Impact of Covid 19 in Building Design- Part 1

Dr. “Saum” K. Nour, PE, Ph.D.

5-11-2020

In the very past seven days, number of my client have either requested to campus wide modification of their HVAC units to isolate and reduce the Covid 19 like virus in their buildings. In addition, the short article in the Linkedin has created a number of phone conversations and  request for a more broader article. Unfortunately, some have used this unfortunate incident for products portraying themselves as a Covid 19 solutions are now spreading on the engineering product advertising. The author requests for all readers to utilize this article as an inception, and expand, critique, modify, and elaborate further for their circumstances and their buildings. And in this collaborative environment, we can safe many future lives and create a safe working/living environments for our greater communities. As we know, at least for now, all of 7.783 billion persons use this the address to reside, namely, Earth. Let us help residence of this address.

Prior to initiate the theme of the topic, one must fully understand, the virus, its transmission, and prevention. The following data will not make us a biologist, yet enough for us to understand selection of the devices or materials in our endeavor. CDC has quite number of articles and under category of Reduce Facility Risk or Implement Engineering Control, many of the topics here are discussed at length.

CDC under Implement Engineering Controls mandates:

Design and install engineering controls to reduce or eliminate exposures by shielding HCP and other patients from infected individuals. Examples of engineering controls include:

• physical barriers or partitions to guide patients through triage areas
• curtains between patients in shared areas
• air-handling systems (with appropriate directionality, filtration, exchange rate, etc.) that are properly installed and maintained

Historically, there are examples of similar pandemic but nothing of this magnitude since 1918. AIDS, SARS, H2N2 (influenza A Virus), Hong Kong Flu, third cholera pandemic, or similar incidences did not have the speed of spread, contagiousness, level of hospitalization, effect on economy, or similar factors of Covid 19 Virus. American Society of Heating Refrigation Engineers has a position paper on Covid 19 and describes the ASHRAE mandates of HVAC guidelines for prevention and transmission of viruses.

At this time based on www.worldodometer.info, there are 7.7832 billion people on earth, 4.2074 million Covid 19 cases in the world with 284,335 dead individuals. Right now, the United States, with 330,731,676 population (4.25% of the world) has 1,367,963 persons (34% of world) infected of Covid 19 and 80,787 deaths (28.41% of the world). Daily addition of death count is equivalent to Katrina, near 1800 persons, or in other words, United States has one Katrina occurring every day.

This disproportionate rate of cases near 33% of the world  yet only having 4.25% of world population is alarming. Till the “herd infection” of the entire world and say 1.5% of the world death (over 11 million person), or an effective vaccine, the current mood the of the social behavior is to stay. Fastest vaccine introduced was a four year process.

Therefore, a force major process may be taken into place, otherwise, last economic depression will seem to be a mild recession in the upcoming future. One may wear a mask and fully geared Personal Protection Equipment to go for an accounting or telemarketing job. Once in the building, the building may not be a hospital setting with infectious disease ward, but it must have all the environment to protect the regular full time essential employees. Most likely, transients, patrons to office will be modified to online services, and non-essential workers (sales force or similar) will never report to office. Our phones will have more capabilities and fiber optics services will carry the highest 5G capabilities to insure an smooth operations.

Before identifying the new design of the work environment, one must understand the Covid 19 virus (0.12 micron), its behavior, transmission, or biological impacts. Note 19 was for the year 2019, the year of discovery or introduction to humans.  Without being a biologist, please see this video, and to our amazement how this virus travels, survives and populates.

https://www.youtube.com/watch?v=7sQCmgCmN7U

Survival rate of Covid 19 virus is assumed to be same as SARS-CoV-2

Survival Environment	Hours
Median half-life  as aerosolized particles	1
Surfaces
Plastic and stainless steel	72
Cardboard	24
Copper	4

Person to Person: Distance Travel as moist	ft
Normal Condition	6
Active, running, gasping	8 to 12
Coughing/Sneezing- Laboratory Studies	26

Material Filtration against 0.02 Micron Particle	% Captured
Covid 19 = 0.12 micron
Surgical Mask	89
Vacuum Cleaner Bag	86
Dish Towel	73
Cotton Blend	70
Antimicrobial Pillowcase	68
Linen	62
Pillowcase	57
Silk	54
100% Cotton T shirt	51
Scarf	49

Typical air exhaled from human has the following composition:

• 5.0–6.3% water vapor
• 74.4% nitrogen
• 13.6–16.0% oxygen
• 4.0–5.3% carbon dioxide
• 1% argon

Exhaled particles from a person range in diameter from 0.01 and 1000 μm depending on generation mechanism and site of origin

The water vapor content becomes the carrier of the virus to travel. The myth about the cold or warm weather affecting the virus transmission is as follows. Although temperature and humidity reduce the transmission rate, yet we have any outbreaks in Florida or Arizona. One of the main reason for the reduction is the fact that in warmer air, people spend more outdoor versus indoor (confined space), hence rate of transmission is reduced.  

N95 masks are the reference standard acceptable device for transmission reduction.

N95 Filtration (0.1-0.3 microns)	Effectiveness
NaCl Particles	95%
0.75 Microns	99.50%
Bacteria Size	99.50%

As noted, we must understand the Covid 19 prior to finding resolutions in tackling this in our building design. We will use the above data in our findings at length.

Subjects of Interest

There are number of subjects in building design that one must concentrate on. In earthquake design, structural elements become parameters of interest. In building fire design, egress path, building material or type of construction, and compartmentalization are of values. What about Covid 19 impact? It seems, that the adaptation and lessons from design of the hospital biocontainment will be our primary reference.

Compartmentalization.

In building design, either for security in a bank or a software company, infectious disease control in a hospital, for containment of fire based on occupancy/population/type of building, the architect lays out the building to satisfy the building owners or local plan examiners.

In the Covid 19 environment, Compartmentalization has caused places such as Walmart to create a one way path in the isles to minimize the impact of two passing shoppers. In Building and Safety departments, patrons are only permitted one area by appointment or only email conversations and plan transmissions. In addition, besides isolation of movement of people, compartmentalization requires,  dedicated air condition system for that compartment. In a school, individual classrooms must have dedicated self contained HVAC units with no cross contamination. As you may have encountered, when one pupil attends school, the classroom or entire section of building becomes ill.

In a new high rise building, the choices in HVAC design varies with number of floors. However, one can select, one air handing unit per floor, or use of water source heat pumps, or a four pipe system, or similar to achieve increased compartmentalization.

In a non-high rise building, the choices increase. The smaller the HVAC zones, ideally one per room, will be the best solution. With the advent of Variable Refrigerant Flow by Samsung provides an easy solution where a Heat Pump system is applicable. Our intention is not to advertise a product, only to show simple solutions exist and are designed currently.  

One of my lessons, in 1992, when I chaired a session in  International conference in Anaheim on Biological Effect of Electromagnetic Field was the word “Prudent Avoidance”.  

Prudent avoidance is a precautionary principle in risk management. It states that reasonable efforts to minimise potential risks should be taken when the actual magnitude of the risks is unknown. (Wikipedia)

Filtration of the HVAC system falls under this category. California Green Code 2019 upgraded the Filtration (fibrous media air filter) to Merv 13. Merv, Minimum Efficiency Reporting Value (MERV),  ranging from MERV 1 to MERV 16 based on the average removal efficiency across three particle size ranges: 0.3–1 μm, 1–3 μm, and 3–10 μm. Other commercially common proprietary test metrics for in-duct air filters are:

MPR                                 Microparticle Performance Rating

FPR                                   Filter Performance Rating

Average Particle Size Efficiency in Microns	MERV Rating
3.0 – 10.0 less than 20%	1 to 4
3.0 – 10.0 49.9%	6
3.0 – 10.0 84.9%	8
1.0 – 3.0 50% – 64.9%, 3.0 – 10.0 85% or greater	10
1.0 – 3.0 80% – 89.9%, 3.0 – 10.0 90% or greater	12
0.3 – 1.0 75% – 84%, 1.0 – 3.0 90% or greater	14
0.3 – 1.0 75% or greater	16
99.97% of dust, pollen, mold, bacteria, and any airborne particles with a size of 0.3 microns (µm)	HEPA,high efficiency particulate air [filter]

Use of HEPA filters is not practical and can be used for hospitals or labs. Best option based on “Prudent Avoidance” principle is to selected MERV 16. Thinnest MERV 16 is 4”, this has to be further research by manufacturers for least depth. Other key parameters are:

• Higher static pressure maybe offset by RPM modifications of the motors,
• the air velocity through filters to be reduced to near 300 ft/min for highest effectiveness of particulates,
• placement of pressure differential device to announce when filters must be replaced, and
• good maintenance practice though the system to insure no leaks or cross contamination will ever exist.

In existing systems, one can add recirculating fan system with MERV 16 filters to insure the higher probability of particulates. In past, I was required to design tobacco/smoke  particulate within Casino environments. A basic supply and return within one zone with filtration can be added to a zone without altering the main system. However, the author recommends both.

Heating, ventilation, and air conditioning (HVAC) systems in health-care facilities are designed to

• maintain the indoor air temperature and humidity at comfortable levels for staff, and visitors
• control odors;
• remove contaminated air;
• facilitate air-handling requirements to protect susceptible staff and patrons from airborne pathogens; and
•  minimize the risk for transmission of airborne pathogens

Decreased performance of healthcare facility HVAC systems, filter inefficiencies, improper installation, and poor maintenance can contribute to the spread of health-care associated airborne infections.

Air Distribution

Based on the South Korean restaurant article with 31 seats (Tables A,B,C,D, and E) nine persons were infected by one person, although they were 6 ft apart and tables E and D had no infection, since the two tables were not in the air conditioning path. See Linkedin “Saum Nour” (Linkedin Article).

Air distribution will be in conjunction with other segment of this article, if the zones become smaller, then the level of contamination reduces. In addition, one can introduce UV and inline filtration, independent of the air handling unit or even central HVAC unit.

Ultraviolet Germicidal Irradiation (UVGI)

National Academy of Sciences, Engineering and Medicine provided basic data on UV Lights.  UV Light produced by the sun and by three special lamps (UVA, UVB, and most Energy UVC). UV energy destroys genetic materials inside viruses and other microbes. Therefore, UVC light is used for disinfection. UVC lamps and robots are commonly used to sanitize water, objects such as laboratory equipment, and spaces such as buses and airplanes.

UVC light has been found to destroy viruses and other microbes on surfaces in hospitals. But it is not widely used in hospitals or other health care settings. The U.S. government and the UV technology industry are working to define standards for UV disinfection technologies in healthcare settings.

Most UV sanitizers have not been tested against the novel coronavirus, SARS-CoV-2. But UVC light been shown to destroy related coronaviruses, including the one that causes the disease MERS.

Use of UV lights in the HVAC system, especially in the condensate pan of the air handler has been very effective. In another incident, UV light wall sconces were installed in a hospital corridor, although very inefficient. After September 11^th, on September 2002, EPA commissioned RTI International from North Carolina to provide a Technology Evaluation Report on  Biological Inactivation Efficiency by HVAC In-Duct Ultraviolet Light Systems -American Ultraviolet Corporation ACP-24/HO-4. EPA announced the formation of the National Homeland Security Research Center (NHSRC)- part of the Office of Research and Development. Their mission was to report on research and technical assistance design efforts to provide:

• appropriate,
• affordable,
• effective, and
• validated technologies and methods for addressing risks posed by:
  •  chemical,
  • biological, and
  • radiological terrorist attacks.

Ironically, this report applied to presence of Covid 19.  EPA, Test/QA Plan for Biological Inactivation Efficiency by HVAC In-Duct Ultraviolet Light Air Cleaners were conducted using three organisms:

• two bacteria (Bacillus atrophaeus and Serratia marcescens) and
• one bacterial virus (MS2). These organisms were selected because their sizes, shapes and susceptibility to UV inactivation make them reasonable surrogates for biological warfare agents (BWAs).

Generally, vegetative bacteria are readily killed and bacterial spores are more difficult. To model use in an HVAC system, RTI used a test duct designed for testing filtration and inactivation efficiencies of aerosol, bioaerosol, and chemical challenges.

Most critical design criteria for the UVGI is the UV Dosage for 90% reduction of the virus. Attached is the 611 micro Joules in every cm square cross sections area. Therefore the cross sectional area of the air handling in cm square must be measured and proper light intensity applied. UV lamps have life expectancy of 9000 hours and then significantly reduce the UV intensity, hence effectiveness. In addition, the other factors is the contact time of virus and the air stream. This mandates careful analysis of placement of UV lamp in the air stream. It is recommended that the air handler area to be stainless or reflective material to amplify the light bouncing the chamber for more effective routing.

Airstream Disinfection
Microbe	Type	Diameter	UV Dose for 90% Reduction
		µm	µJ/cm2
Coronavirus (incl. SARS)	ssRNA	0.11	611
Influenza A virus	ssRNA	0.098	1935
Ref: Walker, Chris & Ko, Gwangpyo. (2007). Effect of Ultraviolet Germicidal Irradiation on Viral Aerosols. Environmental science & technology. 41. 5460-5

Surface Contamination.

In a hospital setting where infectious diseases are rampant, all surfaces are subject to question in designing a facility. Given the life expectancy of the Virus on different surfaces, they can survive up to 3 says. In a research by this Author for the Doctoral thesis, multiple papers were published on particle deposition in turbulent flow over rough surfaces (Khosrow Nourmohammadi, Ph.D. Thesis, Nuclear Engineering, U. of Illinois- Urbana-Champaign, 1982). Based on this study for Uranium mines, the rougher surface caused higher deposition of radioactive materials of surfaces of mine. Therefore, all areas, surfaces, furniture, obstructions must be redesigned for least accumulation of virus.

Best Management Practice.

It is evident that all theories and articles and guidelines are only as good as they are implemented, applied, and maintained, even though mas casualty pandemics occur once in a century. A rigid protocol with weekly assessment is mandatory and essential for safe keeping of the occupants.

Summary

This article was more detailed than previous articles and the intent was not use to bore the reader. The intention was simply open up the dialogue. Compartmentalization, filtration, UV systems, surface contamination, air distribution, system selection, and quite number of other untold parameters become step stones of designing and creating a building while living through this pandemic.

Please Stay Safe.

And May God Bless all who have lost their lives due to Covid 19.