designing high performance schools in new orleans

NREL is a national laboratory of the U.S. Department of Energy Office of Energy Efficiency and Renewable Energy operated by the Alliance for Sustainable Energy, LLC

Gulf Coast Green

Ian Doebber

April 16, 2009

Designing High Performance Schools in New Orleans

NREL Building Technologies Program

NREL is a national lab for the US Department of Energy with a single mission to develop and promote renewable and energy efficiency technologies

National Renewable Energy Laboratory Innovation for Our Energy Future

• Commercial & Residential Building Energy Efficiency

• Technical Assistance to DOE’s EnergySmart Schools Program

• Advanced Energy Design Guides

• Computer Simulation Tool Development


Presentation Overview

• K-12 Advanced Energy Design Guide

• Rebuilding New Orleans Schools : Quick Start Schools

• High Performance Schools in Humid Climates


K-12 Advanced Energy Design GuideGuidelines, based on climate zones, to help K-12 school owners and designers achieve 30%

energy savings over ASHRAE 90.1 – 1999

• Recommendations only, not a code

or standard

• Applies to new construction and

major renovation• Case studies showcase schools

nationwide that have achieved or

exceeded 30% energy savings

Focus of Recommendations

Building envelope– Fenestration– Wall/Roof Insulation

Lighting systems– Daylighting– Electrical lights

Heating, ventilation and air-conditioning (HVAC) systems– Building automation and controls– Outside air (OA) treatment

Service water heating (SWH)

Guide looks at integration of these systems – savings goal dependent on the interaction



Where to get the K-12 AEDG?

www.ashrae.org/freeaedg

• 170,500 AEDGs

have been

downloaded or sold

• 13,000 AEDG-K-12

hard copies provided

to every school

district

Download a copy at no charge -or- Purchase a print copy

http://www.ashrae.org/freeaedg


Quick Start Schools

RFQsSchematic

DesignConstruction Documents

Construction 2009 Opening

Next 10 Years

~44 New Schools

>40 Major Renovations

LEED for Schools Silver : 30% Utility Savings over AHSRAE 90.1 - 2004

Kick Off Design Charrette – Guided based on the K-12 AEDG


Quick Start Schools: Lighting Design

ZONE CATEGORYPROPOSED LPD

[W/ft2]

OFFICE 1.0

CONFERENCE ROOM 1.0

GENERAL CLASSROOM 1.2

COMPUTER CLASSROOM 1.2

ART CLASSROOM 1.3

SCIENCE LAB 1.4

MEDIA CENTER 1.1

LOBBY/PREFUNCTION 0.8

AUDITORIUM n/a

MUSIC/THEATER/DANCE 1.4

GYM (play area) 1.2

GYM (spectator area) 1.2

FITNESS CENTER 0.8

LOCKER ROOMS 0.6

KITCHEN 1.1

WALKIN FREEZER D 0.4

WALKIN COOLER D 0.4

SERVERY 1.2

DINING AREA 0.7

CORRIDOR 0.5

ASHRAE 90.1 – 2004

1.4 W/ft2

K-12 AEDG

1.1 W/ft2

Quick Start Schools

0.8 – 0.9 W/ft2

8% - 10% saving!!

Quick Start Schools: Daylighting Design


From AEDG Classroom Daylighting Recommendations


Quick Start Schools: Cooling Systems

OA Pre-Treatment Main System

Desiccant WheelWater Cooled

Magnetic BearingCentrifugal Chiller

Chilled Water

Enthalpy Wheels&

Packaged DX Units

Water CooledHigh EfficiencyScrew Chillers

Air CooledScrew Chillers


Quick Start Schools: Savings

Percent Savings Annual Utility Savings*

30.5% $98,000 [$0.61/ft2]

35.1% $77,500 [$0.80/ft2]

26.2% $98,000 [$0.45/ft2]

*Based on Energy Model


Quick Start Schools: Lesson Learned

Feedback to the next phase K-12 AEDG• More Aggressive Lighting Design• Classroom Daylighting (Solving Glare-More Flexibility)• Demand Controlled Ventilation (System or Zone)

• Insulation Levels (integrate with infiltration reduction)

Major Short Coming was FOCUSING how following the K-12 AEDG Recommendations REQUIRED a dedication to conquering Humidity otherwise forgo significant thermal comfort and energy performance


High Performance in Humid Climates

Story of an Architect and Two Engineers…

Previous Success : LEED Platinum on a High Rise Office Building in Phoenix, AZ

Project Scope

100,000 ft2 K-5 Elementary School in New Orleans

Conceptual Design thru Construction Administration

LEED for Schools Silver

Minimum of 23% Utility Savings over ASHRAE 90.1-2004


Designing within Silos

Architect Silo

Engineer 1 Silo

“Loads Based”

Engineer 2 Silo

“System Based”

Maximized Daylighting

0.8 W/ft2 LPDbuilding [1.1 W/ft2 LPDclassroom ]

High Performance Glazing

Zone by Zone Humidistats

Ventilation : ∑cfm/occ + ∑cfm/ft2

Loads as Usual : 1.4 W/ft2 LPDclassroom

0.3 ACH Infiltration…

High EER Roof Top Units

High COP/IPLV Centrifugal Chiller

Premium Motors

Efficient Centrifugal Airfoil Fans


Resultant School’s Performance

After a year of operation…

Complaints of Cold, Damp Conditions

Extremely High Utility Bills

Each Silo’s Design Focus was Implemented EXACTLY

With 4 more schools under design, School District decided to form a Forensics Team


Building Forensics : Infiltration

Problem : Increased Fenestration Details

0.3 ACH

1.0 to 1.5 ACH

Remedy : Sealed Construction Details but too expensive to fix vestibules

Can not rely on Building Pressurization!


Building Forensics : Duct Leakage

Looking at Testing and Balancing Report yielded ~30% Leakage Rate

Remedy : Reduced to ~10% Leakage Rate by improving to seal class B based on ASHRAE 90.1 following SMANCA Guidelines


Building Forensics : RTU Sizing/Control

Remedy : Replaced with smaller Roof Top Units?

Anyone else got any cheaper ideas?

Roof Top Units oversized and short cycling

Problem : Relying on Rules of Thumb and Lack of Communication

Direct Evaporative Cooling


Building Forensics : Ventilation

Problem : Misinterpretation of ASHRAE 62.1 Ventilation Rate Procedure for Multi-Zone Systems

Ventilation =∑cfm/occ + ∑cfm/ft2 All Zones All Zones

No Diversity 50 ft2 / occ

4 – 6 times actual school population

Remedy : Calculated necessary Ventilation and reduced Outdoor Air Intake


Building Forensics : Reheat Dilemma

Problem : Limitation of using only DX or Chilled Water Coils to provide both Cooling and Dehumidification

Result 1 : Cold, Damp Conditions

Remedy 1 : Eliminate Zone by Zone Humidistats

When the supply air flow required to dehumidify the space exceeded the supply air flow required to meet 75ºF.

Result 2 : Significant Reheat yielding High Utility Bills

Remedy 2 : Do Nothing


Psychometric Review 1

Properties of Air

Temperature Moisture Content

Relative

Humidity

mass of water

mass of dry airMoisture Content =

grains of water

pound of dry air=

Imagine 100% Relative Humidity at these Temperatures


Psychometric Review 2

40ºF

40 gr/lb

50ºF

55 gr/lb

80 gr/lb

60ºF

110 gr/lb

70ºF

100% Relative Humidity

50% Relative Humidity


Conventional System

75ºF

FanDX-or-

Chilled Water

52ºF 55ºF

57 gr/lb

65 gr/lb

75ºF

Moisture Potential

Temperature Potential

Siamese Twins : Temperature & Moisture Content

North Facing Classroom

1,000 ft2 Classroom

31 occupants

1.4 W/ft2 Lighting

0.9 W/ft2 Plug Load

0.3 ACH Infiltration

Supply Air = 55ºF & 57 gr/lb

R-13 Walls / 0.5 SHGC

0.4% Design Day Conditions (Sunny)

Space Air = 75ºF & 65 gr/lb

Thermal Load Requires = 1,000 cfm

Moisture Load Requires = 850 cfm

Cloudy

Lights Off

No Plug Load

500 cfm


Psychometric Chart

75ºF

65 gr/lb

Cold and Damp are the Worst Conditions in Regarding Reheat

Technologies to Battle Humidity

1. Hot Gas Reheat

2. Heat Pipe or Sensible Wheel

3. Desiccant Wheels

4. Enthalpy Wheels

5. Combination of all of the above

Following Systems provide Energy Efficient way to

Supply Air at HIGHER Temperature (55ºF to 65ºF) but

LOWER Moisture Content (57 gr/lb to 53 gr/lb)


Hot Gas Reheat

65 gr/lb

75ºF

DX Hot Gas

53 gr/lb

65ºF50ºF


Heat Pipe or Sensible Wheel

65 gr/lb

75ºF

DX


53 gr/lb

65ºF50ºF

Exhaust Air

-or-Chilled Water


Desiccant Wheels

65 gr/lb

75ºF

DX

53 gr/lb

65ºF57ºF

Hot Gas


Enthalpy Wheels - Regenerative Braking

65 gr/lb

75ºF

DX

Exhaust Air

Hot Gas

53 gr/lb

65ºF50ºF

Most Cost Effective Means of Dehumidification


Enthalpy Wheel & Heat Pipe

65 gr/lb

75ºF

Exhaust Air

53 gr/lb

65ºF50ºF


DX-or-

Chilled Water


Dedicated Outdoor Air System (DOAS)Trifecta Decouple

1. Moisture - Centralized System that provides “Dry” (~50 gr/lb) Outdoor Air between 55ºF-75ºF (~65ºF)

2. Temperature – Local Fan Coil Units or Water Source Heat Pumps to maintain 75ºF setpoint

K-12 AEDG

3. Ventilation – Dampers on 100% Outdoor Air Supply controlled by Zone CO2 sensor


What Happened to our Design Team

1. Used the K-12 AEDG as a starting point :-Lighting Design-Daylighting Design-Envelope Design-Started the Discussion of Mechanical Systems EARLY in Conceptual Design

2. Focused on how to conquer humidity by balancingEnergy Efficient Dehumidification while minimizing Reheat


Architects Review

Infiltration : Focus on Construction Details and Vestibule Design to minimize Infiltration

Access to Exhaust Air : Coordinate room layout to provide access to Exhaust Air

Coordinate Space Requirements : Equipment using Desiccantor Enthalpy Wheels often need double height space

Reference : “ASHRAE Humidity Control Design Guide”


Engineer

Start the Mechanical Conversation EARLY : Work with the rest of the Design Team in Conceptual or Schematic Design to determine the Optimal System

Duct Leakage : at least leakage class B

READ “ASHRAE Humidity Control Design Guide”

Ventilation : Understand ASHRAE 62.1 Ventilation Requirements but do not need to Over Ventilate

Energy Efficiency Dehumidification without Comprimising Reheat

designing high performance schools in new orleans

Education

energy futurequick

energy futurek

sustainable energy

energy futurewhere

us department of energy

national laboratory

schools silver

computer classroom1