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Passive House in the Woods Goes Energy-Positive

A PV array helped a Passivhaus project in Hudson, Wisconsin, exceed net-zero-energy performance in 2011

Posted on Feb 27 2012 by Richard Defendorf

As the clock wound down on 2011, marking a full year of monitoring for Passive House in the Woods, in frosty Hudson, Wisconsin, it became clear that the building’s design, construction, and renewable-energy systems had combined to deliver net-zero-energy performance, and then some.

Tim Eian, of Minneapolis-based TE Studio, designed the home to meet the Passivhvaus standard and teamed up with Morr Construction Services, of Shoreview, Minnesota, to turn the plans into reality. The 1,940-sq.-ft. home was certified by the Passive House Institute U.S. in October, and Eian recently reported on the TE Studio blog that it had produced more energy than it used in 2011.

The home's above-grade walls are built from 11-in.-thick insulated concrete forms (ICFs) clad with an exterior-insulation and finish system (EIFS) that brought the overall R-valueMeasure of resistance to heat flow; the higher the R-value, the lower the heat loss. The inverse of U-factor. of the walls to 70. The slab, which sits on 12 in. of extruded polystyrene, is designed to deliver R-60 thermal resistance, and the flat roof, with an average of 14 in. of polyisocyanurate insulation, is rated at R-95.

The house is equipped with a solar hot water system, a 4.7-kW photovoltaic(PV) Generation of electricity directly from sunlight. A photovoltaic cell has no moving parts; electrons are energized by sunlight and result in current flow. system, and a ground-loop system and liquid-to-air heat exchangerDevice that transfers heat from one material or medium to another. An air-to-air heat exchanger, or heat-recovery ventilator, transfers heat from one airstream to another. A copper-pipe heat exchanger in a solar water-heater tank transfers heat from the heat-transfer fluid circulating through a solar collector to the potable water in the storage tank. designed to pre-warm, pre-cool, and dehumidify the ventilation air as needed.

Getting to positive
Based on PHPP calculations, Eian explained, as much as 80% of the heat load over the course of the year has been covered by passive solar gain.

“While we predicted this with our energy models,” Eian wrote in the TE Studio blog, “we found and learned through monitoring that some equipment and appliances use more energy than assumed. On the flip side, user behavior plays a major role as well and can effectively lower energy consumption over the predicted model.”

Eian also pointed out to that more performance tracking will be needed to create an accurate picture of monitored usage. TE Studio summarized the monitoring data for 2011 in a report to the building’s owner, Gary Konkol, a general-practice physician, but at this point that information isn’t being released to the public.

So monitoring will continue and, Eian adds, “no changes to the building's systems or performance are scheduled. On whole, the building performs as predicted and the owner is very excited about it.”

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Image Credits:

  1. TE Studio

Feb 27, 2012 10:46 AM ET

Net Positive
by Doug McEvers

Nice work, Tim Eian

I will say 2011 seemed a bit more sunny than usual and I see it in the monthly energy use of our house here in Minneapolis. Tim, are you considering yearly solar data (percentage of normal) as part of your long term monitoring of this home?

Feb 27, 2012 11:06 AM ET

MN was sunny & warm
by Eric Sandeen

Doug, you're right, it was a very .... interesting winter around here. OTOH it doesn't say how much they beat "net zero" by - maybe it was a lot? If they squeaked by, it'll be interesting to see a colder winter.

Also, although it was warmer and possibly sunnier around here, my rooftop array still underperformend PVWatts estimates this winter.

Feb 27, 2012 11:53 AM ET

80% of heat load covered by passive gain
by Doug McEvers


This is fabulous, for a crusty superinsulator like myself, I am impressed, tell us more!

Feb 27, 2012 12:19 PM ET

Passive solar heat contribution
by Martin Holladay

Tim Eian reports that "80% of the heat load over the course of the year has been covered by passive solar gain." So what percentage is contributed by internal gains (people, the refrigerator compressor, lighting, the television, etc.)? And what percentage is contributed by the heating system?

I'm guessing that Tim forgot to include internal gains when making the 80% calculation.

Feb 27, 2012 7:59 PM ET

Well done, but...
by Garth Sproule 7B

Great job on getting that much heating from passive solar. My question is, how do you deal with summer and early fall heat gains? It looks from the pic that there are two walls with a lot of glass...means that one of these walls faces east or shading strategy??

Feb 28, 2012 2:52 PM ET

Edited Feb 28, 2012 2:53 PM ET.

Summer Shading
by Paul Brazelton

Garth, the house uses motorized exterior blinds to manage solar gain. Just about everyone on the project frequents GBA, so maybe they can go into more detail.

Feb 28, 2012 3:24 PM ET

Making Money With Your Extra Energy
by Kevin Dickson, MSME

In Colorado, at least, it's not very profitable. It highly depends on the rate structure.

Feb 28, 2012 7:10 PM ET

Details on a Net-Zero House
by Lee Dodge

It would be nice to have more complete information about energy generation and energy use. I try to provide more complete data for my near net-zero source energy house in Colorado at It was better than net-zero source energy over the first year, but we'll see how it does as the PV system ages and the weather varies from year to year.

Feb 29, 2012 7:17 PM ET

Sounds expensive
by Elizabeth Kormos

Impressive results but what did it cost? We need houses that cost around $135 per sf so the average buyer can afford them.

Mar 1, 2012 11:58 PM ET

Edited Mar 2, 2012 12:33 AM ET.

Quick replies
by Tim Eian

In order:

Lee, the house utilizes approx. 4.5 kW of PV, and one solar thermal panel for DHW.

Garth, the windows are "actively" shaded with motorized exterior blinds to enable a high degree of solar control over the course of the year. The system can be automated with weather station and programming. Windows offer 64% SHGC. They are effectively the heaters, with the shades acting as thermostats.

Martin, I don't have access to the report at this moment. If I remember, I'll post the internal heat gain number.

Others, we try to gauge the weather conditions in respect to the performance analysis. It is one reason why we chose not to publish the first annual report, since weather in western WI is all over the map in any given year. Over time, the numbers will bear out the "true" performance of the building under "average" conditions.

For those who want to go deeper, the building has its own blog at You can also find it on our website at in the Portfolio section. Thanks for your comments.

Mar 3, 2012 4:06 PM ET

Building price
by Bill Keenan

I've never seen a building price connected to this house. I know they used a lot of products from Peak Building Products LLC. All excellent, very high-end products. I priced some of them out and they are not for mere mortals. I can only imagine what the sq. foot price is, but only people with an unlimited budget can build such a house. Don't get me wrong, I'm a fan of this house, but thinking that the cost is anywhere near the $135 per sq ft mentioned by an earlier poster is fantasy. I'm guessing it's easily double that.

Mar 4, 2012 8:53 PM ET

by shane claflin

I guess the doc likes the industrial look!

Mar 11, 2012 10:49 PM ET

Building Price
by Elizabeth Kormos

All stories about houses should include what they cost, the basic configuration (bedrooms, bathrooms, basement space, etc. and square footage. Without the cost revealed how can we know what we can and cannot afford to replicate.

Read Dr. Carl McDaniel's book Trail Magic (available on Amazon). He built a positive energy home for $146 per sq. ft and estimated it would cost $110 per sq. ft without the upgrades he choose to include in the house. We need more examples like his.

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