Large Connecticut Home is ‘Zero-Energy-Ready’

Climate Zone 5A, Derby, CT

Jun 11 2015 By | 16 comments

General Specs and Team

Location: Climate Zone 5A, Derby, CT
Bedrooms: 4
Bathrooms: 2.5
Living Space : 4456 sqf

Builder: Mark Nuzzolo, Woodbridge, CT, Brookside Development

Rater: Steven Winter Associates, Matt Slattery

Construction

Foundation: Conditioned basement with R-10 foil-faced rigid insulation from top of wall to 3 ft. below grade; no horizontal insulation under the slab.

Walls: 1 inch (R-6.5) polyisoPolyisocyanurate foam is usually sold with aluminum foil facings. With an R-value of 6 to 6.5 per inch, it is the best insulator and most expensive of the three types of rigid foam. Foil-faced polyisocyanurate is almost impermeable to water vapor; a 1-in.-thick foil-faced board has a permeance of 0.05 perm. While polyisocyanurate was formerly manufactured using HCFCs as blowing agents, U.S. manufacturers have now switched to pentane. Pentane does not damage the earth’s ozone layer, although it may contribute to smog. on exterior side of OSB sheathingMaterial, usually plywood or oriented strand board (OSB), but sometimes wooden boards, installed on the exterior of wall studs, rafters, or roof trusses; siding or roofing installed on the sheathing—sometimes over strapping to create a rainscreen. ; 2x4 16-in. o.c. walls with R-18 flash and batt insulationInsulation, usually of fiberglass or mineral wool and often faced with paper, typically installed between studs in walls and between joists in ceiling cavities. Correct installation is crucial to performance. ; vinylCommon term for polyvinyl chloride (PVC). In chemistry, vinyl refers to a carbon-and-hydrogen group (H2C=CH–) that attaches to another functional group, such as chlorine (vinyl chloride) or acetate (vinyl acetate). siding.

Windows: Vinyl windows with double-pane, argonInert (chemically stable) gas, which, because of its low thermal conductivity, is often used as gas fill between the panes of energy-efficient windows. -filled, low-eLow-emissivity coating. Very thin metallic coating on glass or plastic window glazing that permits most of the sun’s short-wave (light) radiation to enter, while blocking up to 90% of the long-wave (heat) radiation. Low-e coatings boost a window’s R-value and reduce its U-factor. glazingWhen referring to windows or doors, the transparent or translucent layer that transmits light. High-performance glazing may include multiple layers of glass or plastic, low-e coatings, and low-conductivity gas fill.; U=0.28, SHGCSolar heat gain coefficient. The fraction of solar gain admitted through a window, expressed as a number between 0 and 1.=0.30; basement U=0.46, SHGC=0.61.

Attic: R-68 (19-in.) of cellulose on attic floor; R-50 of closed-cell spray foam in cathedral ceilings.

Heating and cooling: 2-ton air-source heat pumpHeat pump that relies on outside air as the heat source and heat sink; not as effective in cold climates as ground-source heat pumps. (HSPF 8, 14 SEER(SEER) The efficiency of central air conditioners is rated by the Seasonal Energy Efficiency Ratio. The higher the SEER rating of a unit, the more energy efficient it is. The SEER rating is Btu of cooling output during a typical hot season divided by the total electric energy in watt-hours to run the unit. For residential air conditioners, the federal minimum is 13 SEER. For an Energy Star unit, 14 SEER. Manufacturers sell 18-20 SEER units, but they are expensive. ); 96 AFUEAnnual Fuel Utilization Efficiency. Widely-used measure of the fuel efficiency of a heating system that accounts for start-up, cool-down, and other operating losses that occur during real-life operation. AFUE is always lower than combustion efficiency. Furnaces sold in the United States must have a minimum AFUE of 78%. High ratings indicate more efficient equipment. gas furnace; ducts inside, MERV 10 filter

Domestic hot water: Tankless gas; EF(EF). Efficiency measure for rating the energy performance of dishwashers, clothes washers, water heaters, and certain other appliances. The higher the energy factor, the greater the efficiency. In some appliances EF reflects the percentage of energy going into the appliance that is turned into useful energy. 0.92

Mechanical ventilation system: 90 cfm exhaust-only system that meets ASHRAE 62.2A standard for residential mechanical ventilation systems established by the American Society of Heating, Refrigerating, and Air-Conditioning Engineers. Among other requirements, the standard requires a home to have a mechanical ventilation system capable of ventilating at a rate of 1 cfm for every 100 square feet of occupiable space plus 7.5 cfm per occupant..

Lighting: 10% LED; 90% CFLCompact fluorescent lamp. Fluorescent lightbulb in which the tube is folded or twisted into a spiral to concentrate the light output. CFLs are typically three to four times as efficient as incandescent lightbulbs, and last eight to ten times as long. CFLs combine the efficiency of fluorescent light with the convenience of an Edison or screw-in base, and new types have been developed that better mimic the light quality of incandescents. Not all CFLs can be dimmed, and frequent on-off cycling can shorten their life. Concerns have been raised over the mercury content of CFLs, and though they have been deemed safe, proper recycling and disposal is encouraged. ; daylight sensor on exterior lamp.

Appliances: Energy StarLabeling system sponsored by the Environmental Protection Agency and the US Department of Energy for labeling the most energy-efficient products on the market; applies to a wide range of products, from computers and office equipment to refrigerators and air conditioners. refrigerator and dishwasher

Blower-door results: 2.03 ach50

Energy

HERSIndex or scoring system for energy efficiency established by the Residential Energy Services Network (RESNET) that compares a given home to a Home Energy Rating System (HERS) Reference Home based on the 2006 International Energy Conservation Code. A home matching the reference home has a HERS Index of 100. The lower a home’s HERS Index, the more energy efficient it is. A typical existing home has a HERS Index of 130; a net zero energy home has a HERS Index of 0. Older versions of the HERS index were based on a scale that was largely just the opposite in structure--a HERS rating of 100 represented a net zero energy home, while the reference home had a score of 80. There are issues that complicate converting old to new or new to old scores, but the basic formula is: New HERS index = (100 - Old HERS score) * 5. Index: 45

Projected annual energy cost savings: $1,730

Projected annual utility costs: $2,110

Annual Energy Savings: 6,319 kWh, 654 therms gas

Solar: House is pre-wired for a future PVPhotovoltaics. Generation of electricity directly from sunlight. A photovoltaic (PV) cell has no moving parts; electrons are energized by sunlight and result in current flow. system and plumbed for a future solar thermal system.

Water Efficiency

EPA WaterSenseProgram developed and administered by the U.S. Environmental Protection Agency to promote and label water-efficient plumbing fixtures. fixtures

Storm water management during and after construction; invasive species removed; rain garden designed to accept all runoff from home; conservation easement planned.

Certification

DOEUnited States Department of Energy. Zero Energy Ready Home Program

EPA Indoor airPLUS

2013 Connecticut Zero Energy

NAHBNational Association of Home Builders, which awards a Model Green Home Certification. National Green Building StandardNational Green Building Standard Based on the NAHB Model Green Home Building Guidelines and passed through ANSI. This standard can be applied to both new homes, remodeling projects, and additions. , whole development

The builder says that the incremental cost of the energy-efficiency features was only $6,000 more than minimal compliance with the the 2009 code

Builder Mark Nuzzolo of Brookside Development has energy savings all sewn up at his new development, Singer Village in Derby, Connecticut. The high-performance homes are located on land surrounding the historic Singer House, once home of the granddaughter of Isaac Merritt Singer, founder of Singer Sewing Machines.

The first home constructed in the seven-home community earned certification from the U.S. Department of Energy’s Zero Energy Ready Home program. The program requires homes to meet a host of energy, health, and durability requirements, including those of the Energy StarLabeling system sponsored by the Environmental Protection Agency and the US Department of Energy for labeling the most energy-efficient products on the market; applies to a wide range of products, from computers and office equipment to refrigerators and air conditioners. Certified Homes program and the U.S. Environmental Protection Agency’s Indoor airPLUS and WaterSenseProgram developed and administered by the U.S. Environmental Protection Agency to promote and label water-efficient plumbing fixtures. programs. In addition, they must meet DOEUnited States Department of Energy. Zero Energy Ready Home prescriptive or performance requirements and a checklist of “renewable ready” solar power measures that ensure the home is wired for a future 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. (PVPhotovoltaics. Generation of electricity directly from sunlight. A photovoltaic (PV) cell has no moving parts; electrons are energized by sunlight and result in current flow.) array and plumbed for a future solar thermal system in case the homeowner ever wants to install them.

The home was honored with a 2013 Connecticut Zero Energy Challenge Award sponsored by the State of Connecticut. The housing development, Singer Village, was designed to meet the National Association of Home Builders’ National Green Building Standards criteria and will become the first development in Connecticut to achieve a multi-star certification. This certification recognizes the builder’s efforts to design a development that reduces storm water impact on local waterways and infrastructures, preserves native habitat and wetlands, minimizes erosion, and reduces environmental impacts during excavation and construction.

The builder got serious about energy efficiency

Nuzzolo, a veteran home builder who has built more than 400 homes over a 30-year career, has been recognized with numerous home building industry awards from the Home Builders Association of Connecticut. Although educated as a lawyer, Nuzzolo chose real estate development and has served as president of the New Haven Home Builders Association and as a current member of the association’s board of directors. He is also a Certified Green Professional. Mark’s wife, D.J. Collins, works with him as a builder, marketer, and coordinator of sales.

Nuzzolo has been participating in the Energy Star Certified Homes program since 2004. He took a serious look at increasing the energy efficiency of his homes in 2008 when oil prices rose and the recession hit hard. “I thought, we’re never going to sell a house in this market doing the same old thing. Let’s change the equation from initial cost of the home to the cost of homeownership. We decided to push the envelope,” said Nuzzolo. Nuzzolo began participating in the Energize CT New Construction Program, which offers incentives to builders who build energy-efficient homes, with tiered amounts based on the level of energy efficiency the builder achieves.

Through this program, Brookside began working with Steven Winter Associates, a research partner in the DOE Building America Program, who told Nuzzolo about the DOE Zero Energy Ready Home program. With one DOE Zero Energy Ready Home done, Nuzzolo plans to build the remaining six homes at Singer Village to meet the program criteria. “The only thing I have to figure out is making the WaterSense water distribution requirement work with all of our house designs,” said Nuzzolo. “The other requirements all make sense. Building a house this tight, you almost have to do the things Building America requires.”

According to Nuzzolo, building to the DOE Zero Energy Ready Home requirements only cost him about $6,000 more than building a home that minimally complies with the 2009 International Energy Conservation Code.

R-68 roof insulation

Nuzzolo starts with a standard 2x4 16-inch on-center wood-framed wall, and insulates between the studs with the “flash and batt” approach (1.5 inches of closed-cell spray foam, followed by unfaced fiberglass batts). “I’ve tried both open-cell and closed-cell spray foam. The closed-cell spray foam increases the strength of the wall and provides exceptional air sealing,” said Nuzzolo.

On the exterior, the 7/16 inch OSB sheathingMaterial, usually plywood or oriented strand board (OSB), but sometimes wooden boards, installed on the exterior of wall studs, rafters, or roof trusses; siding or roofing installed on the sheathing—sometimes over strapping to create a rainscreen. is covered with 1 inch (R-6.5) of foil-faced polyisocyanurate rigid foam. This continuous layer of foam provides a thermal break between the framing and the siding, reducing thermal bridgingHeat flow that occurs across more conductive components in an otherwise well-insulated material, resulting in disproportionately significant heat loss. For example, steel studs in an insulated wall dramatically reduce the overall energy performance of the wall, because of thermal bridging through the steel. through the studs.

The polyiso is taped at the seams to provide a continuous drainage planePath that water would take over the building envelope. Concealed drainage-plane materials, such as building paper or housewrap, are designed to shed water that penetrates the building’s cladding. Drainage planes are installed to overlap in shingle fashion (weatherlap) so that water flows downward and away from the building envelope. for any rainwater that might get past the vinylCommon term for polyvinyl chloride (PVC). In chemistry, vinyl refers to a carbon-and-hydrogen group (H2C=CH–) that attaches to another functional group, such as chlorine (vinyl chloride) or acetate (vinyl acetate). siding. The walls have a total R-valueMeasure of resistance to heat flow; the higher the R-value, the lower the heat loss. The inverse of U-factor. of R-25.

The vented attic has 19 inches of cellulose (R-68) piled on the attic floor. All cathedral ceilings are insulated with R-50 of closed-cell spray foam.

Heating and cooling systems are in the basement

The heating and cooling equipment is located in the basement, which is insulated from the ceiling to 3 feet below grade with R-10 of foil-faced, glass-fiber-reinforced, polyiso rigid foam insulation. (While the 2012 International Residential Code requires R-15 in this location, R-10 meets local code requirements.)

The builder chose Thermax polyiso because Thermax offers a code-accepted thermal break, i.e., building codes allow it to be left without a covering of drywall. Therefore, the basement can be left for the homeowner to finish as desired. Beneath the slab is 10 inches of packed gravel and a polyethylene vapor barrier to keep moisture out of the slab and minimize radonColorless, odorless, short-lived radioactive gas that can seep into homes and result in lung cancer risk. Radon and its decay products emit cancer-causing alpha, beta, and gamma particles.. There is no horizontal rigid foam under the slab.

Space heating equipment consists of an air-source heat pumpHeat pump that relies on outside air as the heat source and heat sink; not as effective in cold climates as ground-source heat pumps. with a gas furnace for back-up. The 2-ton heat pump has a heating system performance factor (HSPF) of 8 and a seasonal energy efficiency ratioSeasonal Energy Efficiency Ratio (SEER) is the total cooling output (in BTU) of an air conditioner or heat pump during its normal annual usage period divided by its total energy input (in Watt-hours) during the same period. The units of SEER are Btu/W·h. SEER measures how efficiently a residential central cooling system operates over an entire cooling season. The relationship between SEER and EER depends on location, because equipment performance varies with climate factors like air temperature and humidity. (SEER(SEER) The efficiency of central air conditioners is rated by the Seasonal Energy Efficiency Ratio. The higher the SEER rating of a unit, the more energy efficient it is. The SEER rating is Btu of cooling output during a typical hot season divided by the total electric energy in watt-hours to run the unit. For residential air conditioners, the federal minimum is 13 SEER. For an Energy Star unit, 14 SEER. Manufacturers sell 18-20 SEER units, but they are expensive. ) of 14. (Minimum federal appliance standards are 7.7 HSPF and 13 SEERSeasonal Energy Efficiency Ratio (SEER) is the total cooling output (in BTU) of an air conditioner or heat pump during its normal annual usage period divided by its total energy input (in Watt-hours) during the same period. The units of SEER are Btu/W·h. SEER measures how efficiently a residential central cooling system operates over an entire cooling season. The relationship between SEER and EER depends on location, because equipment performance varies with climate factors like air temperature and humidity.). The high-efficiency gas furnace has an annual fuel utilization efficiency(AFUE) Widely-used measure of the fuel efficiency of a heating system that accounts for start-up, cool-down, and other operating losses that occur during real-life operation. AFUE is always lower than combustion efficiency. Furnaces sold in the United States must have a minimum AFUE of 78%. High ratings indicate more efficient equipment. (AFUEAnnual Fuel Utilization Efficiency. Widely-used measure of the fuel efficiency of a heating system that accounts for start-up, cool-down, and other operating losses that occur during real-life operation. AFUE is always lower than combustion efficiency. Furnaces sold in the United States must have a minimum AFUE of 78%. High ratings indicate more efficient equipment. ) of 96%, far exceeding the federal minimum of 78% AFUE. The system includes a MERV 10 filter.

All of the HVAC(Heating, ventilation, and air conditioning). Collectively, the mechanical systems that heat, ventilate, and cool a building. equipment and ducts are located within the home’s conditioned spaceInsulated, air-sealed part of a building that is actively heated and/or cooled for occupant comfort. .

The heat pump works in conjunction with natural gas fuel

The builder worked with Steven Winter Associates to select the HVAC equipment and settings. They recommended setting the heat pump switch point to 50°F, which means if the outside temperature drops below 50°F, the heating system will switch to the natural gas furnace. “Analysis by Steven Winter Associates showed the heat pump lost its cost effectiveness below 50°F because we have natural gas on the site,” said Nuzzolo.

The home was designed with enough roof space and the proper orientation to permit the installation of 5 kW of PV panels. Metal conduit has been installed from the attic to the electric panel to accommodate the future installation of a PV array. “We have tremendous solar capability on the site,” said Nuzzolo. The local electric utility lets the meter spin backwards, crediting the homeowner for every kilowatt-hour produced up to the amount used by the home, at a rate of 19 cents per kilowatt-hour. But, once the meter reaches 0, any surplus electricity produced is credited back to the homeowner at 4 cents per kWh rather than 19 cents per kWh. With the dual-fuel system, the homeowner can adjust the switch point on the heat pump to rely on electric power (the heat pump) for heating after the meter has reached zero to “absorb” the excess electricity, explained Nuzzolo.

To further increase energy savings, the home is equipped with an Energy Star refrigerator and dishwasher. The lighting includes a mix of high-efficiency strategies – the exterior and interior lights that are used most often are LEDs (about 10% of the total fixtures); the remaining 90% are CFLs. There is a daylight sensor on the exterior lamp. The ceiling fan in the master bedroom is Energy Star rated. The water heater is a tankless gas water heater with an energy factor of 0.92.

Clean air measures include active and passive ventilation and low-VOC products

The home meets all of the EPA Indoor airPLUS requirements for healthy air including a passive radon venting system; low-VOC paints, finishes, and carpets; moisture management details; and an exhaust ventilation system that meets ASHRAE 62.2A standard for residential mechanical ventilation systems established by the American Society of Heating, Refrigerating, and Air-Conditioning Engineers. Among other requirements, the standard requires a home to have a mechanical ventilation system capable of ventilating at a rate of 1 cfm for every 100 square feet of occupiable space plus 7.5 cfm per occupant. ventilation requirements.

After completing his first DOE Zero Energy Ready certified home, Nuzzolo said that he enjoyed the experience and he’s learned from it. “I’ve got the expertise now. The next house we do, we’re streamlining the design and possibly reducing the size to go for a lower price point,” said Nuzzolo. “I may adjust the products and reduce the size but I don’t want to compromise the energy efficiency. Your best shot at getting an energy-efficient house is to build it that way from the start. Once the envelope is closed in, you’ve pretty much lost your opportunity.”

Lessons Learned

Mark Nuzzolo says that building highly energy-efficient homes requires some homework, teaching ability and collaboration.

"The first hurdle to overcome is gaining the science knowledge which enables you to teach. Take a building science course, lecture, read a lot of articles. Do it more than once as it takes time to absorb. I am still learning," said Nuzzolo.

"Once you acquire the knowledge, you must commit to a strategy. Do you want to get to zero at any cost, or do you want to reach the point of diminishing returns? Either way, you must team up with a competent, experienced, and knowledgeable rater.

"After committing to a whole-house strategy, you are able to seek supply chains and subcontractors and teach, teach, teach. Also, measure everything to determine value and effectiveness," he said.

Working to high energy standards can be frustrating because the code and knowledge lags behind cutting-edge technology.

"The whole concept of green building is to reduce the demand which enables you to use fewer resources to satisfy the demand. Most challenging is saving the money and resources after lowering the demand. The industry workers beginning with engineers right down to the HVAC(Heating, ventilation, and air conditioning). Collectively, the mechanical systems that heat, ventilate, and cool a building. mechanics force you to design to current standards, partly because the codes and standards lag and partly because they have little or no experience with high performance building and lack confidence," said Nuzzolo.

"I have been doing this for some years now, and I am content with my current systems. However, technology is changing every day. You must keep pace," he added.

The benefits of green building still suffer from a lack of awareness by both the pubic and the building industry.

"This is the next biggest or maybe even the biggest challenge. Builders, realtors, appraisers and customers have very little experience with high-performance homes and therefore cannot place a value on it. The sales force needs to be very educated and passionate and demonstrative. In order to get people's attention, we have guaranteed the energy costs," he said.

"Our economy (in Connecticut) has severely lagged the nation, we have had an exodus of employers and households. We have a large amount of foreclosures and short sales which have kept prices low. Development costs, building costs, and lack of demand has kept new homes at depressed levels. It is very difficult to obtain commensurate appraisals and there is therefore little incentive to add costs to a home," said Nuzzolo.


Courtesy of the U.S. Department of Energy

Tags: , , , , ,

Image Credits:

  1. Brookside Development

1.
Jun 11, 2015 6:31 PM ET

Large Connecticut Home is ‘Zero-Energy-Ready’
by daniel hagan

NET zero is NOT zero.


2.
Jun 11, 2015 7:35 PM ET

Are these walls really R 25?
by Reid Baldwin

When I calculate the wall R value for a flash and batt 2x4 wall with an inch of polyiso, I get something considerably less than 25. What do others get?


3.
Jun 11, 2015 8:01 PM ET

Yup, something less.
by Andy Chappell-Dick

It is mindboggling that code allows this to be a nominal R-25. De-rate the exterior polyiso in cold weather; account for massive thermal bridging in what appears to be a VERY complicated conventional framing design with lots of corners, figure on installation imperfections with the spray foam and batts, and you've got a compelling argument for a performance-based standard. The attic cellulose is nice, though, although it looks like it's more cathedral than attic.


4.
Jun 12, 2015 12:43 AM ET

Zero Energy Ready
by KEVIN ZORSKI

I'm sorry to appear so snobbish and maybe protective of this site, but WTF is this article doing here?A 4400 sq. ft. behemoth is going to be "zero-ready" with the possible 5Kw PV system and its 2x4 walls?I guess only one person is going to live here and they go away in the winter to Florida.


5.
Jun 12, 2015 6:08 AM ET

Edited Jun 15, 2015 7:01 AM ET.

Response to Kevin Zorski
by Martin Holladay

Kevin,
Not all builders in the U.S. are at the same level of proficiency when it comes to energy details. Some crews are now building their fourth Passivhaus; others are just beginning to learn about air sealing.

GBA tries to provide a mix of stories, including this one -- focusing on a builder who is just beginning to learn about air sealing and energy efficiency. I have no reason to doubt the report that the methods that Mark Nuzzolo used to build this home were a substantial improvement over the way he used to build.

GBA expects its sharp-eyed readers to know the difference between a truly superinsulated building and one that is taking beginning steps. No one is trying to pull the wool over your eyes. (And this is a good time to remind our readers that GBA welcomes submissions from readers. We are always on the lookout for homes for our Green Homes department -- so if you are proud of your new green home, share your pride with the world. The ideal submission is a first draft of an article, including photos. For more information, contact me anytime: martin [at] greenbuildingadvisor [dot] com.)

I learned something from this article: that the requirements of the DOE's Zero Energy Ready Home are a pretty low bar. It's evidently possible to meet the program's requirements with double-glazed windows, R-10 basement insulation, and no horizontal insulation under the basement slab. Understanding the requirements of the various programs that are out there helps stimulate discussion on this web site and contributes to a dialogue on appropriate standards.

I can think of two possible reasons for this low bar. The first possibility is programmatic and boring: It's simply that the DOE set the bar low to encourage participation by as many builders as possible.

The second possibility is a technical one and is more intriguing: It's possible that the cost of PV modules has dropped so far that there is no way to justify the installation of triple-glazed windows, R-15 basement wall insulation, or sub-slab foam in Connecticut. If that is the correct answer, it's interesting.


6.
Jun 12, 2015 8:20 AM ET

Spray foam
by Dwight Harris

That's a lot of spray foam... He must have already been using a whole lot of it for there to only be a 6k total up charge.

Also, is there any concern about the OSB being unable to dry out since it's sandwiched between closed cell and poly iso?


7.
Jun 12, 2015 8:51 AM ET

Edited Jun 12, 2015 9:18 AM ET.

Response to Dwight Harris
by Martin Holladay

Dwight,
I'm trying to avoid piling on with criticisms of this home's details -- but you have identified one that also caught my eye. In general, if a wall has exterior rigid foam, you don't want to install any closed-cell spray foam on the interior side of the sheathing. A vapor-permeable insulation (for example, dense-packed cellulose or open-cell spray foam) would have been a better choice for this location.

In 30 years, we'll have a better idea of whether this type of foam sandwich results in failures.


8.
Jun 12, 2015 7:49 PM ET

PV array size for net zero
by ven sonata

So at first glance the place seems modestly insulated. Still... do the numbers. They spent $6000 to reduce their costs by $1700. Good. 3.5 year return on investment. And they are short $2110/year for electric production. Sounds like a lot until you realize the grid is 19cents/kwh. So they are short about 10,000kwh per year. In their apparently ideal solar orientation that would require a 7kw pv array. At the national average of $3.34 watt that is $23,380. With Tax credit 30% about $16,000. That is an 8 year payback. Overall excellent. So they did the right thing without the triple glaze and double stud walls. They simply could not have done those items for $16,000. Yes, with PV prices the way they are (and falling) it doesn't take much to hit net zero and to basically outdo many technologies such as triple glazing.


9.
Jun 12, 2015 11:18 PM ET

Zero- Energy
by KEVIN ZORSKI

Martin - Thank you for your response, and for explaining the choice of this article. Ven - I appreciate your "back of envelope" analysis. The article, however, mentions 5kW capability. How does the natural gas fit into this analysis?How about hot water usage with 4 bedrooms for a potentially good sized family? How can 5kW pv make this house "ready" to be net zero? Are their electric usage and savings numbers realistic? I've read that 5kW pv just won't cut it for even a fairly thrifty and careful small family, And that 7-10 kw is more realistic. So, Ven, 2 hard questions: 1. Are these numbers realistic? and 2.How does the natural gas usage fit into the net zero capability? If you are willing, I think answers would be helpful for a lot of us. Thanks.


10.
Jun 13, 2015 6:05 AM ET

cold slabs
by shane claflin

The uninsulated slab is the achilles heel in this building, providing a continuous 50 degree thermal break year round. Are the poly-iso seams caulked or sealed before they are taped?


11.
Jun 13, 2015 5:01 PM ET

Can Light in Image 5
by Jeremy M

In Image 5 there's a can light that's air sealed (I believe) and then a flexible duct coming off of it? It caught my eye since it's so bent, but now I'm just confused what it's doing if that's just a can light, as it appears and as the image title/text states.


12.
Jun 13, 2015 6:19 PM ET

kevin Zero energy reply
by ven sonata

The PV will make it net zero electric, not net zero energy. The gas water heater and the gas furnace will not be cancelled by a 7 kw array. They do have heat pumps which will cancel the "shoulder season" gas requirements. Apparently the HVAC guys have recommended not to use the heat pumps below 50 degrees! A higher efficiency rating on the heat pump would help, however at 19cents kwh, PV beats heat
pumps at any efficiency. If they want net zero energy they would need about 12 kw PV. That will cancel their hot water and heating requirement. And it will still be cheaper than triple glaze and Zendher HRV. So yep....more PV!


14.
Jun 13, 2015 7:33 PM ET

Net Zero ELECTRIC
by KEVIN ZORSKI

Thanks, Ven. I knew from eyeballing these numbers and claims that they weren't right. For a more modest sized house, at what rough price do you think that PV beats mini-splits? At this point does PV always beat them, assuming the current price range of most utilities ? If and when I build new, I suspect I'll use mini splits anyway, as a way to not overload the grid on cloudy days, as long as it isn't too much more of an investment. I don't want you to do more complicated calculations, as I feel I've abused your willingness and expertise already. You have a great way of providing simple estimates for comparisons. Thanks !


15.
Jun 13, 2015 9:45 PM ET

Kevin heat pump vs pv
by ven sonata

Bascically at $3.50 watt PV beats Heat pumps at $4000. It also beats Hrv and Triple Glaze windows, but not super insulation. But if you don't want to stress the grid in winter then heat pumps ,if they have a high cold climate rating reduce your usage in "real" time. Net zero pv uses the grid as storage and if you have feed in tariff you can get that power back (theoretically in winter when the PV is not producing so well. I have done the numbers and some curious things result. For instance a heat pump is a better investment on a poorly insulated house than a super insulated house because you use it a lot. The shoulder seasons are when the heat pump is most effective and a super insulated house hardly needs heat in the shoulder season. However in the coldest part of winter the heatpump is less efficient. So this is an irony of insulation. PV lifespan is more than 30 years heat pump 15-20 plus possible repairs, at 19cents kwh the heatpump is paid off in about 8 years and returns its full value by the time it expires. pv can return twice the value at 19centskwh. There is a long thread on this subject a few months back on GBA. The realization dawned on me after Martin showed that PV had surpassed solar hot water panels in "Solar thermal is really, really dead" Heat Pumps got wounded in that shootout!


16.
Jun 14, 2015 6:20 AM ET

Response to Jeremy M (Comment #11)
by Martin Holladay

Jeremy,
Q. "In Image 5, there's a can light that's air sealed (I believe) and then a flexible duct coming off of it?"

A. I'm not sure what the photo shows. It's possible that there is a bathroom exhaust fan under the cover, not a recessed can light. If so, that would explain the duct.


17.
Jun 15, 2015 6:27 AM ET

Edited Jun 15, 2015 7:42 AM ET.

Almost Good Enough for Fine Homebuilding Magazine
by Sonny Chatum

Tried to delete the whole comment, but couldn't. Comments were valid, but maybe a little mean.


Register for a free account and join the conversation


Get a free account and join the conversation!
Become a GBA PRO!