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Reaching for Net-Zero Energy article

Reaching for Net-Zero Energy and Deep Energy Discounts in Your Home

Did you know that buildings guzzle up more fossil fuel than cars, airplanes, and the entire transportation sector?


Credit:  Architecture 2030 ( http://architecture2030.org/the_problem/buildings_problem_why )

If you’re feeling it at the pump when you fill up your car, you’ve got lots of other choices.  Maybe use a more fuel-efficient car, car pool, car share, take public transportation, bike, or walk.  But if your home is an energy hog, what can you do?  TrekHaus, home of Ella Wong and Randy Hayslip, is a living learning experiment on how to reduce home energy use in the Pacific Northwest.  Ella and Randy recruited architect Rob Hawthorne (PDX Living) and Bart Bergquist (Willamette Valley Remodeling) to design and build two mirror-image side-by-side net-zero energy Passivhaus townhomes in an infill lot in Portland.  The TrekHaus mission- to seek out new and better ways to achieve deep energy savings for homes in the Pacific Northwest.  To do this, TrekHaus has partnered with the Green Building Research Laboratory (GBRL) at Portland State University, who will be monitoring these two nearly identical homes.  GBRL will be studying the effectiveness of energy efficient Passivhaus construction methods and potentially transformative new energy saving building products (see later sections on phase change material and heat pump water heater). 

TrekHaus drawings by Rob Hawthorne

Building in progress photos by Randy Hayslip


Many Paths to Net-Zero Energy:  Which One to Take?

A net-zero energy home produces as much energy as it consumes in a year.  To do this with the smallest footprint, TrekHaus is all-electric and does not use any kind of fossil fuel.  The energy generated will be renewable, from solar photovoltaic panels.  

There are lots of ways to design a net-zero energy home.  In order to minimize building energy requirements, the TrekHaus team decided to use highly energy-efficient Passivhaus (or passive house) construction methods.  Like a thermos, a passive house stays warm in the winter and cool in the summer.  The passive house builder pays close attention to airtightness, thick well-insulated walls, and high-performance windows.  A heat recovery ventilator (HRV) brings in fresh filtered air 24/7 without losing heat.  Space heating is passive- relying on solar and heat generated by appliances, electrical equipment, lighting, and body heat of occupants.  There is no need for a furnace.  The interior is quiet and comfortable.  No drafts and uneven temperatures to chill.  Passive house may be new to the United States, but there are many such homes in Europe, and a growing number are sprouting in the Pacific Northwest.  While easier to apply to new construction, passive house methods are effective on retrofits too.

Passive House Diagram (http://commons.wikimedia.org/wiki/File:Passive-house_scheme_HQ.png)

TrekHaus windows are placed and sized to takes advantage of natural light.  Electricity use is low with energy efficient appliances and lighting.  Occupants have a role too, and will be able to monitor home energy use and modify behavior accordingly- like, hey unplug or turn off the bleeping…

The minimal building energy requirements of a passive house allows TrekHaus to get to net-zero energy with a smaller photovoltaic system.  Ella and Randy can’t afford to buy solar panels upfront…but these days, there are great solar lease options (like SolarCity and SunRun) that make going solar a real deal.


Phase Change Material (PCM)

TrekHaus will be testing an innovative energy saving building material called BioPCM, a potential game changer.  BioPCM is a soy-based phase change material that can be installed in walls, floors, ceilings, and attics of new builds as well as retrofits.  BioPCM is an easy way to increase thermal mass and improve thermal comfort by minimizing indoor temperature fluctuations.  When the house gets hot, BioPCM stores heat by changing from solid to liquid.  As the house cools down, BioPCM changes from liquid to solid and releases heat.  The thermal mass of one installed sheet of BioPCM (about half inch thick) is like adding a 12 inch layer of concrete!  


BioPCM mat is 16 inches wide and comes in 8 feet rolls that can be cut to length.

Photo credit:  Santiago Rodriguez

Heat Pump Water Heater

Lab tests say a new electric heat pump water heater (HPWH) is two to three times more energy efficient than a standard electric water heater.  How well these HPWHs perform is dependent upon climate.  TrekHaus will be testing the suitability of HPWH for home use in the Portland area.  HPWH works like a refrigerator in reverse, extracting heat from room air to heat water.  The HPWH is noisier, so is better in a garage or basement.  When operating, it will cool the room it is located in.  At TrekHaus, the cooler air from the HPWH will be counteracted by warm air from the nearby solar PV inverter.  Retrofit add-on versions are available that can be attached to an existing gas or electric water heater.

Heat pump water heater example:  AirTap HPWH by AirGenerate is first model to incorporate NEEA’s Northern Climate Specifications into its design.   http://www.airgenerate.com/


Retrofit add-on version



Integrated version


What you can do:

You too can get deep energy discounts in your home.  Join Ella and Randy on their trek to be more energy-wise.  You can start by getting a free home energy profile from Energy Trust of Oregon- http://oregon.energysavvy.com/.  Clean Energy Works Oregon (http://www.cleanenergyworksoregon.org/) can help with free home energy assessment, no-fee financing, and rebates.

 

Learn more at these websites:

Building Energy Statistics: http://architecture2030.org/the_problem/buildings_problem_why

TrekHaus:  trekhauspdx.com or https://sites.google.com/site/trekhauspdx/

PDX Living, LLC: http://www.pdxlivingllc.com/

Green Building Research Lab at Portland State University: http://greenbuilding.pdx.edu/News.php

Passive House Northwest: http://www.phnw.org/

Passipedia (Passive House resource): http://passipedia.passiv.de/passipedia_en/

Bio-Based Phase-Changing Material Adds Instant Thermal Mass: http://www.treehugger.com/files/2010/11/bio-based-phase-changing-material.php

Heat Pump Water Heater: http://www.energysavers.gov/your_home/water_heating/index.cfm/mytopic=12840

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