California development to offer zero-net-energy housing
California house builder De Young Properties is to start work on the state's largest zero-net-energy housing development, with completion targeted for Q2 2018. Under the 36-unit scheme, which is backed by Utility Pacific Gas & Electric and the Electric Power Research Institute, homes will be constructed with an extended thermal boundary, as well as specially designed solar capacity. Additionally, when not consuming power the buildings can not only plough excess electricity back into the grid, but, with the use of appliances and heating, ventilation and air-conditioning systems working at noon, prevent solar dumps on to the grid as well.
California’s largest net-zero-energy housing development is coming next year to the Central Valley.

Third-generation homebuilder De Young Properties unveiled the 36-unit project Tuesday in Clovis, northeast of Fresno. The company has spent years redesigning its signature floor plans to include cost-effective energy efficiency improvements. The goal is to minimize the building’s electrical load and install enough rooftop solar to cover what remains, matching consumption and production over the year.

In practice, that boils down to improvements in the building envelope, which keeps air conditioning in and summer heat out. That’s not so hard in temperate coastal zones, but it’s a whole different story in the sun-baked Central Valley, which was forecast to hit 108 degrees Tuesday.

California is driving new home construction to net-zero energy by 2020 through the building code, as part of a broader climate goal to cut greenhouse gases from its economy. The first homes in De Young's EnVision community will be completed in Q2 2018.

"We know that at some point the state will require everyone to do this. Why not learn it ahead of time, get used to it and figure out how to bring costs down earlier?" said Executive Vice President Brandon De Young. "You're spending less on your energy bill, and the home's going to be more comfortable as well."

That quest has attracted some notable allies: Utility Pacific Gas & Electric and the Electric Power Research Institute (EPRI) partnered in the endeavor to gather data on the energy improvements and the broader impact on the grid from this type of development.

All about the envelope

Achieving this level of load reduction requires a lot more than buying fancier appliances.

Reducing the energy load needed for climate control starts with higher density insulation, better insulated windows, an electric heat pump and high-efficiency air conditioning.

On top of that, De Young added a thicker frame by switching out 2x4 wall studs for 2x6 lumber. That simple change demanded redesign, re-engineering and re-permitting for all the plans.

The homes sit on concrete slabs, so the duct work for heating and cooling goes in the attic. Historically, attics haven’t been insulated, and can get up to well above the outside temperature in extreme heat. That means the HVAC system uses extra energy to counteract the heat that’s fighting its way into the ducts from the attic.

All that energy usage, by the way, makes it possible for homes in this area to pay $800 to $1,000 a month for the utility bill, De Young said.

His way out of the steamy attic scenario: Insulate the roof, rather than the ceiling. This extends the “thermal boundary” and buffers the existing ductwork against the outside heat; the attic stays pretty close to the temperature inside the living quarters.

Once all that is done, the designers size the solar capacity to match the total annual demand of the house. Homeowners will lease from SolarCity (now Tesla) or buy the system outright as an additional feature on the home.

Yes, but is it cost-effective?

De Young Properties has been iterating models of energy-efficient home packages since around 2009. Since then, De Young said, prices have come down for efficient components.

"The cost for upgraded windows in 2009 was a pretty significant premium," he said. "If we included it, we had to market the heck out of it to make sure people knew they were buying a better product. Now the windows that were expensive then are pretty commonplace."

The company built its first zero-net-energy pilot home in 2013 and has been optimizing design components to bring costs down since. The upfront premium for one of the new net-zero homes versus a comparable equivalent is down to single digits, De Young said.

Whether that investment succeeds in zeroing out energy bills will depend on a family's consumption patterns, he cautioned (and there are fees that prevent anyone from truly getting to zero). If the monthly bill to beat is $1,000, though, it's hard to see these homes not making a massive improvement for a resident's energy budget.

EPRI's role is to analyze the performance of the homes to verify the cost-effectiveness of the improvements.

"The ultimate goal is to achieve market transformation that leads to our decarbonization goals," said EPRI principal program manager Ram Narayanamurthy. "Anytime we are trying to push the envelope as we are doing, we have to figure out what works and what doesn't."

That group's work with an earlier net-zero home project built by Meritage in Fontana had a felicitous outcome. The extra cost to achieve net zero was less than $20,000, or about $8 per square foot, Narayanamurthy said. When you break that out into additional monthly mortgage payments versus energy bill savings, the customers save more than they spend.

De Young's use of basic insulation materials in the attic to drive significant efficiency savings sets it up well for cost-effective performance, he added.

"It's about how you rethink your standard practice," Narayanamurthy said. "Once you move to the new normal, it's really not that much more expensive."

A duck curve in every kitchen

PG&E's involvement may come as more of a surprise, given that an aim of net-zero homes is to minimize the net flow of money from customers to their electric utility.

Under current regulatory policy, though, PG&E doesn't make a profit on kilowatt-hours sold, said Peter Turnbull, the zero net energy program manager there. Regulators have tasked the utility with increasing both renewable generation and energy conservation, and the De Young project is a test case for both.

Plus, the utility also has a stake in understanding what an influx of net-zero houses means for grid integration.

"Until you actually do it, there are some unknowns," Turnbull said.

Each house will generate its own family-sized duck curve: demand in the morning before work, then an abundance of solar production for the middle of the day and an evening peak as the sun tapers off and residents arrive home after work.

Since these homes aren't configured with battery storage, they could push a lot of kilowatts onto the grid at the same time as all the other solar generation rushes onto the grid. Then again, if the smart appliances and HVAC systems can crank at midday to take advantage of the surplus power, they could prevent irksome solar dumps on the wires.

The total load of these homes will be considerably smaller than equivalent-sized homes without the net-zero makeover, so that should minimize the broader impact as well.

There are enough variables here to demand a proper study before drawing conclusions. There's a little over two years left to learn before this becomes standard practice across the world's sixth-largest economy.