Schools Vent Frustrations
Those problems include crumbling roofs, leaky classrooms, and hvac equipment that is no longer up to snuff.
One of the primary targets to be fixed in many schools is the ventilation system, which all too often is either nonexistent or inadequate in many buildings. Teachers, students, and parents have all called attention to the problem by complaining about the lack of ventilation or the poor quality of the air coming from the ventilation system.
Some have even said that the ventilation system itself is making them sick.
Unfortunately, many of the problems rest on the shoulders of the engineers who designed the ventilation systems. By the time technicians get to the scene for maintenance or repair, there may not be a lot they can do to ameliorate the problem.
But techs can be aware of how the system operates, and when they spot a problem, they can either fix it, if possible, or at the very least, bring it to someone’s attention.
When installers are involved in new construction, they need to keep an eye open for potential problems, and again, bring them to the engineer’s attention.
Common ProblemsJohn Williams Jr., CM controls specialist with Bradley/ Sciocchetti Inc., Merchantville, NJ, has seen his share of poorly designed ventilation systems in schools.
As a controls technician for the last 14 years, he often works on upgrading controls systems for the existing units in schools. These upgrades occur on unit ventilators, air handlers, and cabinet unit heaters, as well as on exhaust fans, supply fans, and the combustion air control.
The most common problem found with any ventilation system — whether or not it’s in a school — is the size of the actual air inlets, says Williams. “They may appear large enough on the outside, but once you take a good look inside, you see how much space is lost with the dampers, wiring, weather sealers, filter rack, etc.
“I have even seen the electrical wiring and water piping run on the front inside of some unit ventilators.”
Williams has also found improper exhaust, which is a particular problem when schools use a common exhaust fan for several classrooms, yet each room has its own supply unit ventilator or air handler. “Now you are supplying more air than you can exhaust at any given time.” He adds that too much exhaust leads to negative pressure in a building, resulting in popping ears in people and static electricity in libraries.
Ductwork that is too small for the application is another problem Williams frequently encounters. He says that ductwork is rarely designed for adequate airflow, which usually leads not only to improper airflow, but also to a lot of noise.
“Moreover, [the problem] is ignored or the teachers are told to deal with it; now how do you explain that? More than once, I have recommended to the designer that there are some reasons that flexible ductwork was invented. For one, it makes a great muffler for airflow, and as long as you or the installer keep it under 7 feet in total length, it will never affect your pressure or volume.”
Williams also notes that ductwork can be too large. He’s even encountered unit heaters that are ducted in, yet the duct is so large that you feel nothing coming out of the registers in the hallway, even though the unit heater is only 6 ft away from the register.
How to Design the Best SystemAside from the actual mechanical problems that result from poorly designed school ventilation systems, many problems have also been created through modifications made over time.
Energy-saving measures may have caused all the gaps in the buildings to be sealed up; these often included the once-operable windows that were installed when the building was originally designed and constructed. So, although a school may be trying to create proper ventilation, it is not making up for all the natural ventilation that was lost when the buildings were sealed.
“In most schools today, you cannot open a classroom window,” points out Williams; “how do you get to breathe the fresh air?
“Maybe the best way to correct the situation is to attack the new buildings being built first, and make sure that the correct ventilation system is designed and then installed correctly. If it is not, correct it before the building is written off.”
Once ventilation in new construction is under control, emphasizes Williams, then start forcing the existing buildings to make the required changes in order to bring fresh air into the building. He’d also like to see schools install the correct size exhaust fans for complete ventilation in the whole building.
Williams’ ideal ventilation system in a school would have a unit ventilator or air handler for each classroom, as well as hot water and cold water coils — and not a one-pipe, dual-temperature system either. He’d also like to see a central exhaust system with an exhaust duct piped into each classroom.
“The exhaust fan would be controlled with vfd and static pressure controls. At each classroom, at an exhaust/relief register there would be a damper controlled by a damper actuator that operates with the same command for the outside/ return air dampers, but it would operate in reverse. So, when we told the dampers to go to 100% open, the outside air dampers would open, the face and bypass dampers would close, and the relief/exhaust dampers would open.”
He adds that in his ideal system, the ductwork would be sized correctly, and it would not be lined duct. Williams prefers wrapped duct for both the supply air and the exhaust air.
Williams has worked in schools that have his ideal ventilation system installed, and he happily reports they have never had a problem.
Sidebar: Words of Wisdom From a Man in the TrenchesJohn Williams has a few more pieces of advice he’d like to share with hvac installers and service technicians:
- Do the best you can with the designs you have.
- If you do not have the right materials, go and get them.
- Do not pass the blame onto someone else; instead, make yourself look great and fix the problems as you come across them.
- Listen to the people — custodians and teachers as well as building engineers — in the building; they will already know it much better than you ever will. Remember, when you are done, you will not be returning to that site and they will be left with whatever is not operating properly.
- Only do things one way — the right way. If you do not know the right way, then go to the library or meet up with someone who can teach you the right way.
(“I have a book printed in 1925 that explains ‘How To Move and Transfer Air,’ and you know what? The residential fan motor did not exist at that time,” says Williams.) — Joanna R. Turpin