December 5th, 2016 update: we are furiously trying to wrap up the project for our big Open House on Dec. 10th. One bathroom is completed, the other bathroom is nearly done. The kitchen cabinets are painted and waiting to be reassembled. The solar array is producing, so we are now working off renewable energy. Appliances are here, and the plumbers have done their thing. The electricians will come four days before the Open House. We received a donation of granite countertops, but they will not be installed until Dec 16th.
Our project is now Greenstar registered. We are going for Greenstar Gold status, plus Zero Energy Capable.
We are calling our maiden project The Brick House. It is located in the EcoVillage in the Hawthorne neighborhood of north Minneapolis.
Tall and but not very wide, the house is at least 100 years old. We will gut the inside and create an open concept with a rather modern look. One bedroom will be at the back of the first floor, with the second bedroom upstairs. We will add a bathroom on the second floor to create a master suite.
Because of the brick exterior, all window openings will remain the same. We plan to install triple-pane casements, sometimes combined with stationary windows beneath them to facilitate some of the tall and narrow openings.
We plan to spray foam the 2×4 stud cavities in the exterior walls, plus fur-out the studs to allow the foam to cover their interior side (to address thermal transfer). This will make the rooms slightly smaller, but much more energy efficient.
Rather than insulate the basement walls, we plan to foam the 1st floor joist cavities, from the basement side, and separate the conditioned envelope from the basement. The threat of water infiltration makes any method of insulating the foundation walls problematic. In addition, unless the concrete slab floor is also insulated (which means removing it, digging out and installing foam, then replacing it; both a big cost and a material waste), the slab functions like an ice cube that draws the heat out of the house. It is simpler and less expensive to let the basement function as unconditioned storage space.
One of CZH’s goals is to demonstrate how craftsmanship benefits the insulation package. Particularly in renovation projects (but true in every construction project), attention to detail and a thorough understanding of the value of a “seamless envelop” can boost the energy performance of a structure significantly when hefty R-Values (like in a Passive House) are not available.
Along with a well-installed seamless envelop of approximately R-28 in the walls and floor, plus R-65 in the attic, we will use Energy Star appliances, LED lightbulbs, and a high-efficiency furnace and water heater. We hope to prove the furnace can be eliminated from our houses. But we expect it will be our 3rd or 4th house before we achieve this goal.
The garage has extensive fire damage and must be torn down. We will replace it with a single car garage coupled with a car port. This provides us with a lot of roof surface for solar panels. The house roof is pitched east-west (not good siting), while the garage will be pitched north-south. The ridge of the garage roof will be off-set, so 3/4’s of the garage roof will pitch toward the sun– maximizing exposure.
We expect the solar array on the garage will not create all the electricity the house will use. A subscription to a Community Solar Garden will make up the difference. Carbon Zero Houses are not concerned with locating the power source on the property. Renewable energy from a wind farm, a Community Solar Garden, or utility-scale solar all offer equal means of neutralizing the carbon emissions from the house. In addition, reducing a house’s load remains Job One. The cheapest kilowatt is the one you never use. It is also the cleanest kilowatt available.
The stairway will float. We anticipate this to be the most interesting feature of the house. We explored constructing a metal stairway, but the costs were prohibitive. We will build it on-site out of laminated veneer lumber (LVL) stringers with oak treads supported by metal brackets. The rail system will be metal, as will the support post for the beam. This will give the inside of the house a kind-of industrial loft feel.
November 8th, 2016 update: solar array was installed today. The kitchen floor has been tiled. We are hanging doors and installing trim on the windows and doors.
September 27th, 2016 update: the exterior work is wrapping up (just as the weather changes). The solar array will be installed this Friday. The house will have its first Tour on Saturday. We are hoping to wrap the whole project in November.
August 18, 2016 update: The new retaining wall is installed. All the windows are installed. The garage constructions is complete; solar will go on the garage roof next month. Sheetrock has been installed and finished inside the house.
June 30, 2016 update: We have the old retaining wall removed, and a new sidewalk installed in the back. Hugels built around the garage. The garage has a roof. The old power pole has finally been removed. The porches have ceilings. And the exterior trim has been painted.
May 25, 2016 update: the garage “box” is framed and sheathed, and we plan to install the trusses and the roof this week, weather permitting. The front porch has been opened, with a new recycled floor. Ditto on the back porch.
May 7, 2016 update: the house is now snug tight with closed-cell spray foam insulation. We have R-28 walls with R-5 foam covering all the exterior framing to create a continuous envelope from the rim joist to the 2nd floor ceiling. Our garage pad will be poured on Monday May 9th.
May 2, 2016 update: this week we are insulating the house, plus pouring the garage pad.
April 16, 2016 update: the garage has been dismantled and deconstructed, loaded out and recycled. Grading of the backyard and preparing a pad for the new garage are on deck.
March 25, 2016 update: all mechanicals– plumbing, heating, and electrical– have been roughed-in and passed inspection. The stairway is in place, and we have a new roof. Our next step is the insulation package, along with repairing and painting the exterior trim, plus radon mitigation.
March 13, 2016 update: the floating stairway has been framed in place. The plumbers are finished, and the heating and AC is close to wrapped. Next week, the new roof will be installed, plus the electrical rough-in.
February 26, 2016 update: The demolition has wrapped up. Framing work continues as the plumbing and HVAC rough-in progresses. Our project is now Greenstar registered. Paul Schollmeier (aka The Efficiency Detective, and a GHI Greenrater) and I did our first walk-through of the house and site yesterday. Paul is a great problem solver.
January 24, 2016 update: We have finally received all clearances from the Department of Health (for lead and asbestos abatement), and the permit has been acquired. The demolition and framing has started. Mechanical rough-ins will occur in February.
The formula for a Carbon Zero house is simple: a fully-electric house powered solely by renewable energy.
While less expensive than a Net Zero home, a Carbon Zero home offers the same solution to the Climate problem.
Power can come from on-site solar, a Community Solar Garden, a wind farm, or a combination of these sources. A Carbon Zero Home can certainly also be Net-Zero. The idea is to use the most manageable economic investment to move the house from a contributor to a resolver of the problem.
Below is a generic plan for such a house.
In reducing the carbon output of a house, we treat it like a puzzle. We take it apart, then reassemble the puzzle using sustainable pieces. Uninsulated walls become well insulated and snug. A gas guzzling furnace is replaced with a high-efficiency unit. Centralized coal-fired electricity is traded for solar power installed on the roof.
Some pieces of the puzzle, like Smart Thermostats, are emerging technologies. But many of the the puzzle pieces have been around for years. Solar panels came on the market in the 70’s. Today’s panels, though, are not only higher quality, they are also significantly less expensive. Solar panels have dropped in price 80% in the past ten years. Icynene (aka spray foam insulation) puts the other options to shame, and it has also become much more reasonably priced than when it arrived on the market.
Despite these puzzle pieces existing for years, they are not getting assembled in older homes because they are regarded as “too expensive”. However, when weighed against the planet’s well-being, and the cost a destabilized climate, they become exceptionally reasonable.
R-33 walls; R-60 attic; R-26 basement. Hot roof. No slab insulation. ACPH goal = below 2.0
Triple pane casements
Heating & Cooling
Mitsubishi ASHP, with 18,000 BTU and 20.2 SEER. System would have two zones—upper floor and main floor. Supplement with 200 sq ft of in-floor electric radiant heat. Wire/install electric baseboard heat as back-up. Ceiling fans in bedrooms and main living area. Nest learning thermostat.
40 Gal. Heat Pump Water Heater, with drain waste heat recovery
Energy star appliances
No dishwasher. Induction range. Front load W/D
10.0 kW system producing a little over 1,000 kWh per month. No solar thermal
Raingarden and zoysiagrass
Details of Plan
24’x24’ house with a 20’x20’ garage, in an lower income neighborhood in Minneapolis, could be purchased for around $150,000. Expectations would be that the house is in poor condition. This should result in approx. 1,500 sq ft of conditioned space (925 of finished space on 1st and 2nd floor.
Kitchen, bathrooms, and a finished basement (preferably, the basement is unfinished) would be gutted. Hopefully, the window and door trim can be salvaged. Also, hopefully, the existing wood flooring can be sanded and sealed. Exterior is hopefully stucco, and would require minimal repair.
Roof is gable style, with a chimney in the center. 12/12 pitch. No fireplace. Not shaded by another building, plus minimal tree shade (western deciduous shade could be useful).
INSULATION AND AIR-SEALING
Remove all exterior wall plaster, plus second floor ceilings. Perform lead abatement per EPA guidelines. I have EPA certification for this.
Add 1 ½ “ offset framing to exterior walls to address thermal bridging. Add jamb extensions to windows and exterior doors. Basement walls would be framed with metal studs spaced away from block walls.
Closed-cell spray foam (icynene) insulation installed in all walls including the basement to create vapor-tight envelope, with blown cellulose added in attic area.
Wall area on main floors = 1,536 sq. ft.
Attic area = 600 sq. ft.
Basement walls = 770 sq. ft.
Total sq. footage = 2,906
Roof would receive new plywood decking (no OSB), taped at the joints, with 2” XPS and 1” Polyisocyanurate (with staggered and caulked joints). Underside of roof decking sprayed with closed cell foam; this will be a “hot roof” system. Any area where roof framing is also ceiling framing, another sheet of 1” polyiso will be added. R-33 would be goal for wall system and rim-joist area, with R-60-70 in attic area, and R-26 in basement, R-45 in sloped ceiling areas.
Whether to insulate the basement slab is an open question. A new build Net Zero house would insulate the slab and the footings. Footings cannot be insulated in an existing house, but the slab could be removed and dug down, 4” of XPS installed with 6 mil plastic, and the slab could be reinforced and poured again. This would be the most expensive aspect of the insulation process, and the cost would need to be weighed against the insulation gain.
WINDOWS AND EXTERIOR DOORS
Energy Star windows and doors installed in all locations, triple-pane if budget allows. Windows would be foamed into their framing and taped to the sheetrock. North facing windows might be reduced in size or eliminated, if that makes sense. South facing windows might be enlarged if they can improve passive solar performance of the house (a site specific decision). Casement windows would be considered due to superior air-sealing ability, despite not fitting house décor.
All penetrations would be sealed with spray foam (caulk, if necessary). The blower door test goal — post insulation and window installation–would be less than 2.0 ACPH. Lack of R-Value can hopefully be made up by exceptional air-sealing. To locate air leakage, a fog machine borrowed from a stage company can be used to track how air travels in each room. This can reduce the cost of redoing blower door tests.
South facing windows could get awnings made with solar panels attached to metal brackets. Blocking would be installed on inside of wall sheathing, for anchoring the brackets. Awnings would be positioned to produce shade in warm months but allow solar gain in winter.
Big strides have been made in smart home technology in the last two years, and the market is poised to introduce more innovation. Thermostats can now learn a household’s patterns and adjust the heating and cooling accordingly; they can also possess motion detectors to sense changes in these patterns. Smart thermostats interact with devices like cell phones to allow remote control of one’s house. Beyond the furnace, these thermostats can also turn lights on and off while homeowners are vacationing, open and close garage doors, even command a washer to refresh your clothes. Blinds can also sense sunlight and lower.
Most of these strides are related to convenience, but the potential for energy-efficiency is also intertwined. A smart thermostat can not only have a relationship with your furnace, but also your water heater, your microwave, your dishwasher, and your TV. Most well insulated water heaters only fire once a day, beyond when used. However, since it oscillates from a low temp to a high one, having it fire up right before people get up and shower makes it more efficient. Having it not fire up while people are away from the house, or on vacation, also saves energy.
Thermostats can also be connected to ghost loads, also known as standby or phantom loads. A ghost load is the energy a device consumes while turned off. According to DOE, 10% of home energy use is from ghost or phantom loads. Also according to the DOE, 75% of the power consumed by home electronics is used while the devices are shut off. In addition, even circuits for receptacles and light use some electricity while not in use. If a house were wired appropriately, a smart thermostat could shut down the ghost loads in the house. With an “away” mode and a “sleep” mode, different amounts of the house could be shut down.
The other potential for efficiency created by smart houses lies in the ability to monitor one’s energy consumption. Most people do a light monitoring of their consumption by paying their utility bills, but the perspective is framed by economics (Is the bill higher or lower than expected?). As long as energy stays cheap, this form of monitoring has little substance. A house than produces its own energy creates a very different dynamic, where monitoring is framed by the balance between production and consumption. When a smart house can email its owner bar graphs, and behavior can make the difference between Net Positive and Net Negative, the occupants might be inspired to greater efficiency.
First house could have a high efficiency furnace as its primary heat system, with ducting that has both a winter and summer mode. Winter mode would send majority of warm air to first floor, with rising heat aiding in warming of second floor. Summer mode ducting would originate majority of cool air in the ceiling of the second floor, with descending cool air dispersing through the house. Baffles in the duct system would allow manual adjustment of winter trunk and summer trunk. Furnace would heat with natural gas (bridge fuel debate set aside). Goal would be to minimize this through supplemental electrical heat.
Option #2 for heat source for initial house is Mini-split Air source heat pump (Mitsubishi MSZ/MUZ-FE18NA), with 18,00 BTU and 20.2 SEER. System would have two zones—upper floor and main floor; each zone would have two indoor units, one at each end of the house.
Mini-splits will be the primary heating, and the cooling source, in subsequent houses after the initial renovation. Balancing their abilities against the insulation quality of the house, plus the additional heat sources, plus the solar array capacity will be the big experiment of the Seed Houses. Using a LNG furnace on the initial house will allow us to work at first with a simpler equation: Elec. Heat + Cooling + Other Elec. Demands of house < or > Solar Array
In-floor radiant electrical would be installed in the kitchen area, bathrooms and entrances (possibly other areas of the house that were applicable (a site specific decision)). Baseboard heat can also be considered. Placing tile floors in areas that would gather southern winter sun would be a passive way to off-set electrical heat consumption, if site allows. Each In-floor system would have its own thermostat, whether using radiant or baseboard electrical. Thermostat for furnace would be centrally located.
In-floor electric heat system of 120 sq ft draws 1.5kWh at peak capacity. 1.5 x 6 hours a day x 120 days a year = 1,080 kWh annually
72” baseboard electric heat draws 2.5 kW = 1,800 kWh annually
The cooling system would be either an AC compressor run through the furnace, or the Minisplit system.
Install ceiling fans with adjustable speeds to supply cooling on not terribly hot days. Fans could be connected to the “Sleep” mode and “Away” modes for the house programming.
Energy Star HPWH
A Heat Pump Water Heater is more efficient than an electric water heater. Hopefully, water heater can be connected to a smart programmable thermostat, and it can have an “Away” mode and a “Sleep” mode
APWH will be supplemented by a GFX Drain Waste Heat Recovery system, which can make the water heating 53% more efficient, which would allow for a smaller WH unit. WHR would be installed on the main stack near basement floor, above all drain tie-ins. Runs from water heater to sources should be as short as possible, and insulated.
Solar thermal water heating can be explored, but it needs to be balanced against losing PV capacity on the roof. In Minnesota, solar thermal in minimally effective in the colder months.
An Energy Recovery Ventilator will be installed to improve air quality, reduce humidity, and protect against the problems inherent in super-insulated air-sealed homes.
Removing shoes (a typical Minnesota habit) is one of the best ways to improve indoor air quality. Heated tile entrances should be cleaned regularly to keep the grout from absorbing dirt.
Energy Star appliances will be used, including an induction range and electric stove, and front load W/D. Initial house can have a microwave (circuited to “sleep” and “away” modes), but no dishwasher.
UPGRADES FOR EXTENDING THE LIFE OF THE HOUSE
Remove any galvanized metal water pipes and replace with PEX. Remove any knob and tube wiring and rewire. A backflow preventer would be installed where main drain exits the house.
Wiring would be designed to allow for a set of switches near the stairway to shut down ghost loads at night and when leaving the house. TVs, computer monitors, appliances, and even receptacles use some electricity when not operating; called a ghost or phantom load. Manually shutting of these ghost loads is the simplest way to reduce their consumption, but requires the most vigilance. Another way is to connect circuits with ghost loads to a programmable thermostat, which could have a sleep mode and an away mode (away would shut down more of the house). A third and better option is extending the ability of a smart thermostat, like the NEST Learning Thermostat, that has auto-away features. These thermostats can also communicate with a smart phone or other device, for remote setting and monitoring.
After the blower door test and any subsequent sealing and testing, sheetrock will be installed on all removed walls and integrated into existing plaster walls. If possible to insulate the attic without removing the ceiling, ceiling plaster would receive 36” vinyl mesh reinforcement followed by skim coats. Sheetrock installed over basement insulation for fire proofing, along with rim joists.
Salvaged trim would be reinstalled, caulked and painted. Painting allows for patching of damaged areas, and eases blending of any trim that needed to be milled to match. Floors would be sanded and refinished.
Bathroom(s) would receive low flow faucets and dual flush toilet(s). Cabinetry would be paint grade—if new– and painted white. Counters would be laminate for affordability, but I would explore reduced cost quartz counters from Cambria (green upscale option). Tile floors and shower walls would be recycled tile if possible; exploring options with tile providers for outdated lines, etc. Fixtures might possibly receive a reduction in price by a supplier interested in promoting itself as a green vendor.
Low VOC paints used, with eggshell finish on walls and ceilings, satin in bathrooms, semi-gloss on the trim.
Average US household uses =10,847 kWh annually (903 per month)
Average MN household uses = 10,200 kWh annually (850 per month)
25 panel (5 kW) system requires approx. 425 square feet of roof space
24×24 house with a 20×20 garage = 1,240 of square feet of roof space (12/12 pitch on house and 5/12 pitch on garage)
South facing roof space = 620 sq ft
Pergola of 10×12 = 120 sq ft
Total south facing capacity = 740 sq ft
740 sq. ft. of south facing roof allows for a 43-panel system, which is an 8.6 kW system, which can produce 10,320 kWh per year (860 per month). That equals 95% of average American household use, and just over 100% of typical electrical use in a Minnesota home.
By adding solar panel awnings above the south facing windows, at a height and tilt that creates summer season shade but direct light in cold weather, plus some north facing panels to generate additional summer energy, a 50 panel system could generate 12,000 kWh per year (1,000 per month), equaling 118% of typical MN home.
Shifting the heating, water heating, plus the cooking, to electric will raise the kWh usage in the CZ Home. But a snug insulated house will reduce this consumption. Living in the house in an energy conscious way will also help reduce consumption, as will energy conserving setups in the house (Smart technology, etc.). Hopefully, a solar production that is 110%-120% beyond the average for MN will allow the house’s consumption and production to achieve balance. Since the average house in MN heats with natural gas, a home with a high efficiency furnace and a substantial solar array should not have much struggle to become Carbon Zero. However, due to concerns about methane as a byproduct of natural gas and methane’s relationship to Global Warming, a fully electric Carbon Zero house is the true goal.
Urban Wind is a Myth
Unfortunately, only a very exceptional urban site would have the capacity to use wind power to help sustain the home. Wind power requires consistent wind speeds of at least 20 mph, and preferably 25 mph. Consistent wind of this speed is typically found higher up, above the tree line, and usually starting at 80 ft off the ground, preferably 100 ft. Code and zoning restrictions would not allow for a tower of this height in a Minneapolis backyard.
Roof turbines — especially vertical axis turbines– are regarded as a myth by the established wind power community. Small wind, as it’s known in the industry, can be effective in the right setting. Wind power is more conducive to a centralized system, using large turbines mounted high off the ground in rural areas.
Low-flow toilets and faucets will be included in the upgrades to the home. Greywater recovery can be explored, but it will probably be too expensive to install in an existing older home.
The City of Minneapolis offers a rain garden design consultation for $100. I would use this program to configure the yard to conserve as much rainwater as possible. Zoysia grass is hardy and can survive long periods of little rain.
Resources for this page include: Carl Seville and SK Collaborative (www.skcollaborative.com), Powerfully Green (powerfullygreen.com), Jim Logan Architects (jlogan.com), City of Minneapolis, True Turtle (trueturtle.com), Bruce Stahlberg (www.affordableenergysolutions.com), and the US Green Building Council.