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…

 

Basalt, Colorado’s energy conservation code requirements

The Town of Basalt, Climate Zone 6, is currently (June 2019) on the 2015 IRC (International Residential Code) and the 2015 IECC (International Energy Conservation Code). Basalt is enforcing separate infiltration tests for ADUs, infiltration limit of 3.0 ACH50 and duct testing when outside the envelope.

Link to Town Building Department website…

REMP (Renewable Energy Mitigation Program)

Basalt has a REMP (Renewable Energy Mitigation Program) that engages anytime exterior uses of energy are used like; snowmelt, pools spas and garages. REMP fees are offset by renewable energy production, fee-in-lieu, or a combination of the two.

Link to entire adoption…

 

SBR (Sustainable Building Regulations)

Link to SBR Commentary…

 

Residential Type I (single-family)

Link to code language…

Points are determined under one of four compliance paths; prescriptive, performance, Net Zero Energy Ready or LEED for Homes.

 

Commercial Type II (multi-family and commercial)

Link to code language…

Most likely will require at least a COMcheck report for permit application submittal.

 

We do that…

Please give us a call and we can help navigate the process in the most cost-effective way. And optimize your construction for performance.

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