042. From Minergie to Minergie-P (rejoice!)

Figure 33. The new calculated energy balance for the house. The numbers are in kWh/(m²). Compare to figure 23.

Back in April I had started to write a little about the calculations of the projected energy usage that had been done based on the components making up the house. Since then much has changed and the structure of the house is now going to be made entirely of wood[1]. The windows have been upgraded to have better energy performance. We also have a new energy planner who is a better fit for our project. He changed the heat pump to a better-tested model, added 4 m² of solar collector (for hot water) and an Erdregister (earth tube heat-exchanger). The result of all these changes is that we now have an optimized system with lower numbers. Numbers that put us firmly in Minergie-P territory!! Read on for more information...

First, the quantities listed in the diagram above are:

- Q_iP: heat generated by the residents.
- Q_iE: heat generated by the electrical equipment.
- The total internally generated energy is Q_i = Q_iP + Q_iE.

- Q_S: heat delivered by the sun.
- The total gain Q_g = Q_i + Q_S.

It is assumed that only 60% of Q_g can be used by the house:
- Q_g,u = 0.60 Q_g
- Q_V is the energy lost through the ventilation system.
- Q_t is the energy lost via transmission through the shell.

Also back in April, in post 021, I had written about the requirements of Minergie. Here again is the relevant equation (refer to the old post for details):

With the new construction plan, the various energy demands are computed to be:
Q_H,eff = 13.9 kWh/(m²·a)
Q_WW = 6.7 kWh/(m²·a) and the rest is met via solar energy
Q_V = 2.51 kWh/(m²·a)

This gives a weighted energy demand of 20.7 kWh/(m²·a). The limit for Minergie-P is 30 kWh/(m²·a), so we are comfortably within this requirement. This is great news!

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[1] In the earlier plan, the lower level was going to be made of concrete and bricks, and the upper level out of wood.