Generic energy modeling verses HERS Ratings

What is energy modeling and why would I want it?

Basically, energy modeling software creates a mathematical simulation of your building over time to estimate how much it will cost to operate. It figures out how much heat is lost through every square foot of the envelope and how much heat is gained by the sun shining through the windows every year. It uses historical weather and solar data to calculate how much heat you will need to put into or remove to keep the indoor environment comfortable. And it can put this data in terms of dollars spent on fuel and utilities.

What’s the point? Optimization. We can swap different windows, adjust overhangs, try differing amounts of insulation, etc. and see what the result to the loads are, so we can find the sweet spot for your particular building. Knowing how much it costs to operate your building will allow you to calculate a return on investment for monies spent on energy conservation upgrades. For example, solar will pay for itself in the long run, but what is the payback period 5 years? 10 years? 20 years? Is it better to add continuous exterior insulation or buy better windows? Is it more cost-effective to add insulation to the attic or buy a few more solar panels?

HERS Rating

So what is a HERS Rating?

The RESNET HERS Rating protocol is a nationally standardized energy modeling system, just for houses, that lets us get to the answers relatively quickly and makes results consistent and comparable across the country.

The value of a HERS Rating over just energy modeling comes in four ways.

  1. Code compliance- HERS Ratings supersede the rigid rules of the energy code and gives you flexibility.
  2. Third-party inspections- we inspect at rough to look for problems with air barriers and insulation. Having an air-tight envelope not only saves energy, it helps prevents rodents, bugs and dust from getting into the house. We grade insulation on the quality of its installation. If we find less than perfect installation, we bring it to the attention of your GC and he can have it corrected before it is too late.
  3. Rebates- many rebates are only available to those that receive a HERS Rating.
  4. Resale- the score goes on the MLS report so buyers get a sense of how efficient the house can be (like a MPG sticker for a car). Embedding the value of energy features in the value of the home also makes it easier to invest in features that have a longer return on investment.

 

What energy modeling doesn’t do…

  1. The model doesn’t know how much anything costs, except gas and electric. So it will not do a cost benefit analysis without help from the rest of your team.
  2. It is not the same kind of zoned load calculations used by HVAC designers to size ductwork or radiant tubing layouts. You will still need a heat/cooling/ventilation distribution design. It will tell us how many kBtu the furnace or boiler should produce, but not how to get the right amount of heat to every corner of the house to maintain comfortable temperatures.
  3. It is just an estimate. Occupant factors, like where the thermostat is set, will skew the numbers accordingly.

 

Why choose Confluence Architecture and Sustainability?

The team at Confluence has been practicing architecture in the extreme climate of the mountains of Colorado since the turn of the century. We started offering sustainability services when the 2009 International Energy Conservation Code was adopted. We know how to play with Owners, Architects, Engineers, Builders and Code Officials. We bring our experience to the table on tangential matters like; air barriers, vapor retarders, ventilation rates, indoor air quality, mechanical systems and optional solutions and alternative methods for code compliance. And we can make recommendations to increase the quality, comfort and durability of your structure.

Hers are some other related blogs…

https://www.confluencearchitecture.com/hers-rating-process/

https://www.confluencearchitecture.com/blower-door-test/

https://www.confluencearchitecture.com/preparing-for-your-blower-door-test/

 

2015 IECC Adoption Western Colorado

Here in western Colorado, local jurisdictions are busily adopting the 2015 building code.  The 2015 IECC adoptions are the most contentious and most heavily modified.  It is hard to keep track what needs to be done to comply with the energy requirements for residential construction.  Below is a cheat sheet table of adoptions and modifications in Western Colorado.  If you need assistance getting the most sustainable home or just figuring out what a jurisdiction wants – give Confluence Architecture a call.  How is the 2015 IECC different than 2009?  See this blog. We do HERS ratings, blower door tests, and code compliance documents for the IECC.

Adopted Residential Energy Codes and Amendments
Jurisdiction IRC IECC Amendments to Code HERS Required HERS usable for permit Blower Door Required
Garfield County 2015 2009 No Amendments to IECC no no no
City of Glenwood Springs 2009 2009 No Amendments to IECC no no no
Town of New Castle 2003 2009 Requires third party checklist, blower door (7 ACH50), CAS test, and ENERGY STAR appliances no yes yes
Town of Silt 2009 no none
City of Rifle 2009 2009 No Amendments to IECC
Town of Carbondale 2009 2009 No Amendments to IECC no yes maybe
Pitkin County 2015 2015 No Amendments to IECC no yes yes
Town of Basalt 2006 2015 no yes yes
Town of Snowmass Village 2015 2015 No Amendments to IECC yes yes yes
City of Aspen 2015 2015 IECC -many amendments no no no
Eagle County 2015 2015 Fenestration U-factor .30 max. no yes yes
Town of Vail 2015 2015 R21 on wood framed can be substituted for continuous insulation no yes yes
Town of Avon 2015 2015 all gas fired boilers used for snow melt minimum 92% AFUE no yes yes
Town of Eagle 2012 2012 No Amendments to IECC no
Town of Gypsum 2003 no none no
San Miguel County 2009 2009 San Miguel County Prescriptive Code if over 5000 sf yes if over 5000 sf
Town of Telluride 2003 2009 Eliminated whole code and replaced with their own that has higher insulation levels, required HERS, blower door, and duct blasting, min. HVAC efficiencies, low flow fixtures, and rough for solar yes yes yes
Town of Mountain Village (Telluride) 2012 2012 HERS rating required, mechanical engineering required, permit fee reduced for good HERS or low exterior energy use yes yes yes

Aspen no longer a leader in carbon reduction policy

I was hugely disappointed to learn that Aspen no longer seams interested in being viewed as a leader in carbon reduction. The City has just adopted, what is, in my opinion, a relaxed version of the International Energy Conservation Code. The Building Department asked me for data. So I went through 140 different blower door tests and HERS Ratings I had on file to get a feeling for how our new construction is looking. Summary of data below…

location number of tests number of tests over 3 ACH50 ACH50 average ACH50 low ACH50 High
City of Aspen 49 26 3.4 1.26 7.08
Pitkin County 42 20 3.23 1.28 6.37
Snowmass Village 8 7 4.12 2.92 5.71
Town of Carbondale 26 13 3.06 1.16 5.8

In terms of HERS Ratings- RESNET says the national average score is 61. Colorado had 12,320 (of 206,583) rated homes last year, with an average score of 55. Remember that lower is better when talking about HERS Ratings. Our average HERS Rating score in the Roaring Fork Valley over the past seven years is a 56. So Colorado is better than average nation wide, but the Roaring Fork Valley is behind the state average. Summary of HERS data below…

Number of Ratings in 2016 Average HERS Index in 2016
Alabama 1,745 71
Alaska* 425 55
Arizona 12,522 63
Arkansas 714 72
California** 1,156 68
Colorado 12,320 55
Connecticut 1,236 53
Delaware 2,067 53
District of Columbia 337 59
Florida 12,484 58
Georgia 8,820 70
Hawaii 31 45
Idaho 1,649 60
Illinois 3,361 60
Indiana 8,951 65
Iowa 5,032 56
Kansas 1,289 69
Kentucky 2,009 65
Louisiana 314 74
Maine 113 26
Maryland 6,513 55
Massachusetts 7,466 55
Michigan 2,944 57
Minnesota 6,494 51
Mississippi 25 65
Missouri 625 68
Montana 115 49
Nebraska 1,249 52
Nevada 4,966 62
New Hampshire 591 61
New Jersey 3,704 61
New Mexico 1,148 56
New York 3,640 53
North Carolina 13,397 66
North Dakota 21 58
Ohio 6,595 60
Oklahoma 4,019 61
Oregon 330 56
Pennsylvania 3,579 61
Rhode Island 334 62
South Carolina 7,740 68
South Dakota 219 53
Tennessee 1,106 67
Texas 40,012 64
Utah 1,522 62
Vermont 388 47
Virginia 7,235 63
Washington 1,316 56
West Virginia 126 67
Wisconsin 2,526 52
Wyoming 63 58

 

Below is a letter sent to the Aspen City Council…

Aspen City Council members,

I intended to speak at the meeting of January 10th but was misinformed about the time and therefore arrived too late. My intention was to recommend denial of the proposed adoption of the 2015 International Energy Conservation Code as amended by the Community Development Department. My preference would be to see the document adopted as written.

My firm, Confluence, has been providing architectural services in the valley for nearly seventeen years. In 2010 the firm began offering energy code compliance services; energy modeling and building testing.

Aspen has adopted a heavily modified version of the code. One that deletes some important tenets of this latest version of the International Building Code. For instance, the requirement for mandatory air infiltration testing has been removed. My professional opinion is that these tests are a valuable check on the condition of the barrier between outside and inside. The data the we have compiled from our work in the valley shows that only about half of that new construction would have passed the 2015 code limits. Research shows us that air sealing is the single least expensive way to reduce the energy consumption of a building.

Aspen’s Climate Action Plan says the community has a goal of reducing greenhouse gas emissions by 80% by 2050. Approximately 32% of Aspen’s emissions come from buildings. If the City were serious about making those goals, then why relax energy conservation building codes at all? Why would the City lowering the bar instead of ensuring that new construction complies with the same code that Pitkin County, the Town of Snowmass Village and Eagle County have adopted?

To me it sounds hypocritical for, Aspen, the home of CORE, the Canary Initiative, Z Green and AREday, not to be doing everything possible to make sure their new construction meets contemporary minimum construction standards.

Final point, it negates the benefits of having an International code system if every jurisdiction completely rewrites the content. It leads to increased confusion, time, money, and potential for mistakes. Why not standardize?

Mark McLain,

Architect & Sustainability Consultant

Pitkin County and Eagle County adopt the 2015 Energy Code

Denver, Boulder and Vail have already done it. Glenwood Springs, Carbondale, Basalt and Aspen will do it soon. But starting today, September 6th 2016, all building permit applications submitted in Pitkin County must demonstrate compliance with the 2015 IECC (International Energy Conservation Code). Eagle County has postponed implementation of the codes until the start of the new year. This will give them time to train staff and educate local architects and builders on upcoming changes. That sounds smart to me, because the changes are not insignificant.

What’s new in the 2015 Energy Code?

Building Department reviews will be looking for new kinds of information on Construction Documents. Drawings will need to tell the story of how a building will be built to conserve energy; insulation, lighting, heating, cooling, moisture management and indoor air quality. Some jurisdictions are requiring that all IECC information be put on it’s own “energy” sheet.

The maximum allowed infiltration rate has decreased to 3 ACH50 and testing is mandatory. The 2009 limit of 7 ACH50 was easy; 3 ACH50 can be a challenge.

Mechanical ventilation is now mandatory. Plan on a HRV (or ERV if you have air conditioning) or some kind of exhaust-only ventilation.

Mechanical systems must be sized with ACCA Manuals J, S & D.

Prescriptive insulation values have crept up a bit in some categories. Chart shows new 2015 values in red.

IECC Prescriptive Insulation Table Headings

IECC Prescriptive Insulation Table

For designer and builders using the prescriptive method of compliance, this means no more 12″ vented roofs. And in zones 6 & 7, no more walls without exterior continuous insulation.

If you want or need to break any of these rules, then you need to choose another compliance path. Using one of the performance path methods (REScheck, COMcheck, HERS Ratings, etc) will make the code easier and more flexible.

Confluence Architecture & Sustainability can help you with all of these facets; from submittal documents to blower door testing. We can help you find the least expensive way to satisfy the building department and inspector, or we can help you design a high-performing net-zero building. Give us a call…

 

Homes Under Construction

Construction season started with a bang here in the Roaring Fork Valley.  Confluence Architecture currently has 5 homes we designed under construction.  A record for us.  We  are working with a range of clients from owner builders to spec builders.  Here are highlights from recent site visits:

construction excavation

Excavation at Crystal River Valley home

 

 

 

 

 

Elk Springs home under construction

Insulation complete and siding in process at Elk Springs home

 

 

 

 

Working on Finishes at Shaw Spec Storybook House.  Check out that helix stair.

20160407_15273820160407_154010

 

 

 

 
framing stage of constructionFraming underway at the Hilleke Home

 

Pass the blower door test the first time

If you haven’t been through a blower door test yet, chances are you will soon. As Pitkin County, Aspen, Basalt and Carbondale gear up to adopt the latest round of building and energy efficiency codes. The 2015 IECC (International Energy Conservation Code) have houses going for a maximum of 3 ACH50 (Air Changes per Hour at -50 Pascal) and commercial buildings going for a maximum of .40 CFM/square foot of envelope area at -75 Pascal. Most builders I work with could get to 7 ACH50 without doing anything extra. Getting to 3 ACH50 will take some extra care. If you are unfamiliar with the techniques of air sealing, then read up or get an expert on the team. A great place to start reading is the ENERGY STAR Thermal Bypass Checklist . Awesome document- do this stuff and you will pass the blower door test the first time.

Test day

I’m often asked, “what do I need to have done before we test?” Completely done, done, done is ideal; but in reality…  below is my checklist of this that should be done before testing so test results are not significantly degraded:

  1. doors and windows installed
  2. door and window hardware and weatherstripping installed
  3. door thresholds installed
  4. hatches to unconditioned attics and crawlspaces installed and gasketed
  5. dampers in place
  6. fireplace doors installed
  7. plumbing traps filled
  8. conduits leading outside sealed
  9. air handlers and ductwork complete
  10. light fixtures installed
  11. plate covers installed
  12. any other gap, crack or hole between inside and outside that you can find

Setting up the Building

When we test a building for air infiltration the building must be setup in a prescribed fashion. The IECC has it’s section (2009 IECC R402.4.2.1 or 2009 IRC N1102.4.2.1)  that describes how to setup a house. RESNET has their official protocol as well, the document ANSI/RESNET/ICC 380-2016.

  1. Exterior windows and doors, fireplace and stove doors shall be closed, but not sealed with tape;
  2. Dampers shall be closed, but not sealed; including exhaust, intake, makeup air, back draft, and flue dampers;
  3. Interior doors shall be open;
  4. Exterior openings for continuous ventilation systems and heat recovery ventilators shall be closed and sealed;
  5. Heating and cooling system(s) shall be turned off;
  6. HVAC supply and return registers shall not be sealed.

Running the test

I usually takes me 20-30 minutes to set up the blower door equipment and check that the house is prepared. I need an exterior door that is not too small or too big to set up in, power nearby and a space to work in. If the house is more than 5000 square feet or so, I will set up double fan equipment.  Then I will need to shut down the air handler and exhaust fans. At this point, anyone opening a door would void the test. But typically I only need the doors closed for five minutes to get an accurate reading. If it hasn’t been done yet, I will need the drawings to calculate the volume of air inside the house. Then do the math; flow (the results of the test) X 60 divided by the volume of the house = the number of air changes per hour. In the end, I create a certificate, that need to go to the building official.

If you want/need someone else’s eyes on the job, then give us a call. Confluence Architecture has a lot of experience with construction detailing, building testing, improving test results and also does HERS ratings, RESchecks, COMchecks, blower door tests, duct blast tests, IR camera inspections, etc.

Confluence Now Offers Solar-Powered Site Visits

Confluence Architecture & Sustainability has been electrically net-zero for a while. Now our surplus solar electric is being used to charge our new Electric Vehicle.

Nissan Leaf

A Gunmetal Grey Nissan Leaf with a level 2 charger to go with it.

Architectural site visits, construction inspections and blower door testing from Confluence will now be carbon neutral from New Castle, Glenwood Springs, Carbondale, Willits, Basalt to Aspen!

Confluence Architecture wins Houzz Award

Houzzbadge_22_8Confluence Architecture of Carbondale Colorado awarded Best of Houzz 2016 for customer service. The Best Of Houzz is awarded annually in three categories: Design, Customer Service and Photography. Design award winners’ work was the most popular among the more than 35 million monthly users on Houzz. Customer Service honors are based on several factors, including the number and quality of client reviews a professional received in 2015. A “Best Of Houzz 2016” badge will appear on winners’ profiles, as a sign of  their commitment to excellence. These badges help homeowners identify popular and top-rated home professionals in every metro area on Houzz.