January 22 2008

Smith House: A Passive House in Illinois

Smith House_Image 01

The Smith House, located in Urbana Illinois, is an all electric house built to the German Passive House Building Standard. To achieve the passive standard, architect and owner, Katrin Klingenberg, created a clean, efficient and comfortable house design using many of the passive house design strategies used in German model buildings. She describes the house as a "simple shed-roofed house insulated on all six sides to at least R-56."

It is worth noting that Klingenberg 'tweaked' the Passive House standards to meet the unique climate conditions of Illinios, but that doing so did not compromise the strict energy efficiency criteria required to meet certification. The measured performance of the house is in fact below the level set by the Passive House standard. "The program specifications were written for Germany," she notes. "But the climate here in Illinois is way more severe." In designing Smith House to meet the Passive Standard in Illinois, the architect used several sophisticated computer models to refine the details of her thermal envelope including consideration for solar heat gain, internal heat gain, occupancy patterns, and energy loss through the skin of the structure. Klingenberg notes, "The surface/volume ration has to be very good... you do not want to have a lot of nooks sticking out of your house... because you lose energy."

The Smith House design contains all the typical elements of single family home but with modifications to meet the Passive House Standard.

Envelope Design

The building foundation is uses a concrete slab poured over a 14" thick layer of expanded polystyrene insulation (EPS). To keep heat from entering the slab at the edges, Klingenberg uses a 10" thick concrete-block frost wall with 6" of EPS on the exterior. Above grade this EPS block wall is shielded by a slate finish.

Smith House_Image 02

Exterior walls of the house are constructed using 12" "Trus Joist" I-joists (TJIs) filled with blown fiberglass insulation. The wall cavity is sealed using OSB on both the interior and exterior sides. The exterior layer of OSB is covered completely in a 2" layer of EPS secured with strapping back through the TJIs. A result of this thick wall is that it overhangs the foundation by 4" and naturally provides a shield for the slate finish below.

Smith House_Image 03

To reduce infiltration into the interior, Klingenberg placed no electrical boxes in the exterior envelope. Instead the electrical boxes are all mounted on the the floor. In addition, light switches needed on the exterior are not hard wired. In leiu of hard wired systems, the architect found wireless light controllers that can be installed in shallow surface-mounted boxes. These two strategies were very important in maintaining the integrity of the air barrier.

The roof of the house is a "shallow-pitched single south facing plane framed with 16" TJI rafters and insulated with blown in fiberglass." Standing-seam galvanized roofing is installed as the exterior finish because of its thermal mass and reflective properties. There is a vent channel located between the roofing material and the insulation to allow built up heat in the summer to escape. You can learn about roofing services for your home here.

190 SF of fixed and operable triple-pane, argon, low-e windows allow natural daylight into the home. Most of the glazing is located on the south facade of the building both to admit daylight and solar heat in the winter months. In order to facilitate heat gain on the south facade glazing was chosen for its high Solar Heat Gain Coefficient (SHGC) of 0.51. That was varied on the west facade to SHGC 0.31 to reduce the impact of the hot western sun in summer months. Overall the glazing is rated to U-factor 0.17, which is roughly double the insulation of even the most efficient typically used glazing panels.

Systems Design

The Smith House uses a typical $450 instantaneous domestic hot water heater by German manufacturer, Stiebel Eltron. Klingenberg chose to use a low-cost low-tech tech system because of the relatively long payback and high maintenance attributes of Solar Domestic Hot Water systems.

Smith House_Image 04

Co-Creator of the Passive House Standard Dr. Feist agrees with this decision in principle by saying:

?We don?t calculate payback times?not on houses and not on solar thermal systems,? says Feist. ?Instead we look at the annual energy cost and at interest costs. We can calculate the cost per kilowatt-hour saved from adding insulation, and compare that to the cost of including a solar thermal system. Solar thermal is by far the highest cost of any of the features we are discussing at the moment.?

The conditioning and ventilation system is designed to be simple and efficient. First, Smith House uses a Heat Recovery Ventilator (HRV or ERV) chosen because of the sophisticated climate controls available on the unit. The ERV uses the control / monitoring system to choose (using a damper) whether air comes preconditioned from an earth tube (8" diameter x 100' long) or, when outdoor temperature allows, directly from the outside. On very hot days air is also taken in using the earth tube to pre-cool the air. The house has no air conditioning (cooling). Heat is provided by an electric resistance heater located in the ERV unit. It is worth mentioning however that in most months the house requires little or no additional heating. "Last January the electric bill totaled only $35 despite the fact that the month included two weeks of -10° cloudy weather.


Building costs were higher than what could be expected for a comparably sized traditional home. Klingenberg notes that the construction is essentially a traditional ballon frame but that the build quality is higher. She estimates a 10% increase in cost to build such a home once contractors and designers become accustomed to the Passive House building standards. Klingenberg does note however that such a premium would be covered in about 10 years when calculating energy savings. The Smith House itself was built for roughly $110 per SF.

Smith House Project Details:

Location Urbana Illinois
Area 1,450 SF
Foundation Concrete-Block Frost Wall
Foundation Insul. 6" Expanded Polystyrene (PS) R-24
Under-Slab Insul. 14" Expanded Polystyrene R-56
Wall Framing Vertical 12" TJIs
Wall Insul. 12" Blown Fiberglass + 4" Ext. Rigid PS R-60
Roof Framing 16" TJIs with vent above sheathing
Roof Insul. 16" Blown Fiberglass R-60
Airtightness UnKnown
Windows Thermotech 3-pane, Argon, Low-e, SHGC 0.51 / 0.31 (west facade) U-0.17
Ventilation System Westaflex WAC 250 ERV
Heating System Electric Resistance in ERV
Hot Water System Stiebel Eltron Instantaneous Heater

For more information read the original article or visit the Katrin Klingenberg / E-co Lab website.

For more information on Passive House design please visit Greenline's previous post on the Passive House Building Standard.

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January 23rd, 2008 at 2:43 AM

Greenline » The Passive House (Passiv Haus) Building Standard

[...] other countries throughout Europe and even the United States. (The American examples include the Smith House and the Waldsee [...]

February 7th, 2008 at 3:57 PM

House Design

[...] Smith House: A Passive House in Illinois [...]

February 11th, 2008 at 12:54 PM


Eric... Thanks for the nice read, keep up the interesting posts.....

February 28th, 2008 at 6:15 PM


Most of this article is reprinted (with permission?) from Energy Design Update. The statement that Katrin changed the PH standard to fit the climate of the American US is COMPLETELY UNTRUE! It is actually built beyond PH standard of 15kWh/sq.m*yr, with monitored performance running at about 10! Please correct this glaringly bad error. Mike Kernagis www.e-colab.org www.passivehouse.us

February 28th, 2008 at 9:50 PM


Mike - No snub was intended. The Smith House is an amazing example of PH in the US and should be an inspiration to more designers. I was referring to mentions in both the Energy Design article as well as other info on the net including wiki that said the house was customized to meet the demands of local conditions. Even in Europe there are several PH standards based in Germany, Scandinavia, Austria etc and while they use mostly the same performance criteria, the means of accomplishing their energy efficiency is different based on region. It is fascinating to see the standard being brought over the pond and will be interesting to see how we adapt the certification for our climate zones.

March 4th, 2008 at 6:42 PM


je cherche les plans de smith house de richard meier

March 31st, 2008 at 9:05 PM


This is truly inspirational, especially at the very reasonably cost of $110 psf. I don't know how that compares to local building costs of average homes, but it has to be very close. The most eye opening features for me were the astounding amount of insulation, the denouncing of solar thermal and the unique use of the HRV with earth tubes and a heating element. Thanks for the great post! Great info on the e-colab site as well.

January 29th, 2009 at 2:33 PM

Kenny Huffstutler

Please feel free to check out out website for ERV information that could be used in your passivhaus. It will have less install cost and better performance in the winter as well as summer. It looks like it is smaller also. Any questions you can also contact me at (800)552-4822.

February 21st, 2009 at 11:02 PM


my house burn, January, 1st 2009 and with my wife stella we have decided to rebuild our 100 year old house with the passive house concept and technology, it is great to build new passive house, but existing house could also be reborn with better energy cost, we need more promotion nationaly this is the future alex yonkers, ny

May 27th, 2009 at 3:20 AM

Greenline Smith House A Passive House in Illinois | Shed Kits

[...] Greenline Smith House A Passive House in Illinois Posted by root 22 hours ago (http://greenlineblog.com) She describes the house as a simple shed roofed house insulated on all six sides to at least r 56 post a comment or leave a trackback trackback url Discuss  |  Bury |  News | greenline smith house a passive house in illinois [...]

June 14th, 2009 at 6:02 PM

Kenny Huffstutler

As houses get tighter and more energy effeicent creates even more of a reason to use ERVs that can bring in fresh air and transfer the energy of exhausting return air and transfers the energy to the outdoor air while turning over the air indoors reducing the Co2 level in your home. making a more comfortable living enviroment. Also for the colder climates that utilize humidifiers, stop exhausting you humidity from your humidifiers. Our RAVE erv allows you to maintain your indoor humidity as the dessicant transfers the humidity from the exhaust air to the outside air, thus allowing you to maintain your indoor humidity in the winter. Kenny Huffstutler

August 13th, 2009 at 10:59 AM

Passive Solar (part 2) Gone Wild

[...] http://greenlineblog.com/smith-house-a-passive-house-in-illinois/ [...]

March 7th, 2010 at 6:03 PM

Harald Giebel

Considering having a new house build, would like to know if North Carolina has contractors that use the Passive house principles. Harald