Green Roofs: From Concept to Reality Sarah Sutton, ASLA, LEED AP Design, Community & Environment

Transcription

1 Green Roofs: From Concept to Reality Sarah Sutton, ASLA, LEED AP Design, Community & Environment Santa Clara Valley Urban Runoff Pollution Prevention Program Annual C.3 Stormwater Workshop June 8, 2010

2 PRESENTATION OUTLINE Greenroof Overview Types, Benefits Getting Started Design Team and Parameters Basic Components Design Considerations and Tips Installation and Warranties

3 GREENROOF OVERVIEW Types of Greenroofs Source: Green Roofs for Healthy Cities, Green Roof Infrastructure: t Design and Install 201

4 GREENROOF OVERVIEW Types of Greenroofs Source: Green Roofs for Healthy Cities, Green Roof Infrastructure: t Design and Install 201

5 GREENROOF OVERVIEW Greenroof Benefits Reduces stormwater runoff Reduces energy consumption Reduces the urban heat island effect Beautifies the City Creates more natural green spaces in urban areas Provides more habitat area for wildlife including migratory birds

6 GETTING STARTED Assemble your design team: Architect Landscape Architect Structural t Engineer Mechanical Engineer Irrigation Designer Cost Estimator Civil Engineer (others) Accredited Green Roof Professional Critical to work with entire team at outset Roofing Consultant

7 GETTING STARTED Establish your goals: Stormwater management Insulation/energy conservation Aesthetics Maintenance Wildlife habitat Outdoor use area (Accessibility issues)

8 GETTING STARTED Assess the site and building: Structural loading must support dead load of assembly, saturated Sun/wind exposure Roof size, slope Penetrations vents, skylights Installation and maintenance access

9 BASIC COMPONENTS Waterproofing Root Barrier Drainage Growing Medium Plants

10 BASIC COMPONENTS Built up vs pre-assembled systems: Pre-assembled cost more but much easier to install and plants are wellestablished Built up may involve different trades coordination is critical Built up materials must be compatible

11 BASIC COMPONENTS Waterproofing Waterproofing membrane (not roofing membrane) Membrane vs liquid applied increase layers Types Bitumen, Thermoplastic, Elastomeric Water test Protect immediately after testing

12 BASIC COMPONENTS Root Barrier Protects membrane from wandering, probing roots Materials: Fiber reinforced concrete rat slab HDPE, TPO Polypropylene EPDM rubber Copper and herbicide embedded fabrics discouraged

13 BASIC COMPONENTS Drainage/Filtering Drains: Domed drain provides more surface area Place in veg-free zone Provide for inspection and debris catchment Redundancy, redundancy, redundancy!

14 BASIC COMPONENTS Drainage/Filtering Drainage Layer: Lightweight and pourous Can support layers above Composite systems with filter fabric Protect from UV degradation

15 BASIC COMPONENTS Growing Medium Lightweight and holds moisture Verify saturated weight limits and roof loading restrictions Mix of organic and inorganic shrinkage Can include: vermiculite, perlite, crushed lava rock, scoria, compost, sand Peat is discouraged

16 BASIC COMPONENTS Growing Medium Specify compaction rate Premix or mix on-site (pros/cons) Test samples before Test samples before installation

17 BASIC COMPONENTS Planting Limited by ygrowing g medium depth 4 6 : 6: sedums, grasses Veg free zone min 2x height of adjacent plants Avoid planting during hot season

18 BASIC COMPONENTS Planting white yarrow Idaho fescue blue-eyed eyed grass foothill needlegrass Sempervivum 'Purple Fuzzy' Sedum anopetalum white yarrow Sedum album

19 BASIC COMPONENTS Planting

20 BASIC COMPONENTS Planting Irrigation Systems Water supply usually from domestic building lines mechanical system provides stub-out Install back flow preventer at each POC Do not place directly on membrane Drip, inline systems vs overhead Moisture Sensors

21 DESIGN CONSIDERATIONS AND TIPS Drainage Slope roof 2% minimum (no flat roofs) Partition roof to isolate leaks Minimize penetrations Plan for overland flow Leak detection systems

22 DESIGN CONSIDERATIONS AND TIPS Flashings Membrane Base and Metal Extend membrane base flashing 8 minimum above green roof surface Metal counterflashing protects membrane Double seal all flashings and Double seal all flashings and penetrations

23 DESIGN CONSIDERATIONS AND TIPS Wind mitigation Fire Department concerns Maintenance safety harnesses and access paths Source: FM Global Property Loss Prevention Data Sheets

24 INSTALLATION AND WARRANTIES Pre-Construction Planning Pre-construction training for entire team Critical path for sequencing Qualified green roof inspector Staging of materials - Staging of materials beware of excess loading

25 INSTALLATION AND WARRANTIES Maintenance Varies with complexity, use, visibility, location First two years are critical 80% coverage = established Careful monitoring of irrigation Weeding - break life cycle Goats on the Roof Country Market, Coombs, BC

26 INSTALLATION AND WARRANTIES Maintenance Fertilization: Growing medium should have sufficient nutrients for at least1year Slow release, organic best Some plants require little or no fertilizer Test soil, observe plants before applying

27 INSTALLATION AND WARRANTIES Warranties Total System Warranties: Covers entire roof system Often include cost to R&R overburden Costs usually limited to % construction cost May cost more up front Can be restricted to specific waterproofing companies

28 INSTALLATION AND WARRANTIES Warranties Material Warranties: Covers R&R of failed membrane due to materials or workmanship Usually does not cover overburden Often restricted to area of leakage only

29 INSTALLATION AND WARRANTIES Warranties read the fine print Questions to ask: Scope of coverage? Length of coverage? Monetary limitations? Is it transferable? Exclusions? Inspections required? Wind speed limitations? Maintenance obligations? Notification obligations? Warranty reserve? Cost of warranty? Litigation limitations?

30 INSTALLATION AND WARRANTIES Warranties Typical obligations: Regular maintenance Payment for periodic inspections Timely notification of changes/alterations

31 INSTALLATION AND WARRANTIES Warranties Potential areas that may void a warranty: Concrete slabs poured over membrane Damage by other trades Chemical contamination Structural movement, settlement, failure Inadequate drainage or maintenance Changes in use or ownership of building

32 RESOURCES Green Roofs for Healthy Cities org/ FM Global Property Loss Prevention Data Sheets ASTM Green Roof Performance Standards

33 Green Roofs: From Concept to Reality Sarah Sutton, ASLA, LEED AP Design, Community & Environment Santa Clara Valley Urban Runoff Pollution Prevention Program Annual C.3 Stormwater Workshop June 8, 2010