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.

Link…

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

Link…

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

Predesign

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

Sustainability

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…

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
JurisdictionIRCIECCAmendments to CodeHERS RequiredHERS usable for permitBlower Door Required
Garfield County20152009No Amendments to IECCnonono
City of Glenwood Springs20092009No Amendments to IECCnonono
Town of New Castle20032009Requires third party checklist, blower door (7 ACH50), CAS test, and ENERGY STAR appliancesnoyesyes
Town of Silt2009nonone
City of Rifle20092009No Amendments to IECC
Town of Carbondale20092009No Amendments to IECCnoyesmaybe
Pitkin County20152015No Amendments to IECCnoyesyes
Town of Basalt20062015noyesyes
Town of Snowmass Village20152015No Amendments to IECCyesyesyes
City of Aspen20152015IECC -many amendmentsnonono
Eagle County20152015Fenestration U-factor .30 max.noyesyes
Town of Vail20152015R21 on wood framed can be substituted for continuous insulationnoyesyes
Town of Avon20152015all gas fired boilers used for snow melt minimum 92% AFUEnoyesyes
Town of Eagle20122012No Amendments to IECCno
Town of Gypsum2003nononeno
San Miguel County20092009San Miguel County Prescriptive Codeif over 5000 sfyesif over 5000 sf
Town of Telluride20032009Eliminated 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 solaryesyesyes
Town of Mountain Village (Telluride)20122012HERS rating required, mechanical engineering required, permit fee reduced for good HERS or low exterior energy useyesyesyes

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…

locationnumber of testsnumber of tests over 3 ACH50ACH50 averageACH50 lowACH50 High
City of Aspen49263.41.267.08
Pitkin County42203.231.286.37
Snowmass Village874.122.925.71
Town of Carbondale26133.061.165.8

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 2016Average HERS Index in 2016
Alabama1,74571
Alaska*42555
Arizona12,52263
Arkansas71472
California**1,15668
Colorado12,32055
Connecticut1,23653
Delaware2,06753
District of Columbia33759
Florida12,48458
Georgia8,82070
Hawaii3145
Idaho1,64960
Illinois3,36160
Indiana8,95165
Iowa5,03256
Kansas1,28969
Kentucky2,00965
Louisiana31474
Maine11326
Maryland6,51355
Massachusetts7,46655
Michigan2,94457
Minnesota6,49451
Mississippi2565
Missouri62568
Montana11549
Nebraska1,24952
Nevada4,96662
New Hampshire59161
New Jersey3,70461
New Mexico1,14856
New York3,64053
North Carolina13,39766
North Dakota2158
Ohio6,59560
Oklahoma4,01961
Oregon33056
Pennsylvania3,57961
Rhode Island33462
South Carolina7,74068
South Dakota21953
Tennessee1,10667
Texas40,01264
Utah1,52262
Vermont38847
Virginia7,23563
Washington1,31656
West Virginia12667
Wisconsin2,52652
Wyoming6358

 

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