 We are into lesson seven now home heating basics. This is a very interesting and Very important chapter. Let me warn you one thing. This chapter has a lot of calculations and in the entire course this is the Most I would say calculation oriented Chapter so I want you to pay attention to this one basically if you have a house and You will be losing heat from various Places like windows like ceiling or walls or Doors, you know through floor everywhere. So in this chapter We will be looking at how much heat loss occurs and By what means you will be losing? Let's say here. Let me explain you Let's say we have this wonderful mansion okay, and We want to keep this interior at let's say 70 degrees all the time and We have a little furnace that puts out heat Okay, and that keeps the interior at 70 degrees when outside is let's say 10 degrees Fahrenheit Heat always tends to get out It can actually go through those solid walls or if we have windows It can go through windows or even roof and when you open doors and windows Air might leak in and out. So that's another way of losing heat So there are several ways in which heat is lost to outside How much heat this furnace has to put out to keep? This temperature of 70 degrees inside constantly Can be easily Calculated or known when we know how much heat is escaping if somehow Ideally if we can seal off this entire place without any heat loss Then once you bring this House to 70 degrees you can turn off the furnace and it'll remain at 70 degrees for the rest of the season But you and I both know that that is not the case So in this chapter you're going to learn how much heat is escaping through various surfaces here and Obviously whatever is Escaping that is the amount of energy that the furnace has to put out which means We have to buy energy and put into the furnace in the form of fuel so if we are losing a million BTUs like this through all these areas and we have to Get million BTUs made up from this furnace and we also know that the furnaces are not 100% Efficient either if we need to get 100,000 BTUs or 1 million BTUs from the furnace We cannot expect the furnace to put out if we put in 1 million BTUs So if we want 1 million BTUs as output Obviously, we have to put more in in the form of fuel So to know how much fuel we have to put in we have to know how much heat loss we Actually have in that house. So we will be looking at residential heat loss and how to calculate that And what are the ways in which we lose heat in this first chapter here or first part of the chapter 7? so we will understand the mechanisms of heat transfer and also Calculate the heating degree days for a heating season, which is basically the number of Degrees that we have to heat our air if the outside temperature is low Obviously, we have to heat our air to a higher temperature or higher number of degrees That's more degrees of heating So we will calculate that how many degrees we have to heat per day and per season and so on and so forth And if we know that we can calculate the heat loss from a solid wall that is Conduction heat loss we will talk about conduction convection and radiation those three mechanisms of heat loss And also once we have a wall Let's another all walls are the same some walls resist more heat loss than the others. So We define a property of a wall a property of a solid material That tells us how much that material resists the heat loss that's called our value. So we will understand and and Articulate the concept of our value here and we can also increase the our value of a wall by increasing its thickness or by increasing by going to a different material and so on we'll talk about that also in here and if we were to have a wall with Lower our value, which means lower resistance We would be losing more heat to outside and we would be requiring more heat Or more fuel to heat that place. So we'll talk about the cost of various fuels in You know for a given heat loss same one million BTUs that we lose if we were to heat With natural gas to get that same one million BTUs. What would it cost? Or if we use electricity, what would it cost to get one million BTUs or if we use propane? What would it cost? But the heat loss is always one million BTUs for the same amount of heat loss Which fuel happens to be cheaper fuel or expensive fuel. That's what we will be Determining here. So we will also understand if we have to put more insulation. We need to borrow more money and If we borrow more money and put more insulation, can we save enough through heat loss to pay back that That we borrowed pay back that money that we borrowed that is payback period You already know the concept and we will do some calculations to see whether it paid whether it Is wise to borrow money and put more into insulation All right, that's basically part of a here and we will also look at part B, which is insulation and home heating fuels and In this chapter or in this part we will talk about various types of insulation materials and how we can improve the walls performance by adding more and more layers to that wall and also if we have a wall that has four different materials together, for example inside we would have a dry wall that we could paint very Easily and behind the dry wall. We have the framework like you know wouldn't frame with wouldn't studs that are used for structural Integrity and between those studs you always pack some insulation material and outside the insulation material is not visible We'll have a plywood or sheathing outside and even sheathing doesn't look good outside So on top of that we put a siding in a vinyl siding or brick or whatever it is So when we have different materials Together, you know one right behind the other they will all together resist the heat loss So we will calculate the heat loss resistivity or our value of a wall that has different Layers of insulation and if we have that, you know how much energy we can save or how we can cut up cut the heat loss, etc and Also, we will talk about the efficiencies the furnaces and how we can distribute the heat Into the house into various rooms, etc. Different material different heating systems We'll talk about that later on in the next chapter So this is basically a calculation oriented and problem-based Kind of chapter or lesson and if we have any more difficulties in this one, I also added On top of this in the practice questions a bunch of practice problems, which explain you how to do how to do New medical problems, for example, if I have given here a bunch of problems Actually using the formulas that we will be looking at here for practice. There are a bunch of problems Okay, about 30 problems or so those of you are comfortable with the material can do yourself these problems and see If you got them by going to this answers page and where the same problems are given with answers So you can actually look at whether you got the same answer or not If you got it, you're happy if you don't what happens is you may feel kind of you know If you lost or if you feel then what you do is you click on this third one here where every problem here We have here a solution actually like audio that I'm speaking to you right now with I've made some movies again for each of these problems that will explain you like a blackboard or a whiteboard rather Look at this So I'm writing here So there are a bunch of problems like this that you can look at and most of the problems have solutions like this So I've tried to make your life simpler So this chapter 7 is a two-week lesson, which means you will have a quiz at the end of two weeks After the lesson is assigned And you take the quiz at the end of this lesson. Good luck