Zero Net Energy. Zero Net CO2 Emissions.

This is the toughest of the zHome environmental benchmarks. zHome starts first with conservation, using a number of advanced energy-efficient construction techniques to reduce home energy use. This gets the homes about two-thirds of the way there. zHome units then use solar panels to generate and offset the remaining one-third to achieve net zero energy use and net zero CO2 emissions over the course of a year.

Super insulated walls.

15%

Reduces energy use by:

zHome uses walls that have nearly twice the insulative value (R-38 walls and R-60 ceilings, for you techies) of a wall built to the Washington State Energy Code. We are achieving this by filling the 2x6 walls with expanded polystyrene (instead of cellulose or fiberglass batts more typically used) and adding an additional 3 inches of expanded polystyrene to the outside of the wall, for a total of nine inches of insulation. The 3 inches on the outside of the structure provides what is called a “thermal break”, meaning that the thermal pathway that the wood provides from the inside to the outside is broken with this layer of insulation.

Double-paned windows.

5%

Reduces energy use by:

zHome will use double pane Fiberglass windows with an overall U value of .33. You might wonder why zHome is not using triple pane windows. Turns out that because these windows will allow solar heat gain to enter the homes during cooler winter months, the solar heat gain benefit of double pane outweighs the benefit of triple pane windows. During the summer months when the heat is not wanted, homeowners can block the unwanted solar heat by using screens combined with their own blind system.

Extremely tight exterior walls.

5%

Reduces energy use by:

Studies show as much as 30% of home energy is lost just to leaks from things like exterior gaps and poorly sealed ductwork. zHome will not tolerate leaks, and strives for a tight building exterior that exceeds code standards, yet also provides adequate ventilation.

Ground source heat pump for heating and hot water

When you decide to use water to heat your home, many opportunities arise because water heating technologies are inherently more efficient than air. zHome uses a ground source heat pump. A heat pump is essentially a refrigerator running in reverse, heating instead of cooling. The overall system starts with a pre-warming loop in the ground. With a ground temperature in Issaquah of 50 degrees, the heat pump then heats the pre-heated water from 50 degrees to the desired temperature, rather than starting from the outside air temperature. It's as if zHome is located in a moderate climate that never drops below 50 degrees!

Reduces energy use by:

25%

Heat recovery ventilator

A tight building envelope requires good ventilation. This system uses an interwoven honeycomb that allows cold air coming into the house to be heated by the warm air that is being exhausted.

Reduces energy use by:

3%

Hydronic heating

Most houses are heated via forced air. But if you think about it, air doesn't hold energy well. But WATER does. So zHome units are heated with water that runs through the floors and walls. And without any ductwork, there is a reduction in energy leaks.

Reduces energy use by:

7%

High efficiency lighting (CFLs and LEDs)

5%

Reduces energy use by:

Compact fluorescent bulbs (CFLs) are becoming an increasingly common high efficiency alternative to incandescent bulbs. Light Emitting Diode (LED) lighting is even more efficient than CFLs — though the benefit versus the cost of using LEDs doesn't quite pencil out yet. Like solar panels, however, as LEDs become mainstream, they will become less expensive. zHome will use a combination of both technologies for in-home lighting.

High efficiency appliances

7%

Reduces energy use by:

zHome uses highly efficient refrigerators, stoves, clothes washers, dryers and dishwashers. All appliances will be at the cutting edge of energy and water efficiency.

Energy feedback monitor

The wild card in getting to zero net carbon/zero net energy is the residents. Studies show that energy use in the same home with different families can vary dramatically. Ultimately, achieving this benchmark will be in the residents' hands (that's right, no plasma TVs!). But zHome will help—the units will include an instant energy feedback monitor, showing how much energy is being used at the moment and over the course of the year. Think of the competition the neighbors could have!

Photovoltaic panels

33%

Offsets energy use by:

This is how zHome generates power to offset the units' energy use. Photovoltaic (PV) or solar panels essentially absorb the sun's rays and turn it into electricity. Interesting fact: solar panels are 70% as efficient in Seattle as they are in Sacramento — this is because a lot of solar energy does make it through our clouds and our days are longer in the summer! Photovoltaic panels are the least cost-effective component of the project, costing about $35,000 per unit, for about 33% of the total energy budget. If you're doing your own zHome-y upgrades, it's more cost effective to save this for last (although, the cool factor is definitely high). However, there is good news, as more people buy PV panels, the cheaper they will become.

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