One of my goals for this website is explaining the concepts and terminology behind home construction. Problems and possible solutions are easier to understand, and you'll be more confident talking to your contractors when you learn understand these heating concepts. We've always known there are different types of heating in our houses — the challenge has been remembering their names and how they work. Everyone has to learn these concepts so if you didn't take physics, here's your chance to get the basics.
This article defines the different ways heat is transferred inside our homes. Whether you heat your home with a furnace, boiler, wood stove, heat pump or electric baseboard, the physics of heat transfer are the same. The concepts are challenging so this article also offers tips on how to remember heating terminology and concepts.
Learning how your home functions is important so you can enjoy your home more. You can also save money by using energy more wisely, i.e. ceiling fans are cheaper to run than your heating system. Here are some basic heat concepts to get started.
- What we consider to be cold is in reality, the absence of heat.
- Every object contains energy stored as heat.
- Heat flows spontaneously from objects with higher temperatures to those with lower temperatures.
- Heat will continue to flow from hotter to cooler objects until both objects are equal in temperature.
- Warm air is lighter than cool air, so warm air rises naturally. That's why ceiling fans aren't just for warm, summer days. When you reverse the rotation of the blades, your ceiling fan will push warm ceiling air back down where you will benefit.
These last 2 points are important when we look at heat transfer in our homes.The more air tight your home is, i.e. less heat transfer, the less time your heating system will need to run to maintain your desired temperature. That's why we now use insulation and double pane windows, to make our homes more air tight.
Ways Heat is Transferred
Let's start with a simple activity we understand and take for granted, putting a pot of water on the stove to boil. Whether the stove is electric or gas, we know that eventually the water in the pot will get hot and boil. What we want to illustrate are the different ways that heat causes the water to boil — conduction, radiation and/or convection.
- Conduction occurs when heat energy travels through a solid or between 2 solids in contact with each other. When you put a pot on an electric burner to boil water, most of the heat transfer is from the the electric coil to the pot which it is touching it.
- Radiation is another type of heat transfer. When the electric burner is on, energy radiates up to the pot directly. The shiny metal under the burners also reflects radiant heat back to the pot through the gaps in the coils. Another example of radiation is when heat is transferred to you from the sun.
- If you put your hand over an electric burner it will get hot. This happens due to radiation and convection. Convection occurs through the motion of a fluid which in this case is the air between the burner and the pot. Yes, in this case air is considered a fluid and please don't ask me to explain this because I can't.
Heat Transfer in Our Homes
Hope you've been able to follow everything so far. We're now going to transition to how heat transfer works in our homes. After considering several different ways to explain how conduction and convection work in our houses (radiation doesn't really play a role in heating our homes), it made the most sense to break the discussion into 2 parts.
- How heat passes from your heating system to the air in your home, to keep you comfortable. You probably know whether you have a boiler and forced hot water system, a furnace and forced hot air system or electric heat. We'll explain which types of heat transfer they use to warm the air in your house.
- How heat is lost due to air leaks into and out of your home. You probably know if your home is insulated and whether you have double pane windows but unless you've had an energy audit recently with a blower door test, you don't know how much heat (or cooled air in the summer) you're losing due to air leaks.
Watch for 2 new articles (coming soon) to explain these 2 important topics as heating (or a combination of heating and cooling) typically represents about half of your energy cost budget.