PPD Case Study
ADDITIONAL CLARIFICATIONS
QUESTION 6:
Assuming an area factor increase of 72% and based on the tables from Resource 4, the maximum allowable area per floor is________ sf. Fill in the blank without units or commas. Example: If the result were 95,430 sf, the correct answer would be 95430.
CLARIFICATION:
Correct answer is 57,660 sf. (57660)
First thing we must do is determine the construction type and the occupancy groups. If the main structural elements are made of protected steel with a 1-hour fire-resistance rating, this will probably be a Type II-A construction (Non-Combustible, protected).
Office space – Occupancy group B
Restaurant and Cafeteria– Occupancy group A-2 (there are no other A types in the resource’s tables, so this helps you determine the occupancy group)
Convenience store – Occupancy group M
Childcare center – Occupancy group E
Per table 504.3 of the IBC 2015 we can determine the maximum allowable height of each occupancy group:
Office (Group B, Type II-A) – 85 feet (Sprinklered)
Restaurant and Cafeteria (Group A, Type II-A) – 85 feet (Sprinklered)
Convenience store (Group M, Type II-A) – 85 feet (Sprinklered)
Childcare center (Group E, Type II-A) – 85 feet (Sprinklered)
Per table 504.4 we can determine the maximum number of stories of each occupancy group.
Office (Group B, Type II-A) – 6 stories
Restaurant and Cafeteria (Group A, Type II-A) – 4 stories
Convenience store (Group M, Type II-A) – 5 stories
Childcare center (Group E, Type II-A) – 4 stories
Per table 506.2 we can determine the maximum allowable area per floor of each occupancy group.
Office (Group B, Type II-A, SM) – 112,500 sf
Restaurant and Cafeteria (Group A, Type II-A, SM) – 46,500 sf
Convenience store (Group M, Type II-A, SM) – 64,500 sf
Childcare center (Group E, Type II-A) – 79,500 sf
Since this is a non-separated mixed-use building, the maximum allowable area must be calculated individually per floor. For mixed-occupancy multistory buildings, the correct formula to calculate the allowable area is the following:
Aa = [At + (NS x If)]
where:
Aa = Allowable area (per floor).
At = Tabular allowable area factor (NS, S1 or SM value, as applicable) in accordance with Table 506.2.
NS = Tabular allowable area factor in accordance with Table 506.2 for a non-sprinklered building (regardless of whether the building is sprinklered or not).
If = Area factor increase due to frontage (percent) as calculated in accordance with Section 506.3.
In this case, the formula should read like this:
Office
Aa = 112,500 + (37,500 x 0.72) = 139,500 sf per floor. The 0.72 represents the 72% Increase factor given in the question.
Restaurant / Cafeteria
Aa = 46,500 + (15,500 x 0.72) = 57,660 sf per floor.
Convenience store
Aa = 64,500 + (21,500 x 0.72) = 79,980 sf per floor.
Childcare center
Aa = 79,500 + (26,500 x 0.72) = 98,580 sf per floor.
Because the occupancy groups are not separated, the most stringent requirements apply to the entire building:
Max. floors: 4
Max. height: 85 ft
Max. area per floor: 57,660 sf
QUESTION 10:
Based on the wall detail and table from Resources 5 and 6, the U-value of the daycare’s wall assembly is _______. Fill in the blank with three decimal digits. Example: If the result were 1.257395, the correct answer would be 1.257
CLARIFICATION:
Correct answer is B – 0.026
From the information given in Resource 5, we know that the wall assembly materials have the following R and U values:
Air film U = 5.88
13” Exposed concrete R = 6.76 (0.52 * 13”)
1” Air cavity R = 1.00
2” XPS insulation U = 0.1
3” Mineral fiber insulation R = 16.5 (5.50 * 3”)
1/2” Fiber board sheathing R = 1.32
5/8” Gypsum wall board (2x) R = 1.125 (0.5625 * 2)
Air film U = 1.47
In order to calculate the U-value of the entire wall assembly we must first convert all values to the same unit.
Air film R = 0.17
13” Exposed concrete R = 6.76 (0.52 * 13”)
1” Air cavity R = 1.00
2” XPS insulation R = 10.00
3” Mineral fiber insulation R = 16.5 (5.50 * 3”)
1/2” Fiber board sheathing R = 1.32
5/8” Gypsum wall board (2x) R = 1.125 (0.5625 * 2)
Air film R = 0.68
U-value is the mathematical reciprocal of R-value, U = 1/R, therefore the combined U-value of the wall assembly equals:
1 / 0.17 + 6.76 + 1.00 + 10.00 + 16.5 + 1.32 + 1.125 + 0.68 = 0.026
QUESTION 11:
Given the information from Resource 1, and without having more information on the curtain wall system, the ____ IGU is the option that better addresses all the client’s concerns and requests. Fill in the blank with capitalized letters in the following format: AA11
CLARIFICATION:
Correct answer is GL24
From all the information given in Resource 1, the main takeaways that might be relevant to this question are:
. Location of the building: San Mateo, CA (20 miles south of San Francisco, close to the Pacific Ocean)
. HVAC system should allow to maintain a relatively constant interior temperature throughout the year
. Layout: All workstations are to be placed within 35’ of the façade
. Security concern: Proximity of the future campus loop to the workspace, making it easy for visitors to see through the glass.
. Views to the exterior are important but glare is also a major concern.
. office floors should rely as little as possible on artificial lighting during work hours.
There are several ways one can go about this question but the easiest way to solve it is by eliminating options, making it easier to choose the best IGU. Typically, one would start by looking at the SHGC and U values, but this is a special scenario for two reasons: most of the options have SHGC and U values that are very similar, therefore they should not be necessarily a deciding factor, especially since the client has many other concerns. Also, the building is located in San Mateo, CA – 20 miles south of San Francisco, close to the Pacific Ocean – so the climate is considered to be marine according to the IECC. This means that the exterior temperature is actually very stable throughout the year, therefore SHGC and U values are less important than in other situations (very hot or cold climates, for example).
If privacy is a major concern to the client, all Series 1 options can be quickly eliminated because of their low values from the Reflectance / Visible Light Out column. This means that regardless of their tint (or absence of it) they allow a considerable amount of see-through from the exterior. Series 3 can also be quickly eliminated because although they perform very well in blocking heat and reflecting light, they allow for very low quantities of visible light to penetrate the IGU, therefore they are not adequate for a work environment that is supposed not to depend heavily on artificial lighting.
That leaves us with the Series 2. GL20 through GL23 perform very poorly in terms of Reflectance / Visible Light Out. GL27 through GL29 also have low values for Reflectance / Visible Light Out and on top of that do not allow for enough visible light to penetrate the building.
We’re left with GL24, GL25 and GL26. Despite the mild climate, and because this is a medium-large commercial building, the HVAC system is still considered to be cooling-driven. And for this reason, SHGC values are more important than U-values, when deciding an IGU make-up. So, despite having higher U-values (the small difference can be considered negligible in this climate), GL24 performs slightly better in terms of solar heat gain. This option also allows for more visible light in (transmittance) and also reflects more visible light out. It addresses all the client’s concerns and requests better than all the other options