NET-ZERO TWO STEP

By Tom Paino

Even with my credentials as sustainable architect, I knew designing my and my partner’s home to the agreed-upon program of net-zero, i.e., the total energy used could not exceed the energy generated netted out for the year, would be challenging.  Starting the design process in 2017, the project entailed the complete renovation of an existing 1960s ranch, a house type found throughout Columbia County.  It also included the addition of a second story and an attached garage.  

The house had to be structurally modified as well as receive substantial insulation/air barrier improvements.  It now meets stringent Passive House standards and is certified with a Home Energy Rating System (HERS) score of 8, which equates to annual energy savings of nearly $6,000.  To put that in perspective, the median score for energy code-compliant houses is 100 (the lower the number, the better). 

With the project meeting this rigorous set of criteria, the remainder of the design involved “right-sizing” the energy-generating component, a roof-mounted solar panel array.  The system is not independent, but feeds into the grid (net metering), which means the local utility dictates the terms of such an arrangement.  One term is the limit on the total energy produced, which is enforced by the NYS requirement, is that utilities cannot buy excess energy generated from residential customers.  The engineering required to satisfy this balancing puzzle is provided by certified solar panel installers – in this case, Lighthouse Solar of New Paltz.  Complicating the calculations was the not-so-perfect orientation of the existing building footprint – south, southwest instead of due south.  There was also some seasonal tree shadow at the southern end of the 26-degree pitched roof.  After projecting the accumulated energy use (heating, cooling, lighting, appliances, etc.), they determined an 8.1 kW array of 27 LG 300 panels would not produce more than 5% excess. 

This projection turned out to be quite accurate, and we were living without electrical bills for almost 2 years.  However, late in 2019, a sooner-than-expected purchase of an all-electric vehicle that was charged at home reverted us into feeding the meter with money instead of the sun.  So, back to the drawing board with Lighthouse Solar to solve the imbalance.   It was easier this time since there was only

a single energy use to be compensated, but also some surprises.  Although it had only been 4 years since the first solar installation, new panels, Q Cell 400 modules, worked more efficiently. Also, a 200-year-old sugar maple was safely trimmed to reduce some of the seasonal shade. This addition increased the total output to 12.1 kW.  The yearly generation is hovering at the 5% excess limit, but the average savings have grown to $8,000 since there is no longer a gas bill for the car.  The only downside is a slight hodgepodge on the roof since the new panels have a different look and had to be installed in the opposite orientation of the originals for greater efficiency. 

Beyond energy cost savings, there is the reduction in greenhouse gas emissions.  We are estimated at about ¼ GHG emissions of the typical northeast stand-alone suburban home.  Are two steps to net zero worth it?  YES!

Thomas Paino, R.A.