Designing for Comfort per ASHRAE Standards 55 and 62.1

The goal of a room air-distribution system is to provide thermal comfort and a healthy living environment for occupants in the space. ASHRAE Standard 55-2010 Thermal Environmental Conditions for Human Occupancy and ASHRAE Standard 62.1-2010 Ventilation for Acceptable Indoor Air Quality provide designers with the guidance to optimize health and comfort in building spaces. Many codes, including LEED 2009, require compliance with these ASHRAE Standards. This article will outline the goals of these standards and illustrate how to comply with these requirements.

The occupied zone as defined by Standard 55-2010 reads: “The region normally occupied by people within a space, generally considered to be between the floor and 6 ft. level above the floor and more than 3.3. ft. from outside walls/windows or fixed heating, ventilation, or air-conditioning equipment and 1 ft. from internal wall.” The space from the interior walls inward 1 ft. serves as a mixing zone where room air is entrained into the supply-air jet and mixes to provide thermal comfort in the occupied space. When designing underfloor air-distribution (UFAD) or thermal displacement ventilation (TDV) systems, the occupied area around the outlets may be excluded to a boundary where the total air jet from the outlet contains velocities greater than 50 feet per minute (fpm). These areas may also be known as the “clear zone,” “adjacent zone,” or “near zone.”

Any design must also include an adequate supply of ventilation air to the breathing zone of the space. ASHRAE 62.1-2010 defines ventilation air as “that portion of supply air that is outdoor air, plus any recirculated air that has been treated for the purpose of maintaining acceptable indoor air quality.” The breathing zone is “the region within the occupied space between planes, 3 and 72 inches above the floor… .” We will discuss additional requirements for ventilation air later in this article.

The primary factors to be considered when determining conditions for thermal comfort in the occupied space are: 1) Temperature, 2) Air velocity, 3) Humidity, 4) Clothing insulation, and 5) Activity level of the occupants. All of these factors are interconnected when determining the general occupant comfort of a space. The ideal temperature in a space (operative temperature) is where the occupant will feel neutral to their surroundings, neither feeling any heat loss or heat gain from the space. While the range of acceptable operative temperatures may vary depending on other conditions, it is a requirement of ASHRAE 55 that the “Allowable Vertical Air Temperature Difference-Between Head (67”) and Ankles (4”) is limited to 5.4 F (3.0 C)”. Ideal air velocity in the space can vary with other factors, but, in general, the goal is to keep spatial velocities less than 50 fpm during cooling mode and less than 30 fpm during heating mode. For many years, Titus has recommended maintaining the relative humidity level in the space between 25-60%. ASHRAE 55 does not define a lower limit and requires the dew-point temperature be less than 62.2 degrees (F). Another factor affecting comfort is the clothing insulation level of the occupant. In most office environments, the Clo level for occupants is between 0.5 and 1.1, where .5 would be a person wearing no socks, sandals, short-sleeve shirt or blouse, and shorts or a skirt. The 1.1 Clo level would include long pants, socks, long-sleeve shirt, and a dress coat or sweater. The range of operative temperatures where both 0.5 and 1.1 occupants are in the same space is very narrow. The final item of consideration for design comfort is the intended activity level of the occupant in the space. In most office environments, the metabolic (MET Rate) is between 1.0 and 1.3. This includes occupants who are sedentary to casual movement about the space.

The three common methods of room air distribution used in commercial buildings in the United States are fully mixed (e.g. overhead distribution), fully stratified (e.g. displacement ventilation), and partially mixed (e.g. most underfloor air distribution systems). Since interior zones usually have adequate heat loads from occupants and equipment, in addition to few heat losses, the discussion for interior spaces will be cooling only. For the perimeter spaces, the discussion will be how to meet the requirements for heating and cooling from the same overhead outlet. Design methods for cooling an interior zone and heating a perimeter zone vary with each method.

For fully mixed systems, the pattern of the air delivered to the space must be considered when selecting an air outlet. Ceiling diffusers typically exhibit flow in a circular (radial) or cross-flow (directional) discharge air pattern. The circular pattern usually provides shorter throw, higher mixing and tends to maintain ceiling effect to low velocity before turning back on itself. This pattern is ideal for variable air volume (VAV) cooling by providing less drop and more uniform temperatures in the space. The cross-flow (directional) air pattern has longer throw, but with less induction may lose ceiling effect, creating drafts in the occupied zone. Plenum slot diffusers typically discharge air in a directional air pattern, but some are available with “spreaders” to produce a more radial discharge pattern. Sidewall grilles equipped with vertical deflectors can be adjusted from zero degree (directional pattern) to a 45-degree spread (radial pattern). So, regardless of the desired type of outlet, the air pattern can be either radial or directional to best meet the comfort requirements of the space. Proper selection for comfort can be insured by using the ADPI selection program in TEAMS.

Typically, for perimeter applications where the same outlet is being used for both heating and cooling, a linear slot diffuser or plenum slot diffuser is employed. When a fixed air pattern diffuser is used, it is typical to supply half of the air across the ceiling for cooling and half down the glass for heating. For perimeter heating, the requirements for table 6-2 of ASHRAE Standard 62.1-2010 must be considered. The intent of table 6-2 is to ensure that the ventilation air supplied to the space be delivered to the breathing zone as well. For ceiling supply of warm air with a ceiling return, the requirements for heated air are to reach a terminal air velocity of 150 feet-per-minute to within 4.5 ft. of the floor. To a terminal velocity of 150 fpm or more, air is temperature independent, which means the distance air will travel will be the same for isothermal air (catalog values), warm air and cool air. This means that during heating, ventilation air will be pushed down into the breathing zone with enough heat energy to meet Standard 55’s requirement for a temperature gradient of less than 5.4 degrees. In addition, the differential temperature between warm supply air and space temperature with a ceiling return must be 15 degrees or less. Thus, the maximum supply-air temperature for a 75-degree room would be 90 degrees. When the heating supply-air temperature exceeds the 15 degree limit, the ventilation air volume must be increased by 25%.

Choosing an auto-changeover diffuser like Dynafuser or EOS does not change the Standard 62.1 requirements, but will lower energy costs and improve comfort in the space. Delivering all the warm air down the glass during heating will save energy. With a fixed-pattern diffuser, half of the warm air will be discharged across the ceiling and with a ceiling return can be short-circuited without reaching the occupied space level. Additionally, higher comfort will be realized in the space since the heated air can be designed to deliver warm air all the way to the floor. Comfort may be increased during cooling as well, as the cool air will be projected across the ceiling eliminating the potential for drafts from the jet protected down the glass with a fixed pattern diffuser.

For partially mixed air-distribution systems (typically UFAD), the core area usually experiences even loading throughout the occupied area. The goal of partially mixed systems is to save energy by comfort-conditioning the lower occupied level in the space and allowing the upper level of the space to stratify. Occupant comfort is achieved by delivering cool conditioned air from the plenum under the floor through swirl diffusers or rectangularly shaped outlets near the occupants’ work area. Individuals can enhance their personal comfort by adjusting the damper at the outlet near their workspace. For common areas such as hallways and break rooms, outlets can be equipped with actuators that are controlled by a common thermostat located in the space.

Perimeter zones for partially mixed systems create a greater challenge, as the loads are dynamically changing due to outdoor solar and air temperature changes. A common method for perimeter zone control is locating a low-profile fan-powered terminal unit under the floor near the perimeter supplying air to linear bar grilled. The fan-powered terminal can be equipped with an electric or hydronic coil. Cool plenum air can be supplied to the outlets when cooling is required and the coil can be employed to warm the air as required during heating conditions. The design challenge is selecting outlets that will limit the throw of the air pattern so that air will not bounce off the ceiling and create drafts in the adjacent occupied area.

Energy to operate the fan terminals can be eliminated and higher comfort can be achieved on the perimeter by using the TAF-L perimeter distribution outlets. With a 6” wide custom design TAF-L bar grille located along the perimeter of the space, the modular 4’ long TAF-L-V (cooling), can be attached to provide up to 225 cfm (at 0.07” plenum pressure) per 4’ unit of cooling. The TAF-L-V damper is controlled by a space thermostat to provide cooling as required. The special arrangement of bars in the grille is designed to limit the throw from the outlet during cooling. The 4’ long TAF-L-W or TAF-L-E heating module can be attached to the TAF-L grille to supply up to 3,000 Btu heat to the perimeter. The heating units operate by combining the cool convection currents from the glass with the warm currents on the floor. The mixture is induced through the heat exchanger with warm air being discharged through the grille and up the glass. Space temperature is controlled by a room thermostat controlling the water flow or electric current flow to the electric heating element. The modular design allows the system to be custom designed for use in multiple climate regions.

A fully stratified design (typically TDFV) conditions a space by discharging cool supply air through an outlet located at floor level. This happens near or in a wall or may be centrally located in the open space. Low velocity air (<80 fpm) is discharged horizontally across the floor. Air moves with little mixing across   the floor until it contacts a heat source such as an occupant or a piece of warm equipment in the space. Cool air will mix with the radiant heat, form the source, and stratify toward the ceiling. The return is usually located at or near the ceiling. The area between the outlet and where the air speed reaches 40 fpm is the “clear zone” and should not be included in the occupied area. Titus provides units with adjustable air patterns so the clear zone can be controlled to meet project requirements for space occupancy. ASHRAE Standard 62.1 (Table 6-2) provides a 20% bonus for TDV systems. This means that ventilation air can be reduced by 20% or the 20% can be used toward the 30% required for an additional LEED IEQ credit 2.

While TDV systems typically require a separate system for heating, Titus has introduced the Plexicon heating/cooling diffuser. A standard rectangular outlet is located near or mounted in a wall that discharges cool air from the upper chamber. When heating is required, an internal baffle is moved to change the flow of air from the upper chamber into the lower chamber where it flows through a linear bar grille to satisfy heating requirements.

Regardless of which type of system you are using on your project, studies have shown that occupants whom are comfortable are more productive. Designing for comfort, keeps paying back dividends forever. 

Please direct questions toward Titus Communications (communications@titus-hvac.com) and/or Titus' Chief Engineer (Grilles & Diffusers) Jim Aswegan (jaswegan@titus-hvac.com).

UFAD Systems offer Comfort, Flexibility, and Energy Savings

Underfloor air-distribution (UFAD) systems have been used for comfort-conditioning office spaces in United States office buildings since the early 1990s. Systems were initially employed in high-tech office spaces where in addition to occupant comfort, ease of office space re-configuration (churn) was a priority for building owners. UFAD systems deliver air to occupied spaces through floor-mounted outlets supplied by conditioned air from a pressurized plenum beneath the suspended floor. 

A properly designed UFAD system takes advantage of thermal stratification. The key is to have a diffuser that rapidly mixes air without penetrating the stratification layer at the ceiling. The pressurized plenum -- the area between the slab and raised floor -- is essentially a large duct maintained at a constant pressure differential to the room above; typically between .05 and .10 in. pressure (w.g.). This pressure is maintained through the supply of conditioned air from a number of supply-duct terminations. The spacing and location of these ducts are dependent on the air supply requirement and the plenum depth which typically ranges from 12” to 24”. If zone control is desired from the underfloor plenum, it can be partitioned into separate zones. The return air for a UFAD system should be located at the ceiling or high sidewall. This allows heat from the ceiling light to be returned before it is able to mix with the occupied zone. There is also a small amount of “free cooling” due to the natural buoyancy of hot air.

Some of the concerns typically associated with these systems are humidity, dirt, spillage, and leakage. A potential problem with the higher supply temperatures used in access floor air-distribution systems is the higher potential moisture content of the 60-65˚F supply air most commonly used in these systems. The supply system must reduce relative humidity to less than 65˚F. Potential solutions are either the reheat or blending of air to achieve a 65˚F supply, 55˚F dew-point condition. System designs utilizing condenser water reheat, run-around coils (face, bypass), and other strategies can be employed to solve these potential design problems. Other options include the use of desiccant dehumidification. Although underfloor air-distribution systems are not recommended for areas with a high potential for spills such as bathrooms, cafeterias and laboratories, small spills are not a problem for most applications. Typical swirl diffusers used within the interior have a dirt/dust receptacle to catch spills and dirt from normal daily use. The dirt/dust receptacle has a basin that will hold anywhere from 4-6 fl. oz. of liquid. The dirt/dust receptacle can easily be removed and cleaned to keep dirt out of the underfloor plenum. Leakage is typically due to poor sealing or the construction quality at window/wall locations, stair landings, electrical outlets, etc. These areas have to sealed and framed so the supply air does not travel up the wall toward the return air. There can also be leakage between the floor panels which can be reduced by staggering the carpet tiles over the floor tiles. The key is to limit the number of penetrations into the raised floor which will reduce the number of areas that need to be sealed.

Since typical floor plenum pressure is less than .10 in w.g. (25 Pa), energy-efficient low-pressure fans can be used. In place of complicated and expensive duct systems required to supply air to each individual air outlet in a ceiling system, UFAD systems deliver air to building zones using a limited amount of ductwork to create an air highway.

Where a traditional overhead mixed system provides comfort-conditioned air from the floor to the ceiling, partially mixed systems like UFAD save energy by providing comfort-conditioning in the lower occupied spatial zone. They allow the upper zone to stratify.  

In the core of the building where loads are relatively constant, round (swirl) or rectangular outlets are located in the floor near the occupants. Outlets typically deliver 80-100 cfm (38-48 l/s) of conditioned air to the space. Some of the units have volume control adjustability by the occupants to increase individual comfort levels. The round swirl diffusers are typically available with an occupant adjustable flow regulator that can be either manually adjustable or by the use of a room sensor that is connected to an actuator mounted directly on the diffuser. Installation of swirl units has been made easy by replacing the mounting ring which was previously attached to the unit beneath the floor tile with spring clips to provide a press fit directly into the floor tile. A recent ASHRAE research project (RP-1373) has also provided data to show that when the height of the air plume to a terminal velocity of 50 fpm (.25 m/s) is limited to 4.5 feet (1.4 m), the air change effectiveness (ACE) is improved in the breathing zone. This research has now been recognized by ASHRAE Standard 62.1-2010 with Addenda A in Table 6-2 by allowing an Ez rating of 1.2 for these conditions. This means that the ventilation (outdoor) air supplied to the zone can be reduced by 16.7%. For LEED projects where the credit point for IEQ credit 2 is desired, this 16.7% can be used in reaching the goal of 30% increased ventilation air.

Some of the biggest challenges for underfloor design occur on the perimeter of the building where loads are higher and dynamically changing due to effects of radiation and temperature conduction on the skin of the building. Where the core of the building is mainly impacted by nearly constant heat loads, the perimeter system must accommodate swings in heat loads and heat losses that can occur in a relatively short period of time.

A common method of handling perimeter loads to locate a fan-powered terminal in the floor plenum near the perimeter. These fan-powered terminals are ducted to outlets located on the perimeter. A typical outlet would be a linear bar grille with either a boot plenum or continuously fed plenum underneath. Equipped with an option hot water or electric heating coil, the fan unit can deliver warm air in response to a space thermostat. Unfortunately, as linear grilles get longer, the mass effect of the discharge air jet projects the air higher than required. If the throw from the outlet is too long and reaches the ceiling, it may deflect downward into the space and create unwanted drafts in the interior zones. In some cases, cool air from the floor plenum is supplied to the perimeter zone through the fan-powered unit.

For LEED projects, the operational cost of energy to run a fan-powered terminal can be minimized by using ECM fan motors. ECM motors operate at an efficiency of 70% or greater. The cooler operation of an ECM motor -- and enhanced construction -- contribute to a longer life and lower life-cycle cost when compared to standard construction PSC motors. An additional benefit of an ECM motor is ability to control the fan speed during operation to provide increased energy savings and better occupant comfort in the occupied space. ECM motors can also utilize remotely controlled speed controllers (pwm) that can be controlled through a building management system.

New technology in perimeter systems can lower installed/operational costs and improve comfort along the perimeter zones. By installing a continuous bar grille along the perimeter, variable air volume (VAV) cooling and plenum heating coils can be attached as needed to condition the perimeter. These cooling and heating units are passive and do not require the use of a fan terminal. The bar grille can be connected together to provide a continuous architectural appearance around the perimeter or can be installed in sections as required for comfort conditioning. The core of the bar grille is removable from the room to provide access to the unit’s working components.

The VAV-cooling units employ an electrically actuated sliding damper, which opens and closes a series of transverse apertures to vary the volume of cool air supplied from the pressurized underfloor plenum into the space. The sliding damper opens and closes to provide the amount of conditioned air required to manage the changing conditions as directed by a room thermostat located in the occupied zone. The transverse apertures manage the supply air to allow room air to be included into the air pattern. Introducing supply air in small bundles helps in managing the projection from the outlet and prevents long throws which create drafts in the occupied space.

The heating plenums also attach to the linear bar grille. The heating plenums are passive in operation and do not require a fan-powered terminal to supply air or heat. Located parallel on the perimeter at the glass, the heating unit mixes the cool convection currents flowing down the glass with warm-air currents traveling across the floor. These mixed currents are induced into the inner chamber of the plenum and flow up through the heat exchanger. The warm current then exit the linear grille at the glass and flow upward via convection to heat the cool air in front of the glass.

The hydronic heating units have a finned-tube heat exchanger with heat supplied through a hot-water pipe and controlled by a water valve to provide the precise amount of heat required to satisfy room conditions. The electric heating units are of fin-tube construction and have an SCR control to match the changing heat requirements in the space. The ETL listed heaters can be found in 120V, 208V, 240V, and 277V supply circuits. The modular construction of the VAV-cooling and the fin-tube water or electric heating units allows the installation to match the requirements of any climate zone. Where winter conditions prevail, more heating units can be installed to meet heating needs. Where hot summer conditions prevail, additional VAV-cooling units can be employed to match the cooling requirements.

To claim maximum energy efficiency and occupant comfort, care should be taken during construction to seal all floor panels. Additional care should be taken to seal all openings through the floor either into the space or into the walls where plumbing or electrical equipment penetrates the floor plenum. Regular inspection during construction will minimize problems upon building completion and commissioning.

In recent years, the application for UFAD systems has shifted from owner-occupied high-tech facilities to a more general variety of building spaces aiming to achieve LEED certification. UFAD provides superior comfort by supplying conditioned air where it is required near the occupant. Additional occupant comfort can be achieved by installing small units in the core of the building with individually adjustable dampers controlled by the occupant. By conditioning only the occupied area and stratifying the upper zone with air supplied form the low-pressure floor plenum saves energy. Additional energy can be saved by employing a passive VAV-cooling and fin-tube heating system on the perimeter. 

For your next LEED project, take advantage of UFAD to provide lower energy (EA c1), controllability of systems for thermal comfort (IEQ c6), and thermal comfort (IEQ c7).

Please direct questions toward Titus Communications (communications@titus-hvac.com) and/or Titus' TU/UFAD Product Manager Derrick Smith (dsmith@titus-hvac.com).

EOS: The Perfect Solution for Perimeter Overhead Heating & Cooling

All engineers want to design the perfect system. But, as most young consulting engineers soon find-out, HVAC design is a game of compromises. Their goals are occupant comfort, energy savings, system controllability, and installed cost.

The air-conditioning of perimeter zones in commercial buildings is a perfect example of these compromises. Almost all buildings require heating and cooling at the perimeter during different times of the year. Most commercial buildings in the U.S. are overhead mixed systems. Overhead systems work well in cooling with proper diffuser selection. Overhead heating is a different story.

A good solution would be to provide overhead cooling and baseboard heating, but providing two systems is cost prohibitive. Here, the engineer is faced with his/her first compromise. A fairly common compromise is to provide a perimeter slot diffuser with either a dedicated down-blow section -- to provide some heat to the floor -- or a diffuser with split pattern control so half of the air can always be directed down while the other half is directed horizontally across the ceiling.

As a compromise, this method works, but it is not the optimum solution. In both heating and cooling modes, half the supply air is being discharged in the wrong direction for optimal comfort and energy savings. In heating, half of the supply air is discharged horizontally causing stratification along the ceiling. In cooling, half of the supply air is discharged vertically causing unwanted drafts along the floor.

The award-winning Titus EOS is a solar-powered, energy-harvesting plenum slot diffuser designed to provide the perfect perimeter solution for those imperfect perimeter compromises. The EOS automatically changes the air-discharge pattern to horizontal for cooling or vertical for heating. 

When 100 percent of the supply air is effectively utilized, the room temperature reaches set-point faster. This allows the HVAC system to run for a shorter duration of time and save energy. Lab tests show the savings to be as high as 30 percent, which makes it a great choice when designing buildings for LEED certification.

The EOS increases occupant comfort and saves energy without the use of any external power source. The auto-changeover ac­tion is powered by a unique energy harvesting system which uses solar or ambient light energy to power a miniature motor/accua­tor assembly. A PC board with temperature sensor uses smart logic to monitor supply air temperature and quickly change the air-discharge pattern.

With the EOS, Titus continues as the industry leader in innovative design by providing an energy efficient and cost effective solution for the perimeter heating/cooling dilemma.

Please direct questions toward Titus Communications (communications@titus-hvac.com) and/or Titus' GRD Product Manager Mark Costello (mcostello@titus-hvac.com).

What are the Minimum Minimums for Digital Typical Controllers?

Minimum minimums are the minimum airflow limits Titus recommends for accurate airflow control on terminal unit inlets. Many customers have noticed that Titus’ 2014-15 Product Catalog contains updates regarding these values. In this entry, we will reference the “DESV - Digital Typical Controller” section found on pg. M14.

The original minimums that we established many years ago were based on factory-calibrated pneumatic controls. It was determined that factory-calibrated controls could maintain an accuracy of +5% if we did not try to set the minimum airflow limit too low. Of course, you can always order a unit set for full close-off because that is not really airflow control.

For the Titus II and IIA, we determined that a minimum airflow based on a sensor signal of 0.03 in wg could be controlled within +5%. The Titus I required a slightly higher sensor signal of 0.05 in wg in order to deliver the same accuracy. Later, analog and digital electronic controls were assumed to be equivalent to the Titus II and IIA controls with regard to the minimum control accuracy.

Here are the minimums for Titus I:

• Size 04 = 55 cfm
• Size 05 = 85 cfm
• Size 06 = 105 cfm
• Size 07 = 135 cfm
• Size 08 = 190 cfm
• Size 09 = 225 cfm
• Size 10 = 300 cfm
• Size 12 = 425 cfm
• Size 14 = 575 cfm
• Size 16 = 750 cfm
• Size 40 = 1800 cfm

Here are the previous minimums for Titus II, Titus IIA, TA1/TA2 and digital controls:

• Size 04 = 45 cfm
• Size 05 = 65 cfm
• Size 06 = 80 cfm
• Size 07 = 105 cfm
• Size 08 = 145 cfm
• Size 09 = 175 cfm
• Size 10 = 230 cfm
• Size 12 = 325 cfm
• Size 14 = 450 cfm
• Size 16 = 580 cfm
• Size 40 = 1400 cfm

During the preparation of our latest catalog, it was decided these minimum values should be reduced in recognition of the improvements that have occurred in digital electronic controls (specifically, their electronic flow sensors).

We reduced the minimums based on a sensor signal of 0.01 in wg. As always, the actual flow-control accuracy depends on the quality of the controller, but our lab testing has shown that some controllers can provide +5% accuracy down to a sensor signal of 0.005 in wg.

Here are the latest minimums for digital controls:

• Size 04 = 30 cfm
• Size 05 = 40 cfm
• Size 06 = 45 cfm
• Size 07 = 70 cfm
• Size 08 = 90 cfm
• Size 09 = 120 cfm
• Size 10 = 145 cfm
• Size 12 = 190 cfm
• Size 14 = 300 cfm
• Size 16 = 385 cfm
• Size 40 = 720 cfm

Titus’ minimum minimums for digital controls are much lower than they have ever been. This should be a welcome change for designers whom want accurate airflow control without increasing the minimum airflow volume to achieve it. We have redefined how low you can go!

Please direct questions toward Titus Communications (communications@titus-hvac.com) and/or Titus' Chief Engineer Randy Zimmerman (rzimmerman@titus-hvac.com).

Seismic-Rated Terminal Units

Titus has Seismic Certification Compliance on our ESV, TFS, and TFS-F terminal unit models through the International Building Code (IBC) and Office of Statewide Health Planning and Development (OSHPD). Certification includes rigid-mounting and spring-isolated installations.

The certification rating is:

More medical facilities are requiring this certification to ensure equipment will remain functional after experiencing a seismic event.

These Titus terminal unit models are certified in the following options:

• Hot water / Electric reheat
• PSC and ECM motors
• All liner types currently available
• All current motor and heater voltages and kilowatt offerings

For ESV single-duct models (AESV, PESV, and DESV), all sizes and configurations that are available on standard units now meet the certification. This option is only available with 20-gauge galvanized material.

For series fan-powered terminal units, the TFS/TFS-F models are certified with all of the options, sizes and configurations available on the standard products as well.

All Titus-branded controls are included in the certification:

• Alpha Digital Controls
• TA1 Analog Controls
• Titus I & II Pneumatic Controls

FMA Controls must carry a seismic listing from the controls supplier in order to be used on a seismic-rated terminal unit.

The IBC is utilized by the U.S. State Department and governs all commercial construction for every state.

It has specific requirements for certain types of buildings and their components where ground accelerations caused by earthquakes are likely to be above a certain g-level.

Active mechanical equipment or electrical components must be tested to verify compliance if they are to remain operational after a seismic event.

In California, the OSHFD is the Authority Having Jurisdiction (AHJ) for hospital construction and for the California Building Code which is based on the IBC.

As an AHJ, OSHPD has defined what the acceptable criterion is for them as it relates to how a manufacturer complies with the building code.

Titus is the first VAV terminal unit manufacturer to receive this certification. We recognize the importance of complying with new codes in different regions as we continue to Redefine your comfort zone. ™

Please direct questions toward Titus Communications (communications@titus-hvac.com) and/or Titus' Terminal Unit, UnderFloor Air Distribution Product Manager Derrick Smith (dsmith@titus-hvac.com).  

Sweating: A Potentially Dangerous Sign of a Bigger HVAC Issue

What is Sweating? 

Sweating is moisture that forms on the faces of lay-in diffusers and T-bar grids adjacent to those diffusers, where it collects/drips into the areas below. 

Why is it a Problem? 

While sweating may be a simple annoyance, it can also be dangerous. Either way, it is a symptom of a larger problem with the HVAC system, the building construction, or both. Dripping moisture is an unpleasant occurrence; With smooth flooring, it can create areas that are slipping hazards. Over time, the accumulation of moisture will contribute to the rusting of the diffuser and damage to the surrounding ceiling system.

Why Does Sweating Occur? 

The sweating phenomenon happens mostly in southern states, coastal locations, or any other location with high levels of humidity. However, humidity is usually just a contributing factor in sweating. Sweating is most common in locations where there is significant traffic between the occupied air-conditioned space and the outside environment where hot/humid air is allowed to get into the air-conditioned room. In those situations, the air-conditioning system runs for longer periods of time. It chills the metal diffuser and tries to maintain a comfortable inside temperature.

Sweating happens when the warm, moist room air contacts the chilled diffuser face while the supply air temperature is below the dew point temperature. Dew point temperature is the temperature at which water vapor condenses into water. The problem is that the supply air temperature is lower than it should be for the current conditions of temperature and humidity.

How do you Address the Issue? 

Simple items to check that can contribute to sweating are:

• Is your air-conditioning unit cycling? If so, switch to a constant running option. 
• Are your returns undersized, restricting return airflow? 
• Are the filters dirty? 
• Are the coils on the VAV box dirty? 

If none of the quick fixes resolve your sweating problem, then there is likely a larger system issue and you will need to look deeper into your system setup or the building itself. 

Since sweating happens when the difference between the room air and the supply-air-chilled diffuser face is below the dew point temperature, you can decrease the difference between the room temperature and the supply air temperature (ΔT). This can be done by adjusting your thermostat to a higher temperature. Doing this, while still meeting the space's load requirements, will require an increase to the CFM's into the occupied space. 

An easier method of preventing sweating is to install an insulation blanket on the backside of the diffuser. This will insulate the diffuser face from the warmer air in the attic space and prevent the face from collecting moisture, thus, decreasing the (ΔT). With the temperature differential minimized, sweating will decrease or be eliminated. 

Another way to avoid sweating in a room using HVAC equipment is to always make the occupied spaces have a positive pressure with respect to the outside areas. Beware that in new construction, you could have some sweating collecting in diffusers and other ceiling equipment because it takes time for the humidity to settle into normal levels. 

As we mentioned before, sweating is only a symptom of a larger problem in the HVAC system. Since sweating manifests first in diffusers, it may be easily perceived as a problem with the diffuser itself. It is important to diagnose and treat the system issues that lead to sweating. In doing so, you will avoid costs due to renovations needed because of rusting and water damage in the ceiling system. After correcting these problems, your HVAC system will run more efficiently.

Please direct questions toward Titus Communications (communications@titus-hvac.com) and/or Titus' Senior Application Engineer José Palma (jpalma@titus-hvac.com).

Open Ceiling Environments Need Special Care

It has become quite popular these days to design spaces without suspended ceilings, leaving ductwork and terminal units partially or fully exposed.

There are items that need to be understood with regard to diffusers and terminal unit selections when ceilings are to be omitted:

• Ceiling tiles tend to block high-frequency noises generated by ductwork and terminal units, and absorb those occurring within the occupied space. The sound spectrum in a space without a ceiling will tend to be somewhat harsh and much more reverberant.

• AHRI Standard 885 “Procedure for Estimating Occupied Space Sound Levels in the Application of Air Terminals and Air Outlets” uses a ceiling/space effect (Table D15) for estimating radiated sound levels for rooms with ceilings.

• AHRI standards are available for free download from their website at www.ahrinet.org.

• An alternate method of calculating a space effect (Table D16) must be used when the ceiling is omitted. The space effect calculation determines the attenuation in each octave band (Hz) based on the size of the room (ft³) and the distance from the listener to the sound source (ft).

• Space effect = (25) – 10 log (ft) – 5 log (ft³) – 3 log (Hz).

• It is interesting to note that this space effect applies the entire volume of the room to each device, regardless of the number of devices located within the space. 

Room example: 

We will start with a typical office that has 2400 ft³ of room volume, a 9 ft ceiling and a 3 ft ceiling plenum. According to Table D15, a typical lay-in ceiling would be expected to provide radiated sounds attenuations (dB) in octave bands 2-7 of 16, 18, 20, 26, 31 and 36 dB respectively. The ceiling/space attenuation from Table D15 applies to a room of any size, because research has shown that the ceiling type is far more important than the room size. If the room in question will not have a ceiling, we will need to calculate the space effect in order to determine the attenuation for the radiated sound path. The distance from the listener to the sound source will be approximately 6.5 ft and the room volume will increase to 3200 ft³ with the ceiling removed. 

Space effect = (25) – 10 log (6.5) – 5 log (3200) – 3 log (Hz)

Using the space effect equation, we can calculate the radiated sound attenuations (dB) in octave bands 2-7 as 7, 8, 9, 10, 11 and 11 dB respectively. 

Bigger space to make up for a lack of ceiling: 

Assume that our room has a 9 ft lay-in ceiling and a 3 ft ceiling plenum. According to Table D15, a typical lay-in ceiling would be expected to provide attenuations (dB) in octave bands 2-7 of 16, 18, 20, 26, 31 and 36 dB respectively. If we omit the ceiling in any size room, our space would need a minimum of 15000 ft² of floor space. Even with a room this large, we would expect to hear more high frequency noises unless we use sound absorption materials to soften the environment. 


Single-duct terminal unit over this room: 

Assume the unit is a DESV size 05 with a maximum design flowrate of 250 cfm that has an inlet pressure of 1.0 in wg. For our room with a ceiling, we would expect to have a radiated sound level of NC23. For the same room without a ceiling, we would expect to have a radiated sound level of NC36. In both scenarios, the NC level is being set by the 3rd octave band, centered on 250 Hz. This means it would be fine to put this unit over a conference room this size with a ceiling (not to exceed NC30) or over a shared office this size without a ceiling (ideally NC40). 


NC might not tell the whole story: 

Room criteria (RC) is another way of looking at room sound levels. Like NC, it provides a numerical sound level (known as a speech interference level or SIL), but it also looks for tonal imbalance in order to provide a letter indication of sound quality. For our room with a ceiling, we would expect RC12R. The R indicates a low frequency imbalance resulting in rumble. For our room without a ceiling, we would have the same rumble. However, the speech interference level is much higher. This is due to increased contribution in octave bands 4-6 (500-2000 Hz). These are known as the speech interference bands. Noise in these bands is both blocked and absorbed by typical lay-in ceilings. 

Luckily, spaces without ceilings tend to be more open and therefore the volume is often much larger than that of a typical office. The best way to keep sound levels low is to put the ductwork as high in the air as possible.

Single-duct terminals rarely cause sound issues, but extreme care must be taken when applying fan-powered terminals. Only the quietest fan-powered units should be used and it may still be necessary to add a partial ceiling – also known as an acoustic cloud – beneath these units. 

Please direct questions toward Titus Communications (communications@titus-hvac.com) and/or Titus' Chief Engineer Randy Zimmerman (rzimmerman@titus-hvac.com). 

Titus Revamps its Blower Coil & Air-Handler Product Line

Titus HVAC, the leader in air management, has upgraded and expanded its blower coil and air-handler product line. We have engineered a low-cost, efficient method of cooling and heating spaces in this market segment. Our new models include the TBL (vertical reduced footprint, bottom return blower coil), TBS (vertical reduced footprint, rear return blower coil), TBH (horizontal belt-drive blower coil), TBV (vertical belt-drive blower coil), and TBM (modular air-handler).

The blower coils’ breadth of options allows them to satisfy the indoor air-quality requirements of commercial applications. Achieving higher airflows than fan-coil units, the blower coils -- which generate 800 to 4,000 cfm -- have the capacity to service much larger facilities. Best suited for schools, healthcare facilities and office/retail buildings, units may be horizontally/vertically aligned and floor/ceiling mounted.

Horizontal blower coils -- which are installed in ceilings -- afford a wide range of application flexibility, while maintaining a simple, easy-to-install design. They are intended to provide comfort cooling and heating within small areas. The vertical belt-drive units -- ideal for closets, hallways and bathrooms -- can be laid on top of each other and are typically utilized in applications with a greater volume. Their belt-drive system provides more flexibility in terms of fan speed and cost advantage over a similarly sized direct-drive system. The revamped line gives engineers and architects the capability to better fit blower coils to their jobs.

TBM units are also configurable in horizontal, vertical, and footprint-savings arrangements. From basic air-handling to sophisticated isolation-room systems, they meet challenging specifications associated with indoor air-quality, controls and sound-sensitive projects. Modules are engineered to produce 600 to 10,000 cfm and may be stacked in a two-high configuration. They may be applied in many types of building structures such as schools, offices, hospitals, apartments/condominiums, assisted living facilities, and stores.

Our blower coils/TBM are shipped completely assembled, reducing field installation time and labor. They are thoroughly inspected and tested prior to shipment, eliminating potential problems at startup.

Additional Features and Benefits:

•  Heater/unit assembly listed for zero clearance; meets all N.E.C. requirements and is cETL listed in compliance with UL/ANSI Std. 1995
• Blow-thru electric heat with single-point power connection
• Hot water, chilled water, steam, and direct expansion coils; cold water/hot water changeover available for all models
•  Low-leak dampers with 2” filters
•  Mixing boxes with standard low-leak dampers, high-efficiency filter sections for 2” prefilter and 4” final filter, and blow-thru electric heat with single-point power connection
• Customized options including double-sloped IAQ galvanized drain pan, direct-drive plenum fans, high-efficiency filters, double-wall perforated lining, external face/bypass dampers, and inspection windows
• Foil faced fiberglass-insulated cabinets, main incoming-power disconnect (non-fused), fusing (main), magnetic contractors wired for disconnecting operations, and fan control package with heater interlock contacts (required for single-point power connection)

For more information on air management products from Titus, visit www.titus-hvac.com.

Please direct questions toward Titus Communications (communications@titus-hvac.com) and/or Titus' CB/DV/FC/AHU Product Manager Meghna Parikh (mparikh@titus-hvac.com). 

Chilled Beams in Healthcare Facilities

HVAC, lighting and additional systems found in healthcare facilities combine to utilize a vast amount of energy. In fact, hospitals consume more than 2.5 times the energy in comparison to average-sized commercial buildings. For this reason, the Department of Energy and ASHRAE have adopted legislation that calls for a 20% energy reduction in existing healthcare facilities and a 30% reduction in new construction.

The reheating of supply air in healthcare facilities has proven inefficient, due to high-ventilation requirements. This has become a primary target in the ongoing mission to decrease building energy use. Recently updated guidelines provide tremendous energy-savings opportunities. 

How Do We Save Energy In Healthcare Facilities? 

This can be accomplished by implementing active chilled beams in patient rooms and other areas in which the recirculation of room air is acceptable. ANSI/ASHRAE Standard 170-2013 Ventilation of Healthcare Facilities establishes revised regulations for ventilation rates and practices. This standard has also been adopted by the American Society of Healthcare Engineers (ASHE) as well as the AIA FGI Guidelines. 

Among the revisions are changes in the ventilation requirements for spaces wherein the recirculation of room air is allowable. They include patient nursing, diagnostic/treatment and labor/delivery/postpartum rooms. These areas previously required 6 air-changes-per-hour -- 2 of which were outside air -- of conditioned and filtered air be delivered to each space. 

The amended standard lowers the air-change requirement for these spaces to 4 air changes per hour. It also allows for the recirculation of room air to count as 2 of those total air changes, provided: 

1. Recirculation is limited to the room air itself and does not include any air from another space. 

2. Delivery of a minimum of 2 air changes of outside air -- filtered through a MERV 14 filter at the AHU -- is maintained. 

The standard also stipulates that no filtering of the recirculated room air is required, so long as it does not pass over a wetted surface. These updates clearly promote the use of fan-coil units and chilled beams to reduce reheating of the supply air. 

One of the advantages a beam system possesses over a VAV system is that it delivers a constant volume (2ACH^-1) of 100% outside air at 65°F, while the VAV system provides all of its sensible cooling by way of its 55°F primary air supply. This primary air provides 3.6 Btu/h-ft² of space sensible cooling; the beam's water-side cooling supplements this to match the room demand. The coil within the beam removes 16.4 Btu/h-ft² of sensible heat to supplement its primary cooling, whereas the VAV system must deliver 5.5 ACH^-1 to meet the 20 Btu/h-ft² design load of the space.

VAV systems and beam systems differ in how they handle periods of reduced demand. A VAV terminal can modulate its airflow delivery between its minimum airflow rate of 4ACH^-1 and maximum of 5.5 ACH^-1; on the other hand, the beam system throttles its chilled-water flow rate. The latter approach saves energy. If the space cooling demand drops below 72% of design, the VAV system must begin to reheat the supply air in order to balance the demand of the space. Additional reheat is required as space demands drop, increasing energy usage. 

That is not the case for a beam setup. The system's minimal primary air contribution -- 18% of the space sensible design -- allows it to respond to an 82% reduction in space demand, before reheat is required. This, combined with the fact the air-handling unit is always tasked to deliver less than half as much air as the VAV system, makes the beam system a hands-down winner! 

Please direct questions toward Titus Communications (communications@titus-hvac.com) and/or Titus' Senior Chief Engineer Ken Loudermilk (kloudermilk@titus-hvac.com). 

Terminal Units: Knowing when to 'Flip-out'

Let's examine a practical scenario that gives you more insight into terminal units:  

You have double-checked your terminal unit order to make sure every detail has been provided. The material, voltage, accessories and controls are selected. Knowing that everything has been evaluated and entered correctly, the order is submitted. Now, on to the next one!

Later, you receive a call about the order you so confidently completed. On the other end of the phone is the installing contractor, and he is flipping-out! This is actually more literal than figurative. 

The units are said to not fit into the allocated critical spaces, due to an improper handing specification. Controls were ordered for the right-hand side, but they have arrived on the left.

Maybe the piping for the hot-water reheat coils should be on the left, but the connections were shipped on the right. All of a sudden, a seemingly minor detail has become a massive emergency. What can be done?

Determining the Solution:

Do you have what is needed to extinguish the fire? Although not every unit can be rotated, it may be possible in your case. 

There are important aspects to understand when deciding if a unit is able to be flipped from its intended working position. We will examine this, unit by unit.

Cooling Only Units:

Single-duct terminals (ESVs) can be turned 90°, 180° and every other degree in between. They do not have any position-sensitive parts or equipment that prohibits their mounting orientation. Further consideration, however, is needed when you add controls to the unit. Pneumatic controls are position sensitive, meaning that PESVs must be adjusted before they are rotated.

Fan-powered boxes may only be rotated 180°. You must take into consideration that all of our units do not have top and bottom accessibility.

TFS & TFS-F units have top and bottom access panels, which allows for access to the motor – after rotation -- from the bottom of the unit. All other Titus fan-powered boxes are unable to be accessed from the top, unless the unit is flipped.  

Parallel units cannot be flipped, due to the gravity-operated backdraft damper that is installed on the outlet of the fan deck. This backdraft damper remains open if the unit is rotated, which hinders the unit’s performance. The position sensitivity of pneumatic controls is applicable to fan-powered units as well.

Units with Electric Reheat:

When it comes to units that utilize electric reheat -- single duct or fan-powered -- careful consideration must be taken. The airflow switch used in Titus’ electric heaters is position sensitive. You can rotate a unit with electric reheat, but you are limited to a full 180°. 

Any other mounting orientation has the potential to impede performance. The airflow switch is an important safety component for the heater. It is better to err on the side of caution and not get too creative.

If ever there is uncertainty, please contact Titus Terminal Unit Applications for more clarification.

Units with Hot-Water Reheat:

With use of hot-water reheat coils trending, knowing whether you can flip one has become a very vital piece of information. The performance of how-water reheat coils is integral to the overall functionality of the unit, so there is concern that flipping a coil will adversely alter performance.

Counterflow is the cause for this concern. Our 1-row and 2-row water coils are of a cross-flow construction, and we do not recommend rotating these coils. Titus does make left-hand and right-hand coils available for 3-row and 4-row. The thing to remember when flipping a water coil is the water always enters through the bottom and exits through the top.

A terminal unit that arrives on site with the wrong handing is not the end of the world. If you find yourself in this situation, remember it may be alright to flip-out!

Please direct questions toward Titus Communications (communications@titus-hvac.com) and/or Titus' Terminal Unit, UnderFloor Air Distribution Product Manager Derrick Smith (dsmith@titus-hvac.com).