Energy Efficiency Comparison Between LEED v2.2 and v3

Energy Efficiency Comparison Between LEED v2.2 and v3
As illustrated by the new ThedaCare Clinic in Darboy, WI

Evaluation of the two LEED rating systems, New Construction v2.2 and v3 is important, not only in the determination of which rating system to submit the project under, but also in order to ensure that we’re achieving the energy efficiency goals that we based the design on. We are fortunate enough to have a knowledgeable partner in August Winter & Sons, Inc. as our HVAC subcontractor on the ThedaCare Darboy project. With the help of Wes Pohlman and Rick Verstegen of August Winter we can take a more in depth look at the differences in the energy efficiency section of these two rating systems.

One of the changes to v3 in the Energy and Atmosphere category is the increase in available points for Credit 1 - Optimize Energy Performance. There are now up to 19 points available for this credit as opposed to 10 points available in the previous version. However, as part of the new credit, the standard used is now ASHRAE 90.1 – 2007 without addenda. The previous standard used was ASHRAE 90.1 – 2004. The new ASHRAE standard raises the minimum efficiencies and standards required for the Building Envelope and HVAC. The following are building envelope examples of changes to the ASHRAE standard for Climate Zone 6 (all but 15 counties in the state of Wisconsin):

For a roof with insulation entirely above deck, the minimum insulation R-value increases from an R-15 to R-20 (a 25% increase in required performance) with the overall assembly u-value changing from U-0.063 to U-0.048 (a 31.25% increase in performance).

A steel framed wall above grade performance changes from an R-16.8 to an R-20.5 for insulation minimum (an 18% increase) with an assembly u-value change from U-0.084 to U-0.064 (a 31.25% increase in required performance).

The standards for vertical building fenestration have also changed. In some cases, values have increased. For example, in the 2004 standard, a building with 20.1 – 30% vertical glazing and operable windows required a u-value of 0.67 and a Solar Heat Gain Coefficient (SHGC) of 0.49. The 2007 standard is now identified by vertical glazing type with Non-metal framing requiring U-0.35, Metal framing (curtain/storefront) requiring U-0.45, Metal framing (entrance door) requiring U-0.80, and all other Metal Framing requiring U-0.55. The required SHGC changes to 0.40. Comparing a Non-metal framing vertical glazing to the previous standard shows an increased performance requirement of 22.5% for the SHGC (0.49 to 0.40) and 91.4% for the u-value (0.67 to 0.35).

An example of this is shown in the energy model created for the ThedaCare Physicians – Darboy Clinic project. Two energy models were created to compare both standards. In the first energy model, comparing the building design to the ASHRAE 90.1 – 2004 standard (LEED NC2.2) showed an increased energy performance of 30.5% which provided 6 LEED credits for EA-C1. The second energy model showed an increased energy performance of 25.4% compared to ASHRAE 90.1 – 2007 (LEED 2009) which provided 7 LEED Points for the EA-C1 credit.

As illustrated, even with the higher minimum performance standards required in the new v3 LEED rating system, energy saving measures are better rewarded.

ThedaCare Darboy

We have been presented with a unique opportunity on this project. We are at a time in the LEED rating system where we can hold on to the LEED NC v2.2 - what we’ve all become familiar with – or move forward with LEED’s new Green Building Design and Construction Rating system for 2009. As a project team executing an integrated design process for our client, we are working together to reach a goal of LEED Silver Certification or above on this project. The trick is to select the rating system that fits the client’s needs, not simply to put a plaque on the wall. Our goal is to create a facility that enhances health care delivery for the client and also is energy efficient and environmentally responsible.

In order to allow us to select either rating system, we registered our project under the LEED NC v2.2 rating system with the ability to upgrade into the LEED Green Building Design and Construction Rating system by the end of the year. By keeping our options open, the project team will be able to effectively analyze the differences between the two rating systems. This period of selecting either rating system is our window of opportunity to not only take steps to achieving our sustainable goals, but also quickly get up to speed with how the USGBC’s rating system is evolving.

After closer examination of the Green Building Design and Construction rating system, we noticed the point total thresholds have increased considerably. We also have an opportunity to achieve more points in the LEED categories. Key differences between the two LEED rating systems are the water efficiency requirements and the updated ASHRAE energy standard. The water efficiency standard has been increased to ½ gallon per minute, meaning it is now mandatory that faucets have a flow of less than ½ gallon per minute to achieve the credit. Under the v2.2 rating system, a ½ gallon per minute faucet was needed to achieve the credit. Given the increased stringency of the standard, we’re now weighing whether or not ½ gallon per minute is suitable water flow for everyday use. Achieving the water efficiency credit or not has a potential for a 4 point swing in our project. While we will all be working to adapt to the new rating system, having a grace period will allow us to find the best solution for the building and our client.

In the next post we’ll discuss more about the updated ASHRAE standard, as well as address some of the Material & Resource credits we’re targeting.

Introduction

Introduction to the WGBA Greenline Blog

A culture of sustainability and a desire for a greener built environment are common ground between The Boldt Company and the Wisconsin Green Building Alliance (WGBA). That’s why it seemed natural to partner in the process of documenting the construction of a LEED certified project. As the industry voice in sustainable building for Wisconsin, the WGBA saw opportunity in partnering with Boldt, a leader in sustainable construction, to journey through the LEED certification process on a new ThedaCare Physicians Clinic in the Fox River Valley. As an embedded third party to the construction process, the WGBA will highlight the ecological construction practices that will bring the project from lines on paper to a sustainable model in our built environment.

What makes the process more interesting is that we’re currently at a juncture in the LEED rating system. Earlier this year, the USGBC introduced the newest version of the LEED rating system. On the heels of chronological improvements to the LEED for New Construction versions 2.0 to 2.2 rating system over the past 10 years, the USGBC released LEED version 3.0, or Green Building Design and Construction 2009. The ThedaCare Physicians Clinic happened upon a unique time in the LEED rating systems where the project will have the choice to proceed with either the LEED NC v2.2 rating system or the Green Building Design or Construction 2009 rating system. So the question is, what is different between the two systems and which rating system will the project ultimately submit for certification under?

Boldt Project Manager and LEED AP Nick Mueller and WGBA Fox Valley Member Circle Chair and LEED AP Heather McCombs will be providing updates on the WGBA website throughout the construction process. These updates will highlight milestones current to the phase of construction, compare and contrast sustainable construction practices, and also weigh the pros and cons of the two LEED rating systems. Perspectives and analysis from subcontractor partners and jobsite progress photos will add some additional depth and insight. You will also be able to take a first-hand walk through the entire process at the 2010 G2B Conference on April 28 in Appleton, Wisconsin.

This is a great opportunity to share sustainable building experiences within the construction industry through the eyes and voice of WGBA and a trusted leader in sustainability, The Boldt Company.