Question-and-Answer Resource for the Building Energy Modeling Community
Get started with the Help page
Ask Your Question

E+ outputs for building heat losses

asked 2016-06-07 12:33:04 -0500

nancynanxiaodan gravatar image

updated 2016-06-08 09:13:48 -0500

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 = UA(Tin-Tout), (the indoor temp is 18C, outdoor temp is around 2C), for this case, there should be always loss from window, not gains.

image description


edit retag flag offensive close merge delete

1 Answer

Sort by ยป oldest newest most voted

answered 2016-06-08 06:12:09 -0500

updated 2016-06-08 06:14:19 -0500

The period where the heat loss is zero is when the heat gain is non-zero and vice versa. I think you'll need to use both of those variables to get to a balance of energy flows.

edit flag offensive delete link more


Thanks Jamie, you are right, if looking at the heat flows which should be = Surface Window Heat Gain - Surface Window Heat Loss - transmitted solar radation. For example if we looking at the results, the heat flow is positive. However, what I am trying to find out is the heat loss through the window, normally can be calculated by the equation: UA(Tin-Tout). When the outdoor temp is lower than indoor, there should be losses from the window. I am trying to find out this results from E+.

nancynanxiaodan gravatar imagenancynanxiaodan ( 2016-06-08 09:03:43 -0500 )edit

Hey Jamie, I've update my questions more detail, if you could have a look and let me know your thoughts on it. thanks

nancynanxiaodan gravatar imagenancynanxiaodan ( 2016-06-08 09:14:27 -0500 )edit

Yes, looks like you have a point. I'm not sure how to explain that but it does look like there must be something missing there.

Jamie Bull gravatar imageJamie Bull ( 2016-06-09 03:19:54 -0500 )edit

Your Answer

Please start posting anonymously - your entry will be published after you log in or create a new account.

Add Answer


Question Tools

1 follower


Asked: 2016-06-07 12:33:04 -0500

Seen: 112 times

Last updated: Jun 08 '16