Building Efficiency Factor vs Ratio?

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huntressj

January 30, 2023 15:52

Does anyone have any insight to this question from the NCARB practice exam?

I don't understand why they multiplied the net square footage with 1.25 when the net to gross efficiency factor is 25%? The community center net to gross factor is 25% in the references.

I thought that building efficiency is net/gross is a ratio. which for the community center should be 80% if you divide 3500 NSF/ 4375 GSF.

 

what is the difference between net to gross factor and ratio?

 

 

 

 

Question 67:

Upsilon Architects is assembling a proposed construction budget. Construction costs are $350 per gross square foot, and the city has provided them with the following guidance for the interior spaces of the new regional community center:

• If 1 Floor: Use 1.0 cost multiplier
• If 2 Floors: Use 1.1 cost multiplier
• If 3 Floors: Use 1.2 cost multiplier

The city has decided on the following supplemental space requirements:

• Community Health Center: 3,500 nsf
• Administration Suite: 2,400 nsf
• Multipurpose Spaces: 8,900 nsf
• Maximum area per floor: 9,500 gsf

What is the construction budget for the interior spaces?

 

$ _______

Your answer: 6058360

Correct answer: 6964650

 

CORRECT RESPONSE

$6,965,000

 

CALCULATIONS
1. Determine gross floor areas:

• Entry Lobby: 600 gsf
• Community Health Center: 3,500 nsf x 1.25 (net-to-gross factor) = 4,375 gsf
• Administration Suite: 2,400 nsf x 1.20 (net-to-gross factor) = 2,880 gsf
• Multipurpose Spaces: 8,900 x 1.15 (net-to-gross factor) = 10,235 gsf

2. Calculate sum of gross floor areas: 600 gsf + 4,375 gsf + 2,880 gsf + 10,235 gsf = 18,090 gsf
3. Calculate number of floors: 18,090 / 9,500 = 1.9 floors = 2 floors
4. Calculate construction cost: 18,090 gsf x $350 = $6,331,500 
5. Calculate floor cost multiplier: $6,331,500 x 1.1 (cost multiplier for a two-floor community center) = $6,964,650

 

CASE STUDY RESOURCES USED

Scenario

Client Space Requirements

 

 

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  huntressj January 31, 2023 19:59

  Thank you! I didn't see that when i searched.

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  Divyang Panchal February 04, 2023 22:10

  I still did not get it. How do we go from 25% grossing factor to using 1.25 as multiplier in the example mentioned above. Can someone please explain ? 

   

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  huntressj February 05, 2023 14:59

  Divyang,

  Sure thing! it took me a while to figure it out. Efficiency factor is different than efficiency ratio.

  The factor is 25% which means the gross square footage is the net + 25% of the net.

  that's why they multiplied 1.25 to get the gross.

  My understanding is the factor is gross/net

  and the ratio is net/gross.

  thats why 

  • Community Health Center: 3,500 nsf x 1.25 (net-to-gross factor) = 4,375 gsf

  4375/3500 = 1.25 building efficiency factor

  and 

  3500/4375 = 80% building efficiency ratio

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  Jesse Gates July 03, 2024 00:43

  The two terms are inverses of each other. Use them to solve problems depending on what information you have available: 

   

  GSF = NSF * 1.25          therefore

  NSF = GSF/1.25             or    

   

  NSF = GSF * (1/1.25)    = 0.8 or 80%

   

  where 1.25 is your efficiency factor (think needing to add support area to increase SF from Net to Gross) 

  and 1/1.25 or 80% is your efficiency ratio (think how efficient did I do in terms of Gross to Net?) 

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