In this tutorial we're going to go over how you define the ground floor in the Zebra model. The ground floor is similar to other elements of the building fabric in that we need to define an area and a U-value for it. However, unlike other elements like the walls and the roof we also need to adjust the U-value to account for the buffering effect from the soil beneath the ground floor, or the cavity if there is one.

In some ways the ground floor is one of the simplest of the input sheets, because it just requires us to define an area and a U-value. However, determining this U-value is a little more involved than on some of the other sheets for the building fabric. New to the input cell for the U-Value there's a note to say that we can see the calculators sheet. We can click on this to go to the calculators sheet, and this gives us some tools to calculate the U-value for our ground floor. As mentioned, this needs to be adjusted to account for what it's sitting on top of, because the ground floor won't lose as much heat because it's buffered by the soil or by the cavity beneath it. There are two cases that you can use. One is a slab directly on the ground and the other is a suspended floor.

For the slab on the ground we can define the U-value which is purely from the construction. This is based on whatever floor coverings you have, or whatever floor insulation you may have. The floor area is taken from the other sheet. The perimeter is also important in this case because most of the heat is lost around the perimeter of the ground floor. So you can determine the perimeter length for your ground floor and then the thickness of your perimeter wall. Based on these inputs the software will evaluate an adjusted U-value which you can copy back into the ground floor sheet.

And once we've done this it will present a summary of the space heating demand by month through the ground floor, and then also the space cooling demand.

The other option on that calculators tab is a suspended floor. This is a little more involved. We put in a U-value. Again, we put in the perimeter length. We also need a u value for the wall, and the the height of the crawl space. We also need the seasonal wind speed. A typical value for the UK will be five meters per second. And lastly we need the wall thickness. Once we have input all these values the spreadsheet will calculate an adjusted U-value for the suspended floor case.

That's all we need to do to input our values into the ground floor. If we increase the complexity level we will find that there are no additional inputs. There's just a more detailed summary of how these summaries have been calculated.