Indoor Air Quality - Post Covid
Let me qualify this, I am not a Professional Engineer.?I have been in the Construction and (Mechanical) Business for 38 years. When I say Mechanical, I mean HVAC (Sheet Metal and Pipe), Plumbing and Process Piping, from Thermal Solar Power Plants, DOE/DOD/COE/Military projects, Los Alamos and Sandia National Laboratories, Data Centers,?Semiconductor Intel/Apple, Education, Hospitality, Retail, Multi Family. I have been blessed to collaborate with some super intelligent people on lots of premier projects.?????
What have we done to improve our indoor air quality (IAQ) post Covid? What did we learn, was it a wasted expensive education?
It might just be me, ?but it seems almost like Covid and all the reactions,?closing schools, businesses, mask mandates, vaccinations never happened.?Regardless of where you stand on how it was or wasn’t handled, adding the rampant infection rates for hospital systems into the equation and it should have been a huge wakeup call on how we really had and have not built HVAC systems to address this in my opinion.?The scary part is there were lots of haphazard things done to address this across the board.
I went to a hospital in Los Angeles at the beginning of Covid to look at a job, and they had taken a window out of a tower and were exhausting the entire floor. I have no idea where that even came from, or if they even understood the impact on the rest of the facility. Yet I am seeing Zero changes to HVAC design and construction requirements of all facilities, business as usual ,where we were pre Covid. With all the technological advances in HVAC equipment not using them is like having Tom Brady on your City league flag football team and you don’t let him in the game. If you do it's done very sparingly and he’s the center.?
I cannot fathom the monetary cost that Covid brought to our economy and businesses, or the long term impacts to all of us personally, and collectively as a society. Yet we just move on, its business as usual. Are we going to stock up on more mask or are we going to make fundamental changes to our infrastructure and supply chain.?
Seeming to be a never-ending cycle of sustainable construction practices with an energy savings backdrop. Federal down to municipal governments mandates and subsequent professional associations impacts on building construction for “Energy Savings”. We spend more money than any other country on health care and are ranked around 32nd by health standards. Yet we cannot upgrade an AHU?
Clarifying terminology
Most commercial HVAC systems are designed by with a minimum code amount of OSA, it can be lowered based on the number of occupants. This does equal energy savings; idea being you don’t have to heat or cool all the OSA and there is energy savings in this design.
These are a couple of common HVAC systems.
1)????(AHU) with an Economizer.?A real basic example would look something like a 50,000 CFM , there are different equations on how much a building needs so let's assume 20% of OSA. A 50,000 CFM x 20% = 10,000 CFM OSA, so we have EA=10,000 CFM and OSA = 10,000 CFM. The OSA now mixes with the remainder of the RA which is 40,000 CFM and we are now back to 50,000 CFM SA distributed and recirculated in the building. The AHU more than likely has a “Outdoor Reset”?meaning the outside air temperature is equal to the required set point, the economizer is modulated to open to 100% OSA, and EA or RA to 100 % of the air, thus free cooling or heating. There are a lot of different variables associated with this and the operation, it can modulate for its minimum setting of OSA all the way to 100%, this is a real basic set up. Designed and installed correctly it will save energy and that equals 1st construction cost savings, and operational cost.
2)?????Packaged AHUs without economizers, its fixed OSA, small packaged systems you see on schools, retail store fronts, restaurants etc. Some do have some economizers and controls available, but they usually are removed as cost savings. Some residential applications require a set amount of OSA, but I don't believe I have come across any that are set up for 100% OSA.??
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In hospitals all rooms and spaces are balanced, setup and designed for air changes, air flow, and pressures from space to space. These are usually designed for what is commonly known in the industry as a variable air flow box (VAV), or a constant air flow box (CAV). Same boxes, different control set up. A VAV can modulate between the minimum CFM and maximum CFM settings and in the CAV the minimum and maximum settings are the same. Commercial buildings are similar but mostly follow the VAV designs.
Not all hospitals do it, but I have personally built large hospital systems that the (EOR) Engineer of Record designed a CAV system, it was Test and Balanced, Commissioned and functioning as designed at turn over, and then go back a month later to discover that this design had been overridden in the controls by Hospital personnel to allow the CAV system to function as a VAV systems to save energy and reduce operational cost, economizers on AHU’s had been disabled and locked?at something less than 10%. They found it is cheaper to run chillers and boilers by not allow the economizer to process all the designed OSA. OSA requires more frequent Air Filter changes thus reducing additional operational cost. A left hook followed by a right cross, now you are not getting the designed air changes in all of spaces, maintaining pressurization zones, nor are you getting the OSA you need.?I would venture to say that they did more harm than good.?
There are many studies about the health impacts of proper ventilation and humidity. There are many products and design scenarios available that allow this and aligns with energy savings, and not the compromise of mixing OSA with possible infected air and spreading germs and viruses throughout any facility, school or home. It is impossible to know how 100% OSA designs could have affected the spread of Covid or any viruses, however I am 100% convinced it could have been a lot less if we had more of this in place.
Where does Humidity and control of humidity come into this ??Outside of some industrial spaces, and hospital systems it is up to 100% ignored. Maintaining a RH of between 40-60%?has so many health benefits is unbelievable that it’s not addressed in every HVAC system. Studies show that proper RH positively impacts health concerns like bacteria growth, virus prevalence, respiratory infections, allergy and asthma symptoms and others. As I stated before RH is water vapor in air at temperature. Atmospherically speaking Cold air will usually be dryer and you require added Humidification, Hotter air will usually require dehumidification. To dehumidify air you need to drop the air temperature below dew point, which removes water vapor from air (condensation). Properly sized residential units can do ok job of this when they are running, however if they are oversized, units will short cycle and that reduces the effectiveness of its ability to provide dehumidification. Preferably Humidification is provided by steam there are small canister style systems available for residential use, and the above AHUs and all HVAC equipment and systems are provided with a means of humidification and dehumidification. Proper controls, proper equipment.
You can go steps farther in UV Sterilization, NPBI (Needle Point Bipolar Ionization), proper filtration. It's all there ready to be installed, all great products if applied and maintained correctly. Existing facilities should be looking to retrofitting their existing HVAC systems with some if not all of these. Have a PE design and select for the facility.
In my opinion there shouldn't be a new HVAC system that's not 100% OSA with the ability to provide or remove humidity. The cost for this is minimal compared to the losses and impacts we will or could be dealing with from Covid or the next Virus and our personal health.
We have seen Zero changes to code requirements thus far.
Let's put that into perspective many Casinos are 100% OSA, however our most important infrastructures, Hospitals, Assisted Living / Nursing Homes, Schools, Grocery Stores, Homes, Airports are not.
Making spaces as Healthy as possible seems like a good starting point.
Small changes across all spaces can have exponential effects for all of us.
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