Ventilation
Now that we are “tightening” the building, we hear a common question…. Don’t buildings need to breathe?
Actually, no. It’s the people inside buildings that need to breathe – not the building. To meet the needs of people inside the building, what’s needed is ventilation, not leakage. Ventilation is needed to provide fresh air to occupants of the building; to dilute contaminants that might be in the indoor environment; and to exhaust odors, excess humidity or other airborne contaminants from places like kitchens and bathrooms.
Indoor air quality at Castle Square is expected to dramatically improve, because of the air sealing and renovated ventilation system!
It goes without saying that people need good air quality whenever they are in the building, regardless of whether it is very cold outside or mild, windy or calm. The ventilation that might occur through leaks and infiltration is not reliable and very much dependent on weather. The rate of ventilation that occurs in a building during very cold or windy weather is likely to be much more than is needed and, therefore, will waste energy. During mild, calm weather, there are not sufficient natural forces to give the building adequate ventilation. And even when the building as a whole might be getting enough ventilation air, it does not mean that every apartment in the building is receiving adequate ventilation: while some apartments might be receiving fresh air from outside due to air leakage, other apartments will have air leaking out and the only air going into these apartments would be stale air from other parts of the building.
In a high performance building, uncontrolled air leakage is reduced as much as possible through air sealing and ventilation is provided in a carefully controlled way to each individual apartment.
Ventilation for High Performance
As part of the Castle Square renovation, we are renovating the existing leaky central exhaust system. To seal air leaks in the ventilation duct work, we are using a method called Aeroseal. Steven Winter Associates provides a great explanation of how Aeroseal works. “As a rule, upper floor apartments (closer to the fan) are over-ventilated, lower floor apartments are under-ventilated and poorly sealed ventilation ductwork can result in roof fans exhausting as much air from building cavities as they draw from the bathrooms and kitchens that actually require ventilation! ….AEROSEAL works by sealing holes from the inside <of existing ventilation ducts> with a polymer based sealing agent that is injected into duct systems after exhaust grilles at each floor are removed and duct openings are temporarily blocked with friction fit foam blocks. The sealing agent does not coat the ducts, remains rubbery over time and can seal holes up to 3/8”. CAR <Constant Air Regulator> dampers are used to regulate airflow at each exhaust grille location. A silicon bladder mechanism expands as the pressure drop across the damper increases, which results in a constant airflow rate over a wide range of conditions. With existing buildings CAR dampers can be installed immediately after AEROSEALING…. Results indicate that the AEROSEALING can reduce ventilation shaft leakage by 90 percent and that CAR dampers can be used to “dial in” exhaust airflows at each floor to precisely meet code requirements.” Party Walls, Steven Winter Associates, Inc., 50 Washington Street, Norwalk, CT 06854. Volume 3, Issue 5, November – December 2007.
At Castle Square, the new ventilation system also includes new high performance exhaust fans on the roof that draw air from the kitchen and bathroom of each apartment. Special Constant Air Flow Regulator (CAR) dampers at each apartment ensure that the exhaust flow continuously delivers an appropriate ventilation rate. Fresh air is provided through technically advanced fresh air inlets. These inlets are passive and allow fresh air intake, but limit the intake to controlled ventilation amounts even when a strong wind blows against the inlets.
Aeroseal is a gel like substance that fills holes in existing exhaust ductwork. The result is that the exhaust ducts don't leak and they draw soiled air from the apartments, instead of from wall cavities or other locations. Here, Aeroseal is being sprayed into the existing duct work from the roof, via temporary plastic tubing.
Here, Aeroseal is being sprayed into the existing duct work. Existing duct work is accessed via the boiler room.
This is the terminal of the Aeroseal machine that sprays existing ductwork, via a pressurized system.
Another view of the temporary installation system.
The existing duct work is coated with a thin layer of Aeroseal, which fills cracks and helps the exhaust sytem perform properly.
After the Aeroseal is installed in the duct work, Constant Air Flow Regulators (CARS) are installed in each apartment. Although they look similar to typical louvered ventilation terminals, they can actually be modulated, via a dial. After installation, a trained professional measures the exhaust air leaving the apartment and moves the dial accordingly, so that the correct amount (i.e., what was designed) of exhaust air leaves leaves the apartment.
A CAR in the kitchen.
Another CAR.
Prior to the renovation, the existing duct work was dirty and ineffective.