A High-Performance Car Can Kill You. A High Performance Home Can Save Your Life.

I have the best assignment on the steering committee of the Metro Denver Green Homes Tour — shooting video tours of the homes we choose to feature. Because of Covid, I’m taking that assignment more seriously than ever, because we may not have an in-person tour this year. (The tour is on October 3rd.)

I post these tours (along with the video tours of our listings) on my YouTube channel. Go there to check out some of the more recent tours.

Those videos, however, are limited in what they can convey in 7 to 10 minutes, so I must leave out a lot of what I learn during the lengthy orientation I get from each homeowner prior to shooting the video.

A good example was my tour last Saturday of Jen Grauer and Josh Renkin’s house in Denver. They scraped a house and built from scratch the best example of a “high performance home” I have come across yet — and I’ve seen a lot of high performance homes.

My 7½-minute tour of the house that Jen completed three years ago could not include a lot of what makes it such a good example of sustainability, so I’ll add to it here.

To be “net zero energy,” a solar-powered home like Jen’s has to be super insulated and super efficient in its use of energy. When a home is that tight, indoor air quality has to be addressed to make the home safe. That job is performed by an Energy Recovery Ventilator (ERV).

The ERV’s job is to bring in fresh air from the outside and to expel bad air while maintaining a healthy indoor humidity level. In the typical home, exhaust fans in bathrooms, kitchens and laundry rooms exhaust air to the outside, thereby drawing fresh air into the house only through whatever leaks exist around doors, windows and other penetrations of the home’s “envelope.” An ERV has one dedicated duct to exhaust air and another to bring in fresh, filtered air. This air is circulated through the house via multiple exhaust and fresh air vents around the home. In addition to maintaining indoor air quality, the ERV transfers some of the temperature (and humidity) of the outgoing air to the incoming air when there is a differential between the two.

Let’s say your home is 70 degrees inside, but it’s 100 degrees outside. The temperature of that incoming air can be reduced to, say, 75 degrees by passing it through a heat exchanger where it doesn’t mix with the outgoing air but acquires some of its temperature. Similarly if the outdoor air is below freezing, the ERV might raise that incoming air to, say, 50 degrees. (I could be way off on these numbers. I’m just trying to convey the concept.)

A conditioning ERV (or CERV) monitors the level of carbon dioxide and volatile organic compounds (VOCs) in the outgoing air. You can set a level that is acceptable (say, 900 ppm maximum) and the CERV will increase the flow of air when those levels are exceeded to bring them back to the acceptable range. Whereas an ERV runs 24/7, the CERV only needs to turn on to bring the levels of CO2, VOCs and humidity down to set acceptable levels. A CERV also has an internal heat pump to add heat or cooling. (See my videos of John Avenson’s and Jim Horan’s homes.)

In Jen’s case, in addition to an ERV, she made sure that the home was built with low-VOC products. For example, instead of using high-VOC particle board, her cabinets are made with zero-formaldehyde birch plywood and her island is solid maple and waterproofed with a zero-VOC oil. Her home has no wall-to-wall carpeting, which typically has VOCs in it. (These items are mentioned in the video of Jen’s house.)

Radon is another pollutant which seeps into every home through their concrete foundation walls and slab-on-dirt. To further improve air quality, Jen installed a radon mitigation system.

In summary, a high performance home can not only save you money in the long run (it costs more to build but nearly eliminates monthly utility bills), it can also create a home than extends your life through improved indoor air quality.

Discover Arvada’s Geos Community, Where the Homes’ Energy Costs Are Essentially Zero

That’s what it’s like for Jim & Patty Horan, who bought their 3-bedroom, 3-bath, 2,135-sq.-ft. home at 15062 W. 69th Place in Arvada’s Geos Community. They paid $525,000 for it three years ago (July 2017). 

Like all Geos homes, this one has no gas service. With only 6kW of solar panels on the roof, the home is heated by a ground source heat pump. It draws heat from the earth via a 300-foot-deep loop under the home. The heat pump uses very little electricity during the summer to further cool the 55° fluid in that loop, and not much more energy during heating season to heat that fluid to 100 degrees.

On Saturday, June 27th, Jim Horan gave me a tour of his home which I recorded for this fall’s Metro Denver Green Homes Tour. You can view the video at YouTube.com/jimsmith145.

Geos Community’s website describes it as “Colorado’s first geosolar development” and is the only subdivision I know that’s built entirely “net zero energy.” There are developers building solar-powered communities like KB Home’s subdivision on the northeast corner of Hwy 93 and 58th Ave., but they don’t come close to being net zero.

There’s a term for such homes — “greenwashing,” which Wikipedia defines at “a form of marketing spin in which green PR and green marketing are deceptively used to persuade the public that an organization’s products, aims and policies are environmentally friendly.” I’ve always marveled that those KB Homes were built with many of the solar panels installed on north-facing roof surfaces.

Getting back to the Horans’ home, there’s more to going net zero than having solar panels and a ground-source heat pump. Those features must be coupled with energy saving features so that the limited number of solar panels are enough to meet the home’s energy needs — with energy left over to charge an electric car.

Here are some of those features which I covered in my video tour with Jim Horan.

First and foremost is the passive solar orientation of the building with lots of south-facing windows and a south-facing roof for solar panels. Also, there are overhangs above each south-facing window designed to shade it from the sun during the summer while allow full sun in the winter when the sun is lower in the southern sky.

Next, the building’s “envelope” has to be very tight. That starts with foam insulation blown onto the interior surfaces of the roof and exterior walls, replacing the blown-in cellulose and fiberglass batting typical of tract homes built by other developers. The windows are Alpen triple-pane windows which also have foam-insulated fiberglass framing. (Fiberglass is better for window framing than vinyl – not as prone to aging and warping.)

Those elements make a house too air-tight for healthy living, so an energy recovery ventilator is installed which constantly brings in fresh air, using a heat exchanger designed so that the heat (or coolness) of the air being exhausted is used to heat or cool the fresh air being brought into the house. A heat pump within this device, called a CERV, provides further heating or cooling of that fresh air as needed.

In the townhomes at the Geos Community, the CERV works with an air-source heat pump mini-split instead of a ground-source heat  pump to heat and cool the home year-round.

Have you heard the term “indoor air quality” or “sick building syndrome”?  It refers to high levels of CO2 or volatile organic compounds (VOCs) which can build up in a home, especially in a home as air-tight as the Geos homes.

The CERV monitors both CO2 and VOC levels in the house and will bring in additional fresh air when those gases exceed the level set by the homeowner. (The Horans have the level for each gas set at 950 parts per million, or ppm.)

What are VOCs?  If you can smell it, it’s probably a volatile organic compound. Examples include new carpet smell and, worst of all, cat litter smells.

Two appliances in Geos homes also contribute to their low energy load. One is the Bosch condensation clothes dryer, which pulls in cool, dry air from the room. The air is heated and passed through the clothes; but instead of being vented outdoors, the air travels through a stainless steel cooling device or heat exchanger. It does heat the room it is in, so the Horans choose to dry their clothes on an outdoor line during the summer, even though their heat pump could handle the additional cooling load if they didn’t do that. Home Depot sells the Bosch 300 “ventless” dryer for $989.

The other appliance is the heat-pump water heater. It has a heat pump above the tank which transfers the heat from the room into the water. I’ve written about this product before. Home Depot sells a 50-gallon Rheem model for $1,299 which earns a $400 rebate from Xcel Energy and another $300 in federal tax credit if purchased by December 31, 2020. Because this appliance emits cold air, it’s in a pantry which the Horans keep closed in the winter and open in the summer. (I would put it in a wine cellar or in a room with a freezer, which emits hot air — a symbiotic arrangement within one room.)

As you are beginning to gather, building a net zero energy home is best done from scratch, when the additional cost is less than retrofitting a home. (My home is net zero in terms of electricity, but we still burn $30 to $50 of natural gas each month, and it takes twice as many solar panels for my home, which has about the same square footage as the Horans’.)

You may be wondering how much more it cost to build the Horans’ house, which they bought new in July 2017. To answer that, I searched all the comparable homes (2– or 3-story, between 1,500 and 2,500 square feet within 1 mile radius) sold during the summer months of 2017, and I found that the $246 per finished square foot paid by the Horans was actually below the median price ($253 per finished square foot) for the seven comparable sales. And those homes probably pay thousands of dollars per year more for electricity (and gas) than the Horans.

If you want to learn more about Geos community, give me a call at 303-525-1851 or visit the Geos website, www.DiscoverGeos.com.

John Avenson of Westminster Is a Committed Teacher of Energy Efficiency

The sponsors of the annual Metro Denver Green Homes Tour, held on the first Saturday each October, are preparing to “go virtual” in case an  in-person tour is not allowed.

John Avenson’s house at 9988 Hoyt Place, Westminster

That will be accomplished by creating online video tours of the most notable “green” homes featured over the past 20 years. Since I’m on the steering committee for the tour and have the equipment and experience from creating video tours of homes for sale, I volunteered to create those video tours, starting with John Avenson’s home at 9988 Hoyt Place in Westminster.

By clicking here, you can view the 41-minute video tour, led by John, which I created last Friday. It is highly educational.

John Avenson

Many people, myself included, have created homes which can be considered a “model” of sustainability, solar power, and energy efficiency, but John is surely the only homeowner who has turned his home into a classroom for teaching it. He even posted pictures and diagrams throughout the house with instructional content about this or that feature, as you will see on that video.

He also hosts monthly Passive House meetings in his home theater which are also streamed online. They can be found at www.meetup.com/Passive-House-Meetup-S-W-Region/

John’s house was originally built by the Solar Energy Research Institute (SERI, now the National Renewable Energy Laboratory or NREL) in 1981 using then-state of the art technology, but John has diligently, and at great personal expense, kept retrofitting his home with newer technology, which he is happy to explain to visitors and which he explains on the 41-minute video.

CERV monitor screenshot

For example, because of increased insulation and Alpen quadruple-paned windows, he was able to get rid of SERI’s supplemental natural gas furnace, installing a conditioning energy recovery ventilator (CERV) which is powered electrically. His grid-tied solar PV system provides all his home’s energy needs and has reduced his Xcel Energy bill to under $10 per month — the cost of being connected to the electrical grid.

Some of the technological innovations featured in my video with John were new to me. For example, the Alpen windows across from his kitchen have horizontal micro-etching which redirects the sun’s rays 90° upward to his ceiling instead of straight through the glass, reducing the need for lighting.

John provided his email address in the video, saying that his “learning center” is open 24/7 and that he welcomes all inquiries and visitors.

Interested in Net Zero Living? Discover Arvada’s Geos Community!

I love showing homes in Arvada’s Geos Community to buyers individually, but there’s a live Zoom presentation sponsored by First Universalist Church of Denver next week which will teach you all you need to know about this great community.

Register for that meeting (Tuesday, May 26, at 7pm) by going to https://bit.ly/FirstU_GEOS.

The homes and townhouses in this community are not only “net zero,” they are “net positive,” creating more energy than the homeowners use, including when they charge an electric car. The homes are so well insulated that they need no furnace, only a CERV, which also monitors and maintains indoor air quality.