quiz

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Chapter One

Introduction HVAC systems are of great importance to architectural design efforts for three main reasons.

1. These systems consume substantial floor space and/or building volume for equipment and

distribution elements that must be accommodated during the design process. According to the

American society of Heating, ventilating and Air-conditioning Engineers (ASHRAE), the required

area is 6-9% of the area served.

2. HVAC systems constitute a single major budget item in building projects, that is not less than 10%

of the total budget.

3. The success of a building depends on the ability to provide thermal comfort with the least

operating costs (maintenance, energy, or replacement). This depends on the HVAC system

design, equipment and controls.

Difference between Passive and Active Systems

Passive design is a system or structure that directly uses natural energy such as sunlight, wind,

temperature differences or gravity to achieve a result without electricity or fuel. Active design is a system

or structure that uses or produces electricity.

The term passive design is most often used with respect to architecture and infrastructure. For example, a

building may have wide windows that automatically let in more light when the building needs heat and

automatically shade when the building is too hot.

Another common area of passive design is wet infrastructure such as drainage systems that generally

often don't consume power but use gravity to move water. Most devices and infrastructure have an

active design as they use electricity. The term is typically only used in comparison to passive designs. For

example, solar panels that produce electricity are often referred to as active solar as a comparison to

using solar passively for heat or to grow plants.

Benefits of Passive Systems

Passive designs are often valued for their simplicity and aesthetic appeal. They also tend to have zero

operational costs. As they often contain no moving parts, passive designs potentially last for centuries.

Electrical components are valued for their accuracy and functionality but may need to be regularly

maintained and replaced. They may also have a higher operational cost and environmental impact.

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Table: Passive System versus Active System

Passive Design Active Design

Definition

Infrastructure, architecture and devices

that achieve a result by directly using

natural forces without first converting it to

electricity.

Infrastructure, architecture and devices

that use or produce electricity to achieve a

result.

Examples

Passive Heating

Passive Cooling

Green Roofs

Rain Gardens

Solar Panels

Wind Turbines

District Heating

Deep Water Cooling

Operating and

Maintenance Cost Almost nil Usually high

Economics of Energy Efficiency

Example One

Which car would you buy if both have the same facilities and amenities, same life span, and same gas

consumption, Honda Accord costing BD. 9,000 or Toyota Camry costing BD. 8,000?

Example Two:

Which car would you buy if:

Accord: cost is BD. 9,000, gas consumption is 50 liters/week, Life span is 10 years.

Or,

Camry: cost is BD. 8,000, gas consumption is 60 liters/week, life span is 10 years?

Example Three:

Two refrigerators with same quality and quantity of service:

Option A: costs BD. 600, draws electricity at an average of 150 W, lifespan is 20 years

Option B: costs BD. 700, draws electricity at an average of 100 W, lifespan is also 20 years

If cost of electricity is BD. 0.09/kWh, which one would you choose?

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Solution

Example Four

What if option B in example three has a lifespan of 15 years?

Solution

Rule of thumb:

Profitability is Excellent if pbp less than one-third of lifetime of investment;

Profitability is good if pbp less than one-half of lifetime of investment;

Profitability is bad if pbp is more than one-half of lifetime of investment.