PHPP (again): ground sheet - area & perimeter dimensions

[Markus Kolb]

Reviewing my area entries for our current project, where we have both a conditioned and an adjoining unconditioned basement. One side of the building is at grade (with both the conditioned and unconditioned exposed there), the other three sides are below grade.

For the ground sheet slab area, according to the PHPP manual: "Calculation of the heated basement should be performed ignoring the shared wall with the unheated basement. The shared wall is considered as a basement ceiling in the heat loss calculation of the unheated basement." (page 56 of the 2007 manual). In the PHIUS 2007 PHPP, the note on the RefDims sheet for the ground area says to use exterior dimensions; however, on p. 58 in the manual it says that "the areas of walls in contact with the ground, e.g. as it occurs with a heated basement are not added to the floor slab area."

So I'm supposed to use exterior dimensions, except I'm not supposed to use exterior dimensions... ?

OK, first off, I assume that the above means I'm supposed to figure an area for the heated slab that goes to the exterior where we're at grade, but does not include the wall below grade nor the walls to the unheated basement (see attached screenshot). The slab area for the unheated basement, then, would be to the interior of the foundation walls and it would include the insulated walls it shares with the heated basement as well as the wall at grade. Am I reading that right?

In terms of perimeter, the note in the PHPP says to consider "only edges which are exposed to the open". In the manual (p. 58), I'm told that "the perimeter lengths bordering on heated rooms are excluded" – doesn't say anything about the perimeter below grade or the perimeter at heated/unheated... Best as I can tell, then only the edges at grade, for both the heated & unheated portions in our project, would count as perimeter.

Can anyone confirm by best-guess read of this? Thanks for everyone's input in advance – what an awesome community!

Cheers,

Markus

[Graham S. Wright]

On Apr 11, 2012, at 4:42 PM, Markus Kolb wrote:

Reviewing my area entries for our current project, where we have both a conditioned and an adjoining unconditioned basement. One side of the building is at grade (with both the conditioned and unconditioned exposed there), the other three sides are below grade.

For the ground sheet slab area, according to the PHPP manual: "Calculation of the heated basement should be performed ignoring the shared wall with the unheated basement. The shared wall is considered as a basement ceiling in the heat loss calculation of the unheated basement." (page 56 of the 2007 manual). In the PHIUS 2007 PHPP, the note on the RefDims sheet for the ground area says to use exterior dimensions; however, on p. 58 in the manual it says that "the areas of walls in contact with the ground, e.g. as it occurs with a heated basement are not added to the floor slab area."

So I'm supposed to use exterior dimensions, except I'm not supposed to use exterior dimensions... ?

As I understand it heated basements are an exception.  For ground sheet purposes you use the inside dimensions.  For the other 3 kinds you use exterior dimensions.

-gw

OK, first off, I assume that the above means I'm supposed to figure an area for the heated slab that goes to the exterior where we're at grade, but does not include the wall below grade nor the walls to the unheated basement (see attached screenshot). The slab area for the unheated basement, then, would be to the interior of the foundation walls and it would include the insulated walls it shares with the heated basement as well as the wall at grade. Am I reading that right?

In terms of perimeter, the note in the PHPP says to consider "only edges which are exposed to the open". In the manual (p. 58), I'm told that "the perimeter lengths bordering on heated rooms are excluded" – doesn't say anything about the perimeter below grade or the perimeter at heated/unheated... Best as I can tell, then only the edges at grade, for both the heated & unheated portions in our project, would count as perimeter.

Can anyone confirm by best-guess read of this? Thanks for everyone's input in advance – what an awesome community!

Cheers,

Markus

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