DNV KEMA Shayne Rolfe Principal Sustainable Design
LEARNING OBJECTIVES an overview of the design process for naturally ventilated buildings
1
the tools and modeling process used in the design
2
the impact of engineered natural ventilation on interior design.
3
designing engineered natural ventilation systems
4
case studies.
NATURAL VENTILATION WHY IS IT IMPORTANT NOW California has mandated ZNE for new construction for residential by 2020, commercial by 2030 we see it happening faster Achieving 30% HVAC equipment savings for T24 2012 and onwards will be challenging for many design teams - maybe impossible with current technology Engineered naturally ventilated buildings could achieve 50-70% HVAC savings above the 30% equipment savings - largely through reduced run times
ANYWHERE AND ANY BUILDING TYPE
THERMAL COMFORT -
MEASUREMENT
PMV/PPD – predicted mean vote/predicted percentage dissatisfied Fanger (1970) model is officially adopted by US to determine thermal comfort in air conditioned buildings. ATC – adaptive thermal comfort model allowances for clothing values & metoblic rates,
Natural ventilation requires a third model studies have determined a direct correlation between comfort and outdoor temperature, seasonal change and the inclusion of mean skin temperature PMV x 0.5
Tools
Climate Consultant
Hours within extended comfort range San Diego - 47% Phoenix - 24% Newport Beach – 52%
TECHNICAL TOOLS & HISTORY
TAS 1990’s 1st bulk airflow tool
TOOLS - INHOUSE DEVELOPMENT
Process Tools
Passive Strategies
NATURAL VENTILATION Natural ventilation - airflow due to wind and buoyancy, through cracks in the building envelope or purposely installed openings Single Sided - generally limited to perimeter zones Cross ventilation - two or more openings on opposite walls, able to cover large zones Stack ventilation – buoyancy driven, large airflow Windcatchers – wind and buoyancy driven, effective in warm/temperate climates Solar induced – using the sun to induce buoyancy, effective in hot climates
DESIGN CONSIDERATIONS Agree to design brief • operational expectations • heat loads • flexibility • comfort tolerance • business culture
Ch2 IMAGE
Plan the airflow path • free area calculations • seasonal changes • pollution • noise sensitivity • night purge • security • core v’s perimeter • identify special areas • ventilation rates • high load zones • treated air • + - pressure zones
Design analysis/tools • estimate driving pressures • wind conditions • daily/seasonal variations • ventilation devices • velocity through openings • robustness • sensitive to use change • code conflicts • control strategies
DO NOT UNDER ESTIMATE THE WORK TO PROVIDE ANALYSIS
FEATURES FEATURES • building form is primary climate control • narrow plan width < 30ft • floor to ceiling ht. >10ft • open plan • solar gain control • controlled internal gains • high thermal capacity • operable windows • vertical/high air intake or exhaust
Case Study
EXISTING INVENTORY
THIS IS WHERE THE NEW MARKET IS
Open Plan
Operable Windows
Air movement Exhaust
before.
before.
after.
Cool Roof- R40
Solar Tubes
Shading
Thermal Chimney
Wall R21 Insulation Thermal Mass
Planting
Shower Tower
Security
Site Generation
Operable Windows
INTERIORS
Exhaust
Air Inlets
External Gains
Edge in â&#x20AC;&#x201C; Center out
External Gains
THERMAL CHIMNEY
CONCEPT
EXPERIENCE – NELHA HAWAII
OPTIONS
A B C
13ft above roof level 400 sft of free area exhaust 26,000 cfm
SHOWER TOWER
WHAT IS IT & WHY FEATURES • extend NV effectiveness • passive evaporative cooling • downdraught flow • security • humidifies • architectural form • pioneered in Phoenix
115 110 105
Temperature (째F)
100 95 90 85 80 75 70 01
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Date: Sun 01/Aug to Tue 31/Aug Air temperature: Unconditioned/Semiconditioned Office Space (dpr phoenix office - scenario 4_augmonth&openingprofile.aps) Dry-bulb temperature: (PhoenixTMY2.fwt)
30
31
01
37
SIZING EQUIPMENT
Questioning assumptions
Skylight condition - not solar tube Revise roof & wall insulation to reduce load
Internal meeting room - how does infiltration occur Space is 100% daylit, why is there lighting load
Does peak design need peak people Define loads
ASHRAE +25% sizing ASHRAE +15% sizing
Results of questioning assumptions Original Load 39.9 tons
Revised Load 25.5 tons
This is a 35% reduction in load
Results
Section diagram illustrating bioclimatic strategies
Solar Chimney
Solatube and Big Ass Fan
Passive Cooling Tower
Overall view of the building at night.
9-13 kWh/sf/yr
18-24
8-12
kWh/sf/yr
kWh/sf/yr
kWh/sf/yr
kWh/sf/yr
kWh/sf/yr
4 9 6
HVAC Energy Cost Savings P E R C E N T
P E R C E N T
LEARNING OUTCOMES 1
the tools and modeling process used in the design Early team involvement - IDP is the primary tool (CFD) Analysis
2
the impact of engineered natural ventilation on interior design. Interiors can no longer be designed in isolation from the systems
3
designing engineered natural ventilation systems The building is the system. Not pieces of equipment The WHOLE team needs to be engaged early
4
case studies. Different solutions, similar outcomes
THANK YOU
Shayne Rolfe DNV KEMA shayne.rolfe@dnvkema.com