Simulating Mixed-Mode Ventilation By Liam Buckley, IES Ltd.

Transcript

1. Liam Buckley ASHRAE Associate Member, M.Eng., C.Eng. MIEI, BEMP Liam.Buckley@iesve.com C: +1 617 840 6101
2. Agenda • Introduction to mixed-mode ventilation • When to implement MM-Ventilation • Codes & Standards • Strategies for Natural & MM-Ventilation • Case-studies (throughout) and lessons learnt
3. Room Mixed-mode Ventilation • What is MM-Ventilation? (Example) ZERO Air Supply CFM Air Extract FCU Recirculation
4. Why Integrate MMV Systems March 2012: “At least 21 commercial buildings in the United States meet net-zero standards, according to a study released yesterday by the New Buildings Institute and the Zero Energy Commercial Building Consortium.” Ref: http://www.scientificamerican.com/article.cfm?id=net-zero-energy-buildings-in-us 1. Reduce energy consumption (EUI), carbon emissions and operating costs of buildings:
5. Where are the ZEBs? Ref: http://newbuildings.org/sites/default/files/GettingtoZeroReport_0.pdf
6. What % were naturally ventilated? Ref: http://newbuildings.org/sites/default/files/GettingtoZeroReport_0.pdf ECMs Daylight HE Lighting HE Envelope Hi R-value Glazing Natural Ventilation HE HVAC Heat Recovery Cool Roof Radiant GSHP UFAD / Displment Energy Conservation Measures Load Reduction Strategies
7. 2. Green building certification (e.g. LEED …) • Optimize Energy Performance • Thermal Comfort • Increased Ventilation • Outdoor Air Delivery Monitoring • …… Why Integrate MMV Systems
8. 3. Improve thermal comfort for occupants Section 5.3 Optional Method for Determining Acceptable Thermal Comfort in Naturally Conditioned Spaces Why Integrate MMV Systems
9. 4. Improve ventilation/IAQ for occupants, and increase efficiency of building function (e.g. student performance in a school or patient recovery in healthcare). ASHRAE Standard 62.1 - Section 5.1 Natural Ventilation: Naturally ventilated spaces shall be permanently open to and within 8m (25 ft) of operable wall or roof openings to the outdoors. The opening area of which is a minimum of 4% of the net occupiable floor area. Where interior spaces without direct openings to the outdoors are ventilated through the adjoining rooms, the opening between rooms shall have a free area of 8% of the interior room, nor less than 25 sq.ft (2.3 m2). Why Integrate MMV Systems
10. When to Naturally (or MM) Ventilate • How many hours are there in one year? • Assume occupied hours 8am-6pm; Mon-Fri • Assumes no occupancy for national holidays
11. NV Potential in North America • Apply limits to 2490 hours annually: New York (TMY2) 26% (644 hours)
12. Actual Meteorological Weather
13. AMY TMY2 & AMY Weather Data TMY2 Moderate vs. Large diurnal range
14. Identify Opportunities
15. Question: • Which office has the highest heating load? ALL: NYC – Office – VE1-2M – 40% Glazing 1 2 3 4 5 6 7 8
16. Capture Dynamic Infiltration! • See www.IBPSA-Boston.com/events • ACPH, cfm, cfm/sf, cfm/sf-façade area • Dynamic Infiltration
17. Infiltration • Be careful with radiant systems ~ low max RH!
18. Codes & Standards • The Best: – CIBSE Applications Manual AM10 & AM13 – Natural Ventilation in non-domestic buildings Ref: www.cibse.org • The worst: – Paintshop! – Conceptually, ok.
19. CIBSE AM-10 • Driving forces of Natural ventilation • Stack Effect (buoyancy) • Wind
20. CIBSE AM-10 Ventilation Strategies • CIBSE AM-10 rules of thumb: • Single sided: W≤(2*H) • Single sided with double opening: W≤(2.5*H) • Cross ventilation: W≤(5*H)
21. Natural Ventilation Strategies 1. Single sided ventilation: W≤(2*H) • :
22. Natural Ventilation Strategies 2. Single sided ventilation 2 openings: W≤(2.5*H)
23. Natural Ventilation Strategies 3. Double sided ventilation: W≤(5*H)
24. MM/Natural Ventilation Strategies 4. What if double sided ventilation: W≥(5*H)? – i.e. ‘Deep-plan’ Building
25. MM/Natural Ventilation Strategies 4. Windcatchers
26. MM/Natural Ventilation Strategies
27. MM/Natural Ventilation Strategies 6. Atrium Design Office was awarded the highest ever BREEAM score of 87.55% when it opened in July 2007.
28. Ventilation Strategies – Atrium Design
29. Ventilation Strategies – Atrium Design Ref: http://www.riai.ie/uploads/files/AI249-Digital.pdf http://archrecord.construction.com/projects/Building_types_study/libraries/2011/westmeath-county-library.asp
30. Ventilation Strategies – Atrium Design • Interzonal Airflow
31. Ventilation Strategies – Atrium Design • Interzonal Airflow
32. MM/Natural Ventilation Strategies 7. Double Skin Façade
33. MM/Natural Ventilation Strategies 7. Double Skin Façade Be careful with the zone control!
34. MM/Natural Ventilation Strategies 8. Trickle-vent Overcomes acoustics issue
35. MM/Natural Ventilation Control • You can control pretty much anything • Allow buffers to avoid simultaneous heat/cool 9. Night Flushing Actuator Control
36. Window Controls Classroom 1 Classroom 2 Classroom 3 Classroom 4 Operable Windows Control Variables 1. Internal temperature above 72°F AND external temperature above 60°F. 2. Internal temperature above 72°F AND external temperature range above 60°F and below 77°F. 3. Internal temperature above 72°F OR CO2 level above 1200 ppm. 4. Internal temperature above 72°F OR CO2 level above 1200 ppm; AND external temperature range above 60°F and below 77°F.
37. Window & Exposure Types
38. Mixed-mode Ventilation
39. Mixed-mode Ventilation 10. MM: Sync HVAC Controllers with openings • Differential temperature, • high-limit override, • CO2-based control
40. Hybrid Ventilation • Summer TO = Outside Air Temperature (80°F) TG = Ground Temperature (47°F) TL = Leaving Air Temperature (65°F) TO = Outside Air Temperature (20°F) TG = Ground Temperature (47°F) TL = Leaving Air Temperature (40°F) • Winter
41. Hybrid Ventilation 11. Geothermal Labyrinth for ventilation air. • Free Heating • Free Cooling 12. Geometrically, solar chimney similar concept
42. Hybrid Ventilation • Increased ‘pre-treated’ ventilation air to AHU. • Air Temperature • Air Velocity Thermal mass concept
43. Hybrid Ventilation – Thermal Mass • Peak Condition
44. Lessons Learnt • Integrate to design as early as possible • Consider the negatives: noise, contamination, security & condensation • Study the climate and use accurate weather data • Include dynamic infiltration • Appropriate Loads Analysis • CIBSE AM10 & AM13! • Commissioning is essential for successful MMV
45. Liam Buckley ASHRAE Associate Member, M.Eng., C.Eng. MIEI, BEMP Liam.Buckley@iesve.com C: +1 617 840 6101