Pitkin County Colorado’s “The Matrix” energy code addendum

Take the blue pill, go build somewhere else, the story ends, you wake up in your bed and believe whatever you want to believe. Or, you take the red pill, you stay in Wonderland, and we dive down the rabbit-hole…

Link to Energy and Land Use Code Information Page

Link to The Matrix

Pitkin County, Climate Zone 7,  has added a residential energy conservation addendum for new construction and remodels, on top of the 2015 IECC requirements. Why? Basically, it is to bring construction in line with the Climate Action Plan. PitCo sponsored some fascinating research. One study says that about 70% of GHG (Green House Gas) emissions in Pitkin County are from the built environment. Another study predicts that more houses will be built in Pitkin County. Yet another study tracked the energy consumption of 900 houses for four years then, consumption was compared to house size. One might expect a 10,000 square foot house to have ten times the consumption of a 1,000 square foot house, but the study shows that the consumption of an average 10,000 square foot house was closer to thirty times the consumption of the 1,000 square foot house! How is this possible? It is because as the houses get bigger, they tend to get more luxurious. This means the house is more likely to be packed with energy-consuming amenities like; high percentages of glazing, large interior volumes, snowmelt, pools, hot tubs, saunas, conditioned wine cellars, conditioned garages, audio-visual-security systems, humidity control, air conditioning, multiple redundant appliances, steam showers, multiple redundant shower heads, heated toilet seats and towel bars and a plethora of other electric-powered gizmos.

The addendum has been come to be know as “The Matrix” because of the table format that outlays the requirements. There are two tiers of compliance; one for houses under 5,750 square feet and one for those over. The Matrix also makes a differentiation between houses that have more and less than 15% glazing. There are special requirements when working with existing construction, including; an energy assessment of the existing structure, air sealing improvements and occupant, crawlspace and attic ventilation compliant with current code.

What does this mean for the Architect?

  1. Significant mandatory requirements; 50%-75% engineered lumber, insulated headers, 24” stud spacing, insulated corners or alternate construction, glazing U-factor of .28, ENERGY STAR appliances, mechanical commissioning of complex systems, sealed ductwork, garage exhaust fans, rough-in for PV and thermal solar and EV charging outlets.
  2. Any house with more than 15% of its walls glazed will be required to use the 2015 IECC UA trade-off (REScheck) or ERI compliance (HERS Rating) alternatives; no prescriptive submittals.
  3. Any house larger than 5,750 square feet will be required to use the 2015 IECC ERI compliance alternative; no UA trade-off or prescriptive submittals.
  4. Get in the habit of retaining an Energy Rater; early in the process.

What does this mean for the builder?

  1. Learn to work with efficient framing, SIPS and/or continuous insulation.
  2. Get in the habit of working with an Energy Rater; through the whole process.

Confluence Architecture & Sustainability can provide all the documentation, modeling, testing and certification required to navigate the Matrix.

Aspen’s energy code amendments could not be more different from Pitkin County’s Matrix. Click here to read about those.

Jump to Aspen Colorado’s energy conservation code compliance page…

Jump to Basalt Colorado’s energy conservation code compliance page…

Jump to Carbondale Colorado’s energy conservation code compliance page…


Aspen Colorado’s energy code amendments

Spoiler Alert! The City of Aspen has customized their energy code. This blog is about the residential code, I’ll tackle the commercial modifications later.

See the amendments text adoption here…Ordinance 40-2016

Link to Aspen’s Community Development Department…

What are the significant changes?

  1. The first change to the code drops the prescriptive allowable fenestration U-factor to .28.
  2. If submitting under the total UA trade-off compliance option, you will be required to go 2% beyond the passing line, in order to compensate for the fenestration glazing U-factor change.
  3. The option for exhaust-only occupant ventilation and air-cycler systems have been taken away, as balanced heat recovery systems are made mandatory. The HRV or ERV must have an efficiency of at least 65% and its fan powered by an EMC motor. All fans are required to meet a higher standard of efficacy; CFM/watt.
  4. Air sealing is still required, but infiltration (blower door) testing is not required.
  5. Mechanical sizing (ACCA Manual J calculations) is not required.

Here’s the interesting part, the City of Aspen, Climate Zone 7, has sought to simplify the code by deleting the IECC ERI compliance alternative and replacing it with their own version. It’s called the Simplified Equivalent Compliance Alternative. Dwellings must meet the following criteria to comply with this alternative.

  1. Equivalent space cooling energy. The ratio of the air conditioning capacity to conditioned space is less than or equal to 12,000 Btu/hour per 1,000 square feet.
  2. Equivalent space heating energy. The ratio of the space heating system capacity to floor area of conditioned space is less than or equal to 32,000 Btu/hour per 1,000 square feet.
  3. Equivalent hot water. The distance from the hot water supply outlet to hot water pipe to the hot water entry to a room where hot water is used shall be no more than 10 feet. This shall apply to the kitchens, bathrooms with showers or tub, and rooms with a clothes washer.
  4. Equivalent lighting. Lamps over 15 watts shall be CFL, LED, or have an efficacy not less than 90 lumens per watt. Or, at least 90% of the lamps or fixtures shall have an efficacy not less than 75 lumens per watt.

This code change deletes equipment sizing, infiltration testing and energy modeling; the very tenets of the energy rating paradigm. I like the simplicity, but I fear it is too simple. I guess time will tell how Aspen fairs under this code.

Confluence Architecture & Sustainability can provide third-party insulation and air barrier inspections, and certification of compliance with the other provisions of this code.

Pitkin County’s “Matrix” could not be more different from Aspen’s energy code amendments. See link below…

Jump to Pitkin County Colorado’s energy conservation code compliance page…

Jump to Basalt Colorado’s energy conservation code compliance page…

Jump to Carbondale Colorado’s energy conservation code compliance page…


PHEV (Plug-in Hybrid Electric Vehicle)

Confluence already uses an electric car for site visits in the valley; 2013 Nissan Leaf.

But it won’t make it to our HERS Rating inspections and blower door tests in Telluride, Mountain Village, Steamboat, Vail Valley and Summit County.

So we have added a PHEV (Plug-in Hybrid Electric Vehicle) to the “fleet”.

A 2018 Toyota Prius Prime…

2018 Prius Prime

2018 Prius Prime

Some features…

  • Hybrid Synergy Drive with Electronically controlled Continuously Variable Transmission
  • 55 city/53 highway MPG
  • 133 MPGe
  • 640-mile EPA-estimated total driving range
  • 25-mile EPA-estimated EV Mode driving range


Energy & Sustainability Services

Recently more jurisdictions have adopted the 2015 IECC or the IgCC and we have been helping several architects & designers with energy and sustainability code compliance.

Go custom! You don’t have to follow the recipe. Make the energy code work for your project.

Farm out the energy work to Confluence. We will be responsible for any or all of these, bring value to the performance of the building, and take the load off of your hands:

  • Energy code compliance
    • Infiltration (blower door) testing
    • Assembly UA trade-off (calculation software)
    • Total UA trade-off (REScheck or HERS Rating)
    • Performance path compliance (REScheck or HERS Rating)
    • ERI path compliance (HERS Rating)
  • Code compliance/optimization and Construction Documents
    • Ventilation calculations
    • Sealed crawlspace & ventilation details
    • Continuous Insulation details
    • Back-ventilating siding and attachment details
    • Efficient framing details
    • Fenestration flashing details
    • Radon mitigation details
    • Thermal and pressure envelope delineation
    • Vapor retarder specifications
    • Air-sealing details
  • Local/municipal Green/Efficient Building Checklists
    • Carbondale, Basalt, Town of Snowmass Village, Telluride, Mountain Village
  • Above-code/Net Zero design and certification
    • LEED, Passive House, HERS Rating, etc.

Very Large Residential and Commercial Infiltration Tests

Confluence can perform very large residential and commercial infiltration tests, or blower door tests.


We set up eight fans in three doorways for this test at Habitat For Humanity’s new ReStore warehouse In Glenwood Springs, Colorado. Although, not the biggest test we have conducted. That honor goes to a 56,000 square foot house built for a Saudi Arabian Prince in the Starwood neighborhood near Aspen, Colorado.



Recent work…

We have recently gotten the chance to photograph some recently completed work.

The Basler Residence at Elk Springs, Garfield County, Colorado…


And this storage banquette…

Here’s a house going up in Oak Meadows…



How much solar do I need to power an Electric Vehicle?

Nissan Leaf

I don’t understand MPGe. A better metric would get me closer to knowing what I really want to know; how much does it electricity does it take to charge my car’s batteries? How far will that get me? What does it cost? How much solar do I need to offset the power consumption of an EV?

We’ve been driving our 2013 Nissan Leaf for one and a half years now and I have some data… the metric that makes the most sense to me is miles/Kwh. We live in a climate that is less than perfect for electric cars; little too hot in the summer, little too cold in the winter and lots of mountains. But still we average 4.5 miles/Kwh annually. I can’t find much difference in efficiency between the different makes and models of EVs. It seems to have much more to do with your climate, geography, topography, and a driver’s tendency to show passengers how fast an electric car will take off from a start. In 2016 we drove 12,108 miles. Assuming 4.5 miles/Kwh, then 2,691 Kwh went into powering the car.

Our solar array is officially rated at 3,240 watts. It was predicted to make us 4,753 Kwh annually, but in 2016 it gave us only 4,000 Kwh (16% less than estimated). The solar guys say this is because their software doesn’t de-rate for “losses” like; snow on the panels, age, azimuth and orientation. Sounds like a weak excuse to me; regardless, 4,000 Kwh is what we get.

The solar panels made enough power to push the car 4,000 x 4.5 = 18,000 miles. Each one of our twelve panels made us 1,500 miles worth of driving electricity. We drove only 12,108 miles, so the rest went into powering the house. To zero-out our total electric consumption, we would need to make a total of about 8,000 Kwh of power, or have a 6,500 system. 2,700 Kwh for our 12,000 miles of driving (34%) and 5400 Kwh for the house (66%).

So, how much solar do you need to offset your drive. Impossible to calculate for sure, but here’s starting point…  wattage of PV array required = (miles driven annually / 4.5 miles/Kwh) X .8  If you have a lead foot, get a couple more panels.

If we bought the electricity to drive the car 12,108 miles (2,691 Kwh x $.138) it would have cost $371. It would cost me about $1,000 for the gas to drive our 2005 Subaru Outback the same distance. Solar is good when offset your home electric uses, but when it keeps you from buying gas- it pays back three times faster! And don’t get me started on maintenance and repairs; oil changes, transmission oil, power-steering fluid,  fan belts, timing belts, head gaskets, catalytic converters, mufflers, oil filters, air filters, fuel filters, hoses, plugs, tubes, valves, sensors, etc. EV’s still have/need; insurance, tires, shocks, air conditioners, windshield wipers, windshield washer fluid, brakes and brake fluid. But I really don’t miss the regular stops at the gas and oil change stations and repair shops. If you have the means and it fits your commuting- buy one! You’ll love it.

Couple creates a deep-green, DIY home in Satank, Colorado

This is a re-posting of an article from Roaring Fork Lifestyles magazine.


Check this Tumbler scrapbook about the construction process, very interesting.


Confluence Architecture & Sustainability was the HERS raters for this home. The HERS is an outstanding -10! The negative means is actually beyond net-zero, it is net-positive. As in, the occupants of this home should never have to pay for heating, cooling, lighting or hot water. Attention to detail got this house crazy air tight. Even with salvaged windows and doors, Steven was able to get this down to .69 ACH50. I’m sure it would have bested Passive House requirements (.6 ACH50) if not for the less-than perfect windows and doors.

Congratulations Steven and Bailey- you have a beautiful, high-quality home. Here are a few teaser photos…

The "Hainestead"



Confluence Architecture’s Design Process


Typically, the process begins with walking the site and talking about the vision for the structure. If it is an undeveloped lot, we often identify the ”power spot”, a point on the site that relates the conceptual center to the design. The program is developed, that is the recipe of spaces and requirements for the house.


Schematic Design

The first schematic sketches are based on; site forces like the sun, views, trees. Civil issues like vehicular access, topography, and drainage. Tangible issues like program, size, and scale. Local vernacular. Confluence typically develops several schematic designs for residential projects.  The diagrams take the form of two dimensional plans and three-dimensional massing models.

Example of schematic site plan

Examples of schematic massing model

Design Development

During design development, the multiple design directions studied in schematic design coalesce into one design direction.  The 2-D plans and 3-D model are developed with more detail showing fenestration and exposed structure.

Example of design development plan

Examples of design development models

Construction Documents

During the Construction Documents phase, the details and materiality of the design are created.  These documents are used for building department, HOA approval, and ultimately to build the home.

Construction Documents

Beyond Construction Documents

On occasion, a project needs more description beyond construction documents.  Confluence can do fully rendered models for sales and advertising, interior drawings and details and more.

Marble Distillery Inn – rendering of hotel room

Photo of hotel room


Marble Distillery Inn – rendering of tasting room

Photo of tasting room


We are committed to keeping up with the state of the art in energy efficient and sustainable construction. Our construction documents will include details for building in an air-tight and durable manner.

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…