Confluence Architecture goes Net-zero (electrically)

This week Confluence Architecture had a 3.24 Kw photovoltaic solar system installed on the roof to offset the electrical consumption of our firm. Our building already sports passive solar heating & a thermal solar hot water system. The addition of these twelve solar panels drops our HERS rating to a very healthy 30. We felt like the time was right to take the plunge because the cost of solar systems has been dropping and incentives are still high. The system will cost us $14,000 out of pocket, but by the time we collect the incentives and take the federal tax credit it will be more like $5,800! If electric costs were to stay at current rates- we could see this system pay for itself in savings in just 10 years. The system is slightly oversized, because our business plan calls for a plug-in electric vehicle as the next step towards carbon footprint reduction. Our inverter can take another string of panels if we find that more would be beneficial. Many thanks go out to the folks at SoL Energy for a first-rate installation job; Ken Olsen, Kelly Kirby, Mike Bouchet and Nirish Kafle.

solar PV installersPV inverterPV-array

Marble Distilling Company

Architectural Renderings

I’m a bit of computer geek and certainly an energy geek. Did you know that the harder you work your computer, the more power it consumes? The one thing that really pushes my computer is architectural rendering software. The computer has to do complex calculations to trace the path of light in a simulated three dimensional space as it bounces around. Every material has its own attributes; shiny, transparent, translucent, etc. Then there is shade and shadow, natural and artificial light to consider. The software goes through a dozen or more layers of calculation for every pixel of an image.
Recently we were retained to produce three images for the Marble Distilling Company. Once a model is set up to be rendered, it can take several hours for the computer to crank through the calculation process. In one case, the computer was working so hard, the power supply actually burnt up! Pop, smoke and dead computer.

dead power supply

The Mable Distilling Company of Carbondale, Colorado is set to open in February. Until then, here is a peak at the interiors and a link to their website.


Distillery tasting room

Hotel bathroom

Hotel room

Effectiveness of Sustainable Construction Techniques in the Roaring Fork Valley

CORE grant awarded for research project

Confluence Architecture and Evaluation Services, LLC in collaboration with Habitat for Humanity Roaring Fork Valley received a grant from CORE (Community Office for Resource Efficiency) to conduct research to better understand the life cycle and return on investment of several energy efficiency construction upgrades to single-family homes in the Roaring Fork Valley climate. The grant funded a study that compares various energy efficiency construction components by their ratio of installation cost to KWH of energy saved and tons of carbon saved. After a year of work, we are happy to share the results here:

Executive Summary

This study seeks to answer a subjective question: How best can additional money and carbon be invested in the construction of an affordable home in the Roaring Fork Valley to minimize lifetime utility and carbon costs?

This question is investigated through the lens of a Habitat for Humanity home currently under construction in Carbondale, Colorado. While not changing the physical design of the home (shape, footprint, floor plan, windows, area etc.) 100+ home configurations are studied through LCA (life cycle analysis), energy modeling and construction cost estimates. The configurations focus on practical construction choices made every day such as wall assemblies, insulation levels, treatment of crawl spaces, attics and mechanical systems.

The study finds, unsurprisingly, that the most expensive home configuration to build saves the most carbon and has the lowest annual energy costs. The perfect mix between initial construction costs and carbon and energy savings is dependent on the values of the investor. In order to illustrate several successful investments, this report contains an in-depth analysis of 8 benchmark home configurations that illustrate practical construction combinations over a range of investment and performance levels. Following is a list of notable trends distilled from the data:

  1. The best way to reduce the carbon footprint of a home is to reduce operational energy consumption, even if it raises the initial construction carbon footprint. The carbon footprint for materials, transportation, and construction of the home is exceeded by the carbon footprint of the annual energy usage in three years for a typical code home and five years for a high performing home. Construction carbon becomes important only as homes begin to reach net-zero and in some key carbon-rich construction materials.
  2. The largest factor in fuel consumption and construction cost is the mechanical system. Avoid electric heating of any kind. Ducted furnace air systems are the lowest monetary cost path to efficient building heat. Hydronic systems provide the best comfort and have an overall lower carbon footprint- with an added monetary investment.
  3. Avoid active cooling. While air-conditioning use is increasing in the Roaring Fork Valley, energy modeling reveals it to be unnecessary for a well-designed and built home in our heating dominated climate. The cooling load is only 3% of the heating needed. Active cooling systems have the potential to use excessive electricity in an area where there is little need, especially if it is used in lieu of passive strategies (like appropriate clothing, opening windows at night, and proper shading of glazing).
  4. Insulation continues to be a cost effective way to increase building performance. The type and location of insulation matter. This study found continuous exterior insulation to be more effective than added cavity insulation. SPF (Spray Polyurethane Foam) insulation proved not to be as cost effective as other insulation types, going against an emerging trend for SPF in the Roaring Fork Valley. Beyond the cost and performance balance, insulation has the single largest impact on initial material carbon of any building component. The carbon footprint of like performing insulations types can vary 500-fold. The lowest carbon insulation option is blown cellulose while carbon intensive insulations are XPS (Extruded Polystyrene) and SPF.
  5. Air Sealing is on par with insulation in its cost effectiveness in increasing building performance. If careful air barrier control becomes a part of standard construction techniques the energy savings reward is significant relative to cost.
  6. Volume is a luxury. Two homes that are identical on the exterior and have the same mechanical systems, windows, and shell construction can vary in energy performance by 5 – 15% due to the inclusion of vaulted interior spaces and conditioned crawl spaces. It is notable that this is one of the few areas where carbon and money are not at odds. More compact interior spaces are cheaper to build, require less initial construction carbon and are more efficient to run.
  7. Photovoltaics are becoming a key component to include in any home shell beyond the basic code minimum. This came as a surprise to the study authors, questioning a rule of thumb where shell upgrades are better done prior to the addition of renewables. Due to continued price declines, PV is proving to be more economical than many shell upgrades such as high performing windows or super insulation.
  8. Net-zero is not out of reach. This study finds several home configurations that can be made net-zero in a construction price range ($200-225/sf) that is in keeping with market rate construction and home sales costs in the Roaring Fork Valley. These homes use typical construction techniques and materials.

Download paper here: (warning it is about 7 MB)   The Effectiveness of Sustainable Construction Methods

Stay posted for a public presentation of the results in January 2015.

Habitat for Humanity house earns LEED Platinum!


Confluence is proud to have provided energy and sustainability consultation services for Habitat for Humanity in the effort to provide the Lavender’s with a home with very small monthly utility bills. Below is a TV news and a newspaper story about the Lavender home.



Creative Repurposing

As Confluence Architecture becomes more and more digital, we have less need to keep file cabinets full of paper documents. I imagine this is true for many homes and businesses. So what becomes of all those unneeded file cabinets? They are typically 100% recyclable, which is good. But Angela had a great idea to convert a couple into storage benches for landscaping equipment.

repurposing file cabinet closed  repurposing file cabinet open

HERS rating nets refund

Soffer HERSA home in Eagle County just received its final HERS rating and received an amazing score of 18.  This score resulted in a refund of 25% of the permit fees paid to Eagle County.  This netted the owner close to $5000 refund.  The refund far exceeds the cost for Confluence Architecture to perform the HERS rating.

Stay tuned, Confluence Architecture is also providing LEED consulting on this home.  The final package for LEED for Homes will be submitted to week.  We are on track for LEED gold.


Summer Construction Round Up

This first day of fall is a great opportunity to celebrate what Confluence Architecture has been working on Spring and Summer of 2014.  We currently have 3 projects under construction with a 4th to break ground withing a month.  We are happy to  again be working with Jeff Dickinson and Energy and Sustainable Design on the architectural design of the Marble Distilling Co.  This distillery, hotel and lounge located on Main Street in Carbondale Colorado is finishing out framing.  This fast track project has been exciting.  Look for it to open early 2015.  Be sure to check out Marble Distilling Company’s website and facebook pages to see the evolution of this new venture.

Marble Distilling Company










View of Tasting Room









In addition, three residential projects have been keeping us hopping.  A modern remodel in Aspen glen, an addition on Missouri Heights, and a new spec home on Four Mile Road near Sunlight Ski Area are all under construction.  Keep tuned here for photo as these projects progress.

Blower Door Test

What does it mean for the Builder?

What is a Blower Door Test? It is also called an air-leakage or infiltration test. It measures the air that moves through a building envelope at a standard pressure difference.

Blower Door Test

The blower door itself is a device with a large fan that is used to push air out of the building through the building envelope. The resulting vacuum draws air in though the envelope and the rate can be measured by the blower door. During the test, the manometer, which is the brains of the blower door displays a number, which is the flow in CFM (cubic feet per minute) at a given standard test pressure. This raw number must be adjusted to compensate for altitude and the density differences of different temperature air inside and outside. This number is then used to calculate even more numbers, that we can use to compare the tightness/leakiness of different buildings to each other and to a standard.

Two common metrics for comparing leakage exchange rates are ACH50 (Air Changes per Hour at 50 Pascals) and CFM/SF75 (Cubic Feet per Minute per Square Foot at 75 Pascals).

ACH50: if you are building a house under the 2009 IECC (International Energy Conservation Code) the maximum allowed air changes per hour at 50 Pascals is 7. To calculate the ACH50 from the CFM50 given by the blower door we need to know the volume of the building. Multiply the flow by 60 to convert to hours, then divide by the volume. (ACH50 = airflow (CFM50) X 60 / conditioned volume) If the number is under 7 then it is a pass. In the 2012 IECC the limit jumps to 3 ACH50. That is tight, but the goal to become a certified Passive House is .6 ACH50!

CFM/SF75: if you are working on a commercial project under the IECC or IgCC, you will see a requirement like this; leakage must be under .40 CFM/FT² (2012 IECC) or .25 CFM/FT² (2012 IgCC) at 75 Pascals . Under this metric you need to know the surface area of the building envelope. Multiply that by standard rate to find the allowable leakage flow at 75 Pascals. If the blower door measures a flow less than the allowable, then it’s a pass.

How long does the test take? If the building is setup (i.e. windows closed and mechanical systems shut down) it takes only a few minutes to assemble the blower door. The test takes only a moment if no problems are encountered. If the goal is to find leaks and seal them, then this is the time to walk the building and search of leaks with an infrared camera, smoke or a hand.

When is the building ready to be tested? Technically a building can be tested as soon as there is enough of an envelope to pressurize. If the test is at rough, then incomplete flues and missing door hardware can be temporarily taped over. If the test is at final, and the goal is to get the best score possible, then put off the test until the hardware, fixtures and switch covers are in place. Although workers may be present for the blower door test, all exterior doors need to be closed and stay closed for the duration of the test.

What is blower door directed air sealing? Running a blower door continuously to find and seal leaks as they are found in an existing building.

Why is air sealing important? As it turns out, air infiltration is typically the single most important way to same energy in a building, and it’s relatively cheap and easy to do, and it also increases building comfort and durability.

How does the builder have an affect on the tightness of the building envelope? Through insulation choices, attention to sealing details, mechanical system choices, etc.

How can the score be improved? Let’s talk about the house. We can provide advice, details and specifications to help you minimize air infiltration.

Now the building is so tight, I have to add mechanical ventilation; isn’t that just silly? Its all about control. It’s true we have to exchange some air to keep the Indoor Air Quality high, and some heat will go with in. But if all of that air moves through a mechanical system, then it can be controlled and conditioned. With the help of an ERV or HRV a great deal of the heat can be captured and put back into the building. It is also an opportunity to filter the incoming air with a high performance air filter instead of that air being drawn through unclean cracks and gaps. Also, if the infiltration moves though the insulation, the insulation loses part of it’s ability to resit heat loss.

How much does a blower door test cost? Confluence charges $250 for tests in Glenwood Springs, Carbondale, Basalt, Snowmass and Aspen Colorado. Contact us for quote outside of that area. Fees increase  if additional equipment is required because the building is very large. We provide you with a report for the Owners and the building department with the test results within 24 hours.

How do I schedule a blower door test? Just give us a call or email. Ample notice is appreciated.

multiple blower door test





Snowmass Village Adopts new 2012 Energy Building Code

2012 IECC

The Town of Snowmass Village is one of the first municipalities in Colorado to adopt the 2012 International Energy Conservation Code for both residential and commercial buildings. Theses codes go into effect December 1st 2013. Confluence can help you with Prescriptive or Performance compliance with the code.  To learn more, read below.

What do the code changes mean to your project?

The 2012 code requires more drawings and specifications, more insulation, a tighter envelope, tighter ducts, and more efficient lighting than the 2009 code. Here is a summary of the important changes for designers and builders in climate zone 7:

  1. Construction Documents must be submitted for review that present a comprehensive strategy to deal with heat and energy in a home.
  2. Blower door testing requirements have become mandatory and more stringent; the 2009 threshold of 7 ACH50 has been changed to 3 ACH50.
  3. All homes will be required to have a whole-house mechanical ventilation system.
  4. Prescriptive wall insulation requirements have become more stringent, builders will be required to install exterior rigid foam insulation (or to use some other comparable wall insulation strategy).
  5. Prescriptive duct tightness requirements have become more stringent.
  6. Prescriptive lighting requirements are now at 75% high-efficacy lighting fixtures.

Permit submittal requirements

Requirements are different depending on whether the applicant is choosing the prescriptive or performance path to approval. But basically, the thermal envelope must be delineated especially its relationship to attics, cantilevers, crawlspaces and attached garages. Documents must include air barrier and water management details, and descriptions of thermal and vapor barrier specifications. If the performance path is used, then energy modeling certificates are required.  Confluence can provide envelope consulation including prescriptive path details or energ modeling for your project.

Air barrier inspection

The new 2012 code doesn’t give builders a choice anymore; builders now have to comply with both the checklist requirements and the requirement to conduct a blower door test. See the condensed inspection list below:

  1. “A continuous air barrier shall be installed in the building envelope. Exterior thermal envelope contains a continuous air barrier. Breaks or joints in the air barrier shall be sealed. Air-permeable insulation shall not be used as a sealing material.”
  2. “The air barrier in any dropped ceiling/soffit shall be aligned with the insulation and any gaps in the air barrier sealed. Access openings, drop down stair or knee wall doors to unconditioned attic spaces shall be sealed.”
  3. “Corners and headers shall be insulated and the junction of the foundation and sill plate shall be sealed. The junction of the top plate and top of exterior walls shall be sealed. Exterior thermal envelope insulation for framed walls shall be installed in substantial contact and continuous alignment with the air barrier. Knee walls shall be sealed.”
  4. “The space between window/door jambs and framing and skylights and framing shall be sealed.”
  5. “Rim joists shall be insulated and include the air barrier.”
  6. “Insulation shall be installed to maintain permanent contact with underside of subfloor decking. The air barrier shall be installed at any exposed edge of insulation.”
  7. “Where provided in lieu of floor insulation, insulation shall be permanently attached to the crawlspace walls. Exposed earth in unvented crawl spaces shall be covered with a Class I vapor retarder with overlapping joints taped.”
  8. “Duct shafts, utility penetrations, and flue shafts opening to exterior or unconditioned space shall be sealed.”
  9. “Batts in narrow cavities shall be cut to fit, or narrow cavities shall be filled by insulation that on installation readily conforms to the available cavity space.”
  10. “Air sealing shall be provided between the garage and conditioned spaces.”
  11. “Recessed light fixtures installed in the building thermal envelope shall be air tight, IC rated, and sealed to the drywall.”
  12. “Batt insulation shall be cut neatly to fit around wiring and plumbing in exterior walls, or insulation that on installation readily conforms to available space shall extend behind piping and wiring.”
  13. “Exterior walls adjacent to showers and tubs shall be insulated and the air barrier installed separating them from the showers and tubs.”
  14. “The air barrier shall be installed behind electrical or communication boxes or air sealed boxes shall be installed.”
  15. “HVAC register boots that penetrate building thermal envelope shall be sealed to the subfloor or drywall.”
  16. “An air barrier shall be installed on fireplace walls. Fireplaces shall have gasketed doors.”

Every new home must pass a blower door test

Once you have completed the air-sealing checklist, you still need to conduct a blower door test.
The maximum air-exchange rate of 3 ACH50 is a significant change. We have performed many blower door tests for new construction throughout the Roaring Fork Valley and I can say that builders had no problem at all staying under the 2009 IECC requirement of 7 ACH50. Staying under 3 ACH50 does take some attention to detail. This can be especially challenging for remodels and additions, where a builder may be forced to conduct air-sealing in the existing areas of the home. Confluence provides blower door testing.

Mechanical ventilation

In the case of Snowmass Village, this one is a bit odd because the 2012 IRC has not been adopted yet. The IECC requires homes to achieve 3 ACH50, but doesn’t have any requirements for mechanical ventilation. That requirement is found in the mechanical section of the 2012 IRC (M1507.3). It says that a house that has an air-exchange rate of less than 5 ACH50 must include a whole-house ventilation system. Regardless of this loophole in the code, any house that has an air-exchange rate of 3 ACH50 should have a mechanical ventilation system.

Above-grade walls

The 2012 IECC ratchets up some minimum prescriptive insulation levels in climate zone 7. The minimum crawl space wall R-value has been increased from R10 continuous to R15 continuous and the new code calls for above-grade walls to have at least R20+R5 insulation or R13+R10 insulation.
The first value is cavity insulation; the second is continuous insulation or insulated siding. So ‘13+5’ means R13 cavity insulation plus R-5 continuous insulation or insulated siding. Note that all of these code requirements are minimum requirements. In many cases, the minimum code requirement for the R-value of the continuous insulation is not enough to keep OSB or plywood wall sheathing above the dew point in winter. Spray Polyurethane Foam and SIPs can be used in lieu of applying rigid insulation. The only options that do not require some kind of foam product are some of the rarely seen wall assemblies like; double-framed walls, ICFs and straw bale.

Duct tightness testing

Like the 2009 codes, the 2012 IECC requires duct leakage testing unless the duct system is located entirely inside of the home’s thermal envelope. The new code has increased the stringency of the duct leakage thresholds. The bottom line: if you must have ductwork outside the thermal envelope, then get out your tub of mastic and seal everything.

High-efficacy lamps

The 2012 IECC requires that a minimum of 75 percent of the lamps in permanently installed lighting fixtures shall be high-efficacy lamps. Basically this means no incandescent lamps or T12 fluorescents.

What is the HERS rating process?

What is your score goal?

Perhaps your goal is being stipulated by requirements from the building department or neighborhood covenants, or a desire to qualify for Federal tax credits. Maybe the house is participating in an above-code program like ENERGY STAR, LEED for Homes or Passive House. Or maybe you just want the benefits and bragging rights that come with a net-zero energy house? In any case, the stated goal tells us much about how aggressive the energy consumption reduction measures will be.

At what point does the process start?

The sooner, the better. There are many ways to reach your HERS goal, but some are much more expensive than others. Early in a project it is easier for your HERS Rater to help you select the most cost-effective methods to achieve the goal. Questions that often come up at this stage; condition or vent the roof and crawlspaces, how good do the windows need to be, is the house letting too much sun in or not enough, what should the insulation strategy be, radiant verses force-air distribution systems, etc. If the process is started late, and your HERS Rater has little affect on the detailing of the house, and the house falls short of the goal, then there are few options. Sometimes an Owner can pay a fee-in-lieu of meeting the HERS goal. If not, then installing renewable energy, i.e. solar, may be the only viable course of action.

What does the process look like?

In a nutshell it goes like this… We do take-offs from the construction drawings and put them in an energy modeling software. We can start off with some assumptions and defaults, but eventual we have to know everything about the shell and mechanical system. We can work from DWGs (2010). PDFs are helpful too, and SketchUp models are great. Then the computer gives us a score. We can adjust the model at that point to get a better score. This is a valuable time to use the energy model to optimize the performance of the house and value engineer the energy features of house. When it gets to a point that works for everybody, then we print the projected HERS certificate for the permit application. During construction we will need to update the model with any real world changes and inspect the insulation before it is covered. At final, we inspect the mechanical system to insure it matches what we modeled and perform any required tests; typically just a blower door test to determine the air exchange rate. Then we send my file to our Quality Assurance provider, EnergyLogic, they check it out. If Okay-ed, they issue the final HERS certificate and upload the results to the RESNET national database.

Which party is typically responsible for shepherding the HERS Rating?

The HERS Rating process can be initiated by the Owner, Builder or Architect. In the end, it is a collaboration between all parties involved.

How do I find and engage a HERS Rater?

Search no further- Confluence Architecture has HERS Raters on staff. As architects, we understand those houses that are out of the standard mold.  Have a 20,000 square foot house?  Have a complicated remodel?  Have unusual construction assemblies?  We are the HERS raters for you.  HERS ratings fees vary with the size and complexity of home and typically range from $1000-$2000.  Call us for an estimate.