minnesota sustainable housing initiative

Minnesota Sustainable Housing Initiative 1

MINNESOTA SUSTAINABLE HOUSING INITIATIVEInforming Healthy, Durable, and Energy and Resources Efficient Homes

www.mnshi.umn.edu

Regents of the University of Minnesota, Twin Cities Campus. All Rights Reserved.

Site Optimization Tool - IntroductionWhy use this tool:The most cost-effective and impactful time to improve energy efficiency and overall project performance comes at the earliest stages of a building’s design - before building orientation, massing, and a site plan have been determined. As design work progresses, opportunities to improve performance decrease, while the costs of achieving set perfor-mance goals increase. Thus, to achieve maximum energy efficiency and project performance with minimal costs, planning is critical from the earliest moments of project design.

ConceptualDesign

SchematicDesign

DesignDevelopment

ConstructionDocuments

ConstructionManagement

Commissioning

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Site Selection

When to use this tool:This tool is designed for use at the beginning of the conceptual design phase - after a site has been selected, but before work on a site plan and building design begin. The tool highlights issues such as building orientation, mass-ing, shading, and site design that have large consequences for energy efficiency and stormwater control. By bringing these issues to mind, the tool will help guide the development team towards solutions that optimize building perfor-mance for a given site.

How to use this tool:Since this tool is used during the earliest stages of design, it is assumed that multiple design options will be tested. For this reason, the tool should be quick and relatively easy to use. Ideally, each option should be evaluated in a half an hour or less. Estimates and rough sketches are ok. However, some preparation time should be spent using overhead site photography combined with a site visit or Google Street View to help identify the heights and locations of shading objects on the site, for example. Good quality overhead photography can be found for free on the web at http://maps.google.com/ and http://www.bing.com/maps/

Users should progress through the tool’s pages sequentially. Pages are arranged around a few key issues including building orientation, passive solar heating, solar shading, stormwater runoff, and site density. In many cases, a rough sketch of the proposed building design or site plan is required, which can then be compared to rated examples or tar-gets shown on the same or following page. More detailed instructions are found on each page.

Additional resources: Additional information supporting the design guidelines used in this tool is available on the web at www.mnshi.umn.edu. An illustrated example of the use of this tool is also available to download as a separate document.

Source: Advanced Buildings Benefits GuideTIME

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Solar Access and EnergyBuilding Shading

Site Optimization Tool, v 1.0

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GOODPoints: 2

VERY BADPoints: -1

BADPoints: 0

OKAYPoints: 1

Goal: Orient the building to maximize southern exposure while minimizing eastern/western exposures.

Use the accompanying diagrams as a guide to orient and shape the building(s).

Ideally, the building’s east/west axis should be 1.5x longer than the north/south axis to maximize southern exposure and minimize eastern/western exposures. In addition, the building should be oriented along the cardinal directions, if possible.

After completing the sketch below, select the diagram that most closely matches the planned building(s).

Points:

Sketch 1 - Using a plan view, sketch the site from above showing the building orientation.

4Minnesota Sustainable Housing InitiativeSite Optimization Tool, v 1.0

Solar Access and EnergyBuilding Shading - South

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BUILDING SHADING - Plan viewDiagram 1

limit shading obstructions

The area directly to the south of the building should be free of shading obstructions within 60 degrees of due south from both south corners of the building as shown by the orange zone in diagram 1.

The following sketching exercises will help identify objects that cast shade on the south facade of the building during the winter.

Sketch 2 - Using a plan view, sketch the site from above and identify obstructions that lie within the orange zone shown in diagram 1. These objects may cast shade on the south facade of the building.

Sketch 3 - Using a section view, sketch the site from the side showing obstructions on the south side of the building. Estimate the height of these obstructions and their distance from the building.

If obstructions are present in the orange zone referenced above, their height should remain below the orange line shown in diagram 2, sloped at 22 degrees from the horizontal. For every 1 foot of height, 2.5 feet of horizon-tal distance from the south facade of the building is required to prevent shading at low winter sun angles.

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BUILDING SHADING - N/S sectionDiagram 2

limit shading

Goal: Site the building to minimize shade on the south facade during the winter to increase passive solar heat gain.

distance to shading object > 2.5 x h

(or)

height of shading object, h < distance to shading object2.5


Solar Access and Energy


Building Shading - South (continued)

Using the sketches from the previous page, select the diagram below that most closely matches the planned building(s).

Shading obstructions at the far corners of the orange plane are preferable to obstructions centered directly in front of the planned building. It may be possible to reduce shading by elevating the planned building, sliding it farther east or west on the site, or using a setback to increase the distance between the building and shading objects across the street. Use the diagrams as a guide to site the building and plan landscaping.

BADPoints: 0

OKAYPoints: 1

GOODPoints: 2

6Minnesota Sustainable Housing InitiativeSite Optimization Tool, v 1.0

Solar Access and EnergyBuilding Shading - East / West

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BUILDING SHADING - E/W SECTIONThe areas to the east and west of the building should provide obstructions that shade the east and west facades. If possible, the shading object(s) should be as tall or taller than the orange line shown in the diagram to the right to provide adequate shad-ing at high sun angles during the summer months. A vertical height equal to the height of the building, Bh plus the horizontal distance, w to the shading object is ideal.

The following sketching exercises will help identify objects that cast shade on the east and west facades of the building during the summer.

Sketch 4 - Using a section view, sketch the site from the side showing shading objects to the east and west of the building. Estimate the height of these objects and their distance from the building.

Goal: Site the building to maximize shade on the east/west facades during the summer to reduce unwanted solar heat gain.

ideal height of shading object, h = Bh + w


Solar Access and Energy


Building Shading - East / West (continued)

Using the sketch from the previous page, select the diagram below that most closely matches the planned building(s).

Tall shading objects that are relatively close to the planned building(s) are more desirable than short objects located a farther distance away. Ideally, shading objects will be as tall or taller than the orange plane shown below. Use the accompanying diagrams as a guide to site the building and plan landscaping.

BADPoints: 0

OKAYPoints: 1

GOODPoints: 2

8Site Optimization Tool, v 1.0 Minnesota Sustainable Housing Initiative

Stormwater Runoff and Quality

Goal: Develop a site plan that provides adequate area to infiltrate stormwater runoff from impermeable surfaces.

1 : 3 Rule. For every 3 square feet of impermeable surface (rooftop, parking lot, sidewalk, etc) provide 1 square foot of per-meable site area, designed to infiltrate or retain stormwater.

If impermeable surfaces are designed to reduce runoff (such as green roofs, permeable pavers, etc), less infiltration area is required.

Remember to locate infiltration areas downslope from imperme-able surfaces.

After completing the sketch below, determine the ratio of infiltra-tion area to impermeable area and compare to the 1:3 rule.

Ratio:

Sketch 5 - Using a plan view, sketch the site from above. Use a grid or take-offs to estimate the areas of all impermeable surfaces and areas de-signed to infiltrate/retain stormwater.

example site plan from www.landscapeonline.com

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Density and Open Space

Minnesota Sustainable Housing Initiative

Goal: Develop a site plan that meets or exceeds density targets while providing high-quality open space useable by residents.

In urban areas, achieve at least 10 d.u. per acre (mandatory Green Communities density) or 15 d.u. per acre for additional credit.

In suburban areas, achieve at least 7 d.u. per acre (mandatory Green Communities density) or 10 d.u. per acre for additional credit.

In rural areas, achieve at least 5 d.u. per acre for detached or semi-detached housing, 10 d.u. per acre for townhomes, and 15 d.u. per acre for apartments (mandatory Green Communi-ties density) or 7.5 d.u. per acre for detached or semi-detached housing, 12 d.u. per acre for townhomes and 20 d.u. per acre for apartments for additional credit.

Set aside at least 20% of the total project acreage as useable open space for residents. If possible, some of this open space should serve multiple functions, such as providing stormwater control.

Projects located within a surrounding Green Communi-ties residential density of 7 d.u. per acre or more qualify as Urban (see pg. 24, 2011 Enterprise Green Communi-ties Criteria).

Projects located within a surrounding Green Communi-ties residential density of less than 7 d.u. per acre qualify as Suburban (see pg. 24, 2011 Enterprise Green Com-munities Criteria).

See page 25 of the 2011 Enterprise Green Communities Criteria for the definition of Rural areas.

* Follow instructions on pages 24-26 of the 2011 Green Communities Criteria to calculate surrounding residential density. Essentially, Green Communities residential density = CNT residential density index x 1.5

CNT residential density index can be calculated at http://htaindex.cnt.org/residential-density.php

Fill out the following chart and compare planned density with Green Communities Criteria.

Surrounding Green Communities residential density* =

Green Communities Neighborhood Classification:

Green Communities Target Density:

Planned number of dwelling units

Site area (acres)

Site density (d.u./acre)

Meets G.C. Criteria (yes/no)

option 1

option 2

option 3