Faq

When mechanical ventilation systems are required by codes, there are two main approaches: using centralized systems, or compartmentalizing them by dwelling unit. The second approach is viable with both packaged terminal air conditioners (PTAC) or energy recovery ventilation (ERV) units.

The main advantage of this approach is isolation between dwelling units, which increases overall air quality and allows individual and independent control of ventilation systems.

Packaged terminal air conditioners operate on the same principle as window-type air conditioners: they are installed directly between the ventilated space and outdoors, drawing intake air and heating or cooling it according to current HVAC needs. The advantage of PTACs is that they consolidate heating, cooling and ventilation into a single unit, and are free from ductwork.

Energy recovery ventilation is a very energy-efficient alternative, which is based on using the exhaust air to precondition the intake air and reduce the total cooling or heating load. Their basic principle is the following:

• In the summer, the exhaust air is used to precool and dehumidify the intake air
• On the other hand, in the winter the exhaust air preheats and humidifies the intake air

It is important to note that ERV units may only be able to meet the full HVAC load under specific temperature and humidity conditions. Otherwise, they must operate in conjunction with an air conditioner or heater

The Fan Solutions does not allow the exhaust air from bathrooms to be used for ventilation of other areas, but drawing in air from other building areas is valid. In the case of apartment buildings, a common injection system can provide air to corridors, which then enters individual dwellings before finally being exhausted by toilet fans. With this ventilation system, there are some important considerations:

• Bathroom extractors deal with the entire ventilation load of each apartment, and they must be sized accordingly. The Fan Solutions allows a combined exhaust system for the kitchen and bathroom
• The injectors providing the outdoor air supply for each corridor must provide an airflow that balances with the combined exhaust of all individual apartments

When installing the air exhaust, there are several space clearances that must be taken into account:

• Two feet away from windows belonging to the same apartment
• Four feet away from windows of adjacent buildings or belonging to another occupancy type in the same building
• Ten feet away from any air intake opening, and ten feet above the public sidewalk

A final consideration is that corrosion-resistant grilles, screens or louvres are required for all intake and exhaust openings. The opening size must be between 1/4 and 1/2 inch

Simplicity is the main advantage of this ventilation system. When all doors in a corridor are closed, positive pressure tends to build up in the corridor while negative pressure builds up inside dwelling units. However, the Mechanical Code does not consider this an issue and pressure tends to balance out throughout the day as apartment doors are opened and closed

The main limitation of this approach is that compartmentalization is poor, which has some effects that may be detrimental to overall ventilation system performance. The impact of the stack effect, in particular, can be significant:

• When the outdoor temperature is lower than that of the building, air tends to leak into the building at the lower levels and out of it at higher levels
• The opposite effect occurs when the outdoor temperature is warmer: air tends to leak into the upper floors and out of the lower ones

The overall effect on ventilation equipment is increased energy consumption and reduced performance:

• In floors where outdoor air tends to leak in, extractors have to work harder
• On the other hand, levels, where air leakage is directed outward, tend to have air quality issues – air may be drawn in from other levels, carrying odours or pollutants

Ventilation system performance can be greatly enhanced with the use of variable frequency drives. Basically, a VFD adjusts fan speed according to the ventilation load, instead of cycling it on and off. Speed control is superior to duty cycle reduction because its savings are quadratic, while duty cycle reduction only provides linear savings.

• A fan running with a duty cycle of 75% consumes around 75% of the energy compared with another of the same characteristics operating all the time.
• On the other hand, a fan running at 75% speed only draws around 42% of the power consumed by a fan running at full speed
• In this scenario, duty cycle reduction to 75% yields 25% savings, but running the fan at 75% speed saves 58% of the energy. In other words, speed control yields 33% extra savings.

Along with space heating and cooling, ventilation plays a key role in maintaining optimal indoor conditions for human health and comfort. There are various potential system layouts, each with advantages and limitations, and at the end of the day, the optimal choice is determined by project conditions and available budget. Compartmentalized ventilation systems tend to have superior energy efficiency at a higher cost; while centralized systems tend to suffer from the stack effect in taller buildings, but are cost-effective in lower height buildings where usage habits are similar across separate dwelling units.

Fans come in all types. They are available in different models and can fit in air ducts (inline fans) or hang from the ceiling (ceiling fans), while size and shape do differentiate them, what is a more determining factor in choosing a fan is purpose. This reduces fans to two types – exhaust and ventilation.

Exhaust Fans
Exhaust fans are removal specialists. They work to eliminate contaminants and other forms of pollutants from the air. In doing so, they prevent the inhaling of such harmful substances into the lungs and the possible medical problems arising from them. A heavy-duty exhaust fan, for example, maybe installed to remove the smoke from an industrial setting or a commercial kitchen.

Ventilation Fans
In contrast, a ventilation fan works to circulate air in a space. This could be commercial or residential. This type of fan draws fresh air inside from an outside source. A ventilation fan, for instance, suspended from the ceiling, spins in circles to circulate the air in a room.

We often hear this question, yet it can’t be answered without a lot more information about your operation. People mistakenly believe that to get effective hood ventilation for restaurants, you just need to choose a hood that can vent enough air volume (expressed as cubic feet per minute or CFM).

In fact, there is a great deal more that you must consider when designing your kitchen to ensure you comply with kitchen ventilation regulations. How effectively your exhaust hood can vent what’s called the effluent from cooking (smoke, grease, heat and by-products from cooking equipment) depends on many factors above and beyond air volume capacity. For example:

• the type of cooking equipment you use (ranges or griddles or deep fryers or ovens, or a combination)
• the food you cook (higher fat products produce more grease)
• position of your cooking appliances in the kitchen (centre island or along a wall)
• how the hood is positioned relative to the equipment (overhead vs wall-mounted, and how much overhang, height and presence of side panels)
• your ventilation design behind the walls, including ductwork, fans and makeup air systems