You have probably heard about the term latent heat in your books, tv, or even the internet. But you still have no idea what does it mean, right? That’s why you are here reading this article.
So, what is latent heat in HVAC? What kind of role does it perform in HVAC systems? And how do you fix latent heat problems in your HVAC?
This article is a complete guide that will answer all of your questions regarding latent heat and HVAC.
What is sensible and latent heat in HVAC
When we talk about air conditioning systems, two main types of heat always come into the discussion.
Latent heat & Sensible heat.
You are probably confused what’s the difference between both. Let’s discuss them one by one.
What is sensible heat in HVAC
Sensible heat is the type of heat that is required to increase or decrease the temperature of a substance without changing its state.
If we make it simple to understand, then we can say that the temperature that appears on the thermostat of your HVAC system is the amount of sensible heat that your air conditioner is removing.
What is latent heat in HVAC
Latent heat is the exact opposite of sensible heat.
Latent heat is the type of energy (absorbed or released) that changes the state of a body without affecting its temperature.
The temperature of the body remains constant throughout this whole process. It neither goes up nor down. Vaporization and fusion are one of the most common forms of latent heat.
The boiling of water is a perfect example of latent heat. When water is boiling, its temperature remains at 100 ℃. No matter how much more heat you add, the temperature will remain at 100 ℃and the new heat will be used for boiling the water. Since that new heat didn’t have any effect on the temperature of the water, therefore, it is called latent heat.
What is latent heat in air conditioning
Now as we have a basic understanding of latent heat & sensible heat, let’s talk about them in the context of air conditioning.
Well, the heat that is generated as a result of an increase or decrease in the moisture by air is called latent heat. In easier terms, latent heat is present inside humidity.
When there is increased humidity inside your home, then you feel very uncomfortable and sweaty. Why? Because you are feeling the latent heat present inside that humidity.
If the thermostat of your air conditioner shows 75 degrees temperature, it would still feel like 80 degrees. The reason is that the thermostat of your AC only monitors sensible heat and it doesn’t measure any latent heat.
If your air conditioner does not remove enough latent heat from your room, then you will feel sweaty and extremely uncomfortable.
Sensible heat vs latent heat
Different factors affect the amount of latent heat and sensible heat that your air conditioner has to remove from your home.
Let’s discuss them one by one.
Factors affecting sensible heat
Quality & volume of insulation
The quality and volume of insulation in your home have a strong impact on sensible heat.
Type of glass in windows
The quality, quantity, and size of glass used in your windows also affect the sensible heat in your house.
Number of stories
The number of stories in your house also affects the sensible heat of your home & air conditioner.
Exposure of your house to the sun
How much of your house is exposed to the sun & how long does the exposure last? It also affects the sensible heat of your air conditioner and home.
Lighting in your house
The number of lights in your home & their working duration have a significant impact on the sensible heat of your house & air conditioner.
Roof overhang
The roof overhanging measurements of your house have a solid impact on the sensible heat in your home & air conditioner.
Factors affecting latent heat
Infiltration of air
The infiltration of external air into your house through random holes, gaps, and cracks in the building directly impacts the latent heat for your home & air conditioner.
Household activities
The frequency of different household activities like cooking, cleaning, bathing, also affects the latent heat in your house.
Number of people
The number of individuals inside your house at a specific time also directly impacts the latent heat.
How to calculate latent heat in HVAC
We know that the thermostat of your HVAC system does not measure any latent heat. It just monitors & measures the sensible heat.
So, how do you calculate the latent heat in your HVAC system?
Well, the basic formula used by experts for calculating the latent heat is:
Formula: L = Q/m
Here
Q = the amount of energy absorbed or released during the phase change of a substance.
M = the mass of the substance.
L = specific latent heat.
What is latent heat gain?
The amount of energy that is added to the space when moisture is added to the same space due to the air infiltration from outside or vapors emitted by the occupants is known as latent heat again.
How to solve latent heat problems in HVAC
When your air conditioner does not remove enough latent heat from your house, then you will feel extremely uncomfortable and sweaty.
Therefore, the problem needs to be solved and your AC unit should remove the right amount of latent heat from your house.
You need to have the right size of air conditioner for your home and then when you will set your thermostat at 75 degrees, you will feel exactly like 75 degrees because the AC is doing its job rightly and there is no latent heat in the humidity.
Here are some tips that will help you:
The right size of AC
You need to have the right size of air conditioner that matches the size and dimensions of your house. Then you will be able to get excellent air conditioning.
Air seal your house
You need to air seal your house and prevent the infiltration of humidity and latent heat inside your house.
It will help you get more effective air conditioning.
Use dehumidifier
If there is too much humidity and latent heat in your area then you should install a dehumidifier.
A dehumidifier will help you get rid of all the humidity and latent heat.
