Quiz #3 (Heating/Cooling and Crop Scheduling)

Question 1

What does temperature regulate in a greenhouse?

Answer 1

Growth, water use, germination rates, flowering, ripening.

Question 2

What are the two unique environments in which plants exist?

Answer 2

1. Media and water
2. Air and water

Question 3

BTU definition

Answer 3

British thermal unit = amount of energy it takes to heat one pound of water, one degree F. (1 pound = 16oz fluid)

Question 4

BTUH definition

Answer 4

Number of BTUs transferred in one hour. BTUH is used to define heating systems in the US.

Question 5

U-value definition

Answer 5

Ability of a material to transfer heat. Measured in BTUs / square foot (ft^2)

Question 6

What is Glazing U-Value?

Answer 6

All glazing materials have a U-value. The higher the number, the more heat that is being lost.

Question 7

What is the simplified heat loss formula?

Answer 7

BTUH= area x diff in temp x U-value.

Question 8

Greenhouse edge effects

Answer 8

The edges of the greenhouse effect heat, light, water, air flow, humidity, pests, space, and maintenance.

Question 9

Conduction definition

Answer 9

Conduction is the form of heat loss through touch. For example; floor heating systems that heat the media of the plants.

Question 10

Convection definition

Answer 10

Convection is the form of heat loss through air circulation, cold air displaces warm air and warm air rises. Fans can help this!

Question 11

Radiation definition

Answer 11

Radiation is the form of heat loss through something giving off heat, like a campfire.

Question 12

Whyt is it important to have a flexible and responsive greenhouse heating system?

Answer 12

Because greenhouses gain and lose heat quickly, it is important to work with a designer, have several heating types and a versatile water system.

Question 13

Hot water heating systems

Answer 13

These systems an carry 3,500x more heat than air, are extremely versatile and widely compatible. for example: Geothermal heating, finned pipe system, floor slab system and benchtop systems.

Question 14

Finned pipe system

Answer 14

finned pipe heating system heats the greenhouse using water temperatures up to 230°F by heating the air around the fin tube and distributing the heat via natural convection. They have an increased surface area, uses less water and has a fairly easy installation.

Question 15

Floor slab system

Answer 15

Evenly spaced rubber or plastic tubes using hot water that can heat gravel, sand, oil and cement.

Question 16

Benchtop system

Answer 16

A bench-top system consists of a series of rubber tubes that circulate hot water under seedling trays. This saves energy because it is more efficient to heat the soil than to keep the entire structure cozy. Good for germination areas.

Question 17

Geothermal Heating

Answer 17

Geothermal energy is the heat produced deep in the Earth’s core. Geothermal energy is a clean, renewable resource that can be harnessed for use as heat and electricity. Geothermal has been historically used to generate power.

Question 18

Geothermal loop installations

Answer 18

• trenches, 5 feet deep, 3’ wide
• Coils continuous pipe are rolled in the trench from the beginning of the trench to the end and back

Question 19

What is Passive ventilation?

Answer 19

Passive ventilation is venting such as roof vents and sidewall vents.

Question 20

What are the two hoop house roll up ventilation methods?

Answer 20

Top down (harder but better) and bottom up

Question 21

What is Mechanical ventilation?

Answer 21

Ventilation adding a motor and a fan.

Question 22

What is a horizontal air flow system? (HAF)

Answer 22

An HAF system is using fans that are lined up in a row along the greenhouse. This naturally mixes the air to avoid pooling of cool/warm air. A few benefits include strengthening plants, pest management and reducing lurking moisture.

Question 23

Transpiration

Answer 23

Water moves from roots, to shoots and out the plants stomata. Vapor pressure increases at the stomata and reduces the ability of the plant to transpire. Having good air movement helps remove the barrier but uneven air movement causes uneven transpiration rates.

Question 24

What are some recommendations for keeping a good heating/air movement environment in a greenhouse?

Answer 24

• Keep an eye on the thermostat
• Clean your fans
• Use all the same brands

Question 25

Crop scheduling is usually based on….

Answer 25

Weeks! but also is based on first and last frost dates, equinoxes and solstices, opening and closing markets, holidays and expected labor.

Question 26

Too early and plants are too
( ?) too late and plants get (?) and require more maintenance.

Answer 26

Small, Leggy

Question 27

Spring frost date

Answer 27

The likelihood of frost forming on or before the date. Wait until after the date to plant frost sensitive plants.

Question 28

Fall Frost date

Answer 28

The likelihood of frost occurring on or after the date. Expect plants to be killed by frost by this date.

Question 29

How do mechanized vents work?

Answer 29

• Negative pressure systems
• Exterior wall fans move air out- creates a vacuum
• Negative pressure allows air to be sucked in through inlets.
  -The difference in pressure inside and outside is the static pressure difference.