Temperature Humidity and Ventilation

Question 1

Define heat?

Answer 1

Heat is a form of energy (the ability to do work); the random vibration of molecules of the body. Adding heat to a substance increases its molecular motion and potential energy, and may cause it to undergo a change of state that is to melt or vaporize.

Question 2

Define the effect that heat has on air volume and air density?

Answer 2

Volume increases as air gets warmer

density decreases as air gets warmer

Question 3

What happens to a substances molecular structure when heat is added?

Answer 3

Adding heat to a substance increases its molecular motion and potential energy, and may cause it to undergo a change of state that is to melt or vaporize.

Question 4

What is conduction?

Answer 4

The transfer of heat through a substance.

Question 5

What is convection?

Answer 5

The transfer of heat by natural motion of a fluid medium.

Question 6

What is radiation?

Answer 6

The transfer of heat by energy waves, similar to light waves and radio waves.

Question 7

What is a BTU relative to water?

Answer 7

1 BTU is the amount of heat required to raise 1 pound of water 1 degree Fahrenheit.

Question 8

What is a BTU relative to air?

Answer 8

1 BTU is the amount of heat required to raise 55/ft³ of air 1 degree Fahrenheit.

Question 9

What direction does heat travel?

Answer 9

Heat travels from warm to cold.

Question 10

What is sensible heat?

Answer 10

The heat required to change temperature in a substance, but not a change of state.

Question 11

What is latent heat?

Answer 11

The amount of heat required to change the state of a substance without changing its temperature.

Question 12

What is specific heat?

Answer 12

It is the number of BTU’s required to raise the temperature of 1 pound of a substance by 1 degree Fahrenheit.

Question 13

How is sensible heat measured?

Answer 13

By a thermostat or by sense of touch.

Question 14

How is latent heat measured?

Answer 14

BTUs

Question 15

What is humidity?

Answer 15

The quantity of water in a particular volume of air.

Question 16

What is relative humidity?

Answer 16

A measure of the amount of water air holds at a certain temperature. it is relative compared to the amount of water that air, at that same temperature, can hold at 100% humidity or saturation.

Question 17

What is saturated air?

Answer 17

When air contains the maximum amount of vapour possible for a particular temperature, the air is said to be saturated.

Question 18

What is dew point temperature?

Answer 18

The temperature that moisture will start to condense from the air.

Question 19

True or false: Hot air is denser than cold air.

Answer 19

False.

Question 20

What instruments are used to measure humidity?

Answer 20

Hygrometer and psychrometer

Question 21

What are the effects of low humidity on people?

Answer 21

Static electricity, dry throat, nose bleeds and dry skin. Having too little humidity in the air will also make you feel cooler. This is caused by the moisture in your skin evaporating which uses heat energy from your body.

Question 22

What are the effects of low humidity on furniture?

Answer 22

Too little humidity can affect the building and objects in side as well. As humidity level drops moisture content in objects such as wood paper textiles also give up their moisture. This will cause wood to shrink and crack, paper will dry out and start to crumble.

Question 23

What is the function of a humidistat?

Answer 23

A humidistat controls the humidifier, turning it on or off as required.

Question 24

What are methods for reducing humidity in a home?

Answer 24

Removing moisture absorbing shower curtains, installing proper ventilation in bathrooms bringing cold fresh air into the duct system and by the use of dehumidifiers.

Question 25

What are the requirements for fresh air in a new residential construction?

Answer 25

Each room must have 5 L/s or 10 cfm of air coming into it except for the master bedroom and undeveloped basements which must have to 10 L/s or 20 cfm.

Question 26

How does an HRV work?

Answer 26

And HRV pre-heats incoming fresh air by forcing it through a heat exchanger core with a fan. At the same time another fan is forcing warm exhaust air through the other side of the core allowing heat to transfer from warm exhaust air to the cooler fresh air without letting the two flows come in contact with each other.

Question 27

True or false: In order for a temperature difference to occur, a latent heat change must take place.

Answer 27

False.

Question 28

True or false: Hygrometers can be used to show direct readings of relative humidity?

Answer 28

True.

Question 29

On a psychometric chart, where is the dry bulb temperature scale?

Answer 29

Along the bottom.

Question 30

On a psychometric chart, where is the wet bulb temperature scale, and what shares it?

Answer 30

Top arching line, shared with dew point scale.

Question 31

On a psychometric chart, what is the arching line running central of the chart?

Answer 31

Relative humidity line.

Question 32

On a psychometric chart, what lines run vertically?

Answer 32

Dry bulb temperature lines.