Carbondale’s new Energy Code adoption

Beginning the 1st of July 2020, The Town of Carbondale revised their REBP (Residential Efficient Building Program). Carbondale is currently on the 2009 IRC (International Residential Code), the 2012 IgCC (International Green Construction Code) and the 2015 IECC (International Energy Conservation Code).

Residential

Link to REBP guidelines and REBP checklist here…

Carbondale has adopted the 2015 IECC and has a REBP (Residential Efficient Building Program). The chart below is the crux of understanding the energy code compliance.

Note that SF in this case refers to a special definition in the REBP glossary. Ignore “floor area” and look to “total square footage”; where it says “for the purposes of this program…”. floor area will mean; inside of walls, include basement, exclude garage, no deduction for unfinished areas, storage or structure.

What are the submittal requirements? Let me try and unpack what this chart means.

Carbondale has made solar PV mandatory in almost all cases. Is this lopsided push for PV is born out of COREs mission to electrify all houses? And why not PV? Because- the point of doing an energy model is to find the most cost-effective path to a set goal. If you declare PV the winner without a fight, you have cheated the science, tipped the scales. PV is pretty great, when would it really matter? When glazing becomes a large portion of the envelope load. When does that happen? Remodels obviously. The math might show that the old windows should really be replaced for reasons of heat loss, service life, comfort, etc. but, the project has already blown it’s wad on a PV system, got all the points they need, window replacement off the table. Another time glazing becomes overwhelmingly important- large areas of glazing facing south or west. I routinely see custom homes in River Valley Ranch with more than 30% glazing factor (30% of the above grade walls are made from glass). In these homes getting the right kind of glazing is huge. Sometimes the SHGC is more dominate than the U-factor! These southern view window walls are the only reason some of these houses require air conditioning. Also, a blind favoritism towards PV will stifle development/implementation of other kinds of renewable energy production, sorry GSHP, thermal solar and Drain Water Heat Recovery. Same argument for CI on the walls. The code does not make CI mandatory, I think, because flexibility is good, and CI can easily be traded off for better performance elsewhere. Ranch style houses typically have more roof area than walls area, why not make CI on the roof mandatory? It would move the needle more. And on the roof, you don’t even have all the technical problems with fenestration openings, siding and stone veneer attachment, etc. CI has many wonderful benefits, and I recommend it for most jobs, but it is rarely the first most cost-effective way to conserve energy. Ok, I’m getting off the soapbox, on with the submittal requirements…

I’m told the “percent better than code” row should be stricken from this chart; it no longer applies.

I’m told the “(option)” under the Tier 1 column means that a less than 2000 square foot house can submit using the prescriptive path as long as 1.5 watts per square foot of PV is provided. I don’t understand why, but they also require a Total UA Compliance calculation to be performed and submitted. No requirement to perform over basic compliance, so it just equal to prescriptive anyway. Or submit a Projected HERS rating of 50 in lieu, PV or not.

So basically what Carbondale is saying is that the prescriptive (402.1), the performance path (405) and ERI (406) are not a compliance option. Every single project will have to submit at least a Total UA Compliance Calculation (402.1.5), and PV design showing 1.5 watts per square foot or a HERS rating.

Currently, the Town is not considering ADUs (Accessory Dwelling Units) as their own unit. No need to include in REBP submittal, HERS rating or blower door infiltration test.

The required points refer to the REBP checklist (an Excel spreadsheet). Points are earned by including features in the house like, efficient framing, water conservation, chemical reduction, etc. Refer to the guidelines to understand how to fill out the checklist. Extra points are awarded for above code HERS (Home Energy Rating Score), infiltration rates and solar. Confluence can perform these tests and produce these compliance reports. Please call us early in the process so we can help you optimize the insulation and comply with the energy code in the most cost-effective way.

Commercial

Carbondale is on the 2009 IBC (International Building Code), but they have also adopted the 2012 IgCC (International Energy Conservation Code).

Link to Carbondale’s heavily amended adoption of the IgCC here…

Navigating the IgCC is a deep subject, but expect it touch every phase of your project. The code requires above IECC insulation and infiltration mitigation, construction waste tracking and structured plumbing. The code requires third-party inspections and testing for the envelope. Confluence has been the code compliance and envelope consultant for six IgCC projects now. The Town of Snowmass Village has also adopted this code. Please calls us early in the process if you are planning a commercial project in The Town of Carbondale or The Town of Snowmass Village.

Jump to ICC’s overview of the International Green Construction Code…

Jump to Energy Conservation Code Hub for; the western slope of Colorado; Aspen, Telluride, Mountain Village, Town of Snowmass Village, Basalt, Carbondale, Pitkin and Eagle County…

 

Confluence turns 20!

April 1st 2020, Happy birthday Confluence Architecture and Sustainability.

Solar-powered inspections…

And Mark became a certified International Code Council certified Residential Energy Inspector/plans examiner and a IECC/HERS Compliance Specialist.

Prince Creek Home – Progress Update

With the beginning of fall and the impeccable Colorado weather, the construction crew has been busy making progress on the Prince Creek home and ADU. The porch timber framing has begun, the buildings are dried-in, and the finishes have begun to appear!

Please let us know how we can help with your deep-green architecture project in Pitkin County, Colorado.

How much solar PV do I need for my electric vehicle?

EV+PV

There is much to like about Electric Vehicles (EVs). There is much to like about Solar Photovoltaic power collection (PV) too. But when you put the two together, something extra happens… You can now think of your solar system as being paid off, not by offsetting the cost of the electricity that runs your house, but by offsetting the cost of the gas you’re not buying.

Below, I am going to list the real-world drive data from our two company cars, a Nissan Leaf EV and a Prius Prime PHEV (Plug-in Hybrid Electric Vehicle). Sorry hybrids, you don’t get to play this game. Then I’ll list our real-world solar array data and calculate the value of the electricity we have harvested from our PV array. And answers some important questions; How much PV do I need to offset driving an EV or PHEV?

3.24 kW PV array:

Number of panels:                           12

Power per panel:                              344 watts

Annual production:                         4,128 kWh

Cost after rebates:                          $5,796

Thermal solar panels on lower roof, PV array on upper roof

Thermal solar panels on lower roof, PV array on upper roof

The calculations will vary, of course, from place to place and car to car and driver to driver. These cars live in Carbondale, Colorado. The climate is pretty good for EVs; not too hot, not too cold. Typically highway driving punctuated by small towns. The road is never level, up valley, down valley, up the hill, down the hill. We run Blizzak winter tires for about five months, and Michelin Energy-savers the rest of the year. I’m no engineer; there is much rounding and estimating used in these calculations. For projections I will use these fuel values:

Street value of a kWh:                    $.11 (summer 2019)

Street value of a gallon of gas:    $2.60 (summer 2019)

Total annual value of electricity produced by PV based on utility cost of kWh:

Total:                                                $520

Confluence company cars at local EV event.

Confluence company cars at local EV event.

2013 Nissan Leaf EV, 24.0 kWh battery

Miles driven annually:                     13,000

Miles/kWh: (average)                      4.4 miles/kWh

Total kWh consumed:                      3,022

Percentage of public charging:      10%

kWh provided by PV:                       2,720

Leaf consumes:                                 66% of our production

Leaf consumes:                                 8.0 panels

Miles per panel:                                1,463

Confluence company cars at local EV event.

Confluence company cars at local EV event.

2018 Prius Prime PHEV, 8.8 kWh battery

Miles driven annually:                      19,000

Hybrid ratio:                                       50% EV : 50% ICE (Internal Combustion Engine)

MPG:                                                    80.5

Gallons of gas:                                   118

Cost of gas:                                         $307

Miles/kWh:                                        5.4 miles/kWh

Total kWh consumed:                      1,713

Percentage of public charging:       10%

kWh provided by PV:                       1,542

Prius consumes:                                 37% of our production

Prius consumes:                                 4.5 panels

Miles per panel:                                 2,111

Total annual value of electricity produced by PV based on gasoline offset:

If 22,500 miles were driven in a gas drive vehicle (e.g. 2005 Subaru Outback, 32 MPG)

Gas offset EV portion of Prius:      $772

Gas offset Leaf:                                 $1,056

Total value of gas offset:                 $1,828 (703 gallons)

 

Every solar PV panel you put on your roof will push your EV 1,500-2,000 miles.

So, the bottom line is that our PV system makes us $520 worth of electricity annually, not bad. It would pay itself off in about 11 years at that rate. But when we put that electricity into an EV, it saves us from buying $1,828 worth of gas over our old ICE car, which translates to a 3.2 year payback!

 

 

 

 

Prince Creek Home Breaks Ground

 

 

 

 

Confluence is excited to announce that Prince Creek Home (outside of Carbondale Colorado) is framing. This home is a modern reinterpretation on an existing ranch home foundation. It will be net zero! To achieve net zero the home uses SIPS, good foundation insulation, heat pump heating system, proper window location and shading and PV.

Eagle County Colorado’s energy conservation code requirements

Eagle County, Climate Zone 6, is currently (June 2019) on the 2015 IRC (International Residential Code) and the 2015 IECC (International Energy Conservation Code). The ECO-build checklist is gone. Link to Eagle County…

Eagle County has an exterior energy usage mitigation program. Exterior energy uses listed below shall offset 50% of energy use through onsite renewable energy resources or pay fee-in-lieu option accordingly:

  1. Snowmelt                 34,425 BTU/sf               $16.00 per sf (first 200 sf exempt)
  2. Spa/Hot Tub           430,000 BTU/sf            $176.00 per sf (first 64 sf exempt)
  3. Exterior Pool           83,000 BTU/sf              $136.00 per sf

A couple of extra mandatory provisions have been adopted; fenestration U-factor of 0.30 maximum value required, and the main heat source to be a minimum of 92% efficient AFUE.

Eagle County is enforcing separate infiltration tests for ADUs, infiltration limit of 3.0 ACH50 and duct testing when outside the envelope.

Confluence Architecture & Sustainability can provide third-party inspections, all the documentation, modeling, testing and certification required to demonstrate compliance with all provisions of this code.

 

Please contact us if we can help you comply with the energy code, wherever you project is located.

Jump to Energy Conservation Code Hub for; the western slope of Colorado; Aspen, Telluride, Mountain Village, Town of Snowmass Village, Basalt, Carbondale, Pitkin and Eagle County…

 

The underutilized U-factor alternative?

I review quite a few residential IECC (International Energy Conservation Code) submittals, and I would estimate that three-quarters of them are submitted as a straight-up prescriptive submittal. That’s when the table below is followed, without deviation. There is nothing wrong with this approach, but if a little flexibility is required, then leave the R-values behind and look at assemblies as U-factors, that can be morphed and traded around.

Table R402

The U-factor alternative (2015 IECC R402.1.4) is a very powerful and useful method, but I don’t see it get used much.

Table R402 U-factor alternative

I think it can be useful to use a chart like the one below to see building assembly alternatives by U-factor. PDF link…  U-factor alternative assemblies

For instance; can I substitute OVE (Optimum Value Engineering) or Efficient Framing for CI (Continuous Insulation) in zones 6 & 7. The Prescriptive compliance alternative would have at least R5 CI installed on the exterior of the above grade walls. The U-factor alternative says; use any wall with a U-factor of .045 or better. So, at a glance, from the list, I see that I could substitute R3.6 CI (i.e. 1.5” ZIP insulated sheathing) for the R5 CI and bump up the cavity insulation number to R23 and build the wall with efficient framing techniques. Don’t like CI at all? Then substitute an efficient framed wall with the cavities foamed solid to R36. Don’t like CI or efficient framing? Then you could use a 6” SIP, ICF or straw bale. Check the total U-factor of your specific assembly, it could vary from the U-factors on the list by a couple of thousands. Here is a super-good online wall calculator for R-values and U-factors including checks for moisture control.

https://www.appliedbuildingtech.com/fsc/calculator

If you still don’t like the choices that the U-factor alternatives gives, then it is time to move up to the Total UA Alternative, AKA RESchecks (2015 IECC R402.1.5). Often, projects get bumped out of the prescriptive path alternative because the insulation can’t easily be provided in a particular location. Then the Total UA Alternative could be used, because it can trade-off different assemblies. For instance, slab edge insulation, often hard to do at a door threshold, patio or deck attachment or behind stone veneer. The uninsulated slab edge can be “traded” for surplus U-factors on completely different assemblies anywhere in the project.

If you still don’t like the choices that the Total UA Alternative gives, or still having trouble reaching the code threshold, then it is time to go fully custom with the Simulated Performance Alternative (2015 IECC R405) or the Energy Rating Index (ERI) Compliance Alternative (2015 IECC R406). Both alternatives can checked by the software at the same time, but the ERI Alternative is more powerful, because it take into consideration low infiltration rates, high efficacy lighting, appliances and renewable energy sources. The only certified ERI program currently is the HERS Rating.

Please contact us if we can help you comply with the energy code in the smartest possible way.

Link to Colorado Energy Conservation Code Hub for; Aspen, Basalt, Carbondale, Eagle County, Pitkin County, Town of Snowmass Village, Town of Telluride and the Town of Mountain Village