How Much (Better)?
When presented with the need to change how we build our homes in the face of the climate crisis, many folks ask “How much will it cost?”
We attempted to answer this question (and more) with a research project aptly called “How Much and How Much Better?”
We compared two versions of the JUST HOME Evergreen House design, as if built on a lot in Duluth, MN. The actual JUST HOME Evergreen House design is planned for zero net energy (ZNE) operation, and operates with electricity for all energy use. We compared the ZNE design with a second version designed to be built to current code standards and with natural gas for heat and cooking.
We created an energy model for each version of the house, obtained a projected HERS (Home Energy Rating System) report for each home, and estimated the cost of construction for each version using real-world, local pricing from local vendors and industry partners.
For each version (ZNE and Code), we looked at the following:
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What will the house cost to build?
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If the homeowner pays 10% down on the house, what will the monthly mortgage payment be on a 30-year mortgage?
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How much energy will the house consume each year?
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How much will the energy used cost the homeowner each month (on average)?
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What are the annual CO2 emissions predicted to be for the home?
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The two HERS scores quantify just how much better the ZNE home performs. The code home is predicted to use 27% less energy than an average home, but still emits 9 tons of CO2 annually. The ZNE home is predicted to produce more energy than it consumes every year, and effectively emit no CO2 annually. Click on the HERS reports below for details.
How Much (Money)?
We found that the ZNE (with the solar array) costs about 11% more to build than the Code version. With a 10% down payment, this additional construction cost requires $4,400 more from the buyer at the time of the purchase; the resulting mortgage payment of the ZNE house is about $200 a month higher than the mortgage payment on the code house. But, the estimated monthly mortgage + energy costs of the ZNE home are actually $2.31 less than that of the code-built home, because the higher mortgage is offset by savings in energy costs. The mortgage payment will remain the same over those 30 years, but history suggests that we can expect energy costs to rise over time. This suggests that ZNE homes are more affordable to live in over the long term.
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Find the breakdown of the incremental cost differences below. For more information, read our technical bulletin.
The Details of Our Analysis:
Building any new home is an expensive undertaking, and current costs of construction have escalated significantly over the past two years. To arrive at our estimated construction costs, we obtained quotes from local or regional builders and suppliers, and also utilized recent bids for a proposed project using the Evergreen House plans.
We estimated the cost to construct each house (exclusive of the cost of land) to be $464,000 for the ZNE Evergreen home and $420,000 for the Code Evergreen home. We broke down our costs into what we call “elements,” to identify and characterize the incremental cost differences between the two versions of the home.
It’s important to note that the whole suite of elements taken together creates a zero net energy home. One cannot choose only some of the elements and be ensured the result will be a high performance, durable, ZNE home. A close look at the elements which changed to get to ZNE illustrates that getting to ZNE may not be as costly or onerous as imagined. But it sure is better.
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This project was also supported by three outstanding students: Sam, Deja and Madeline. Click on the images or links below for additional documentation.
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This research project was conducted in partnership with the UMD Office of Sustainability and with support from the UMN Institute on the Environment and the Minnesota Center for Energy and the Environment.