LEED BD+C: Homes v3 - LEED 2008
The Kantor Residence
LEED Platinum 2010
* This profile has been peer-reviewed by a USGBC-selected team of technical experts.
The below stakeholder perspectives address the following LEED credits:
AEc1.3, MRc3.2, SSc2, SSc4.1, WEc1.1, WEc1.2, WEc3.2, IDc1, EAc3, EAc5, EAc6, MRc1, EQc5.2, EAc1
Goals and motivations
What were the top overarching goals and objectives?
Pursuing LEED on this project was not a high goal in building our house. My main considerations included living in harmony with nature, using alternative energy and recycled materials, and conserving water and other natural resources. Once we were asked about participating in the LEED rating system, we thought it a good idea to challenge ourselves. But from the onset, I was determined to make the house as sustainable as possible, regardless of whether LEED points were granted or not.
What were the motivations to pursue LEED certification and how did they influence the project?
- Design Innovation
- Waste Reduction/Avoidance
What were the most notable strategies used to earn LEED credits?
More than 90% of construction waste was diverted from landfills for recycling. The recycled material was common construction debris including wood, paper, and gypsum. A roof made of 80% post-industrial recycled rubber and plastic resembles slate shingling and houses solar thermal panels that heat domestic hot water. On mounting posts in the yard, 14 photovoltaic panels supply nearly all of the home's electricity needs. There are two buried cisterns that hold up to 1,250 gallons of rainwater. These are used for the minimal irrigation needs and for topping off the pool each spring (thereby keeping pool water trucks off of the roads).
PV on mounting panels in natural landscape. Photo by Karla Donnelly.
Traditional design features are plentiful despite a commitment to high technology features. The home has a root cellar and a community garden that supplies local food pantries. Permaculture landscaping includes a meadow, edible gardens within walking distance of the kitchen, and fruit orchards. Stones from the property were used for the poolscape and permeable walking paths further the local connection.
What cutting-edge strategies or processes were implemented?
I would say that there is nothing conventional about this house. The composting toilet and graywater system stand out most. I would have wanted all of the toilets to be composting, but that would have been too costly. So, I was satisfied having one in the master bathroom and installing a graywater system to pump non-potable water to the other toilets. Several people told me that a graywater system was not necessary, including a civil engineer. But with only 2% of the total water on the planet being potable, it seems insane to flush fresh water down the toilet. So, from my point of view, a graywater system belongs in a sustainable house.
If most people knew how depleted our soil is in this country and how we need to use more chemicals to grow food every year, then they would recognize the value of compost toilets in returning nutrients back into the soil. Nature's cycle requires the nutrients that are plentiful in human manure, which when composted properly through the thermophilic process, is transformed into valuable fertilizer.
How was the integrative process applied and what was the greatest benefit gained?
The project team and owner worked together to find systems, materials, and products that were not only attractive, but also cost-effective and sustainable. This effort began from the very start as the Kantors worked with the architect, builder, and green consultant for several months before construction began. During this time, the project team detailed the envelope's constructability to optimize the home's placement, footprint, material usage, and energy consumption. This collaboration continued throughout construction. Many meetings were spent discussing details. It started with identifying what the owner wanted, getting the architect's opinion, and then determining what materials would get us there.
One discussion that highlighted collaborative negotiation was the radiant slab heating system. The Kantors wanted a radiant slab on the entire first floor. Not only would this have been very expensive to install over such a large area, but it also would not support cooling, so duplicate systems would have been required for heating and cooling. As the builder, we stressed that given the building envelope with its high R value, we did not need to have radiant heating throughout to achieve the comfort they desired. Because the high R value equates to warmer inside walls and glass surface temperatures in winter, there is less demand for heat; if the system was installed throughout the entire floor, it might not have provided the warm floor they were looking for due to limited demand. In the end, we installed a 2.5-inch, stained concrete slab on wood framing in only the dining room and living room. The integrated design process really helped the whole team understand the costs and benefits of this decision. Ultimately, the Kantors gained the comfort of a radiant slab heating system at a lower cost by targeting key areas for installation.
Aside from LEED certification, what do you consider key project successes?
The near-net-zero energy custom home was built to realize the Kantor's vision of achieving luxury with minimum environmental impact. A key success was that, in addition to maximizing sustainability throughout the home, their achievements are ideal for educating the public through educational workshops and tours hosted by Connecticut Clean Energy Fund, Connecticut Green Building Council, and Fairfield University.
What were the most important long- and short-term value-add strategies and what returns on investment (ROI) have been experienced or anticipated?
A high performance thermal envelope offered these homeowners the best ROI strategy for this home. Our load analysis of the home showed that triple-insulated windows, strapped walls/roof framing, a highly insulated basement level slab/wall system, and a very tight building envelope required a very small heating system for the home as compared to a typical house of this size. The focus on longer lifecycle systems, such as the thermal envelope, minimizes the need for shorter lifecycle systems, such as mechanical equipment. Keeping the owner-requested large masonry fireplace and wood stove mass fully inside the thermal envelope and air tight was an added challenge.
The results speak for themselves, with the homeowners comfortable in their new home at 64 degrees with little heating required, even during an East Coast winter. The use of spray foam insulation throughout the house minimizes leakage to the outside, reduces thermal transfer, and ultimately removes the need for traditional heating. Most of the year, the Kantors actually sell more electricity than they buy.
Of all envelope strategies, I think the best return was on the triple-insulated window glass. The extra 1.5-inch of R-4.5 insulation from adding strapping to the inside of the 2x4, 24-inch on center walls gave the walls a robust R value, providing warmer interior surface temperature of the glass and windows. We focused on getting maximum R value in the floors, walls, and ceilings in a cost-effective way to match the owners' budget.
What project challenges became important lessons learned?
Building a highly insulated and airtight envelope with a wood-burning fireplace proved to be one of the largest obstacles. Nate Kantor wrestled with the desire to have a New England style stone fireplace. Ultimately, the project team designed a wood-fired fireplace in the post and beam living room and gas fireplaces in the second-floor office and basement. They share a beautiful stone chimney, but the wood-burning fireplace has outside combustion air and permanent glass doors that are sealed and gasketed. Backdraft potential is always a concern with wood-burning fireplaces and extremely tight homes (this one tested 2.0ACH50), so energy recovery ventilators were installed to keep the home balanced and to counter the stack effect.
If the homeowners had chosen a high cubic-foot-per-meter kitchen exhaust, an automatic switch would have been tied to the energy-recovery ventilators to deliver make-up air. But the Kantors have a convection cooktop and reasonable (175cfm) kitchen exhaust.
The mechanical side was more complicated than initially planned as we settled on three heating systems: solar thermal for primary heating; European wood pellet boiler (new to the U.S. market) for backup heating; and a high-efficiency, sealed-combustion, gas-fired boiler as secondary backup heating if all else fails. All three heating systems support a hydro-air heating system for most of the home, with radiant heating added to the living room, dining room, and master bath. Adding to the complexity, we also had to heat an outdoor pool and hot tub, so we supported these loads with the same equipment.
Side view of pool and solar thermal panels. Photo by Nate Kantor.
As a result, we had many heating systems supporting many loads. Since we were dealing with a custom system, we needed a custom controls solution, few of which were available at the time. In the end, we used multiple stand-alone controllers to communicate between the three heating systems and various loads. Ideally, one smart controller should have been used.
What was a pivotal moment that impacted the project's direction?
Etta Kantor persuaded the Connecticut state inspector to approve a cutting-edge graywater reuse system that directs excess water from the low-flow showers and sinks into the toilets. The graywater tank is a biological filtration system with a ten-gallon reservoir for the supply, used to flush the one-liter Sealand micro-flush toilet and other low-flow toilets in the house. Excess graywater is shunted to the leach field.
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