Glossary
139 terms, each defined where it first appears in the course. Search also finds them.
A
- Activated carbon
- A filter material that traps many chemicals that cause bad taste and odor. It does not kill germs or remove nitrate. Lesson 18
- Air barrier
- A continuous layer that stops air from leaking through the envelope, with every seam and gap sealed. Lesson 9
- Alternating current (AC)
- Electric current that reverses direction many times a second. Most household outlets and appliances use AC. Lesson 24
- Aquaponics
- A system that links fish and plants. Fish waste feeds the plants, and the plants help clean the water. Lesson 38
- Aquifer
- An underground layer of rock, sand or gravel that holds and gives up water. Lesson 15
B
- Backdrafting
- Air, smoke or combustion gases being pulled down a flue or chimney into the house, often by exhaust fans in a tight house. Lesson 11
- Backfeeding
- Sending generator power into house wiring through an outlet or homemade cord. It can kill utility workers and start fires. Lesson 27
- Bearing wall
- A wall that carries load from above. It can look the same as a non-bearing wall, which only divides space. Lesson 8
- Blackwater
- Water from toilets. Many codes also count kitchen sink and dishwasher water as blackwater. Lesson 19
- Blower door test
- A test that uses a fan in a doorway to measure how leaky a house is. Lesson 9
- Botulism
- A rare but serious and sometimes fatal illness from a toxin made by Clostridium botulinum, which can grow in improperly canned low-acid food. Lesson 39
- Building code
- A set of minimum rules for how buildings must be built to be safe. Most US places adopt and amend model codes such as the IRC. Lesson 12
- Building envelope
- Everything that separates inside from outside, the roof, walls, floor, windows and doors. Lesson 9
C
- Calorie gap
- The difference between growing your own vegetables and growing enough food energy to live on. Vegetables supply few calories. Lesson 34
- Carbon monoxide (CO)
- A poisonous gas with no color or smell, made by burning fuel. Generators must never run indoors or near openings. Lesson 27
- Carbon-to-nitrogen ratio (C:N)
- The balance of carbon-rich browns and nitrogen-rich greens in compost. Roughly 30 to 1 by weight suits compost microbes. Lesson 41
- Catchment area
- The surface that collects rain. For a roof, it is the footprint seen from above, not the sloped area. Lesson 16
- Certificate of occupancy
- The document a building department issues after the final inspection, saying a home can be lived in. Lesson 12
- Charge controller
- A device between solar panels and a battery that manages charging so the battery is not overcharged. Lesson 24
- Chill hours
- Hours of cool winter weather, usually counted between 32 and 45 °F (0 and 7 °C), that many fruit trees need before they flower well. Lesson 36
- Coefficient of performance (COP)
- How many units of heat a heat pump delivers per unit of electricity it uses. A COP of 3 means 3 kWh of heat from 1 kWh of electricity. It falls as outdoor air gets colder. Lesson 31
- Cold frame
- A bottomless box with a clear lid that traps the sun's heat over a small bed. Lesson 35
- Cold-climate heat pump
- A heat pump built to keep heating well below freezing, though its output and COP still drop on the coldest nights. Lesson 31
- Composting toilet
- A toilet that breaks down human waste with little or no water, using air, time and a dry cover material. Lesson 40
- Condensation
- Water vapor in the air turning to liquid on a cold surface. Lesson 7
- Conduction
- Heat moving through a solid material, from molecule to molecule, such as through a wall or window glass. Lesson 30
- Contingency
- Money set aside in a budget for surprises. A common rule of thumb is about 10 to 20% of project costs. Lesson 43
- Convection
- Heat carried by a moving fluid, such as air or water. Air leaks are the costly kind of convection in a house. Lesson 30
- Cooling degree days (CDD)
- A yearly total of how far, and for how long, the daily average temperature rises above 65 °F (18 °C). More CDD means more cooling. Lesson 3
- Creosote
- A tar that builds up inside chimneys from wood smoke, faster with wet wood and smoldering fires. It can cause chimney fires. Lesson 31
- Critical loads
- The loads you most need during an outage or cloudy spell, such as the fridge, well pump and a few lights. Lesson 27
- Cycle life
- How many charge and discharge cycles a battery gives before it holds much less than when new. Lesson 25
D
- Days of autonomy
- How many days a battery can carry your loads with little or no sun. Lesson 25
- Dead load
- The weight of the building itself. Lesson 8
- Depth of discharge (DoD)
- How much of a battery's capacity is used before recharging, as a percent. Deeper discharge usually shortens battery life. Lesson 25
- Derate
- A reduction applied to a solar estimate for losses from heat, dust, wiring, the inverter and charging. Lesson 24
- Design temperature
- A cold outdoor temperature that a place drops below for only a small share of hours each year. Heat loss at this temperature sets the size of a heating system. Lesson 30
- Direct current (DC)
- Electric current that flows one way. Solar panels and batteries make and store DC. Lesson 24
- Direct-vent appliance
- A fuel-burning heater or water heater that draws combustion air from outside and sends its exhaust outside through a sealed pipe. Lesson 31
- Diurnal swing
- The difference between daytime high and nighttime low temperatures. Night flushing works best where it is large. Lesson 32
- Drain field
- Buried pipes or chambers in soil or gravel where liquid from a septic tank seeps out and is treated by the soil. Also called a soil absorption field. Lesson 40
E
- Electric resistance heat
- Heat made by running electricity through a resistor, as in baseboard and space heaters. Its COP is 1. Lesson 31
- Energy
- How much electricity is used or made over time, measured in watt-hours or kilowatt-hours. Lesson 21
- Evaporative cooler
- A device that cools air by evaporating water into it. It works well in hot, dry climates and poorly in humid ones. Lesson 32
F
- First-flush diverter
- A device that holds back the first, dirtiest water from each rain so it does not reach the tank. Lesson 16
- Food forest
- A planting that copies the layers of a natural woodland, from tall trees down to ground cover, using mostly useful plants. Lesson 36
- Frost heave
- Lifting of the ground, and anything on it, when water in the soil freezes and expands. Lesson 8
- Frost line
- The depth the ground freezes in a hard winter. Water lines are often buried below it. Lesson 17
- Frost pocket
- A low spot where cold air drains and pools on still, clear nights, bringing frost earlier than the land around it. Lesson 4
- Frost-free season
- The days between the average last spring frost and the average first fall frost. Lesson 35
G
- Greywater
- Gently used water from showers, baths, bathroom sinks and laundry. It contains no toilet waste. Lesson 19
- Grid-tied system
- A solar system connected to the utility grid, usually without batteries. It shuts off in an outage. Lesson 26
- Groundwater
- Water held underground in soil and rock. Wells and springs draw on it. Lesson 15
H
- Hard month
- The stretch of the year when a budget is closest to running out, such as December for solar power or August for a rain tank. Lesson 2
- Hardening off
- Setting indoor-grown seedlings outside for longer each day over about a week so they adjust before planting out. Lesson 38
- Head
- For micro-hydro, the vertical drop from the water intake to the turbine. Lesson 28
- Heat pump
- A device that moves heat from one place to another instead of making it, using much less electricity than resistance heat. Lesson 23
- Heat-loss estimate
- A rough count of how fast heat leaves a home, adding up area times temperature difference divided by R-value for each surface, plus air leaks. Lesson 30
- Heat-pump water heater
- A water heater that moves heat from the surrounding air into the tank. It can be about two to three times as efficient as a standard electric water heater. Lesson 33
- Heat-recovery ventilator (HRV)
- A balanced ventilation system that passes warmth from outgoing air to incoming fresh air. An energy-recovery ventilator (ERV) also passes some moisture. Lesson 11
- Heating degree days (HDD)
- A yearly total of how far, and for how long, the daily average temperature falls below 65 °F (18 °C). More HDD means more heating. Lesson 3
- High tunnel
- A walk-in, unheated, plastic-covered structure over garden beds, also called a hoop house. Lesson 35
- Homestead
- A home plus the land and systems that meet some of its basic needs on site. Lesson 1
- Homestead brief
- A one-page statement of a homestead plan, covering climate zone, site, people, ranked goals, budget range and must-haves. Lesson 6
- Homestead budget
- Any resource a homestead has to balance over a year, what comes in, what goes out and what is stored. The course uses energy, water, heat, food, money and time. Lesson 2
- Household hazardous waste
- Household products that can catch fire, react, poison or harm water if thrown out with regular trash, such as batteries, paint, fuel and pesticides. Lesson 42
- Hybrid system
- A grid-connected solar system with batteries that can keep selected loads running in an outage. Lesson 26
- Hydroponics
- Growing plants without soil, with roots in nutrient-rich water or an inert material. Lesson 38
I
- IECC climate zone
- A climate region used by US energy codes, numbered 1 (hottest) to 8 (coldest), with a moisture letter A (moist), B (dry) or C (marine). Assigned by county. Lesson 3
- Interconnection agreement
- The utility's approval to connect a solar or battery system to the grid. Lesson 26
- Inverter
- A device that turns direct current (DC) from panels or batteries into alternating current (AC) for household use. Lesson 21
K
L
- Laundry-to-landscape
- A simple greywater system that uses the clothes washer's pump to send water to mulch basins around plants. Lesson 19
- Lithium iron phosphate (LFP)
- A type of lithium-ion battery common in home storage. It can be used deeply and lasts many cycles, but cannot charge below freezing without heating. Lesson 25
- Live load
- Weight that comes and goes, such as people, furniture and stored goods. Lesson 8
- Load list
- A table of every load with its watts, hours of use and daily watt-hours. Its total is your daily energy use. Lesson 22
- Load path
- The route a load takes through a building, from the roof through the framing, walls and foundation to the soil. Lesson 8
- Load shedding
- Switching off loads that can wait so backup power and batteries last longer. Lesson 27
M
- Manufactured home
- A factory-built home built to the federal HUD code rather than local building codes. Lesson 7
- Micro-hydro
- A small hydropower system, up to about 100 kW, that makes electricity from flowing water. Lesson 28
- Microclimate
- The local climate of a small area, such as a warm slope or a cold hollow, which can differ from the wider region. Lesson 3
- Microgreens
- Vegetable and herb seedlings cut when just a few inches tall, often 1 to 3 weeks after sowing. Lesson 38
- Modular home
- A home built in sections in a factory to state or local building codes, then set on a foundation on site. Lesson 7
- Molt
- The yearly shedding and regrowing of a bird's feathers. Hens usually lay fewer eggs or none while they molt. Lesson 37
- Mulch basin
- A shallow pit filled with wood chips around a plant, where greywater soaks in below the surface. Lesson 19
- Must-have
- A requirement the plan fails without, as opposed to a nice-to-have. Lesson 6
N
- Net metering
- A utility arrangement that credits you for solar power you send to the grid. Rules vary by state and utility. Lesson 26
- Night flushing
- Cooling a house by pulling cool night air through it, so thermal mass cools down and soaks up heat the next day. Lesson 32
- Nutrient loop
- The cycle that returns nutrients to the soil as scraps, garden waste and manure become compost that grows more food. Lesson 41
O
P
- Passive solar design
- Using a building's shape, windows and materials to collect, store and spread the sun's heat, with few or no moving parts. Lesson 10
- Pathogen
- A germ that can make people sick, such as a bacterium, virus or protozoan. Lesson 18
- Peak sun hours
- The number of hours a day of sunlight at full test strength (1,000 watts per square meter). It varies by place and month. Lesson 24
- Pellet stove
- A stove that burns small pellets of pressed sawdust fed from a hopper. It needs electricity for its fan and feed. Lesson 31
- Perennial
- A plant that lives for three years or more, such as a fruit tree, berry bush or asparagus. Lesson 36
- Phantom load
- Power a device draws while it seems to be off or idle. Also called a standby load. Lesson 22
- Phasing
- Building a homestead in planned stages over months or years, in an order where each stage supports the next. Lesson 5
- Photovoltaic (PV) module
- A solar panel that turns sunlight straight into electricity. Lesson 24
- Pounds per square inch (psi)
- A unit of pressure. Each foot of water height adds about 0.43 psi. Lesson 17
- Power
- How fast something uses or makes electricity right now, measured in watts. Lesson 21
- Pressure canning
- Canning in a pressure canner, which gets hot enough to destroy botulism spores. It is required for low-acid foods like most vegetables, beans and meats. Lesson 39
- Pressure tank
- A small tank with an air cushion that keeps water under pressure so the pump does not start every time a tap opens. Lesson 17
R
- Radiation (heat)
- Heat moving as invisible infrared light, straight across open space, such as warmth from a stove or the sun. Lesson 30
- Rainwater catchment
- Catching rain from a surface, usually a roof, and storing it for later use. Also called rainwater harvesting. Lesson 16
- Relative humidity
- How much water vapor the air holds compared with the most it could hold at that temperature, as a percent. Lesson 11
- Resilient
- Able to keep working, or fail gently, when something goes wrong. A home with backups for each system is more resilient. Lesson 1
- Reverse osmosis (RO)
- A treatment that pushes water through a very fine membrane to remove many dissolved chemicals. It wastes some water. Lesson 18
- Root cellar
- Any cool, dark, humid space for storing whole crops like carrots, beets and potatoes through winter. Lesson 39
- Rootstock
- The root part of a grafted fruit tree. It largely decides how big the tree grows and how soon it bears. Lesson 36
- Runoff coefficient
- The share of rain that reaches the tank after splash, evaporation and other losses. Often 0.75 to 0.9 for metal and shingle roofs. Lesson 16
S
- Season extension
- Protecting plants with row cover, cold frames or tunnels so you can grow earlier in spring and later in fall. Lesson 35
- Seasoned wood
- Firewood that has been split and dried, for at least 6 months, until its moisture is below about 20%. Lesson 31
- Self-sufficient
- Providing more of your own basic needs, such as water, energy, heat and food, and knowing where the rest comes from. In this course it is a range, not all or nothing. Lesson 1
- Septic system
- An on-site system that treats household wastewater, usually with a septic tank and a drain field. Lesson 40
- Solar heat gain coefficient (SHGC)
- The share of the sun's heat a window lets in, from 0 to 1. Higher lets in more sun heat. Lesson 10
- Solar thermal collector
- A panel that heats water or another fluid directly with sunlight, unlike a solar electric panel. Lesson 33
- Standby loss
- Heat that leaks out of a hot water tank and its pipes even when no hot water is being used. Lesson 33
- Staple crop
- A food that supplies a large share of calories and stores well, such as potatoes, grains and dry beans. Lesson 34
- Stock and flow
- A stock is a store, such as a tank or battery. A flow is what moves in or out, such as rain or daily use. Lesson 2
- Succession planting
- Planting a little at a time, or following one crop with another in the same bed, to spread out the harvest. Lesson 35
- Surge (starting watts)
- The short burst of extra power a motor draws as it starts, often two to several times its running watts. Lesson 22
T
- Temperature and pressure relief valve (T&P valve)
- A safety valve on a water heater that opens if the tank gets too hot or the pressure too high. It must never be capped or removed. Lesson 33
- Thermal bridging
- Heat moving quickly through parts of the envelope that conduct heat well, such as wood studs or steel, bypassing the insulation. Lesson 9
- Thermosiphon
- Natural circulation of water as hot water rises and cool water sinks, used in some solar and wood-fired water heaters with no pump. Lesson 33
- Tiny house on wheels
- A small house built on a trailer. Often built to recreational vehicle standards, and limited by road size rules and local zoning. Lesson 7
- Total coliform bacteria
- A group of bacteria used as a warning sign in water tests. Finding them suggests germs may be getting into the supply. Lesson 15
- Transfer switch
- A device, installed by an electrician, that safely connects a generator to house circuits while keeping it separate from the grid. Lesson 27
U
- U-factor
- How fast heat passes through a whole window or door. Lower is better for keeping heat in. Lesson 10
- Ultraviolet (UV) treatment
- Shining ultraviolet light through clear, flowing water to stop germs from reproducing. It does not remove chemicals. Lesson 18
- Urine diversion
- Separating urine from solids in a toilet, which keeps solids drier and cuts odor. Lesson 40
V
W
- Waste hierarchy
- A ranking of ways to handle waste, from best to last resort - reduce, reuse, recycle and compost, then dispose. Lesson 42
- Watt (W)
- The unit of power. A thousand watts is a kilowatt (kW). Lesson 21
- Watt-hour (Wh)
- The unit of energy. One watt used for one hour. Lesson 21
- Windbreak
- A row of trees, shrubs or a structure that slows the wind and shelters what is downwind of it. Lesson 4
Z
- Zoning
- Local rules that decide what can be built where, such as allowed uses, minimum home size and setbacks. Lesson 12