ARE BS

P (pressure) =

0.433 (constant) x h (height)

High SHGC

0.7-0.9 allows high levels of solar heat in

Convection (infiltration)

1.08 x CFM (air changes/hr x volume / 60 min/hr) x ∆Temp

Convection equation for the rate of heat exchange through air in BTU/hr

1.08 x CFM (volume of air in ftˆ3 per min) x ∆T

Water boiling temperature in Denver

195˚

H (height) =

2.3 (constant) x P (pressure)

Water boiling temperature in a pressure cooker

230˚

Typical minimum fixture pressure requirements range from

4psi-20psi

Pressure in a city main typ.

50 psi (sometimes 75 psi)

Earth's temperature

55˚

Heat pump

A machine that uses a reversible compressive refrigeration loop, so that both coils may take the role of either evaporator or condensor

Type K copper pipe

Best choice for a line buried as an underground water supply. Heaviest type and suitable for underground.

Steady heat flow vs. periodic heat flow

Building buffers uncomfortable exterior temperatures wth constant heating and good insolation vs. heating at night and cooling during the day (thermal mass can temper the internal swings)

Heating Degree Days (HDD)

Calculated by subtracting the average daily temperature during the heating season from 65˚, then adding the differences from each day for the total of the season. = sum(65˚-˚F average daily temp.)

Heat wheel

Can remove moisture from intake air. Needs a drain from condensation that occurs when cooling in humid climates

Winter thermal concerns

Conductance (higher ∆T = higher conductivity)

Rule of thumb for thermal mass

Design an area equal to 3 to 6 times the area of solar glazing, Use dark colors, and position under a window or where the sun can "see it"

Zones are separated by the following

East vs. West (Solar exposure), air quality needs, internally generated heat, schedule

Typical heating

Enters a 70˚ room at 145˚ ∆T of 75˚

Typical cooling

Enters a 75˚ room at 50˚or ∆T of 25˚ - larger ductwork required to remove heat than adding it

VAV Pros

Good for large buildings, energy efficient (fewer fans), low initial cost, fewer AHUs, less ductwork

Summer thermal concerns

Latent heat gains through breathing, showers, coffee makers, and industrial equipment. Other sources of thermal gain is through solar gains and internal gains (occupants, lighting, equipment)

Best winter time PV performance angle

Latitude + 15˚

Best summertime PV performance angle

Latitude -15˚

Waste from these is classified as greywater

Lavatories, washing machines and showers

Comfort zone

Located roughly between 68˚-78˚ and between 20%-80% RH. Summer and winter have slightly different zones due to thermostat set points and the amount of clothing one is wearing.

Bathroom fixtures require one of these

Main stack

VAV cons

Poor fresh air intake control, cannot heat one zone while cooling another (uses dampers to control the amount of conditioned air passing through)

Volume of air needed to heat a space

Q =1.08 x CFM x ∆Temp (duct hot air - temp setting)

Passive cooling

Shared shading - spacing buildings close enough to shade their neighbors - used in hot arid climates that don't need cross ventilation

Best control over fresh air in a zone

Terminal reheat 1

Cools and heats the same air

Terminal reheat 2

Solar Heat Gain Coefficient (SHGC)

The net fraction of heat transmitted by glazing in comparison to clear single glass (plus the portion of the absorbed heat into the glass itself) - impacts a building's heating and cooling loads

Q conduction

U-value (or 1/R) x Area x ∆Temp

Direct gain spaces

Used to heat Skin load dominant buildings. South facing windows, thermal mass places in front of high SHGC windows.

Cannot heat one zone while cooling another

Variable air Volume (VAV) 1

Lower initial cost for large buildings

Variable air Volume (VAV) 2

Emissivity

a material's propensity to give off or receive radiant heat. (black car interiors are high, Low-E glass allows less heat to pass through)

Direct gain spaces in winter time

are generally mechanically heated

Multi-zone and dual duct systems

are phasing out because they are inefficient. Preheat and pre cooled air go into a mixing box to achieve desired temperature into the room.

Type L, K, and M pipe

available in soft and hard types

Pressure loss through valves, fittings, piping and the water meter

can be as great as 25psi

ERVs (Energy recovery ventilators)

capture some of the heat from exhaust air and preheat some new incoming air or cool it in the summer. Exchange through a heat wheel or coil-fluid head exchanger. Up to 95% efficiency in heat exchange. Can remove moisture from intake air in the summertime.

Cooling loads are primarily a function of what

conductive heat gains through the building skin and convective heat gains through infiltration or ventilation.

Heating loads are primarily a function of what

conductive heat losses through the building skin and convective heat losses through infiltration or ventilation.

If the outdoor temperature is warmer than the balance point temperature

cooling is required

Wet bulb temprature

described on the psychrometric chart along the skewed axis

Latent Heat

describes the embodied energy in moisture in the air. It is the heat energy required for a change of state (water to water vapor). It is measured by the wet bulb's temperatures relationship to the dry bulb temperature.

Relative humidity

describes the moisture content of an air sample relative to the amount of moisture that air can hold at a given temperature. Warm air is capable of holding more moisture than cooler air. Represented as curved lines on the psychrometric chart. Increasing with the higher dry bulb temperature

High thermal resistance

generally consists of small air bubbles

Terminal Reheat pros

good for large buildings, fewer AHUs, less ductwork, can heat and cool simultaneously, good fresh-air control

Low E glass

has a low solar heat gaAzsxin coefficient (SHGC)

Radiation

heat moving through electromagnetic energy, Travels in a straight line provided there is a temperature difference between two bodies. "Draft" experience near a window is the exchange of a cold material to a warm body.

Sensible heat

heat that we feel. Describes the kinetic energy of air molecules in a space. Measured by a dry bulb thermometer (horizontal axis in the psychrometric chart)

Convection

heat transfer within a fluid or between a solid and a fluid (gases and liquids). Air passing through infiltration, ventilation, mechanical heating, or cooling. When air of different temperatures s combined in a space and radiant heat exchange occurs and an equilibrium temperature is reached.

why is humidification needed in winter?

heated air is conditioned cold outside air, which does not have much moisture.

If the outdoor temperature is cooler than the balance point temperature

heating is required

FCU installation locations

hotels, loading docks, corridors, storerooms, high-rise residential buildings, and schools

Psychrometric chart

includes many variables to describe the energy, moisture, and temperature of moist air.

Heat gain includes several factors:

internal gains from people, lighting and equipment. latent heat gains from the humidity from summertime ventilation, people and equipment. solar heat gains from windows.

Internal load dominated buildings

involve programs with significant internal gain gains from people, lighting, and quipment (factories). Interiors require mostly cooling, benefit from low SHGC to minimize solar heat gains

The boiling point of a fluid

is a function of pressure.

Warm coolant

is condensing

Cold coolant

is evaporating or boiling

Low pressure

lowers the boiling point and induces boiling (evaporation).

Conduction

mode of heat transfer through two solids. Measured with U-value and R-Value

Ground source heat pump

moves water through a loop under ground to regulate the temperature and reduce the load on the compressor to evaporate water during heating months and condense water from air during the cooling months

FCU cons

need supplemental system to supply fresh air, noisy

FCUs (Fan coil unit) Pros

no ductwork, simple design (fan, heating and cooling coils supplied by a boiler and a chiller), versatility (in ceiling, walls or floor), good thermal control and inexpensive

Sunspaces

occupied only when thermal conditions warrant. Unused when it is too cold.

Changing gas into liquid (condensation)

produces large quantities of heat

High pressure

raises the boiling point and induces condensation

A cooling tower loop

removes heat from the condenser side of the chiller and deposits it into the air. Pumps move water to it, where water cascades over baffles, and is cooled by exterior air. Transfers energy through a heat exchanger.

0.433 psi

required to lift water one foot vertically (2.3 ft for every lb per square inch of pressure)

Terminal Reheat cons

same air is cooled and then reheated (less efficient)

Most practical for very small buildings

single zone units 1

Better thermal control

single zone units 2

Most ductwork required for a given number of zones

single zone units 3

Northern hemisphere

south-facing glazing will create passive solar gain, to maximize effectiveness use thermal mass to store heat and prevent over heating.

Passive heating

spacing between buildings, ensuring full sunlight. Solar envelope constrains the built form.

Passive heating and cooling stategy

stretches the balance point temperature, water loop heat pumps to move heat from warm rooms to cooler rooms.

Changing liquid into gas (evaporation or boiling)

takes large quantities of heat

Set point temperature

the design point temperature (set on thermostat)

Enthalpy

the total heat content of air. Sensible + Latent. nearly parallel to the wet bulb temperature. Sliding to the right equals greater enthalpy.

Humidity ratio (or absolute humidity)

the total quantity of moisture (water vapor) in the air. measured as the vertical axis on the psychrometric chart.

Altitude

the vertical axis of the sun's position in the ski. Describes the sun's angle above the horizon. Describes the sun's position relative to the cardinal points N, S, E, W. Usually measured in degrees from south

Skin load dominated buildings

thermally controlled by the conditions outside: temperature, humidity, solar radiation (insolation) and wind. Typically small and thin with large skin to volume ratios. Warehouses with low levels of heat gain by internal sources (people, lighting, equipment, etc.) They require heat when weather is cold.

Type L copper pipe

thinner and most common for supply lines in building systems.

Type M copper pipe

thinnest and best for low pressure supply

Optimized year round PV collector angle

tilt to the south at angle from the horizontal equal to the latitude of the site.

East, West and North facing windows

typically lose more heat than they gain - do not contribute to a passive solar system

Type DWV pipe

used only for drainage, waste or vent piping (also low pressure), stack vent,

Kitchen sinks require these

vent stack

Blackwater

wastewater containing human waste or food waste

Applications that can reuse greywater

water closets, urinals, sprinklers

Globe valves

water is variable or frequently controlled (at faucets)

Pressure in pipes causes

water to rise

Gate valves

where water can be shut off for maintenance

Check valves

where water is allowed to flow in only one direction to combat water supply contamination