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Green Building News

Affordable Rental Units Are Designed to Be Net Zero

A development in Illinois aims for exceptional energy efficiency, with help from renewable-energy systems

Image 1 of 3
Wind turbines and photovoltaic arrays. The 1,230-sq.-ft. homes feature R-21 walls and R-49 roofs, and are designed to provide net-zero-energy performance.
Image Credit: Sachs Electric (images 1 and 2); Capstone Development Group (image 3)
Wind turbines and photovoltaic arrays. The 1,230-sq.-ft. homes feature R-21 walls and R-49 roofs, and are designed to provide net-zero-energy performance.
Image Credit: Sachs Electric (images 1 and 2); Capstone Development Group (image 3)
Recharged by both photovoltaic panels and wind turbines, batteries on the 16 streetlights serving Lexington Farms Subdivision can store enough power to keep the lights working for about seven days. The lights, which use LED lamps, are designed to operate off the grid. Lexington Farms broke ground in mid-September 2010.

Lexington Farms – a nearly completed subdivision of 32 single-family homes in Jerseyville, Illinois – represents a small but promising step toward the Illinois Housing Development Authority’s plan to add almost 2,500 affordable rental homes to the market.

Each home in the development, which is about 40 miles north of St. Louis, includes 1,230-sq.-ft. of interior space and leases for $590 a month to families earning at or below 60% of the area median income (up to $40,980 for a family of four). Tenants who stay at Lexington Farms for at least 15 years can apply to purchase, on favorable terms, the property they’ve been leasing.

Wind power on the Plains

Another sweetener here, as we noted in September when the project broke ground, is that the homes are designed to operate at net zero energy – or at least as close to it as occupant behavior allows.

The builder, Capstone Development Group, teamed up with two other companies in the region, MidAmerica Solar and Sachs Electric, to blend solid construction and renewable-energy features in ways that were both economical and effective. Exterior walls are insulated to R-21 and attics to R-49, and air leakage rates are low. The homes are equipped with 7.2-kW photovoltaic systems and mast-mounted wind turbines that can deliver up to 1 kW.

PV panels and wind turbines also power the community’s 16 LED streetlights, whose battery packs have enough storage capacity to power the lights for about seven days.

As affordable-housing projects go, Lexington Farms might be a bit unusual, but other communities like it could soon emerge in the state: the Illinois Housing Development Authority imposes green-building requirements on affordable-housing developers who want federal low-income-housing tax credits. So as the rest of the 2,500 affordable rental homes slowly emerge on the Illinois landscape, don’t be surprised if more than a few lay claim to a high level of energy efficiency.


  1. JustHousing | | #1

    more information is needed to show that this is exceptional
    I think you missed the mark on this one, Richard. These homes do not appear to boast "exceptional energy efficiency," even with the R-49 attics. What is the wall construction? What is the measured air tightness? "Air leakage rates are low" doesn't tell us much. A 7.2 kW pv array for a 1230 ft2 home sounds a bit like a project out of balance. Can you provide more information? I'm always eager to read about making affordable housing more affordable to operate and maintain, not to mention healthier. I hope more information will make this project appear even more exceptional.

  2. Expert Member
    ARMANDO COBO | | #2

    I second Rachel's opinion...
    I'm also concerned about the size of that PV system for such a small house, plus wind???. It'll be nice to know the wall and roof assemblies details, plus other green features of the house not detailed in this article nor in September's. Can you tell us the HERS rating as well?
    The pictures show PVs on the south facing roofs of the north facing houses, where are the PVs of the south facing houses? I sure do like the PVs and turbines on street light poles... that's cool.

  3. user-723121 | | #3

    Greenwashing is intentionally vague
    The builders are hoping no tough questions are asked about this development. Did someone mention tax credits?

    The first net zero homes were built business as usual with about 500k in solar panels tacked on the roof. A truly energy efficient house would get by with a very modest solar array.

  4. GBA Editor
    Martin Holladay | | #4

    Response to Doug McEvers
    You wrote, "The first net zero homes were built business-as-usual with about $500,000 in solar panels tacked on the roof."

    This urban myth is false. The first net zero home in the country was the Habitat for Humanity house in Wheat Ridge, Colorado. It is a 1,200-square-foot house with an R-30 floor, R-49 walls, and an R-60 roof. The PV array is rated at 4 kW.

    By the way, there's no way you can put $500,000 of solar modules on a "business-as-usual" house, because the roof isn't big enough.

    It has always been cheaper to build an excellent envelope than to buy more PV modules.

    One final point: there is quite a bit of greenwashing in this story, because there's is no way that those little wind turbines on short stubby towers are cost-effective.

  5. user-723121 | | #5

    Net zero behemoths

    I know about the Golden Habitat house, Paul Norton with NREL was involved. There were other earlier claimed net zero or near net zero homes that were large and super expensive due to vast solar arrays and other gadgets. One was in Texas and another was in the DC area I believe, neither home had impressive building envelope performance or was affordable.

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