thermal mass | How to save big within a zero energy, passive, sustainable house.
Thermal mass | heat exchange
The best comparison to explain the thermal mass would be a cheetah running after a gazelle. From 11am to 3pm usually you have infinite amounts of energy from the sun.
You can make electricity with it, you can heat up water or air in the pipes. It’s “limited” to 3,4 hours and then it’s gone.
It’s like a cheetah running after the prey. It catches it and it has unlimited amount of food. More food that it can eat.
The problem is he has to eat quickly because the other chaeta’s, hyenas, lions will take away the food.
Even if the cheetah in some miraculous way would remain “alone” with the meat the heat in a few hours it would start to rotten. The cheetah would need a fridge.
That’s a great idea. It’s quite simple but there is a catch. I know I’m the most evil person here but there is an urban myth about concrete.
Some say: 0.0001% of the population that concrete it’s not a good insulator. Sure it’s not. It was irony.
Basically it’s one of the worst materials to insulate something. However for one thing is flawless. It has thermal mass.
That’s the battery. That’s the chaeta’s fridge. That’s why I prefer brick and concrete houses instead of wooden ones, the temperature it constant.
While the wooden house heats up instantly and loses its temperature quite fast: the concrete and brick feels stabile. It “locks” the temperature.
It does not insulate better it just feels so. Let’s get back to the cheetah.
Heating up a wooden house it’s like running after the pray. In 15 seconds the animal has the flesh in its mouth but: it has to run every time.
The fridge|heat exhange
Every time the animal wants to eat it has to run. The cheetah might be fast, but it needs massive amounts of energy every time.
The thermal mass is the fridge. The bigger and heavier the thermal mass, the more you can store. Concrete is the fridge, an excellent one. We must put as much concrete (or even better, granite) in the house as we can.
Or water. This acts like a fridge to. The water has the advantage that it flows. So we can redistribute the heat or cold even better.
The main idea is how can you run with 120km/h from 10am to 2pm when the sun is up (after the gazelles) and store them in the fridge. Note. Concrete in direct contact with earth is like a fridge with an open door.
You have to insulate it. At least 40cm. Read about this here. Brick walls and earth are not good insulators. Let’s say they are average.
Their thermal mass is also average. However it feels stabile compared to wooden houses and we use them.
Another explanation to thermal mass. The material stores up the power of the sun in heat.
The heat is released with delay.
Just imagine at 10am you put your hand on a 2mm metal sheet. It will probably burn your hand.
At the same hour you put your hand on the concrete pavement and it will be cool. It slowly starts to accumulate heat. After the sun is gone the metal sheets cool down almost immediately.
However you can feel the heat “radiating” back from the concrete several hours after twilight. That’s why you can’t sleep at night.
Your walls radiate back heat, slowly but surely. Let’s use this in our advantage. Most people put concrete and brick walls on the outside.
That’s one of the biggest if not the biggest mistakes. It’s like putting the cheetah in the fridge instead of giving it the fridge.
Ice cream | all at once ?
And the door is wide open. It doesn’t make sense. We feel better in brick homes. It’s because of the thermal mass.
If you open the window for a long period of time when you close it again the air in the house will get back to normal in record time.
Wooden houses don’t have that significant thermal mass, so if you open the window the temperature drops will be significant.
The cheetah will have to run again. A huge south facing facade, tons of cheap electric panels, water pipes, wind turbine will make the cheetah run lightning fast.
The heavy insulation, tesla accumulators, concrete, will be the “thermal mass”. The bigger it is, the bigger the animal that the cheetah can store.
The electric cables, water pipes, sensors, air movements in symbiosis with the underground lake, the Arduino systems is like the ability to open and close the fridge when needed.
That’s the cutting edge.
The electronics …the brain of the system. It’s a bit like eating “ice cream” every 2 hours and not eating 20 ice creams in 5 minutes.
This system calculates when to open and shut the valves and pumps: to gather, store and redistribute the energy.
This is the brain, the “artificial intelligence” that makes decisions based on temperatures, wind, light intensity and weather forecast for the upcoming days.
This system is the electronic part of the “fridge” that stores the extra heat within the battery.
Pick concrete, granite and water instead of brick. Put it in the core of your house and insulate it really well.
Let the greenhouse effect do it’s job and you will live careless and “free” for the rest of your life.
Gravel within the aquaponics system it’s the substitute for soil/earth.
The rocks and water are the thermal mass.