My last post in this series discussed some of the previously published works on net-zero and near net-zero homes. Today, I’m going to begin the process of describing the 20 homes that participated in my research.
I found roughly 60 net-zero designed or near net-zero designed homes in New England, back in the summer of 2011. I’m sure there were more, but not that many more. I did a lot of internet searching, and also received a little help from NESEA, the Northeast Sustainable Energy Association, in publicizing my request for participants. Eventually, I had contact information for about 30 homeowners, most of whom agreed to join the project. In the end, I had 10 net-zero homes, 9 near-net zero homes, and one control house (my own), for a total of 20.
The homes were scattered around New England, which is what I wanted. Though the six states that make up New England are relatively small in size, they make up for this in their diversity. Thus, I had homes right on the coast of CT, where winters are relatively mild but so are the summers. I had homes in the foothills of the Green Mountains, ones in major cities, homes in the country and homes in suburbs. Here is a map:
Part of the agreement with the homeowners was that I would never release their names or addresses. Hence, I always refer to their letter designations, e.g., House A, House N, House R, etc.. There are three homes overlapping in the map above (A, B, and C), plus P & J overlap, too.
This set of homes, besides being geographically diverse, also varied in design and occupant characteristics–big time. On one extreme, House O had 10,000 sq ft of finished floor area (FFA), while house G under 1000. House O was also the most expensive at $2 million dollars while House X cost only $170,000 to build. Note that building cost does not include the cost of the land/lot, just the house itself. I’ll get much more into the costs and economics of these homes in later posts, but for now just realize that net-zero and near net-zero energy homes can come in all sizes and prices.
Most of the homes were single family, detached homes, though there were four (A, B, C and X) that were each half of a duplex. Most were new construction, but two were full or deep energy retrofits (K and Z). One was an apartment (W), and all were grid-tied except for House G. The number of full time occupants ranged from 2 to 7. The size of the photovoltaic systems ranged from 1.1 kW to a whopping (for a home) 14.4 kW. Several homes also used solar thermal for hot water and/or space heating. One home, Q, had a PV system AND a wind turbine. Two homes did not have any PV system: House M had a large solar thermal system for heating both air and water, while House R had no on-site renewable energy system.
House R was our home. I picked it to be a “control” house for several reasons. First, it was built at about the same time as all the other homes (between 2008 and 2011). Second, it is an Energy Star certified home, meaning it is relatively energy efficient but still a few notches below the near and net-zero homes. Third, it would be easy to install energy monitors and temperature measuring devices (aka “data loggers”), since I obviously had complete access to the home. Finally, my wife and I do our best not to waste energy at home, so our habits were likely to be similar to those of the other owners. All this would make a good apples to apples comparison for my research. As you will see when I get to the results, the differences between our home’s performance and cost and the other homes’ are striking. Here’s a photo of our home:
So, remember House R is NOT a net-zero or near net-zero home, just a relatively new home built to be more energy efficient than a typical new home (it has a home energy rating system, HERS, score of 67, for those of you who are curious).
Unfortunately, I’m not going to be showing photos of any of the other homes, since I never asked permission from the owners to publish them on-line in a blog. However, if you open up my complete thesis you will find photos of most of the homes inside (you can get to the thesis by going here: http://www.nhsolarconsulting.com, which is my “personal” webpage–not a business page).
There was also a large diversity in HVAC equipment in the homes, i.e., some used ground source heat pumps (GSHPs), aka geo thermal systems, for heating and/or cooling. Some used so-called mini-split air source heat pumps (ASHPs), while others relied on more conventional (but highly efficient) natural gas fired furnaces for heating and/or domestic hot water heating. Here are a couple of charts that show this diversity:
I think you get the picture (even without actual photos…) that these homes represented a wide range of sizes, costs, and systems. They also varied on construction type (traditional framed, double-walled, SIPs, etc.), number of bedrooms, finishes, size and types of electrical appliances, and so on. This diversity was excellent, since it meant my research would expand beyond the relatively homogeneous homes from the previous works.
Next time, I’ll finish discussing the subject homes by describing what features they DID have in common, and then move on to my methodology for collecting my data.