarked, “This is not going to be an active legislative congress,” as he dismissed the Energy Savings and Industrial Competitiveness Act (which has been bogged down in the Senate).  Rep. John Shimkus (R-Ill.) agreed, claiming that efficiency would account for only a small percentage of energy use.

Nothing could be further from the truth. As pointed out in Navigant Research’s report, Energy Efficient Buildings: Global Outlook, commercial buildings accounted for 22% of total national energy consumption in 2012.  Currently, the efficiency standards of these buildings are set locally by state and municipal government.  ASHRAE 90.1 – a standard developed by the American Society of Heating, Refrigerating and Air-Conditioning Engineers that sets minimum requirements for building envelops, heating, ventilation, air conditioning (HVAC) and lighting efficiency, and controls – has been adopted by many states in some form. But not every state has adopted the 2010 version, and some states that have adopted it are trying to revert to an older, less-strict version.

Cutting Demand

Provisions of the current version, ASHRAE 90.1-2010, translate to energy savings of about 18% from the 2007 version, according to the Pacific Northwest National Laboratory.  The Energy Savings and Industrial Competitiveness Act establishes ASHRAE 90.1-2010 as the national baseline for energy codes, and requires incremental energy efficiency increases on top of that.  This would have a profound impact on the country’s energy demand.  To put an 18% reduction in commercial building energy use in perspective, an energy use reduction of just 1.3% for the existing commercial building stock translates to a savings equivalent to the output of a typical nuclear power plant.  In other words, energy efficiency is a big deal. Similarly, The National Academies explains how 98% of the chemical energy stored in coal is wasted between generation and a typical incandescent light bulb.

Thankfully, Rep. Diana DeGette (R-Colo.) offered a reasonable perspective, calling energy efficiency “the low-hanging fruit,” insisting that Congress must come to a bipartisan agreement on the subject.  Indeed, the Energy Savings and Industrial Competitiveness Act has gained support from industry (the American Chemical Society, the National Small Business Association, the U.S. Chamber of Commerce, and the National Association of Manufacturers), environmental groups (the Sierra Club, the Natural Resources Defense Council, and the Environmental Defense Fund), not to mention the Christian Coalition of America.  Despite legislative gridlock on this bill, a more stringent regulatory environment is likely to take hold in the United States over the next several years.

 

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