WUFI

Dear Sirs;

In order to apply Plus 3.0.3 for evaluating hygrothermal performances of timber framed detached house, we ran a simple benchmark case.　It consists of a single zone of 6 x 6 x 3 m with windows of 4 x 2 and 4 x 1 m.

In the graphical results of heat flow (monthly), the monthly heat flow on the opaque elements seems to be unacceptable since it shows the gain through the whole year.
Please explain the reason why it shows a heat gain in the severe winter period.
The average insulation level is specified to the opaque envelope.
We would suspect that it might absorb unreasonable solar radiation on the exterior surface.

* Please notice that the attached input file and the result was in Sendai not in Tokyo.
If we switched the city from Sendai to Tokyo, the result would become the more unacceptable.

Thank you in advance for your cooperation and answer.

Regards,

In order to follow up our question, we checked the results on a similar example case with no windows.
In the result of heat flows (monthly), the exchange with opaque partitions became gains in summer and losses in winter.
However we don't know the precise definition of each elements appeared in the heat flows (monthly) bar chart,
we could suspect that the value of exchange with opaque partitions contains the radiant part of solar heat gain added to the conduction and convection based heat flow of the interior surface of opaque partitions.

It would be highly appreciated if you could show us the definition of each items appeared in the heat flows (monthly) bar chart.

Sorry for the delay. In fact this is confusing and we are working on a better explanation of the bar chart and energy balances and more detailed results.

The bar chart show the monthly summarized hourly heat flows calculated in the zone.
The heat flow for solar gain (past window, shading,…), ventilation, interzone ventilation, inner source convective is regarded for the air in the zone. The heat flow in the zone balance for opaque components is defined at the internal component surface. So the shown exchange with opaque components is the sum of all adjoined components inner surface heat flows, no matter if they have the outer climate or another zone at the outer side. You suspect absolutely correct, this value of exchange with opaque partitions contains the radiant part of solar heat gain added to the inner surface. For the simulation the solar gain (the defined part of it) and the inner source – radiant (only a source for the component surface) is handled correct for the inner enthalpy balance.

The part of the solar heat is defined in “other parameters” for a zone: “solar radiation to inner air”. Per default this value is 0.1 means 10% of the solar gains heat the zone air, 90% is spread to the components.

Another part, maybe missing in the heat flow bar chart (regarding it as energy balance) is the heating and cooling demand and the latent heat because of humidification and dehumidification. They have their own bar charts (at the moment).