Green Buildings -- Learning to Count

Transcription

1 Green Buildings -- Learning to Count Dr John F. Straube Assistant Professor Dept of Civil Engineering & School of Architecture University of Waterloo Ontario, Canada Sustainable development is development that meets the needs of the present without compromising the ability of future generations to meet their own needs Our Common Future (Brundtland Report) United Nations, 1987.

2 UIA/AIA Declaration 1993 We commit ourselves as members of the world s architectural and building-design professions, to Place environmental and social sustainability at the core of our practices and professional responsibilities Overview of Presentation Definitions and Semantics Product and Process Goals and Strategies

3 Buildings Provide space for human use & occupancy Usually control the interior environment 1. By passive means e.g. caves (the enclosure) 2. By active means e.g., fire (services, HVAC) Buildings Buildings are a major part of a countries infrastructure physical - 90% of our time indoors, 80% urban economic - worldwide 3.4 trillion USD/yr US Commercial real estate replacement: 21 trillion US annual construction 850 Billion social - we meet, work, sleep, eat in them!

4 Buildings Buildings also part of the environment Consume matter and energy Pollute, displace and provide habitats A durable good Running shoe (1 yr), car (10 yr), bldg (100yr?) Requires more careful long-term design (hence gov t society involvement) A Small Problem... Buildings consume 35-50% of total world energy in production and use Buildings consume 40+% of physical resources Collections of Buildings (cities) and connections between buildings (roads) consume land they displace natural systems change solar and rainwater absorption

5 Population Growth 10 Expect 50% (3 billion) increase in next 50 yrs Billions Consumption Growth Increasing affluence means increased consumption e.g., Chinese per capita GDP growing by 6-10%/yr bigger houses, more appliances, cars replace labour maintenance with materials/energy American house 1950: 2000: 400 sf/person or 1600 sf/house (4 people) 750 sf/person or 2400 sf/house (3.2 people) 1 in 6 new US homes have a 3 car garage Germans 400 sf/person Boat <100 s/person

6 Impact Impact = consumption population damage reduce each! Impact = Population consumption damage 1900 Year 2000 Depletion: Energy Ecological Damage

7 Production of Pollutants and Toxins Resource Extraction Green Buildings Recognize buildings have an impact Minimize or eliminate: non-renewable resource use non-renewable energy consumption damage to the local and global ecology production of waste and pollutants

8 Good Buildings Are... Functional meet the program of today s and future occupants Healthy few chemicals given off, no mould, fresh air Durable so that they can be used for a long time Adaptable for many uses so they can be re-used easily Energy & Resource efficient in operation and in construction Capital Efficient to allow investment on other uses Non-polluting in operation and production Good Buildings Are Green No magic material, widget A holistic approach is required Trade-offs, compromises Optimal design requires a broad understanding: people and their behaviour city planning transportation ecology appliances materials & production building science & technology

9 The Future Paradigm shift from least evil to as much good Buildings must eventually Produce energy Clean air and water Enhance local ecology, provide habitat Reuse materials, low-energy recycle Sun Local Building System Operation The Building Enclosure HVAC Energy Resources Pollutants Pollutants, Waste, Energy Activity Energy Pollutants Resources (Waste?) Pollutants: Moisture, odour, dust, sewage, + +

10 Conception why? fill a need Design define what Construction how to build Building Lifecycle Operation Maintenance & Repair Owner s and Operators Manual Conversion Reuse Demolition & Recyling of materials/sub-systems Life Cycle & Environment Upstream Interactions Extract Process Assembly Use Reuse Recycle 1st level 2nd level

11 Durability Physical durability weather and exposure maintance and repair Functional durability fitness for use, changing needs and standards Economic durability e.g, Las Vegas hotels, multi-storey factories, downtown land values Social durability aesthetic, etc. Building Science Physical Durability Deterioration Slow Deterioration Maintenance Coversion or Upgrade Repair Bad Repair Neglect

12 Performance Deterioration Premature deterioration requires energy and resources to repair Poorly built or non-durable buildings are not green Must understand deterioration mechanisms to design against Do not squander resources to avoid deterioration - optimal design Required for physical + functional durability Large expense consumes material, energy, time, money e.g., Golden Gate Bridge: US$ per year Life-cycle analysis req d

13 Maintenance and Repair Maintenance, Repair, & Replacement - plan for: window weather stripping EIFS cladding and sealants window IGU, hardware etc. stucco vs underlying sheathing roof membranes vs structure Design Life should be specified for each component design for maintenance repair and replacement Functional Durability Future uses? Changes? Office to Condo Warehouse to Office/Gallery/Retail Factory to Retail/Residential in 10 years? In 100? Promote functional durability by Structural Flexibility Movable interior partitions Upgradable Services Replaceable / Upgradeable Building Envelope

14 Social & Economic Durability Economic and social durability enhanced by physical and functional durability Process

15 Process Decide on shared goal with client Define green, local, natural, toxic, etc. Choose strategies to achieve goals Develop metrics Design Choose Predict & measure performance Modify design and consider alternates iterate! Measuring Green Building Precision is difficult relative impact of choices is more important than absolutes Basic strategies can be used (BREAM, LEED) Count resources used in construction and maintenance energy used for operation Don t miss the forest for the trees Examples: a 6000 sq ft strawbale house likely no better than a 2000 sq ft smart wood frame home foam plastic may save enough energy to be a good choice

16 Measuring Green Building Resource Use - in construction and operation Depletion of limited resources Renewable? Recyclable Energy Use - in construction and operation Embodied in materials and construction Operational Ecological Damage Pollutant Production Habitat destruction Strategies

17 Strategies Conserve/Reduce Material Choices Energy Efficiency Daylighting Natural Ventilation Green Roofs Renewable Energy Technologies Water collection Water treatment Conserve / Reduce Less resource and energy use always better Don t build! Build small Avoid use of unnecessary material E.g. Good building enclosures (insulated, airtight, solar control) reduces NEED for conditioning energy, ducts, pumps, fans, furnaces, money, etc.

18 Energy Efficiency Not an end to itself! EE is not good but reducing non-renewable total energy consumption is Reduce energy use is best first approach Do not expend many resources to achieve 50% energy reduction of 1% of total when 20% reduction of 30% of total is easier Good EE requires predictions/models of energy use system-wide analysis of alternate choices Exergy, e.g., electricity or natural gas? Curtainwalls Slide 36

19 Curtain Walls/Windows Available: krypton gas fill quad glazing (to R7) super spacers thermally broken is not enough - specify total system U-value R= 2-4 Thermal break - a must Lots of glass

20 Thermal Bridging Thermal bridging: heat flow Cold Exterior Siding Sheathing Batt + Framing Drywall Simple R-value Thru Cavity Clear Wall R-value Warm Interior Corner Window Opening Material Choices Local to avoid transportation and unintended consequences to promote local economy and interdependence Renewable (or Plentiful) avoid resource depletion Low Habitat Destruction Low Embodied Energy non-renewable energy Low Embodied Pollution including some measure of quantity and quality Reusable or Recyclable to minimize need for future production

21 Material Choices - 2 MUST consider system impact not just material E.g. Wood/Steel/Concrete/Masonry Does the material perform many functions (e.g., masonry is a structure, a finish, and enclosure) Does the material require finishes How much waste is produced? From how far is it transported? Bookshelf as wall divider Daylighting & Natural ventilation Polished Concrete floor Unworked wooden posts rye grass board and glass-cement counters

22 Material Choices -3 Embodied energy can be large Transportation is often small part Operating energy usually larger! Embodied to operating ratio in the range of 5 to 15 years E.g. Adobe Renewable and Local, but Green?

23 Strawbale Only walls Natural Ventilation Reduces fan energy to move outdoor air indoors Make use of stack effect and wind to provide fresh air

24 Naturally Ventilated Buildings Natural Ventilation Cooling Can reduce need for cooling by flushing heat when combined with thermal storage Cannot control humidity Works for cooling in climates with low humidity or low peak temps What to do in Toronto? Hot humid days cant be solved with ventilation Difficult to A/C and ventilate outdoor air!

25 Air Temp Dewpoint Temp 33% of summer hours above 22 C # of hours/july Temperature

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27 You can t ventilate big buildings 1916, 36 floors m 2 Spin off Benefits Daylighting and better indoor air quality (IAQ) increases productivity, sales, morale Better HVAC (e.g., 100% fresh air) = better IAQ Less noise and drafts from over-taxed cooling systems More tolerant to power failures Passive energy (PV, wind, solar) is diffuse, so lower loads = viability

28 Other Ways to Keep Heat Out Provide deciduous planting (on walls, roof?) Well insulated roof, especially on low rise consider light coloured roofs Orientation! West/East is BAD for windows Allow natural ventilation in swing seasons Airtight during summer (high RH) /winter Renewable Energy Tech Not without environmental damage Biomass Methane Alcohol Firewood Hydropower Wind Photovoltaics Solar Thermal

29 Passive Solar Design South-facing glazing tuned to heating need Provide thermal mass to store heat overnight Avoid west-facing over heating Most solar buildings are over-glazed and underinsulated Solar Gains - July N Solar Gain (W/m North Wall East Wall South Wall West Wall Roof Hour of the Day

30 Solar Gains - Jan 45 N West Wall 600 Roof 500 Mother 400 Nature is try to tell you something Solar Gain (W/m2 900 North Wall 800 East Wall 700 South Wall Hour of the Day Not Renewable Fuel Cells Electric Cars Geothermal heat pumps These may be more efficient but they are not renewable

31 Daylighting Replace electrical lighting with daylighting Beware excessive glare and solar gains Has major benefits of improved productivity and occupant satisfaction Real Good Main Store and Office

32 Daylighting

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34 Control glare! The role of active systems Heating, Ventilating, and Air Condition equipment Must understand the whole system to do the job Must use systems engineering to optimize the system, NOT the component Requires interaction between architect, lighting, enclosure, and structural engineer, etc

35 Sun The Local Building System The Building Enclosure Energy Resources Pollutants Active HVAC systems make up for imperfect Pollutants, passive Waste, Energy systems, Energy they do not replace them Activity Pollutants Resources (Waste?) Pollutants: Moisture, odour, dust, sewage, + + Functions of Mechanical Heating and cooling remove heat when there is too much add heat when there is too little Ventilating fresh air provided, stale air removed air conditioning add or remove humidity filter airborne pollutants Plumbing water supply and waste removal

36 Loads for Commercial Bldgs Cooling can dominate, EVEN in Vermont Sun is usually the largest load Lights - 15 to 25+ W/m 2 (5 possible) all this heat must be removed by HVAC People W each. This conference room Ventilation (use heat/enthalpy recovery) fresh air must be conditioned for moisture/temp Equipment W/m 2? computers, copiers, fax, etc Office / Institutional Space 30 ft = 10 m 8 ft 2.5 m 30 ft =10 m Bungalow Surface Area= 1860 ft m 2 Floor Area= 900 ft m 2 Volume= 7200 ft m 3 FA:SA= 0.5 V : SA = 3.9 ft 10 storey 11 m - 36 ft depth 80 ft= 25 m 110 ft =35 m 80 ft =25 m Office Surface Area=41600 ft 2 =3125 m 2 Floor Area= ft 2 =6250 m 2 Volume = ft 2 =21875 m 3 FA:SA= 1.5 V : SA = 17 ft

37 Office / Institutional Space 20 ft 6 m 2 storeys 200 ft = 60 m 70 ft =20 m Bungalow Surface Area = ft 2 = m 2 Floor Area = ft 2 = 2 400m 2 Volume = ft 3 = m 3 FA:SA= 1.1 V : SA = 11.3 ft Floor Area: Enclosure Area High ratio (simple shape, large building) load dominated cooling often the major energy user Low ratio (small building, complex shape) enclosure dominated heating may be important if poor insulation Depending on occupancy ventilation may be the biggest energy user e.g. classrooms, conference rooms

38 Internal Gains Large office spaces have large internal gains and small enclosure area (FA:SA = large) Result : If well insulated - no heating required when in use, just at night (or use store w/mass) Not many losses from building cores Hence, we cool and heat at the same time! What to do: Large Bldg Insulated/airtight enclosure to make interior surfaces warm keep core/perimeter at same temp avoid/minimize heating needs Control internal gains reduce cooling reduce energy costs <R15, no thermal bridges

39 Controlling Heat Loss Highly insulated airtight enclosure = more comfortable eliminate perimeter heating & separate system reduce heating energy cost minimize condensation more money to passive enclosure, less to active equipment Design Space Heating Load (W/m 2 ) Reducing Uglaz=2.0 Design Heating Load based on outdoor R2.8 temperature need of -20 C, and for average of heating 10 m R4.3 Uglaz=1.3 R7.0 Uglaz=0.8 1/4 Lighting Load Power Level distance from enclosure to center of building 4 F and 35 ft deep Better glazing = less need for perimeter heating 0 0% 25% 50% 75% 100% Percentage of Vertical Enclosure that is Glazing

40 Saving Energy, Resources, $ Reduce loads! Save operating costs and Reduce need for cooling Improve equipment efficiency pumps, fans, chillers costs more, but smaller equip required Choose the right size equipment for building requires careful analysis hour-by-hour computer modelling almost mandatory The System Cascade E.g., reduce lighting so cooling is reduced, so chiller, fans, and ducts are reduced, so smaller plenum space floor to floor and reduced square footage so you save lots of money and energy! Now repeat for enclosure, equipment, ventilation loads. Individual cost benefit may not be positive, but system benefit is!

41 How to reduce loads? Use efficient or no lighting use daylighting and occupancy controls Use top quality building enclosure minimize heat loss/gain stop air leakage control solar heat and light (spectrally selective) Use efficient equipment printers, computers, fans, pumps, faxes, etc. Sun is biggest and easiest load to control use it for heating, avoid it for cooling Solar Gains - July N Solar Gain (W/m North Wall East Wall South Wall West Wall Roof Hour of the Day

42 Solar Gains - Jan 45 N West Wall 600 Roof 500 Mother 400 Nature is try to tell you something Solar Gain (W/m2 900 North Wall 800 East Wall 700 South Wall Hour of the Day Shade it now or shade it later

43 Solutions? Exterior shades Reflective and/or tinted glazing Spectrally selective coatings Opaque walls! Use Exterior Shade

44 Interior or Exterior Shade Less Glazing Area & Solar Glazing

45 Other Ways to Keep Heat Out Provide deciduous planting (on walls, roof?) Well insulated roof, especially on low rise consider light coloured roofs Orientation! West/East is BAD for windows Allow natural ventilation when cool (evening, spring and fall) Airtight during summer (high RH) /winter The Energy Efficient Office Tightly controls solar and internal gain reduce size of chiller and ducts, fans, pumps Reduces heat loss with high insulation levels reduce boiler, avoid perimeter heat Is very airtight -- but provides plenty of fresh air control air quality Controls light levels based on sun / occupancy uses daylighting - saves energy, improves comfort Uses heat and enthalpy recovery on fresh air don t throw away what you bought

46 The Future Sustainable Office Practical Implementation example: Limits glazing area to less than 50% of exterior High R-value glazing system -- U < 1.0 W/m 2 /C (R>5) Employs shading devices or low SHGC (<0.30) glass Dimmable, controlled fluorescent lighting 100% Outdoor supply air with ERV & dehumidification Radiant cooling panels remove sensible heat Optimal thermal mass Embodied energy analysis of alternate designs minimum aluminum, plastics, stainless, steel, etc. Off-gasing budget Green on the Grand E.g., Vermont Law School

47 Spin off Benefits Daylighting and better indoor air quality (IAQ) increases productivity, sales, morale Better HVAC (e.g., 100% fresh air) = better IAQ Less noise and drafts from over-taxed cooling systems More tolerant to power failures Passive energy (PV, wind, solar) is diffuse, so lower loads = viability What to do: Smaller Bldg Insulated/airtight enclosure to make interior surfaces warm keep core/perimeter at same temp reduce heating needs Capture solar gains in winter Avoid Cooling in summer mass, shade, night ventilation

48 Smaller Bldgs min R25 walls, R60 attics, R4 windows avoid thermal bridges South facing windows Shade on south, few west Some mass is useful for night cooling Slide 95 Conclusions More efficiency requires more informed, better systems approach reduce loads (improve enclosure) use cascades beware cooling loads in large buildings Understand System R-value beware thermal bridges Control air leakage Insulated sheathing is an moisture control strategy Inspect and building right