Figure 22. Heat lost and gained by the house.
At the simplest level considering conservation of energy, once we have the house at a temperature we're happy with, we want to balance the heat gain and the heat loss so as to maintain a steady state on the inside. In figure 22[1] the blue line represents the total heat energy that is lost from the house through ventilation and transmission (details at → post 028) and the red line depicts the total heat energy that is added to the house, mainly through solar gain (details at → post 027).
It is clear from the graph that in the winter months more energy flows out of the house than flows in. In order to maintain a constant temperature[2] we must add heat and the blue shaded regions represent roughly the amount of heat that must be added[3]. In the summer, the situation is reversed unless some action is taken to suppress the gain. For example, by shading the windows as they're responsible for the largest amount of gain in our case[4]. Another way to cool the house is to bring in cooler air from the outside during the nighttime. Both of these can be automated to reduce "user error", e.g. a situation where we forget to close the window shutters when we leave the house one summer morning.
[1] The numbers here are raw numbers in that I have not included the effect of some weighting factors and such. They make a small difference.
[2] It is not true that we maintain the same temperature throughout the year. In the winter the temperature is taken to be 20°C (68°F). Exactly what the maximum summer temperature is taken to be, I do not know yet, however 22°C to 24°C (71°F to 75°F) is probably not unreasonable.
[3] The gain is pretty much maximized in this case. However there is room to play in the loss side of the equation, i.e. more insulation and reduction of heat bridges. As with most things, it's a matter of optimizing the system within the parameters of affordability.
[4] If we happened to run a computer farm at home, we'd have to implement some additional cooling methods.
Hi ersie
ReplyDeleteThe temperature in summer goes up to 33°C without shading.
Whith solarcollectors in the right angle you get energy to heat the water during the summer and for the roomheating during spring and autumn.
wellingtonia
I'll add to the solar collectors comment that one also has to have a properly dimensioned storage tank integrated with the heating system to make good use of the collectors.
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