# E+ outputs for building heat losses

Dear all,

I am trying to find out the correct variables of defining the heat loss of one building. What I am looking for are:Heat loss from the wall, roof, window, floor and infiltration/ventilation.

Up to now, after doing the searching and going through the InputOupt EP reference, what I come up with is:

Heat losses from walls, roof, ground floor = Surface Inside Face Conduction Heat Transfer Rate [W]

Heat losses from windows = Surface Window Heat Loss Rate [W]

Heat losses from infiltration = Zone infiltration Sensible Heat Loss

Heat losses from ventilation = Zone Ventilation Sensible Heat Loss

However, when I am looking at the results that the surface window heat loss rate is zero value for some time period(around 10am-3pm). I am wondering if I am looking at the right output.

one results shown below which is one window heat flow, including window heat gain, heat loss and transmitted solar radiation.

From the definition:

**Surface Window Heat Gain Rate**:
The total heat flow to the zone from the glazing, frame and divider of an exterior window when the total heat flow is positive.

**Surface Window Heat Loss Rate** :
The absolute value of the total heat flow through an exterior window when the total heat flow is negative.

**Window heat gain = Window Heat Gain [W] - Window Heat Loss [W] - Window Transmitted Solar [W]**

When calculate this window heat gain, I got positive numbers roughly around 10am-3pm. However, from the basic calculation of heat loss = U*A*(Tin-Tout), (the indoor temp is 18C, outdoor temp is around 2C), for this case, there should be always loss from window, not gains.

Thanks