Environmental Controls Final Exam Review

(From Simon's Review Slides)

Energy

Represents the total capacity to do work

Power

The rate at which energy is used

True/False: Are energy and work the same thing?

True! Energy = Work

Formula for energy/work

Power x Time

Energy Units

BTU (calories) or foot-pounds (joules) or kWh

Renewable Resources

Those that are available on a recurring cycle without substantial depletion

• wind

• solar

• geothermal

• biomass and biofuels

• hydroelectric

Nonrenewable energy sources

Resources that, once exhausted, can be replaced in a time frame that is meaningful to the human race

• coal

• oil

• natural gas

The largest source of greenhouse gas emissions from human activities in the united states is from __

burning fossil fuels for electricity, heat, and transportation

Major green house gases

• carbon dioxide

• methane

• nitrous oxide

• fluorinated gases

Embodied energy of materials

inherent energy captured within the product itself + energy used during the entire life cycle of the product’s manufacture, transport, and disposal

Bioclimatic design

The link between climate and comfort

Microclimate

INteraction of the characteristics of climate (sun, ambient temp, humidity, wind, precipitation, air quality) and site (topography, soil, ground surface, vegetation, water, views, structures, transportation, heat, noise, water, etc.)

Urban heat island effect

Built up areas are hotter than nearby rural areas because of the increased impermeable concrete surfaces, causing

• increased summertime peak energy demand

• increased use of cooling mechanical systems, reducing their efficiency

• considerable decreases the potential of passive cooling strategies

• causing heat-related illness and mortality

• decreasing water quality

What are the three types of rays shown in the diagram (there’s a spoiler)

Albedo

Measure of a surface’s reflectivity of solar radiation

Albedo = 0 → absorbs all solar radiation

Albedo = 1 → reflects all solar radiation

Paved surfaces constitute __ of developed urban areas

30-40%

What is the functional difference between a green roof and conventional roof in terms of urban heat island effect?

There is a 80 degree temperature difference between a green roof and conventional roof (with the green roof being cooler)

Extensive vs. Intensive Green roof characteristics

Extensive (low profile, eco-roof)

• low growth

• lightweight

• low growing plants

• non-accessible and non-recreational

• slopes up to 30 degrees or higher

• less expensive

• low water requirements

• low maintenance

Intensive ( high profile, roof garden)

• heavier weights

• trees shrubs and more

• huge plant variety

• designed for human recreation

• more expensive

• irrigition necessary

• high maintenance

What is the difference between IEQ, IAQ, and thermal comfort

IEQ (Indoor environmental qualtiy) includes

• vibration

• odor

• vision

• sound

• air

• thermal

• water/microbiome

IAQ is only the “air” component of IEQ

Thermal Comfort is driven by

• metabolism

• clothing

• air temperature

• humidity

• air flow

• mean radiant heat (MRT)

Thermal Comfort Variables (6)

Personal:

• Metabolism (Met)

• Clothing (Clo)

Environmental

• Air temperature (dry bulb)

• Humidity (Wet bulb)

• Air flow/motion (fpm)

• Mean Radiant Heat (MRT)

Sensible heat

The energy exchanged by a thermodynamic system that ONLY effects the change of air temperature (dry bulb temperature)

Latent heat

The amount of energy exchanged that is HIDDEN

• present within moisture in air

• increases wet bulb temperature

When does sensible heat loss occur?

• radiant loss to cooler surfaces

• convection loss to cooler air which is heated and rises

• dry respiration loss to cooler air through lungs

When does latent heat loss occur?

• latent respiration heat loss

• water diffusion through the skin

• evaporation of sweat

Principles of Thermal Comfort

• improving occupant comfort

• understanding the impact of physical components of a space (ie. room geometry, materials, etc.)

• defining passive cooling/heating/ventilation strategies

• reduction of energy consumption by buildings

ASHRAE Standard 55-2004

Defines “comfort zone”, which is a “condition of mind which expresses satisfaction with the thermal environment and is assessed by subjective evaluation”

ASHRAE Comfort Zone based on:

• relative humidity

• average of mean radiant temperature (MRT) and ambient air (dry bulb) temperatures AKA operative temperature

• two seasons - adjusted for clothing insulation

• air motion and metabolic rate are fixed

Localized discomfort

Overrides comfort even under thermal neutrality

• radiant asymmetry (a fire pit in a cold evening)

• drafts

• contact with hot or cold floors

• vertical temperature differences

• sensitive parts of body (chest, fingertips, chine, upper lip, nose)

Thermal comfort arises chiefly from __

a mismatch between the environments people expect and the environments they encounter

Adaptive approach to thermal comfort:

Individual control is the key to comfort (ie. ceiling fans and operable windows)

Solar constant

average amount of electromagnetic radiation received from the sun per unit area on a surface perpendicular to the sun’s rays, measured at the Earths average distance from the sun

represents the total solar energy reaching the top of Earths atmosphere per square meter

Insolation

Amount of radiation reaching a given area

Solar radiation

Energy emitted based on temperature of the surface of the sun