performance based design: executing the...

Copyright ©2013 Sefaira Ltd.

How to leverage performance analysis to refine, optimize, and keep designs on track

in the later stages of design.

PERFORMANCE BASED DESIGN: EXECUTING THE VISION

Copyright ©2013 Sefaira Ltd. PERFORMANCE BASED DESIGN: EXECUTING THE VISION

SUSTAINABLE DESIGN BRIEF

Performance Based Design: Design Development & Documentation

Performance Based Design is an approach in which performance analysis

is used to inform design, rather than in its traditional role as a validation

tool. Appropriate analysis can be used to answer relevant questions at

every stage of design—providing the design team the information they

need to address performance in a creative, flexible way.

Having set the design on good footing by leveraging analysis in the early

stages of design (see the earlier Sustainable Design Briefs in this series),

the design team can continue to optimize and improve the design through

design development and technical documentation.

In these stages architects can use performance analysis to (1) refine

and optimize key sustainable strategies such as shading, insulation,

and glazing properties, (2) investigate the potential contributions of

renewable energy, and (3) study the effects of proposed design changes.

This design brief uses a multi-family residence in Denver, Colorado to

illustrate these investigations.

This is the third installment of a three-part series on how to leverage performance analysis to drive decisions at each stage of the design process.

Preparation / Pre-Design

Concept / Schematic

Design

DesignDevelopment

Technical DesignDocuments

Proposal / Bid

3


Optimize Passive Strategies

In the previous Sustainable Design Brief, we showed how designers could find combinations of passive design strategies that could deliver breakthrough performance. With the basic building design now defined, the design team can begin to fine-tune these strategies. Advanced parametric analysis can be used to find optimal values for elements like shading, insulation levels, reflectance, and glazing properties. These properties can be used to inform wall sections, details, and specifica-tions, as well as providing inputs into BIM models.

Sizing these strategies appropriately can improve a project’s bottom line. For instance, finding the right length for shading devices can prevent the design team from over-sizing these devices—an error that would increase capital cost as well as operational cost.

For our design, we used Sefaira’s Response Curves to study the behavior of glazing solar heat gain coefficient (SHGC) or g-value, shading, and insulation levels. We found the following:

• Shading: We were able to find an optimal shading specification for each facade: 2-ft (0.6m) horizontal shades on the south facade, and 1-ft (0.3m) vertical fins on the east and west facades. Using these parameters as a guide, we modeled a number of custom variations to find the most effective design that achieved both performance and aesthetic goals.

• Glazing Solar Heat Gain: When combined with shading, we found that standard double-glazing was optimal for our building. This prevented us from accidentally making the glazing “too good”—in this case, additional reflectivity would actually increase total energy use by keeping out beneficial solar gain in winter months.

• Wall R-Value (U-Factor): Insulation values exhibited diminishing returns. We were able to use these results, in combination with cost estimates, to determine the most appropriate insulation levels for our project so we could achieve the best performance for the least cost.

Because each of these factors is interrelated, changes in one part of the design are likely to have impacts elsewhere. Therefore, we will continue to perform this type of analysis as the design continues to evolve.

Fig. 1. Parametric analysis can be used to fine-tune sustainable strategies.

SHADING

SOLAR HEAT GAIN COEFFICIENT (OR “G-VALUE”)

WALL INSULATION

4


Study Renewable Energy

Performance analysis can help the design team evaluate which types of renewable energy sources are worth pursuing, and determine the fraction of total energy use that renewables may be able to supply. This type of analysis can also help to build a case for passive design strategies or efficiency measures, because such measures make it easier to supply a greater portion of energy from on-site renewables.

For instance, our example project had a goal of supplying at least 10% of the required energy with on-site renewables. We studied the impact of building-integrated pho-tovoltaics for both a baseline case and a “high performance” case, which included a number of passive strategies that together reduced annual energy use by 45%.

We were able to meet the 10% goal for the baseline case if we covered nearly the entire roof with high-efficiency photovoltaic panels. For the “high performance” case, we found we could achieve the same goal with half as many solar panels.

Fig. 2. The “High Performance Construction” option made it possible to achieve the goal of 10% on-site renewable energy generation with roughly half the number of solar panels as the baseline case.

5


Study the Impact of Design Changes

As the design moves through Design Development and Technical Documentation, design changes inevitably arise. These may come from client requests, coordination with consultants, value engineering exercises, or a myriad of other sources. Architects can use performance analysis to quickly evaluate the impact of these changes. This can result in clearer communication, faster decision-making, and a better understanding of trade-offs that result from changes.

For example, say we are considering removing the shading devices from our design for cost reasons. We analyzed the building with shading removed, and found that annual energy use increased by 4% and peak cooling load increased by 31%. The additional cooling loads would require a larger mechanical system, with its attendant costs and required rework. We also explored a second alternative: removing shading, but improving the glazing specifications to reduce solar gain. Our analysis showed that this option still meant a 10% increase in peak cooling and 3% increase in energy use. When combined with cost estimates, these results painted a clear picture of the available options and allowed a decision to be made quickly and efficiently. In this case, removing shading resulted in less than 1% savings on con-struction cost (because of the increased cost of mechanical systems); and substituting high-performance windows actually increased construction cost. After evaluating the trade-offs, the client decided to keep the original design.

This type of rapid feedback can save time, reduce performance-related rework, and lead to a more satisfying experi-ence for both the design team and their client.Energy Use

2,202,964 kBTU 23 kBTU/ft2Water Use

1,152,214 gal 18 gal/personCO2 Use

749,607 lbsCO2 4,164 lbsCO2/person

High Performance Envelope

Massing: Massing 1

Energy Use

Energy Footprint (kBTU)

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

Month

0

50000

100000

150000

200000

250000

kBT

U

LightingCoolingHot WaterEquipmentHeating

Peak Space Heating Demand (ton)

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov DecMonth

0

10

20

30

40

ton

Peak Demand

Peak Space Cooling Demand (ton)


Month

0

20

40

60

80

ton

Annual Estimated Utility Bill

$1/ft2

Uses of Energy (kBTU)

Energy Use




No Shading

Massing: Massing 1

Energy Use



Month

0

50000

100000

150000

200000

250000

kBT

U




0

10

20

30

40

ton

Peak Demand



Month

0

20

40

60

80

ton


$1/ft2


Energy Use




No Shading + Improved SHGC

Massing: Massing 1

Energy Use



Month

0

50000

100000

150000

200000

250000

kBT

U




0

10

20

30

40

ton

Peak Demand



Month

0

20

40

60

80

ton


$1/ft2


Energy Use





Massing: Massing 1

Energy Use



Month

0

50000

100000

150000

200000

250000

kBT

U




0

10

20

30

40

ton

Peak Demand



Month

0

20

40

60

80

ton


$1/ft2


Energy Use




No Shading

Massing: Massing 1

Energy Use



Month

0

50000

100000

150000

200000

250000

kBT

U




0

10

20

30

40

ton

Peak Demand



Month

0

20

40

60

80

ton


$1/ft2


Energy Use





Massing: Massing 1

Energy Use



Month

0

50000

100000

150000

200000

250000

kBT

U




0

10

20

30

40

ton

Peak Demand



Month

0

20

40

60

80

ton


$1/ft2


Energy Use





Massing: Massing 1

Energy Use



Month

0

50000

100000

150000

200000

250000

kBT

U




0

10

20

30

40

ton

Peak Demand



Month

0

20

40

60

80

ton


$1/ft2


Energy Use




No Shading

Massing: Massing 1

Energy Use



Month

0

50000

100000

150000

200000

250000

kBT

U




0

10

20

30

40

ton

Peak Demand



Month

0

20

40

60

80

ton


$1/ft2


Energy Use





Massing: Massing 1

Energy Use



Month

0

50000

100000

150000

200000

250000

kBT

U




0

10

20

30

40

ton

Peak Demand



Month

0

20

40

60

80

ton


$1/ft2


Energy Use





Massing: Massing 1

Energy Use



Month

0

50000

100000

150000

200000

250000

kBT

U




0

10

20

30

40

ton

Peak Demand



Month

0

20

40

60

80

ton


$1/ft2


Energy Use




No Shading

Massing: Massing 1

Energy Use



Month

0

50000

100000

150000

200000

250000

kBT

U




0

10

20

30

40

ton

Peak Demand



Month

0

20

40

60

80

ton


$1/ft2


Energy Use





Massing: Massing 1

Energy Use



Month

0

50000

100000

150000

200000

250000

kBT

U




0

10

20

30

40

ton

Peak Demand



Month

0

20

40

60

80

ton


$1/ft2


Energy Use





Massing: Massing 1

Energy Use



Month

0

50000

100000

150000

200000

250000

kBT

U




0

10

20

30

40

ton

Peak Demand



Month

0

20

40

60

80

ton


$1/ft2


Energy Use




No Shading

Massing: Massing 1

Energy Use



Month

0

50000

100000

150000

200000

250000

kBT

U




0

10

20

30

40

ton

Peak Demand



Month

0

20

40

60

80

ton


$1/ft2


Energy Use





Massing: Massing 1

Energy Use



Month

0

50000

100000

150000

200000

250000

kBT

U




0

10

20

30

40

ton

Peak Demand



Month

0

20

40

60

80

ton


$1/ft2


Energy Use





Massing: Massing 1

Energy Use



Month

0

50000

100000

150000

200000

250000

kBT

U




0

10

20

30

40

ton

Peak Demand



Month

0

20

40

60

80

ton


$1/ft2


Energy Use




No Shading

Massing: Massing 1

Energy Use



Month

0

50000

100000

150000

200000

250000

kBT

U




0

10

20

30

40

ton

Peak Demand



Month

0

20

40

60

80

ton


$1/ft2


Energy Use





Massing: Massing 1

Energy Use



Month

0

50000

100000

150000

200000

250000

kBT

U




0

10

20

30

40

ton

Peak Demand



Month

0

20

40

60

80

ton


$1/ft2


BASE CASE(current design)

SHADING REMOVED IMPROVED GLAZING(instead of shading)

ANNUAL ENERGY CONSUMPTION

24 kBTU / ft2

ESTIMATED CONSTRUCTION COST

$20 million

PEAK COOLING DEMAND

61 tons


4%


<1%

PEAK COOLING DEMAND

31%


3%


2%

PEAK COOLING DEMAND

10%

Fig. 3. Quick comparisons can help the team understand the impacts of design changes and proposed alternatives.

6


How Sefaira Can Help

About Sefaira

Sefaira makes high-performance building analysis a seamless, integral part of the design process. Its Strategies and Bundles framework and powerful parametric analysis capabilities make it easy to do the types of comparisons and optimizations described above.

Sefaira allows architects to perform more analysis, more frequently, and at lower cost, helping to set projects on the right trajectory and ultimately delivering better-perform-ing, more sustainable buildings.

Sefaira was founded in 2009 with a mission to promote more sustainable buildings by helping the building industry design, build, operate, maintain and transform all facets of the built environment.

Sefaira’s proprietary cloud-based technology, built upon deep building physics exper-tise, offers an integrated approach to sustainable design analysis, knowledge manage-ment, and decision support. Sefaira helps designers analyze and compare sustainable building strategies for new build or retrofit projects in a fraction of the time and cost previously required.

Visit us online at www.sefaira.com

Sefaira allows architects to

perform more analysis, more

frequently, and at lower cost,

helping to set projects on the

right trajectory and ultimately

delivering better-performing,

more sustainable buildings.

linkedin.com/company/sefaira

twitter.com/sefaira