I've been slowing working my way through the results of the energy calculations that the energy planner did for the house based on the provisional plans. The document is about 60 pages long. Parts of the input information and intermediate steps in the calculations are not in it so I first have to try to reconstruct it. Then I can put the information together in a format I want for the purposes of posting here. Let's start to look at the calculation of the energy balance of the house in parts. I won't go into a discussion of the details right now there are already sites[1] where that's done.
Figure 20. Heat gained by the house passively.
Figure 20 shows the passive heat gain predicted for the house, broken down by month. I believe this is before the sun-shading system is taken into account for the summer months. It is clear that without the proper system to suppress the heat gain in the summer, the house would become unbearably hot. Note the drop in June. This must be related to the input data (see figure 16[2] in post 024) and my first reaction was to think this can't be real. However, I've found a similar thing in a plot on another site[3] so it's still an open question for me. On the other hand, it's not really very important.
As I understand, these detailed calculations are usually only done for passive houses, i.e. houses with energy demands that are about half —15 kWh/(m2·a) instead of 38 kWh/(m2·a)— of what ours is going to have. These houses have such low heating needs that the heat generated by people[4] and appliances have a substantial influence. In the graph the lowest two lines represent these internal heat gains. The heat output of a person is taken to be 70 W and a daily 12 hour presence is assumed. The appliances are estimated to contribute 15 kWh/(m2·a). The heavy grey line at the top is then the sum of the solar heat gain and the internal gain. In my next post, I'll talk about the other side of the energy balance (the losses) and the need for additional heating.
[1] One good example is here (in English) → Energy Balances Passive House
[2] Direct link to figure 16 → Solar data from Buchs
[3] PHPP → Passive House Design Package
[4] One passive house joke is that if you feel your house is too cold then you can invite a few of your friends over for dinner to warm it up. We'd have to invite a dozen or so.
Hi ersie
ReplyDeleteReal god link's of the passivehouse-institute.
Have you seen the treatment about the sun gains - the not usable part !
This part heats your house over the point of comfortable.
wellingtonia
Hi Wellingtonia,
ReplyDeleteThat's right. Later today or tomorrow I'm going to try to do a post where the losses and the gains are considered together and where the problem of overheating from summer solar gain is addressed.