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What is a NEt Zero Home?

I'm Tony Marnella with Marnella Homes. Marnella Homes has been building for over 20 years and we adopted green building practices from early on. We recently completed this net zero home in Camas, Washington. Net zero is defined by a home that actually is producing as much or more energy as it consumes. Green building is not just about putting efficient equipment in a home. It's about the systems and processes of the assembly. It's how the furnace is installed. It's how the duct work is installed in the home. It's how the framing is assembled. Every single structure we build is advanced framed.  Advanced framing means 24 inches on center.  It means hollow corners so, you can get insulation into them and not be cold spots. All the headers are used with narrower materials so you can insulate it and it's just little things like that that make up a much better insulated shell and again, relates to a much more comfortable environment for the homeowner.


We install all of our HVAC systems inside the condition space. That means inside the home and our efficiency is exponentially better than any system you'll ever install in the garage. The next step in the process is insulating and air ceiling. In this particular home we used a company called AeroBarrier. AeroBarrier creates an air tight environment. They spray tiny foam particles that fill holes and gaps as large as a half-inch by adhering to each other to seal up these openings. Then we can drive that air exchange down to 0.3 or 0.4 which is phenomenal. The purpose for a tight home is to control air flow. How this benefits our homeowners is it minimizes incoming airborne contaminants as well as air loss. Air loss from a home affects the occupants comfort and energy performance. We manage air flow in the home with the tight exterior and fresh air exchange, which creates a healthy, comfortable indoor environment.


Pyramid Heating and Cooling installed the WaterFurnace geothermal system in this home. These systems utilize the constant temperatures in the earth by circulating water through ground loop piping systems buried in the earth. It's a very durable plastic that's used for the tubing. It's virtually indestructible and once they've tested that system and they lay it in the ground, you basically turn your back on it. There's nothing more that you would ever have to do with it. During the heating cycle, geothermal systems transfer energy from the earth to the house and during the cooling cycles, they transfer heat from the house back into the earth. Since the system only requires electricity to operate the heat pump, it eliminates the need for an additional energy source such as natural gas or propane. Much like solar, these systems have dropped in price while performance continues to improve. 


One of the things that we've adopted for every structure we build is we use a vented rainscreen. Code only requires a crinkle wrap weather barrier.  Wherever that crinkle wrap gets compressed, you're going to trap water. A true vented rainscreen we feel is the best practices and is what every structure built in our climate zone should have.  What that consists of is you have furring strips that are placed vertically every 12 inches roughly around the perimeter of the home. So you have constant air flow behind your siding all the time. In addition to our vented rainscreen installation method of siding, it's important due to our wet Northwest climate to utilize the number one brand of siding. James Hardie is the largest producer of fiber cement. James Hardie is engineered for climate, providing a tough exterior and low maintenance siding. The complete James Hardie exterior includes not only the siding but also the trim. These products align with our company's green values of sustainability, durability and low maintenance. 


One of the main components to the net zero on this home is the solar. This home was designed and built with 44 panels provided by Sunbridge Solar that will produce about 13.2 kilowatts of electricity each year. Based on the modeling of this home, the solar is expected produce more power than the family will use. The roof was designed with a large South facing plane to accommodate the immediate need for solar panels as well as room for future expansion. The home also has a 9.3 kilowatt LG battery backup system that will power the home during outages and allow for self-consumption of the solar electricity at night. With a drop in price of solar over the last several years, the performance and the technology of the systems continues to advance, tax credits and incentives being offered by the state and federal government make solar a great way to hedge off future power increases and create a more sustainable consistent power source. The solar will also save the homeowners tens of thousands of dollars in energy costs over the 30 year lifetime of the solar equipment.


We certify all of our homes to the National Green Building Standard. One of the requirements of the NGBS is that we only utilize a third party verifier and the verifier is involved from the inception of the home. They do energy modeling to determine that the performance that we're trying to achieve for the home is on target with the right installation measures, the windows, the heating and cooling systems and so forth. Then they come back at the very end and actually do a performance test. So they're testing the home for leakage and they're testing the ACH (air exchanges per hour). With the conclusion of this, we were recognized by Clark Public Utilities, a new home performance program as being the most efficient home certified through their program. This particular home was certified to perform at 32 and a half percent over Washington state code. The new homes program has estimated that this home will save around 6,095 kilowatts per year. This is a year over year benefit and the savings and the comfort of this home are going to reward this family for years to come.

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