This inquiry is regarding the envelope criteria for energy modeling of a new building (ASHRAE 90.1-1999, Section 11.4.2). Based on LEED Energy Modeling Protocol and ASHRAE 90.1, "the budget building design shall have identical conditioned floor area and exterior dimensions and orientations as the proposed design" The proposed new Barrel Aging Room (5805 s.f.) was initially designed by a local architect as a standard above ground facility, similar to other structures in the region. The winery\'s interest in sustainability drove the decision to pursue burying the building as an energy conservation measure. The current architectural firm was asked to redesign the project and completed the design as an earth-covered building. The intent of burying the building was to save energy by eliminating most of the building\'s cooling load.(see note below) In modeling the PowerDOE proposed building (underground), standard procedure requires that the first foot of the walls be calculated as "underground-wall type" in order to estimate the associated edge loss to the first foot of soil, the remainder of the wall is modeled as an "interior-wall type." When changing the proposed model to the budget building, the "exterior wall type" was used to model the walls, as is typical of an above ground building. The dimensions of the building have not changed, only the dimensions attributed to each required wall type designation. This credit interpretation is being submitted to obtain approval for comparing the proposed walls that are modeled as "below-grade" to the baseline walls modeled as "exterior." The conditioned floor area between the two models remains unchanged. The exterior dimensions and orientation on the site between the two models remains unchanged. Summary We believe our proposed modeling method meets the spirit and intent of EA Credit 1 to optimize energy. If our modeling method is accepted, the project will pursue 8 points under Energy & Atmosphere Credit 1: Optimize Energy Performance. (Note) The average ground temperature in Oregon is about 53
The measure you are proposing is, in effect, additional insulation in the wall system, and a reduction of the delta t across that wall system. Using this interpretation, the budget building design does have identical conditioned floor area, exterior dimensions and orientations as the proposed design. This approach is reasonable provided that the top of the wall is modeled accurately. The accuracy of this modeling approach depends upon several specific details of the wall system. As you point out, the \'deep\' ground temperature is almost ideal for your purposes. However, as you get closer to the surface, air temperature will affect the heat loss rate of the system. Soil has an approximate R-value of R-2.5/foot, so near the surface, this will have a substantial effect on the heat loss of the wall system. Likewise, concrete, at R-1/ft. will transmit heat from lower in the wall to the cold upper part of the wall. As you suggest, modeling the near-surface wall as \'exterior\' will help to identify this effect. However, if your wall is totally uninsulated, heat will move from at least the top several feet of the wall surface toward the \'cold spot\' at the top. (This is why some energy codes require at least 2 ft. of perimeter insulation at slab edges.) The accuracy of your modeling strategy therefore depends on the minimum depth below grade (minimum soil thickness) , AND the insulating strategy used (and modeled) at the top of the wall. If you clearly make the case that you have accurately characterized the performance of the near surface wall area, this modeling strategy seems reasonable. Applicable internationally.