Net-Zero Energy homes are a hot topic these days, especially as prices for rooftop solar photovoltaics and LED lighting continue to plummet. More than ever, net-zero homes can be built for little to no added expense, and are often cheaper when considering the “monthly nut” (the total monthly cost, including mortgage, utility bills, and maintenance). This means net-zero homes are emerging from the niche of “tree-huggers” into the mainstream. But the story goes far beyond saving a few bucks, or trying to reduce your impact on the earth. Net-zero homes are built as a holistic system, understanding that all of the components act together and impact each other. Spending more on windows and insulation means spending less on the mechanical system. And it doesn’t just save energy, it makes the home more comfortable and healthier. This blog will outline the benefits of a net-zero home.
(NOTE: While there are many definitions of Net-Zero Energy (NZE) homes, we’ll use a simple one for these purposes: A home that produces as much energy (through renewable sources) as it consumes in a given year.)
Components of a Net-Zero Home
In order to help understand the benefits of a net-zero home, it is important to first take a look at how it is built. Building a NZE home starts with good insulation and air-tightness. High R-value walls, windows, ceilings and basement/crawlspaces reduce heat loss and as a result, smaller heating/cooling systems are needed. Air tight construction, resulting in less than one air change (with the outside) every 24 hours, eliminates drafts and further reduces the size of the heating system (fresh air is provided by mechanical ventilation with heat recovery). High efficiency mechanical systems, lighting, and appliances all reduce energy consumption. After good insulation, efficient mechanicals systems, appliances, and lighting have been installed, the balance of energy consumed is usually offset with solar photovoltaics (PV) installed on the roof.
A well insulated, air-tight home means the home has a uniform temperature throughout – drafts and cold windows are a thing of the past. A smaller heating system means less air movement is needed to condition the space, further increasing comfort (moving air cools the skin – think ceiling fans in the summer). And, to top it off, that smaller system will be quieter and run less frequently.
NZE homes are built air-tight, with fresh air provided by mechanical ventilation. Thus, the fresh air is controlled (and can be filtered), rather than entering the home through cracks, gaps, attics and crawlspaces. Less air movement due to a smaller heating/cooling system creates less dust in the home. Careful attention to building science reduces opportunities for mold growth. All of this results in significantly better indoor air quality and better health. This is especially important if you or a family member suffers from allergies or asthma.
As we build tighter and better insulated homes, we have to pay careful attention to moisture control, exterior water management (rain and snow), and proper installation of materials. Often, today’s builders will improve insulation without considering the impacts to building science. Most net-zero projects will involve an energy consultant early in the project to help with building science and perform inspections.
Durable wall assemblies that are installed properly protect the home from UV degradation, and keep rain and snow from entering the home. Tight construction makes it harder for pests to enter the home, and reduces problems with moisture entering walls, roofs, and other building components. Third party inspections ensure proper installation of exterior flashing, insulation, and mechanical systems. This results in a house that needs less maintenance and will perform as designed for years to come.
A NZE home is more resilient during many natural disasters. If the power goes out during a snow storm, the increased insulation and air tightness result in a home that can go without heat for a significant period of time, or can even be heated with small alcohol stoves. Back up batteries, like the Tesla Powerwall, mean that your home can have power even when there’s a power failure. Recharging the batteries with the PV system is possible for longer outages. Lastly, building a tight, well insulated house also increases fire resistance, which is especially important in the foothills and mountains.
Net-zero homes reduce the use of fossil fuels and the attendant release of CO2 . This not only reduces the impact on our climate, it also reduces the need for resource extraction, and reduces systemic health issues caused by poor air quality.
And, of course, there’s the savings. Net-zero homes are often estimated to cost 5%-10% more than a conventional home, though more and more examples of cost neutral solutions can be found. The additional costs can often be reduced with utility, state, and federal rebates. Be sure to consider all of the cost savings (e.g. not running gas service for an all electric home) when performing the calculation. When taking into account low/no energy bills and financing mechanisms (and the fact that mortgage interest is tax deductible) the “monthly nut” of the home is often the same or less when all is said and done. Also consider that this will be your monthly payment for the length of the mortgage, regardless of fluctuations in electric and natural gas prices.
There are many good reasons that your next house should be net-zero. Whether it’s concern for your family’s health, a desire to reduce your impact, or simply a desire for a high quality, comfortable home, a net-zero home will change the way you think about the place you live. Many analyses of net-zero homes only focus on the increased cost, and whether there’s a return on investment (ROI) when considering energy savings. What’s amusing is that we don’t do that calculation for a host of other upgrades, such as granite countertops or a professional grade kitchen. What’s the ROI of your family’s health and comfort for years to come?
About the author:
Mark Bloomfield is the Managing Principal of Sustainably Built, LLC. He has been working with green building, sustainability and energy efficiency for over a decade, and has extensive experience with energy modeling, HERS ratings, LEED Certification and Enterprise Green Communities. Mark has worked on a wide variety of projects, from custom homes to 200+ unit apartment complexes and small commercial buildings. He has a depth of experience incorporating budget requirements into projects, resulting in a cost-effective approach to energy efficiency and beyond code certification. Mark is passionate about bringing affordable net-zero buildings into the mainstream.