Step 1 - Generative Design Framework
- Building Construction and Material Costs in terms of time and money: This refers to the total cost it will take to construct a building given a certain type of material or design feature.
- Design Variables
- Building Height (in ft)
- Material Costs (for Steel, Wood, and Concrete Price Ranges in $/ft2)
- Internal HVAC Systems Cost (VAV Ranges versus Radiant System Cost Ranges in $/ft2)
- Labor Costs (for VAV Ranges versus Radiant System Cost Ranges in $/ft2)
- Evaluators
- Total Total Material Cost (in $)
- Total Internal Systems Construction Cost (in $)
- Internal Systems Labor Costs (in $)
- Time to Construct the Building (in hours)
- Most Important Tradeoffs to Consider
- Costs of materials versus design aesthetics: Some design features are costly to implement but architecture is important as well.
- Labor costs versus material costs: The labor costs of implementing one system over another may result in a higher overall price even if the original option is less expensive material wise.
- Material availability versus materials desired: There can be supply chain or talent availability issues. This is especially important when using radiant systems in the United States where there is a lower number of general contractors that know about implementing a radiant system when compared to some countries in Europe where these systems are common.
- Time to construct the building versus overall cost: In some cases, the schedule might be able to be completed at the same rate even with a less expensive option.
- Sustainability and Energy Efficiency: This refers to designing a building based on sustainability metrics and energy use.
- Design Variables
- Building Footprint (in ft2)
- Building Height (in ft)
- HVAC Systems Cost (in $/ft2)
- Window to Wall Ratio
- Evaluators
- Total rooftop solar PV Potential (in kWh)
- Total cooling and/or heating load of the building (in kWh)
- Total energy needed from the grid to meet building energy demand (in kWh)
- Total energy used from a battery (in kWh)
- Total cost of implementing a battery in to the system ($)
- Most Important Tradeoffs to Consider
- Design features versus building Energy Use Index (EUI): Some large glazing features for example can be worse for EUI metrics.
- Solar potential versus the capital and operational costs of solar PV panels: While solar PV panels can reduce the overall energy consumption from the grid, the costs to the building owner may be too high.
- Implementing a battery in a building versus the costs of energy from the grid: If the energy costs of buying from the grid are constant and do not depend on peak demand rates, a battery may not make sense.
- Unit Availability for Market Rate and Affordable Housing: This refers to creating a mixed use building that has affordable housing and market rate rental spaces.
- Design Variables
- Building Floor Area (in ft2)
- Building Height (in ft)
- % of commercial spaces
- % of affordable housing spaces
- Market rate (in $/ft2)
- Affordable housing rates (in $/ft2)
- Tax benefits from local, state, and federal resources
- Evaluators
- Total profits made from affordable housing (in $)
- Total profits made from market rate use (in $)
- Total construction and maintenance costs (in $)
- NPV (in $)
- Most Important Tradeoffs to Consider
- Number of affordable housing units versus number market rate units: An entirely affordable housing unit may not be possible because of high construction and operation costs of the building, but social equity is also an important factor to consider.
- Tax benefits in the current date versus tax benefits in the future: In some places, tax benefits may continue to help fund affordable housing, but some places may not be concerned with this issue.
- Design for affordable housing units versus market rate units: Some places make affordable housing units smaller, but this could prevent these units from being used as market rate housing in the future.
Step 2 - Generative Design Study
I decided to run with the analysis of building construction and material costs (Design Consideration 1). For this model, I am specifically interested in the material type (steel, wood, concrete) that would optimize costs without sacrificing too many aesthetics and design features that would increase material costs. I am also interested in learning about the differences in constructing a VAV versus a radiant HVAC system.
Objective: My objective is to understand what the total cost of using different building materials for the walls and roof of a building by assuming variable material costs. I also wanted to understand how implementing different internal ventilation systems, specifically a VAV versus a radiant system, can change the overall cost of a building. Lastly, I wanted to understand how the building height plays a difference in the amount of time it takes to construct a building.
Model: Under my simple model that I hope to further refine for the final, I assumed that my radiant and VAV systems would be under the ground floor of the building (though they would likely be present in other parts of the building as well), that the time it takes to build one extra foot of the building is 10 hours, and that the material costs can be modeled through the amount of wall and roof area for the different materials.
I used three building profiles to create the building geometry. In a different class, we are currently modeling an energy efficient office building that is to only have 4 sides, and I wanted to do something similar to the study I am conducting for that project, but with some to the building height and number of sides.
Design Variables: As variable inputs I decided to use the building height (in ft), material costs (in $/ft2), internal HVAC systems costs (in $/ft2), and labor costs (in $/ft2).
Constants: I used building volume (in ft3), time to construct one foot in elevation of a building (in hour / ft), and the number of sides the building has as constants.
Evaluators:
I extracted the building wall area, roof afea, and ground area using the code block provided in the example.
For my evaluators I decided to have total building cost, total internal system costs, total internal system implementation costs, and time taken to construct a building as my evaluators as originally stated in my design idea.
Step 3 - Generative Design Study Results
For the generative design study, I decided to implement realistic variable inputs into the design options.
For the building height, I based the range of values off of the energy efficient building design I am working on for a different class. The total height range should be no more than 60 feet or less than 30 feet for the design.
For material costs, I researched the typical costs of materials in $/ft2 for steel, wood, and concrete buildings. I found that concrete will be in the $90-$100 per ft2 range, wood is in the $15-$30 per ft2 range, and steel is in the $15-$25 range. For this analysis, I just used the minimum material cost and the maximum material costs as the range for the material costs because these values can also vary by geographic location, supply chain availability, and many other factors. A more sophisticated study would require more in depth research of material costs for a given location. I used these sources to help determine these ranges:
Concrete costs:
For internal system material cost, I researched the typical costs of a VAV and a radiant system in $/ft2. I found that the VAV system will be in the $25-$45 per ft2 range and a radiant system is in the $6-$20 per ft2 range. For this analysis, I just used the minimum and the maximum costs as the range for the internal system costs because these values can also vary by geographic location, supply chain availability, labor availability, and other factors. A more sophisticated study would require more in depth research of internal system costs for a given location. I used these sources to help determine these ranges:
VAV System Material Costs: https://cdn.ymaws.com/www.aspenational.org/resource/resmgr/Techical_Papers/2014_July_TP.pdf
Radiant System Material Costs: https://www.forbes.com/advisor/home-improvement/radiant-heating-floor-cost/#:~:text=Hydronic or water-based radiant,%245 a day to run
For labor costs, I researched the typical costs of constructing a VAV system and a radiant system $/ft2. I found that a VAV system will typically cost $4-$8 per ft2 and radiant system labor costs $8-$12 per ft2. For this analysis, I just used the minimum cost and the maximum costs as the range because these values can also vary by geographic location and many other factors. A more sophisticated study would require more in depth research of material costs for a given location. I used these sources to help determine these ranges:
Radiant System Labor Costs: https://www.bobvila.com/articles/radiant-floor-heating-cost/
* One limitation of this generative design analysis framework is the exact certainty in the price of products. If this project were actually for a client, then it would be necessary to know the exact numbers.
Generative Design Results:
Here is the Parallel Coordinates Graph of my four inputs and outputs:
One tradeoff that I studied was the time to construct the building and the overall material cost. There are some cases where the building material cost increases, but the time to construct the building is the same (with the assumption that constructing a wood, steel, or concrete building would take the same amount of time). This is shown through the scatterplot where the multiple points along horizontal lines indicate that the material cost is increasing, but the time to construct the building is staying the same. In this case, I would choose the steel building because it takes the same amount of time to complete with a lower cost (when no other factors are considered):
Though it wasn’t required, another tradeoff that I studied was the labor costs versus the internal system cost. In this case there seems to be a somewhat linear correlation between costs of internal systems versus the labor costs. Realistically, this consideration would need even more variables such as the labor availability to construct the appropriate internal system.
Lastly, here is the completed image of the Dynamo Study Graph:
Image of my design:
