Final answer:
HVAC ducts at perimeter windows being fed fresh air from below allows for efficient air distribution and maintenance of air quality and temperature levels. Reducing the hum from rooftop AC units involves vibration damping. Natural convection is a different method that uses gravity to circulate air effectively.
Step-by-step explanation:
The query about HVAC ducts at perimeter windows being fed fresh air from the ducts located in the ceiling of the floor below primarily deals with the principles of mechanical ventilation in the context of building engineering. This practice allows for a more efficient distribution of conditioned or filtered outdoor air within a building, aiding in maintaining consistent air quality and temperature levels across different floors. The air exchange rate facilitated by these systems significantly impacts indoor environmental conditions, as fresh air can displace stale or pollutant-rich indoor air, while preserving the building's energy efficiency.
With regards to reducing the hum caused by air conditioning units on rooftops, materials or methods that dampen vibration and noise, such as rubber pads or noise barriers, may be implemented to alleviate this issue.
The concept of natural convection as described in Figure 14.17, where air heated by a gravity furnace rises and forms a convective loop, starkly contrasts the forced air systems that use ductwork. Natural convection systems capitalize on the tendency of warm air to rise and cool air to fall, thus managing energy use more efficiently in certain environments.
Efforts to design environmentally friendly homes include strategically positioning windows to benefit from solar radiation and allowing for natural convection, aiming to reduce conventional heating and cooling requirements and to strive towards the creation of zero-energy houses.