How does the national Green Building standard rate vs energy star
Andy Rosenthal
| Posted in General Questions on
I am a builder in Montgomery County Maryland. The County Council has mandated that by 2010 all new homes must be energy star rated. The bill also leaves the door open for alternatives that are comparable. I need to be able to have the information available for the Department of Environmental Control that compares a home that is rated by both Energy star and The national Green Building Standard to demonstrate that the national Green Building Standard would be a viable additional alternative for a builder to choose when building a new home in the County.
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Andy,
On the National Green Building Standard's performance path, a house at the lowest level — the bronze level — must be 15% more efficient than a house built to the 2006 International Energy Conservation Code (essentially the same as an Energy Star qualified home). Silver, gold, and emerald homes must be more energy efficient than houses that minimally comply with Energy Star standards.
Having lived through the Energy Star reset that happened in 2006 (homes that I was building at 65% better than code were suddenly 30% better than code) I can see your reservation about linking your local county to that single standard. I cannot imagine any way to build a home that meets the National Green Building Standard that is not also 15% better than code.
I have scored an affordable green house by one of our local builders from a few years ago that is the most "value engineered" green home I know. These builders, Danny Winters and Craig Morrison of Cimarron Homes in Durham NC, are my personal green heros, in todays market they are building and selling homes that are green and Energy Star for less than $145,000 including the lot. If anyone can figure out the cheapest way to build green and Energy Star it's these guys.
Of course, their base house scored better than minimum in the national standard but it gave me a real world place to start from which I subtracted green features and energy features down to the absolute minimum.
I created a separate log-in for this project at NAHBgreen.org so you can log on as me and see what choices I made. Please don't change everything on me. the log-on is "[email protected]" and the password is "chandler"
If any one wants to try to show me a real world way to build an NAHB standard home that is less than Energy Star have at it, just start a new project and show me how. Since most builders build variations of the same spec and house there is a button you can select to make a copy of the project that is in there and modify the specs to experiment. It won’t allow more than one person to sign on at a time so if the sign-in doesn’t work try later. If you want to spend a lot of time there please create your own account, it's free after all, courtesy of your local Home Builders Association...
Below is the print-out for the energy section at the absolute minimum value engineered level to meet the National Green Building Standard for a 1,939 sf 3 BR 2.5 bath production home. Note that the minimum 30 points required to score bronze must come from the envelope section not from additional or innovative practices. Most raters are interpreting the 701.3 mandatory review of the “intent of the standard” to mean RESCheck software and points are awarded for this in 703.1 total building UA >10% better than code which helps to give a whole house approach to energy modeling.
Looks a lot like Energy Star, Certainly a reasonable alternative.
Michael
Project Name - Dannys house
Project Description - Single Family Residence
Scoring Path - Single-Family New Construction
Square Footage of Dwelling Unit - 1939
Total points claimed in this Project - 228
Green level achieved for this Project - Bronze
Point Minimums for this Project: Bronze: 222 Silver: 406 Gold: 558 Emerald: 697
CHAPTER 7 - Energy Efficiency
Practice 701.3 Mandatory practices: Third-party Review
A review of the design has been conducted by a third party to confirm that the intent of the Standard with respect to energy provisions has been met.
Practice 701.4.1 Mandatory practices: HVAC systems
Space heating/cooling sized per ACCA Manual J.
Documentation Required - Provide software output report using ACCA Manual J or equivalent with recommended HVAC equipment sizes.
Practice 701.4.2 Mandatory practices: Duct systems
Ducts sealed with UL181 tape, mastic, or gaskets. Mandatory for certification, if applicable.
Documentation Required - " For buildings with ducted systems provide product spec or trade contractor's scope of work to confirm use of duct sealing using UL 181 tape, mastic, gaskets, or an IRC or ICC/IMC approved system. If building uses NO DUCTS check N/A box at right. "
Building cavities are not used as supply ducts. Mandatory for certification.
Practice 701.4.3 Mandatory practices: Insulation and air sealing
Insulation is installed in accordance with the manufacturer's instructions or local code. Mandatory for certification.
Documentation Required - Provide insulation installation requirements, either manufacturer's instructions or specific local code guidance. Evidence of an approved local code insulation inspection can be used as acceptable evidence for this verification.
Shafts opening to unconditioned space are sealed with blocking or flashing; gaps are sealed with caulk or foam. Mandatory for certification.
Floors: a) insulation installed to maintain contact w/ subfloor underside, enveloping ductwork & w/out compression or air gaps; b) batt & loose-fill insulation is held in place by permanent attachments. Mandatory for certification, if applicable.
Crawlspace wall insulation permanently attached to the walls. Exposed earth in unvented crawlspaces covered with continuous vapor retarder with overlapping joints that are taped or masticed. Mandatory for certification, if applicable.
Windows and doors: Caulking, gasketing, flashing tape, foam sealant, or weather stripping forms a complete air barrier. Mandatory for certification.
Documentation Required - Provide window and door installation detail on plans showing how installation will form a complete air barrier.
Band & rim joists insulated & air sealed. Mandatory for certification, if applicable.
Documentation Required - Plan details to show how band or rim joists are to be insulated and sealed. If building has NO BAND JOISTS OR RIM JOISTS check N/A box at right.
(a) Sill sealer is installed between foundation and sill plate; AND (b) Seal the bottom plate of exterior walls. Mandatory for certification, if applicable.
Skylight shafts and knee walls are insulated to the same level as the exterior walls. Mandatory for certification, if applicable.
Code required building envelope insulation and air sealing are not disrupted at exterior architectural features such as stairs & decks. Mandatory for certification, if applicable.
Attic access (except unvented attics), knee wall door, or drop-down stair is covered with insulation and gasketed. Mandatory for certification, if applicable.
Recessed light fixtures that penetrate the thermal envelope are airtight, IC-rated, and sealed with gasket, caulk, or foam. Mandatory for certification, if applicable.
Where ceiling/attic assemblies or designs have eave vents, baffles minimize air movement into or under the insulation. Mandatory for certification, if applicable.
Practice 701.4.4 Mandatory practices: Fenestration
Use the ENERGY STAR Window Requirements Tool to determine the window requirements for your zip code.
NFRC-certified windows, exterior doors, skylights, and tubular daylighting devices (TDDs) are ENERGY STAR, or Table 701.4.4.1 (see VRG). Mandatory for certification.
A building complying with the Performance Path (Section 702) must exceed the ICC IECC by at least 15%. A building complying with the Prescriptive Path must obtain a minimum of 30 points from Section 703. Both Paths require min. 2 items from Section 704.
Prescriptive Path chosen. This project is eligible to achieve the Bronze, Silver, or Gold Level. Select the Performance Path to be eligible for Emerald.
Section 703 -Prescriptive Path
Practice 703.1.1 Building envelope: Total UA
Where the total building thermal envelope UA is less than required by IECC Section 402.1.4, the total building thermal envelope UA is in accordance w/ Table 703.1.1 (see VRG). A documented analysis is performed using RESCheck version 4.0.1 or equivalent.
Climate Zone 3, 10% UA improvement
Documentation Required - Provide RESCheck 4.0.1 or other equivalent analysis method to show either 10% or 20% UA improvement. Provide indication in analysis which climate zone applies and whether UA improvements are attributed to insulation. Provide documentation of 3rd party insulation installation grading results.
Practice 703.2.1 Insulation and air sealing: Third party verification
Insulation and air sealing installed per VRG.
No third-party verification performed
Documentation Required - Provide signed 3rd party report that all items in 703.2.1 were followed in the foam insulation, air sealing, plumbing, wiring, HVAC register boots, masonry fireplace, air barrier, together with the wall, ceiling and attic insulation.
OR
Provide checklist signed by the builder that all items in 703.2.1 were followed in the foam insulation, air sealing, plumbing, wiring, HVAC register boots, masonry fireplace, air barrier, together with the wall, ceiling and attic insulation.
Practice 703.3.1 Fenestration: U-factor & SHGC
The NFRC-certified U-factor and SHGC for windows, exterior doors, skylights, and TDDs are in accordance with Table 703.3.1(a) or (b). See VRG.
Practice 703.4.4 HVAC: Heat pump heating efficiency
Heat pump heating efficiency is in accordance with Table 703.4.4. Refrigerant charge is verified for conformance with manufacturer's instructions.
9.0 HSPF (12.5 EER), Climate Zone 6-8
Section 704 -Additional Practices
ENERGY STAR or equivalent appliance(s) are installed.
Dishwasher
HVAC contractor and service technician are certified by a nationally or regionally recognized program.
Total points claimed in Chapter 7 - Energy Efficiency: 38
Point Minimums for this Chapter: Bronze: 30 Silver: 60 Gold: 100 Emerald: 120
Michael, Thanks for posting the NAHB parameters and the password.
I will take a better look at the site and experiment with the variables.
It is a nice set of standards.
One thing that seems to be missing at first glance.....Window Area.
It seems to me that it would be possible to pass the NAHB standard yet flunk Energy Star if you choose to use large quantities of glass.
Some of the LEED homes here in North Texas have so much glass area that I doubt they would pass Energy Star without the offset of some kind of high performance mechanical or Geothermal Bling.
Anything beyond 18% glass to floor area will count against you (rightly so) on the HERS index.
If you are careless with window orientation you can also bring down performance and HERS but not be "penalized" with the NAHB standard.(based on my first glance)
Overglazing is probably not an issue with the affordable homes that you mentioned...but could be with a custom home...... especially if you have a wonderful view or if a LEED Architect is involved ;-)
Just kidding..some LEED Architects are responsible with glass.
We just added/remodeled a new section to the encyclopedia (which will grow shortly) on [green ratings](node/12594 "Green Rating Systems With a National Reach — and Some Local Programs"). I put up the overview page comparing the major nationals and we'll put up the individual pages for LEED, NGBS, EFL, and Locals soon.
They're almost ready, but not quite.
Regarding Martin's comment on the efficiency levels in the Standard, the program does not require performance testing, so the efficiency levels can be based on inexact calculations based on visual inspections and specified insulation levels. Watch out for several articles on LEED and NAHB that will be posted on this site in a few weeks.
What doea it cost to get a home energy star certified in your area? In my area it is about $450. At that price why not just get it certified for energy star even if you are using another green certification. At least then you will have a point of comparison.
Chaz
I don't know of any builders who are getting green certified that are not also getting Energy Star certified.
But there are many in the green building community who are suspicious of the NAHB green building standard because it allows for a house to be green certified without blower door and duct blaster performance testing if it meets REScheck plans analysis (to 10% better than code in zone 3) as well as an Energy Star type thermal bypass standard, has properly taped and sealed Energy Star rated windows, doors & skylights, has properly installed insulation and duct mastic, no building chases used as ducts, BOTH sill seal and caulked bottom plates, 9.0 HSPF/15 SEER heat pump (in zone 3) .64 EF gas tank water heater, energy star dishwasher, programmable thermostat and factory trained HVAC installers.
I think its reasonable to assume that a house meeting this prescriptive standard would test equal to Energy Star.
There are production builders for whom even a $300 minimum energy star fee plus the time to deal with the Energy Star HERS rater is too onerous. The NAHB working group left this option open in hopes of bringing these builders to Green Building certification and to uncouple the Standard from Energy Star in hopes of allowing another path to verification to open through market forces.