The story of how a small committed team in Bozeman, Montana, is quietly changing the way homes are built.
Much new-home construction is based on meeting the market criteria for a given demographic. This usually boils down to square feet and the number of amenities in the home. The formula goes something like this: Three bedrooms, two baths, and granite countertops; nice, but not too expensive, finishes. Home performance, low energy bills, and resource use are often talked about but seldom put into practice. Building is a risky business, and most builders choose standard materials and techniques to minimize risk.
The fact is that we don’t see much large-scale systemic innovation happening in the industry here in Montana. And when home sales pick up, there is little incentive to build better homes when a standard home sells just as fast. When home sales are flat, there is no incentive for innovation.
Earlier in my career, I weatherized a home in Montana occupied by a single, working mom. There was snow on the living room floor that had blown in through cracks around the front door. Today, with the ability to build efficient, high-quality homes at affordable price points, no one should live like this.
My partner, Bernhard Uhl, cofounder of YesHaus, was brought up in Germany and trained there in building science. He says, “Construction here is very different, and I never experienced the need for energy-efficient buildings as I do here. I realize we have the possibility to create long-lasting buildings for the future.” But it’s about more than just energy efficiency and durability.
“There are houses and there are homes,” says Bernhard. “I am talking about something different. A home is a space I am coming home to. I am coming home and I am nurtured by my home. It’s spiritual and it creates being. I come home, and home has a quality that does not consist of square feet. Home is something different that creates sanctuary.”
A traditional German farmhouse has thick walls to keep the cold out in the winter and the heat out in summer. These homes were built with very small south-facing windows (before double- and triple-pane windows existed). At YesHaus we are building with a combined experience of 60 years working in building and energy efficiency, and traditions going back hundreds of years. We have not developed our own thing—nothing we can patent. We are putting together what is known in a new way.
In 2010, while looking at contemporary American home-building practices, we decided to build a home that was energy efficient and comfortable while being beautiful and cost competitive with similar new homes on the market.
Was this even possible? We weren’t sure. We put our own money and livelihoods on the line to find out. A team of local and national building professionals who shared our vision soon joined us.
At the time of this writing, we have completed five homes with two under construction in Bozeman and Big Sky, Montana, and more are planned. We have proven the construction technique, the business model, the energy performance, and the demand in our regional market. The YesHaus’s build price is $127–$135 per square foot, not including land or landscaping.
The YesHaus goes beyond the energy efficiency of a standard house built to the IECC 2009 National Code. We do that by substantially increasing the airtightness and insulation of the ceiling, walls, windows, and floors, and by using the most energy- efficient lighting available at a reasonable cost (see Table 1).
We use structural insulated panels (SIPs) for the walls. Our first homes were built with 10-¼-inch walls. Windows are triple-pane casements with a U-value of 0.24. Floor systems are
10-¼-inch SIP panels built on a crawl space. We are changing the floor system to an insulated concrete foundation wall and a conditioned crawl space to better control air leakage.
Our biggest and most interesting challenge in the YesHaus design was finding a heating system to meet the ultralow heat load. In Bozeman, Montana, we have average annual heating degree-days of 8,156 and cooling degree-days of 205. Although the cooling season is short, we do have long summer days with highs in the 90s in July and August. More and more home buyers want cooling systems, which adds yet another design criterion.
“Why live in a house when you can live in your vision?”
~ D.J. Hofer, YesHaus Owner
We chose a mini-split air-to-air heat pump to meet the calculated heat load of 15,000 Btu per hour. The mini-split condenser unit is mounted on a first-floor wall. Conditioned air is circulated throughout the home using an ERV and ductwork. Because of the tight construction, high levels of insulation, and low heat load, the home is evenly and effectively heated and cooled from the mini-split system.
We installed backup electric baseboard units to make sure that the home would never be cold. Call it a low-cost insurance policy against callbacks.
Our domestic hot water (DHW) system is a heat pump water heater located inside the thermal boundary. We included a wastewater heat recovery device to capture the heat from showers, bathing, dishwasher, and washing machine. With this system we have reduced water-heating costs to $5 per month. By locating the water heater in the conditioned space, we provide cooling to the home in the summer. Conversely, we do extract heat from the home in the heating season, creating a slightly higher heat load in the home.
The heat pump water heater cools the laundry and mechanical room year-round. We inform our clients of this and suggest that they use the room as a cooled pantry. Admittedly, one of our first homeowners was surprised by the cool temperature in the laundry room. The water heater does make noise, which is not overly obtrusive when the mechanical room door is closed, but is noticeable when the door is open.
Our first three homes have achieved the results we aimed for—an ACH50 of less than 1.5. Here are the numbers (house names refer to street names): Julie Court house, 1.47; Tilton house, 0.52; and Ridgeline house, 1.03.
“We are changing the way homes are built. We are creating a new conversation of energy efficiency, comfort, and affordability.”
~ YesHaus Team
The standard measure of a home’s energy performance is the HERS score. HERS raters have evaluated the HERS scores of over 1 million homes nationwide. HERS scores range from 0 to 150, with the lowest scores representing the most energy-
The YesHaus in Bozeman, Montana, the Julie Court house, achieved a HERS score of 47. This means that the YesHaus is 53% more efficient than a typical newly built home and uses 83% less energy than most homes in the United States.
We are committed to achieving HERS scores of 50 or less for all of our homes. Thus far we have scores of 47 for the Julie Court house, 46 for the Tilton house, and 44 for the Ridgeline house. Working with other local green-building professionals, we are informing the local market about the importance of the HERS score as a way to compare homes.
We chose electricity as our only fuel source. Given the currently low natural gas prices, this choice may at first seem counterintuitive. With a less efficient building envelope, we might have chosen a gas-fired system. However, with the low heat load, we are able to take full advantage of the high efficiency of the electric heat pump, as well as the low first cost and the simplified, ductless installation.
When we studied our average winter temperatures we were quite surprised at the heat pump performance. Why? Did it perform better than expected? It is certainly less efficient at the coldest times of the year. Even then, we have found that performance, installation, and operating cost combine to make this an efficient “sweet spot” choice overall.
We have not been able to obtain reliable performance curves on the mini-split heat pump systems. Based on utility use, it is clear that the units perform well for us down to about 10°F. Efficiency probably drops off below 25–30°F, but even then we are getting near 100% end-use efficiency. The bottom line is that we see our highest energy use in our homes from late December to mid-February. Then, as outdoor temperatures begin to rise, heat pump efficiency increases and the cost of heating diminishes. No big surprise, but nice to get real-world confirmation.
Certainly one would not normally suggest the use of an air-to-air heat pump in a cold climate. And for that matter, I would not have considered electric heat in a new home in the past. However, the clincher here is that the heat load is so small that one of our challenges was to find a heat system that was less than 20,000 Btu per hour. This is where the mini-split excels.
Learning from Our Mistakes
An important part of any project is to learn from our mistakes. Before that, we have to admit our mistakes. And to do so in a national energy publication like Home Energy requires more than a little humility.
One problem that we failed to account for was worst-case temperature extremes. In the winter of 2013–14, we experienced extended lows below 0°F, with dips down to –30°F. Below about 10°F, the mini-split units were inoperable, causing our electric baseboard backup to activate. This was one of our most significant design errors. The problem was that we had always considered the baseboard to be a supplement to the mini-split, and it was not designed as a worst-case system. Consequently, we had to install some additional baseboard units to provide a true backup for ultralow temperatures.
One of the first mistakes we made with YesHaus was to design strictly for energy performance. Given our tendency to be energy geeks, we leaned toward energy overdesign. The result was that we tried for the best product possible from an energy performance standpoint, without considering the basic laws of physics pertaining to diminishing returns. Therefore, we ended up with a product that has 10-inch walls, 10-inch floors, and an R70–R90 attic, and that included many cost-intensive features, such as wall-hung toilets with the tanks inside the walls, and a waste heat recovery device in the crawl space.
The upshot is that the energy performance is astounding, but the project cost much more to build than we had expected. I had to remind myself that in order for energy-efficient housing to be widely accepted—even to become the norm—we builders have to design effectively and to do so in such a way as to create a profit. Without a profit, energy-efficient homes will be limited to buyers with deep pockets. Since we don’t fall into the deep-pocket category, we’ve had to revise our initial approach and design for optimal efficiency coupled with profitability.
There is little incentive to build better homes when a standard home sells just as fast. When home sales are flat, there is no incentive for innovation.
~ Duke Elliot
We have several questions remaining in terms of design, including which wall system is optimal for our particular climate (see Figure 1).
For example, it seems clear that an 8-inch wall may be a better wall system for our Montana climate than a 10-inch wall. Some people in our company even argue that a 6-inch wall would be adequate with a stronger focus on air leakage. These are some of the questions we are grappling with.
The other change we’ve made within YesHaus—and the jury is still out regarding performance—is that we switched from an SIP floor to an insulating concrete form (ICF) foundation. Common sense tells me that the insulated floor will perform better than a conditioned crawl space. For me, this is logical since we are reducing the conditioned space (even considering we will not condition the crawl space to the same temperature as the living space). Interestingly, the predicted performance indicates a conditioned crawl space, while adding volume to the home, will outperform the insulated floor. What is clear is using the insulated concrete foundation is more cost effective than the insulated floor system. We do not have adequate data at this time to determine which system will indeed perform the best. And, if the ICF foundation performs less well, would the cost savings for this system be sufficient to justify the change?
YesHaus Energy Performance Results
Each YesHaus comes with a TED energy monitoring system to enable the builder and the homeowner to monitor home energy loads. By using this system, we can track heating and DHW loads separately.
The first YesHaus in Bozeman, Julie Court, with 1,960 square feet, three bedrooms, and two baths, had a predicted heating bill of just $239 per year. The proof is in the utility bills. There are two adults and one child living in the house, and we gathered ten months of energy use data (see Table 2 on p. 40 for a year of data on heat energy and total energy use at the Julie Court house).
EMC has established weatherization training centers across the United States and created the trademarked Master That, which provides mobile training tools to deliver expert guidance direct to jobsites.
Find out more about EMC and the YesHaus.
We pay your heating bill for three years!
We are so confident that heating costs will be low that we pay the heating bills in the YesHaus for three years. We can do this because of our attention to engineering, design, quality, and performance.
But it’s not just about energy. We asked one of our clients how they liked the YesHaus. We expected to hear, “It’s warm and quiet and we like the doors.” The answer was, “Our son slept through the night for the first time.”
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