Cost estimation of curtain wall in early design stages

This note discusses only the cost that can be localized within a limited context. Global attributes such as type diversity and configuration complexity that might add on  cost in fabrication and installation are not included.

Consider three components,  the locking devices, supporting frames and panels. 

1. locking devices to the structure system
   Considering the entire facade as one piece, the locking devices that are required to firm the entire facade to the structure system are depend on the vertical loads caused by gravity and horizontal loads caused by wind pressure. For this, the cost estimation can be summarized as a function on the panel type and area of the curtain wall system. For each type of panel, consider its weight of unit area. However, this part of cost can be integrated to supporting frame and avoid double counting.
   
2. supporting frame
   Supporting frame is most likely coincident with the panel vertices and edges.  Edge length would be an important factor linearly related to the cost for material, fixation, seaming, insulation and so on. Panels are supported by the frames and the weight and wind load would be important factors to design profiles for the supporting frame. Vertices would add on some cost for cutting, joining or  locking devices that would take materials, machining and time for fabrication. The panel area and type would also contribute to the cost of supporting frame due to the weight and wind load. The construction cost of each panel can be linearly proportional to the edge length of each panel.
   
   I would consider summarizing the construction cost as a weighted linear sum of

   numberOfVertices

   totalEdgeLength

   panelSurfaceArea

   panelType: which is attributed with estimated weighting factors for the above parameters, and weight per unit area for the panel.

   The calculation also needs reference to windLoadContourMap , which is supposed to be derived by some simulation or regulations.

3. panel
   The panel type and surface area would be the most important factors. For each type of panels, the  cost of material, coating, paints, insulation, ... are proportional to area. Installation would takes one basic cost plus a part that is proportional to the weight and dimension. The dimension can be abbreviated with the sum of width and length for its bounding rectangle. Cost for fixation and seaming have been counted in the supporting frame and are ignored for panel. Wind load would add on some cost that is proportional to the surface area.
   
   I would consider summarizing the construction cost of each panel as a weighted linear sum of

   surfaceArea

   widthOfBoundingRectangle

   lengthOfBoundingRectangle

   panelType: , which is attributed with estimated weighting factors for the above parameters, and weight per unit area for the panel. The calculation also needs reference to windLoadcontourmap, which is supposed to be derived by some simulation or regulations.

Note for curtain wall

Facade curtain wall design

(for example: Given a 16 floor height building facade for curtain wall design. The structure frame has four 7.2m width spans with 3.6m for floor heights. )

A more general description for coding:

class Facade:
Mesh panelDissection
int[] panelTypes # -1 represent undecided
double[] panelInsulationLevel,
double[][] panelConstructionCostParameters
double[][] windLoadContourMap
double[][] solarRadiationContourMap)
DecisionTree dtree

def constructionCostEvaluation
def solarRadiationHeatGain

The architect needs to make decisions on the followings:

1. Dissections of the curtain wall
 The choices for vertical dissections are one, two or three divisions for each span between columns. (just for example, can be any mesh though)
 The choices for horizontal dissections are one, two or three divisions for each floor. (just for example, can be any mesh though)
 The facade can be represented as a Mesh, with faces as panels on the curtain wall, edges as the supporting frame and vertices as the joints.

2. For each panel, the architect need to make choices among types of panels.
 glazing with low E coating or regular
 metal panel with high insulation or regular insulation

Evaluation

1. Construction cost evaluation: a function of panel geometry
double facadeConstructionCost( Mesh facade,
int[] panelType,
double[][] panelConstructionCostParameters
double[][] windLoadContourMap)

 Construction cost of each panel depends on number of vertices, total edge length, surface area, and panel type.
 For panels that need to withstand high wind pressure, extra cost proportional to the panel area is applied to the original cost.
 A contour map on the estimated wind load is given. The wind load requirement for each panel is estimated with the surface integral of the wind load.

2. Energy consumption against solar radiation.
double facadeHeatGain( Mesh facade,
int[] panelType,
double[] panelInsulationLevel,
double[][] solarRadiationContourMap)

 Total score is graded as the amount of heat gained directly or indirectly from solar radiation.
 The insulation level of each type of panel is measured based on some experimental analysis.
 Given a contour map that shows intensity distribution of solar radiation on the facade based on some simulations.
 The head-gained of a panel is estimated as the product of its insulation level and the surface integral of solar radiation.
This is assuming the situation in the stage of conceptual design, when the architect has to decide the building mass with some concepts about the outlook. In most cases, building mass concerns site situations, urban code regulations and design objectives. The architect might come up with a few design alternatives for building mass, each of which would accommodate enough floor areas for required functional spaces and could be associated with some conceptual design schemes for the overall outlook of the building, probably illustrated with some sketches over the main facade or the entire building. The described setup starts at when the architect has decided the building mass and works on the elevations. When curtain wall has been chosen as one of the possible constructions for the part of the envelope, the architect might take her hands on decisions upon surface dissections and materials, for that would largely define how the building look like after constructed.
The architect may start to think about curtain wall dissections and materials with some knowledge regarding how building envelope may greatly affect the construction cost and energy consumption for the operation of the building. However, estimations on construction cost and energy consumption rely on surface material properties, distributions and quantities, which are unavailable until the design of building envelope system is completed.

MCTS
void mcts( List facades, 
List 
double[][] constructionCostParameters,
double[][] solarRadiationContourMap,
double[][] windLoadContourMap,
The objective is to find good facade designs that fulfill both construction cost and energy saving criteria. The search starts with a facade’s unfinished design as a mesh, with none or some panels assigned with panel types. The search process starts to do expansion, simulation and back propagation and continuously updates and shows the expected value of current partial design. The designer may run serval design alternatives at the same time. The designer may choose any of the design alternative to go on for more detail design, which is to assign some panels with some specific types. The process goes on until the designer finally choose types for every panels.