Lesson video

This lesson is called, "Heating and cooling our school sustainably" And it's from the Unit, "Climate Change and Living Sustainably." Hi there.

My name's Mrs. McCready and I'm here to guide you through today's lesson.

So thank you very much for joining me today.

In our lesson today, we're going to describe different ways of reducing the need for heating or cooling in a school.

And we're going to come across a number of keywords in our lesson today.

They're listed up here on the screen for you now.

You may wish to pause the video to make a note of them, but I will introduce 'em to you as we come across them.

So in our lesson today, we're going to first of all look at thermal insulation and how that can be used to reduce heating, before we go on to consider how the environment can help reduce heating and cooling.

So are you ready to go? I certainly am.

Let's get started.

So let's look at thermal insulation and how that can be used to reduce heating.

So the less heating a building needs to keep it at a nice steady temperature, the cheaper it is to heat, and we can help a building maintain its temperature both in summer and winter by using materials called thermal insulators.

So thermal insulators can reduce the amount of energy that is needed to heat a building, and they can make it easier to heat a building using only renewable resources because less heating is required in the first place.

So what is a thermal insulator? Well, a thermal insulator is a substance through which thermal conduction happens very slowly.

So thermal conduction is about passing heat from one substance to a next or one part of a substance to the next part.

And in a thermal insulator, that transfer of heat happens very slowly.

So wood is a good thermal insulator, and if we heat one end of a wooden rod, it will take a while for that heat to very slowly move or conduct through the wooden rod because wood is a good thermal insulator and therefore does not allow heat to transfer quickly through it.

Conversely, if a substance is a good thermal conductor, it transfers heat through it very quickly.

So metals are good thermal conductors.

If you heat one end of a metal rod, the other end will heat up very quickly.

The heat will transfer through the metal rod very quickly because metal is a good thermal conductor.

It can transfer heat and energy through it really quickly and easily.

So that means there are some materials which are poor thermal conductors and others which are good thermal conductors.

And those materials which are poor thermal conductors make good insulators because they don't transfer heat very easily.

So poor conductors include air, wood, water, and wool.

and good conductors include glass and metals.

Metals are the best types of conductors.

They conduct heat and they also conduct electricity, which is why we use metals for sauce pans for cooking, and also as metal in wires for running electricity from place to place.

So we can say that air, because it is a poor conductor, it is also a very good insulator.

So which of these is the best thermal insulator? Glass, brick or wood? I'll give you five seconds to decide.

Okay, so you should have chosen wood as the best thermal insulator.

Well done if you did.

Now, buildings are usually insulated with sheets of insulation material built into key parts of the building, so into the ceilings, into the walls, and into the floors.

So in this school building for instance, the windows are double glazed.

And what that does for having two sheets of glass, that's what double glazed means.

That's useful because it has a layer of trapped air between the two glass layers.

So glass is a reasonably good conductor of heat, but it is made a better insulator because of the trapped layer of air.

So the two layers of glass are separated by this air gap, and the air gap is a poor conductor of heat, a good insulator.

And so it's that gap which is what makes double glazing a good insulator.

Now obviously if we have big holes in the walls of our building such as windows and doors propped open, then the heat that is trapped inside the building can escape.

So if we leave doors and windows open, then heat can get out through those gaps and escape into the external environment and that means that we need to heat the building up more in order to maintain a steady temperature.

And this is even worse if it's cold outside because the temperature difference will mean that heat will escape, will transfer into the external cold environment faster because there's a bigger temperature difference between the inside of the building and the outside of the building.

But we can help to manage that situation by making doors and windows close more easily or perhaps even automatically.

So many doors do close automatically.

They slam shut or they have a closing mechanism on them, and a similar idea can be fitted to windows.

Now of course, people aren't moving through windows, they're not coming and going through windows, but nevertheless, hinges can be fitted onto windows so that they close automatically perhaps if they've reached a particular temperature or if they've been open for a certain length of time.

Another thing we can do to help reduce the amount of heating that is needed for a building as well as closing the doors and insulating it, is to set a thermostat on the heating.

And that will help to keep the building at a constant temperature, not colder and not hotter than the temperature that we have chosen.

So if the room becomes too hot, perhaps sunlight is blazing in through the window and the room heats up really nicely, then the heating can get turned off because the temperature has gone above what we would want it to be at.

And that reduces the amount of energy that is needed to keep the building at a constant temperature because instead of heating the room and letting it all escape out through the window, we've just turned the heating off and then kept that heat inside instead.

So there are two different types of thermostats that can be used.

Those which control the ambient temperature of the room by monitoring the room, and they are usually wall-mounted thermostats.

And then thermostats can also be fitted to radiators so they can monitor the temperature of the room local to the radiator and then turn the radiator off directly at the radiator itself.

And both of these types of thermostats can help us to manage the temperature of a room or the building and prevent having to lose excess heat by opening a window because the temperature is being better managed inside the building in the first place.

So which of these will reduce the cost of heating a school? Closing doors, setting thermostats to a higher temperature, opening windows or fitting double glazing? What do you think? I'll give you five seconds to decide.

Okay, so you should have said that closing doors and fitting double glazing will all reduce the cost of heating a school.

Now it's not always very easy to add extra insulation to school buildings.

It's relatively straightforward to add extra insulation into roof spaces.

That's quite low cost, so quite cheap, and it's very effective because heat rises and so stopping it from leaving the top of the building is a very effective way of keeping it trapped inside the building.

It is also quite straightforward to add insulation into the gap between the two walls of the building.

So most buildings, especially relatively modern buildings, are built with two walls.

The external outside wall, which is usually quite nice to look at, usually made of brick or some kind of cladding material, and then the inner main structure of the building, which doesn't look very nice, but provides the bulk of the support and the structure of the building.

And there's a gap between these two layers of bricks and blocks.

And in that gap it is possible to put insulation in as well, especially if it hasn't already been done, say at the time of when the building was built.

So if we add insulation into that air gap by pumping it in through holes that we drill into the outside of the walls, and maybe you've had cavity wall insulation fitted in your own home, that's relatively straightforward to do, it's reasonably cheap to do and it's a good way of retrofitting a building so that it is better insulated.

By filling this gap between the two layers of bricks.

It's also relatively easy to fit insulation that can stop warm air from escaping around the edges of doors, for instance.

So you can put strips around the edges of the doors to fill in and seal the gaps made when the door is fitted into the frame.

There's always a bit of a gap and these strips can help to seal that.

And then adding a brush to the bottom of the door to close the gap between the door and the floor and seal that gap as well.

And again, these are cheap and easy to fit pieces of insulation that just helps to stop the amount of hot air that is leaving the building via these smaller gaps.

You can also apply these measures to windows to make sure that they fit tightly into the window frames as well.

So there's lots of different ways of reducing the amount of heat that gets lost by adding in insulation.

Some are easier and cheaper than others, but they all certainly help to reduce the amount of heat that is needed to keep the building at a nice constant temperature and therefore reduce the amount of energy and the cost of that.

So how do insulation strips around the edge of a door help maintain the temperature of a building? Do they A, increase the loss of warm air.

Or B, reduce the loss of warm air.

Or C, increase thermal conduction through the door.

Or D, reduce thermal conduction through the door.

What do you think? I'll give you five seconds to decide.

Okay, so you should have said that they reduced the loss of warm air.

Well done if you chose that option.

So let's summarise this first part of our lesson, looking at thermal insulation to reduce heating by considering this scenario.

So the head teacher of this school wants to reduce the heating needed to keep this building comfortable.

So what I would like you to do is to describe what needs to be checked to help the head teacher decide what to do next.

So make a list of all the things that they need to go around and check before they decide how best to proceed.

So pause the video and come back to me when you are ready.

Okay, let's check our work.

So you might have said that the head teacher needs to check how much insulation is in the roof space, if the cavity walls are filled with insulation already, if the doors close automatically and if the gaps around the doors have insulation strips, if the gaps around the windows have insulation strips, if there are thermostats in each room to help control each individual room's temperature, and if those thermostats are set to the correct temperature.

You might have added some extra things to your list as well, but well done if you've included many or all of those things as well.

Okay, let's move on to looking at how the environment can help environ to reduce the amount of heating and cooling that a school might need.

So we've all been there, I'm sure, on a cold day it feels really cold if there is a wind blowing at the same time.

So with Andeep here for instance, the temperature of his face is nearly as high as his core body temperature at about 37 degrees centigrade.

And because his face is warm, it means that his face is heating the surrounding air, and your face is doing that at the moment as well.

You might not think it is, but it is.

Heat is coming away from your body and heating the environment near to you as a result.

Now, if we add a cold wind blowing as well, then as cold air passes Andeep's face, it is warmed by his face and then moves on, and that means that the warm air has already moved and has been replaced by colder air.

And because it's cold air, there's a greater temperature difference between Andeep's face and the cold air and so heat moves from his face to the cold air really quickly, and then that gets blown away because it's a windy day and more cold air takes even more heat away and so his face gets really, really cold and it feels quite bitter to be in that sort of condition.

The same thing can happen to buildings on cold days.

So on cold windy days, the building is, like Andeep's face, radiating a little bit of heat.

Some of the heat inside the building is escaping into the external environment, so it's heating up the surrounding air a little bit.

And if there's a strong wind blowing, especially if it's a cold wind, then it's blowing that warm air which has been heated by the building, it's blowing that air away and replacing it with colder air.

And the colder air then takes more heat away from the building, and that means the building cools down much more quickly.

And you'll see the same will be happening with your home.

On cold windy days, you will need to heat your house up more than on warm and non windy days.

Now, if we use the environment to help us reduce the amount of cooling that happens by the wind, then we can reduce the amount of heating that the building needs in the first place.

So planting trees near to the building will help to act as a wind break.

And by reducing the speed of the wind that is travelling past the building, we can reduce the amount of heat that is being whisked away by the cold air, and that means that although the building is still heating the surrounding air a little bit, it only heats it a little bit because the air gets warm and stays warm rather than being constantly replaced by another lot of cold air, which takes heat away from the building really quickly.

So if we plant trees, if we have trees near to a building, on windy days, they can reduce the amount of heating that the building will require.

So, on cold and windy days, trees can increase the temperature of the air.

True or false? So you should have said that that is false, and that is false because trees do not increase the temperature of the air, but they can reduce the amount of wind blowing away the slightly warmer air around heated buildings, which means that the buildings cool down more slowly.

Well done if you got both of those parts right.

So we've seen how by planting trees and bushes around a school, it can help keep the school warmer on cold windy days because there is less wind blowing over the building to cool the building down and therefore the building needs less heating to maintain its temperature and therefore it costs less in order to heat it.

Now we can also use those same trees and bushes to help keep the building cooler on hot sunny days.

And that's because on hot sunny days, those same trees and bushes will be providing shade, and if they're positioned well around the school, the shade can then help to keep the buildings cool instead.

Another benefit of having trees and shrubs in the school grounds on hot days is that because water evaporates from the leaves of plants, and this happens quite quickly on warm days, it helps to cool the air temperature down a bit.

And so having trees and shrubs around the school site helps to cool the building down by putting shade onto the building and also by cooling the air through water evaporating from the leaves of the plants.

So on hot and sunny days, trees and bushes can reduce the need for the school to use air conditioning to cool the buildings down and maintain a comfortable temperature because they are adding shade, which means that less heat is falling on the buildings themselves and because of the evaporation process that is cooling the air around them down as well.

Although the large majority of their function will come by providing shade to the building.

So on hot sunny days trees can reduce the temperature of the air.

True or false? Okay, so you should have said that that is true, and that is true because on hot days water evaporates from the leaves of trees and that evaporating water helps to cool the surrounding air.

Also, the shade cast by trees reduces the warming of this cooler air.

So well done if you've got both of those points.

So what I'd like you to do to conclude this part of the lesson about using the environment to reduce heating and cooling is to add trees and bushes to the plan of the school that will reduce the need for heating on cold days and cooling on hot days.

So you can see the plan of the school there with its sports field, main building, sports block and science block, plus its car park with a perimeter fence and one tree and some bushes have already been planted for you.

But where are you going to put other trees and bushes in the school grounds? And can you describe the reasons for your choices? So pause the video now and come back to me when you've finished all that planning.

Okay, let's see what you might have designed.

So here's one design.

You can see a mixture of trees and shrubs around the school perimeter fence, dividing the sports field from the main building and the sports block, and around the main building in between the sports and the science blocks, around the car park as well.

But you may well have positioned them differently.

Maybe you've used more trees and fewer bushes or maybe you've used more bushes and fewer trees.

That's up to you.

What I also wanted you to do was to describe why you have positioned those trees and bushes where you have put them.

So you might have said that trees and bushes around the buildings can slow down the wind on cold days so we need to heat the buildings less, and on hot sunny days they provide shade and shelter, which helps to cool the school.

Also, hedges and other trees provide shelter for pupils around the school, especially when they're out on break and lunch.

And all of those things are good ways of heating or cooling the school down and keeping it at a nice comfortable temperature.

So as long as you've written some kind of an explanation along those lines, that is what I was looking for to compliment your school plan.

Well done.

Okay, we've reached the end of our lesson now and we have seen how thermal insulators can reduce the amount of energy that is needed to heat a building.

And that means it is easier to keep a building warm using only renewable resources instead of having to use fossil fuels instead to heat the building.

We've also seen how using a thermostat can help to control the heating in a part of the building to keep it at a particular chosen temperature.

And we've seen how on cold days the wind can blow warm air away from the building and cool the building down more quickly.

And this means that more heating is required to keep the rooms inside nice and warm.

But if we use trees and bushes, it can reduce the amount of wind chill that is being experienced by the building, so how much the wind is cooling the building down.

And this means that less heating is needed to keep the building and the rooms inside at that nice warm temperature.

We've also seen how trees and bushes can work on hot sunny days to help reduce the need for schools to use air conditioning, for instance, to cool the building down to a comfortable temperature because they can provide shade.

So thank you very much for joining me today.

I hope you found it interesting and maybe that's given you some ideas about what changes your school might be able to make to help your school reduce its electricity bill.

So thank you very much for joining me today and I hope to see you again soon.

Bye.