Insight

Beyond 21st Century Design has released a 100-plus page guide titled “A Clearinghouse of Resources to Aid in Reopening Schools”, which includes analyses of design and space requirements to safely educate students in the midst of a global pandemic. There is a powerful desire among teachers, parents, and even students to return children to classrooms. This guide provides insight from industry experts on how to safely educate students of all ages in the midst of a pandemic.

Our President, Jeff Alban was the only MEP contributor in the guide. Jeff provides valuable insight on refining K-12 design to accommodate emergency situations. Jeff is the lead contributor to Topic 5 – “HVAC & Air Purification” and also contributes to Topic 6 – “Sanitizing Schools”. Jeff is the only contributor to Topic 5, and this topic is what we will be summarizing.

In Topic 5 ; “HVAC & Air Purification”, there are 3 main takeaways. These takeaways are to control airborne infection, upgrade health/nurses’ station, and to utilize outdoor air to flush the indoor environment.

Integral to determining rational engineering interventions is having a clear understanding of how effectively the virus is transmitted through the air by infected people and understanding the types of controls utilized by hospitals and other high-risk facilities to reduce the spread. Ventilation and filtration provided by heating, ventilating, and air-conditioning systems can help reduce the airborne concentration of SARS-CoV2-like and thus the risk of transmission through the air.

1) Control Airborne Infection

• – Apply the highest efficient MERV filter possible. MERV 12 us the minimum and MERV 14 is recommended.
• – Utilize portable HEPA filter units in classrooms.
• – The use of UV-C lamps kill microorganisms and can be used in spaces when not occupied, in occupied spaces near the ceiling, and in air handling equipment.

Use of UV-C energy to kill microorganisms used in conjunction with high efficiency filters to capture particles is an effective combination method to kill and capture viruses. ASHRAE recommends consideration of using UV-C in healthcare suites and in high density spaces in non-healthcare buildings.

The use of higher efficiency filters to capture particles used in conjunction with UV-C provides an effective capture and kill approach for cleaning and disinfecting the air. ASHRAE recommends consideration of using the highest efficiency MERV filter achievable and portable HEPA filter room air-cleaners with due consideration to the clean air delivery rate. For high risk healthcare suites local HEPA filtration should be considered. Appropriate PPE is recommended when changing filters.

2) Upgrade Health/Nurse’s Station

• – Upgrade health/nurses’ suites and treat as isolation rooms using:
  • – 100% exhaust/100% outside air
  • – Maintain proper pressure relationships and follow ASHRAE Standard 170 design guidelines for “isolation mode.”

Increasing outdoor air per person can occur by reducing the number of occupants in the space. Adjusting control sequences can provide extra outdoor air for dilution of contaminates in the space. Exhaust systems are recommended for higher risk areas of concern. Dilution utilizing higher outdoor air rates per person (dilution) should be used in conjunction with upgrades to mechanical air filtration (capture) and disinfection systems (kill).

3) Utilize Outdoor Air to Flush the Indoor Environment

• – Utilize outdoor air to flush the building. Maximize/increase outdoor air flow rates to dilute contaminates.
• – Maintain indoor temperature and humidity design criteria

Maintaining a clean and sanitized environment will depend not only on the training of the staff to follow defined protocols, but also on the effectiveness of the mechanical system to introduce outdoor air, provide ample air changes, and filtrate the air before it enters spaces. For suggestions on the upgrading and maintenance of the mechanical system, see the HVAC and COVID 19 section.

It is obvious that empty buildings need less heating and cooling than occupied ones. Many buildings around the world have been empty/unoccupied for weeks due to COVID-19. You may save a little money switching off the HVAC in an unoccupied building, but it is a terrible decision in the long-run. Most people may think that the only purpose of HVAC systems is for human comfort, however, this is very wrong. HVAC systems are meant for protecting your building and the equipment inside the building from damage.

A building that turns off HVAC for long periods of time results in uncontrolled humidity. Uncontrolled humidity can damage the building and end up being very expensive, and will need many repairs. These repairs and damage will result in delays of normal operation, since the building and equipment will have to be fixed. So even after all stay-at-home orders are retracted, you still won’t be able to get into your building. Below are three reasons to keep your HVAC running during this global pandemic.

1. Bacteria/Fungi Issues

When HVAC systems are turned off, this will lead to high humidity inside your building. Mold, bacteria and fungi stem from high humidity. Having this in your building can be very dangerous, and sometimes even fatal. It is imperative to keep your building from high humidity levels.

The American Society of Heating, Refrigerating and Air-Conditioning (ASHRAE) recommend to keep a relative humidity of 40%-60% for building interiors. With a humidity range of %40-%60, this minimizes the reproduction and spread of viruses, fungi, and bacteria.

2. Deterioration of HVAC Components When Inactive

If HVAC systems are turned off, it can leave a very negative impact on the service life of many components and equipment. When the HVAC equipment has been inactive for a long period of time, the equipment may fail without warning.

Issues are detected more easily when the HVAC equipment is running, because there are warning signs such as unusual noises and vibrations. When the systems are turned off, you will have no warning signs of issues. Other issues of inactive equipment include the rusting of piping due to stagnant water, and motor equipment becoming jammed if the bearings accumulate rust.

3. Data Center Functionality

Data centers are used by most buildings to be able to operate different types of applications. Most of these applications run 24/7, especially when your clients/customers are in different time zones. Also, a good majority of companies are using a virtual private network (VPN) to access company files.

The VPN extends a private network across a public network and enables users to send/receive data across shared or public networks, as if their computing devices were directly connected to the private network. In order for the VPN to work, the data center hosting the information and applications must stay on, or the work will be disrupted.

Data centers and servers produce an immense amount of heat, which is why they need permanent air-conditioning. If data centers are operating without air-conditioning, this can lead to serious issues. Best case scenario is the servers will shut down automatically to prevent overheating. Worst case scenario is the expensive equipment will be damaged by heat, leading to purchasing new, expensive equipment.

Conclusion

When it comes down to it, HVAC systems need to operate for a business to be able to operate. If you keep your HVAC systems off during COVID-19, they will deteriorate, cause bacteria/fungi, and could ruin your expensive IT equipment. The best move is to keep your HVAC systems running even in an unoccupied building. This will save a lot of money in the long run, it is better and cheaper to protect your equipment during the pandemic, rather than dealing with unplanned repairs/delays in the future.

Want to learn more?

School districts all across the country have been on the never-ending pursuit to keep their schools as safe as possible, no matter what. New technologies and techniques are helping schools manage who gains access to their facilities. Investing in upgrades that add layers of security before visitors are able to get through the front door is one of the more popular moves over the last few years.

There is no secret as to whats been going on in America over the last few decades. Since 2009, at least 177 of America’s schools experienced some sort of shooting. School shootings are increasing, and no type of community is safe from this. In the last 10 years, there were 356 victims who lost their lives due to schools not being safe. Security vestibules aim to control this problem by not letting anyone in their school unless they are trusted.

Security Vestibules

Security vestibules/secure entries require school visitors to enter through the main office, after being buzzed in, and signing in after presenting valid photo ID. Security vestibules are used as a strategy to funnel visitors into the main office, providing administrators more control over who has access to the school. This design has become the standard for new school construction and renovation projects. In wake of the massive school shootings over the past 10 years, it is absolutely essential to include security vestibules in any K-12 school, regardless of the area.

School districts around the country have been making a push to include security vestibules in everyone single one of their schools. Unfortunately, there are still plenty of schools around the country where visitors are able to just walk right in. This is a growing concern of communities nationwide.

Safety- The Most Important Thing

The hundreds of school shootings over the past decade has forever altered the way school buildings are designed/renovated. Safety has been moved to the most important thing when designing/renovating a school. Schools across the country are supposed to be a safe place for students to learn and teachers to educate. Students and faculty should never have to fear for their lives while they are in school.

Schools that have been built over the last few decades weren’t built to protect students from a gunman, they were built to educate students. Now, in the new decade, the number one priority is protecting students/faculty from a gunman.

In this day and age, it is much more important to be safe than sorry. Security vestibules need to be implemented in every school in the country, to ensure a safe place for teachers to teach and students to learn.

Alban Engineering is currently working on supplying many schools with security vestibules. Want to learn more?

As warmer weather slowly approaches we will begin a new cooling season with a rise in air temperature and relative humidity levels. Indoor relative humidity levels is a component along with temperature and pollutants that determine Indoor Air Quality (IAQ) within buildings. Poor indoor air quality is typically associated with Building Related Illness (BRI) and Sick Building Syndrome which can lead to performance losses of personnel. During the 1970’s, 1980’s and 1990’s significant changes in code requirements led to tighter building construction and use of different construction materials which can contribute to moisture buildup within the indoor environment. This moisture buildup or high indoor relative humidity conditions can have significant negative effects on the building and its occupants. Mold growth is a common concern as is the potential destructive nature of building components including within exterior walls that can’t be easily inspected. There are many different reasons why high indoor relative humidity conditions exists however, three (3) primary sources include infiltration through the building envelope (roofs, walls, windows, doors, attics, basements, etc.), generation of moisture in the building and the buildings air conditioning system. A leaky building envelope or how the envelope was designed/constructed are often easily visualized, felt and or diagnosed. Moisture generated by occupants or activities such as cleaning are also known.

All too often the building’s air conditioning system is the reason for high indoor relative humidity levels.

As building codes required tighter building envelope construction, reducing air leakage and increasing insulation requirements our buildings no longer breathe for the sake of reducing energy usage. These tighter more efficient buildings cause pollutants generated by occupants (e.g. carbon dioxide) to buildup. As a result of these findings, code required ventilation rates were increased. Ventilation essentially is outdoor air introduced into the building by the Heating, Ventilation, and Air Conditioning (HVAC) system to dilute these pollutants to provide indoor air quality that is acceptable to human occupants and that minimizes adverse health effects according to ASHRAE. Ventilation rates vary based on the floor area and use of the space (office, classroom, etc.). Occupant density (people per square foot) is also defined by code based on space function.

Atmospheric air used for ventilation air purposes is a combination of dry air and superheated steam (water vapor) in a low pressure condition (i.e. moisture).

Specific humidity is the mass of this water vapor present in a unit mass of dry air. Relative humidity expresses the amount of water vapor in the air relative to the amount of moisture it would hold if saturated at that temperature or percent saturated.

Air is a compressible fluid. The volume of air increases with increased temperature and decreases on a reduction of temperature. As we move into warmer weather conditions warmer air can hold more moisture relative to its saturation point or 100% relative humidity (raining). This is why our buildings are dry during the heating season and wet during the cooling season. As Engineers, we can easily calculate these conditions using a psychrometric chart and equations. Take for instance, on a 40°F day at 50% relative humidity outdoor air is introduced into a 70°F indoor space. The resulting indoor relative humidity is 15% as warmer air has more volume to hold molecules of moisture than the cooler outdoor air. During the summer however, outside air is warmer than the occupied space and if outside air is only cooled but not dehumidified the indoor relative humidity increases. As an example, when outdoor air is 85°F at 60% relative humidity is introduced into an occupied space that is air conditioned to 75°F the resulting indoor relative humidity is approximately 85%.

Dehumidification is typically a byproduct of air conditioning however, supply air needs to be cold enough leaving the cooling coil for dehumidification to occur. As HVAC Engineers we design for the peak or maximum cooling load condition yet these conditions only occur a few hours during the year. At part load conditions supply air can be cooled but not made cold enough for moisture to be extracted out of the air stream. The mixture of return air from the occupied space and outside air required for code required ventilation has to be cooled low enough for this moisture to be condensed out of the air stream which we call dehumidification. This condensation occurs when the cooling coil is at or below the dew point temperature of the mixed air stream. The condensation effect is no different than taking a can of your favorite beverage out of the refrigerator and placing it on your counter or taking it outside. If the can surface temperature is below the dew point temperature of the surrounding air then water droplets/condensation will form on the surface of the can until the can warms up.

When a building is experiencing high indoor relative conditions, primarily on part load conditions during the cooling season it could be that the HVAC unit is injecting moisture from outside into the building via the ventilation air and the air conditioning unit may be cooling the air to satisfy the space thermostat but not making the air cold enough to dehumidify. Most problematic areas will be large gathering spaces with a single thermostat or spaces with large fluctuation of occupants. Other conditions can be an unoccupied building that is operating as if it was occupied or spaces that are subcooled (i.e. less than 75°F).

If these conditions occur and condensate is not draining out of your air conditioning unit there are two (2) general approaches which should be looked into. First, try to make the supply air colder, typically between 55°F – 59°F without sub-cooling the space. The space air conditioning load is satisfied by the air flow rate and the supply air temperature. As the load varies either the supply air temperature or the supply air flow rate needs to vary. To achieve a lower supply air temperature condition, lower the fan speed/air flow. Sometimes air conditioning units have two (2) speed fans or ECM adjustable speed motors that can change air flow and larger air handling unit fans can be equipped with a variable speed drive.

Secondly, reduce the source of moisture by reducing your outside air flow rate by using space carbon dioxide sensors in a code compliant manor. When there are less occupants in the building or space the amount of outdoor air can be reduced accordingly. Additionally, if a space just needs to be cooled but is not occupied, mechanical ventilation is not required. This is particularly true for assembly spaces and/or buildings not used continuously but still cooled (churches, schools). An occupancy sensor can be used to determine occupancy or occupancy can be scheduled through a time clock feature of your air conditioning unit controller.

High indoor relative humidity levels can be very problematic for the building and its occupants during the air conditioning season. Sometimes understanding why it occurs and ways to reduce it is not simply recognizable.

Buildings including residential consume approximately 40% of the world’s energy followed by transportation and industry.

On January 1, 2015 the State of Maryland adopted the 2015 International Energy Conservation Code or IECC with adoption and enforcement on July 1, 2015. One tool to determine compliance is called COMcheck which allows the equivalent of ASHRAE (American Society of Heating Refrigerating and Air Conditioning Engineers) Standard 90.1-2013 Energy Standard for Buildings. Maryland and Vermont were the first two states which adopted this standard. As of this writing two additional states, Alabama and New Jersey have adopted this standard.

This baseline standard for high performance buildings has significantly changed how buildings are designed, constructed and operated over the past decade. While various types of buildings have different energy savings results, on average 30% energy savings were realized between ASHRAE 90.1-2004 and ASHRAE 90.1- 2010 standards. An additional +7% energy savings is anticipated for buildings designed to ASHRAE 90.1- 2013 standards.

It’s both a challenging time and exciting time for engineering innovative products and then applying them in a building design. Previous creative high performance building designs used in the past have been adopted by codes as requirements today. More than ever designing buildings to meet or exceed these code requirements is a holistic team approach.

There are several basic considerations and steps when designing buildings to optimize energy savings and comply with these mandatory requirements.

Reducing heat gains and losses through the building envelope (walls, windows, and roofs) is easily accomplished by increasing the insulating values of materials used, the reflectivity and thermal mass of those materials as well as the solar orientation of the building.

Reducing internal heat gains also significantly affects energy savings. Energy efficient lighting and products not only reduces the energy these devices consume but it also reduces the air conditioning loads. Lighting power density limits alone have been reduced from 2.0 watts per square foot or more to .9 watts per square foot or less depending on the application. LED lighting systems are quickly becoming standard design practice. The most significant changes are the requirements for lighting controls utilizing daylight harvesting/automatic dimming, occupancy and vacancy sensors, etc. to be able to automatically turn lights on or off. Additional controls are also being implemented to de-energize receptacles during unoccupied/night times.

The reduction of heat gains and losses through the building envelope coupled with the reduction of heat producing equipment and lights allows the heating and cooling equipment capacities to be reduced thus also conserving energy.

While significant changes have occurred through the type and control of lighting systems, the current code requirements also significantly changes how Heating, Ventilating and Air Conditioning (HVAC) systems are designed since these systems are the largest consumers of energy in a building. There are two primary components which affect energy usage, the generation of the heating and cooling medium and the transportation of the medium to where needed in the building. While manufacturers are responsible for developing energy efficient equipment that complies with the minimum efficiencies required by code to generate the heating or cooling medium it’s still the responsibility of the design engineer to apply this equipment in a system to maximize its performance at peak and part load conditions. The code has also become more stringent in limiting the energy consumed by building systems to distribute the energy, by fans and pumps, through the building. Pipe and duct sizes are larger today to meet reduced frictional pressure losses. Distribution equipment needs to be strategically located to reduce the most critical pressure drop path so as to minimize pump and fan motor brake horsepower. Together the design of the water and air distribution systems have to meet these power limitations.

Another way the code has significantly changed over the years and is a result of changes in technology is the use of variable speed drives (VSD) and electronically commutated motors (ECM) to vary the speed of motors. For example, a 10 HP fan operating at 50% capacity uses 1.25 HP of energy. ECM’s have burst on the scene replacing inefficient shaded pole and permanent split capacitor fractional horsepower motors typically used for fan coil units, heat pumps, exhaust fans, in-line circulators, etc. and are becoming available in larger horsepower motors. ECM motors can also vary in speed based on load (temperature sensor signal).

The mandatory use of heat recovery is becoming more stringent in each update of the code as well and we see that trend continuing in the future. Air side heat recovery uses building relief or exhaust air stream to pass through a heat recovery device to reclaim and reuse energy to precondition outside air for code required ventilation before wasting it to atmosphere. While air side heat recovery has been predominate the past decade, new equipment and system designs are incorporating water side heat recovery. Water side heat recovery can capture and reuse waste heat from air conditioning equipment to make useful heat for heating the building when both mechanical cooling and heating are needed. All in all, the codes are directing the system design to reuse every possible BTU of energy before wasting it to the atmosphere or ground heat sink.

As with lighting systems much is dependent on automatic controls to maximize energy savings for the equipment applied to an engineered system that is unique to each building. Carbon dioxide sensors are being required in smaller assembly spaces to control how much outdoor air is being introduced into the building to meet ventilation requirements. Robust weather sensors to determine ambient air conditions, devices controlling speeds of large motors and meters used to measure flow all play an important role to sequence equipment in the operation of the system while meeting all code setpoints and reset requirements.

Most importantly however is selection of system type, its associated equipment, and the system design for a building. There is no silver bullet solution as each building is unique to itself. Geothermal systems are a popular choice since for every one BTU of energy consumed, on average three BTU’s of useful energy are free. Central heating and cooling systems using boilers, chillers and air handling equipment have long been the system of choice. A relatively new system to the US market, a variable refrigerant volume (VRV) or variable refrigerant flow (VRF) offers a new energy efficient choice. This system is refrigerant based, uses a variable speed compressor to transport energy and has the fewest amount of heat exchangers which increases the efficiency of a system.

The use of energy modeling at the earliest concept stages of design and through life cycle cost analysis can help in determining the type of system.

Industry standard equipment, building design, conventional design and operating parameters and how systems are controlled are in the state of change. Today’s building design engineers need to be innovative and creative in the development of systems while using the laws of engineering to maximize the coefficient of performance (COP) for each building.

Alban Engineering is a Mechanical/ Electrical / Plumbing Consulting Engineering firm specializing in LEED Certified and High Performance design for Public and Educational Facilities. Jeff Alban has won several Regional ASHRAE Technology Awards for innovative designs which incorporate ASHRAE standards.