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An Affordable Zero-Energy House in Massachusetts

The shape is compact, the windows are few, and the thermal envelope is extremely tight

Posted on Oct 16 2014 by David Posluszny

Recently I designed and built my home in Shirley, Massachusetts. The design goal was to build a net-zero-energy house. However, it had to be comfortable to live in, easy to build with low-skilled labor, and very affordable.

I had to keep it simple because I had my family for laborers, and they do not have construction skills. The home also had to be comfortable to live in, with adequate daylightingUse of sunlight for daytime lighting needs. Daylighting strategies include solar orientation of windows as well as the use of skylights, clerestory windows, solar tubes, reflective surfaces, and interior glazing to allow light to move through a structure. and easy circulation. The budget demanded that the house be kept small, but several design tricks involving lines of sight were used to make the space feel much larger than it actually is.

Most of my research showed that net-zero-energy houses were too expensive. However, becoming net-zero was one of the parameters for the house that I refused to compromise on.

No combustion appliances

In January 2012 my wife and I purchased a one-acre lot in Shirley. The lot had a crumbling house and a halfway decent garage on it. The newest thing on the site was a code-approved septic system installed in 2008. The garage proved to be a good storage shed during construction and is still serving that purpose today.

Over the past few years I had been developing a plan for the eventual home. The method of construction that made the most sense to me for net-zero was a simple wood-framed home with high levels of insulation. I did several heat-loss calculations and compared different heating systems to the cost of installing them, the cost of maintaining them, and the fuel cost.

In the end I decided that the least expensive way to go was to not purchase a fuel-burning heating system at all. I saved tens of thousands of dollars by making this choice. I do not have a chimney, boiler, air handler, carbon monoxide detectors, gas line, gas meter, fire proofing around a boiler, combustion appliance zone venting and testing, distribution systems such as hydronic baseboards or circulators, a gas permit, or the associated labor to install all these systems.

Saving this money allowed me to afford the extra insulation and solar panels.

Reusing the existing crawl space foundation

Early in the design we were confronted with the town’s bylaws about road frontage and constraints on the house. In the end we decided to build on top of the existing foundation. This made the project a renovation and not new construction.

With the help of friends and family, we tore down the existing house which had two bedrooms, an oil boiler, and a propane range. The bulkhead lead to a 5-foot tall basement area just large enough to house the oil boiler. Then it stepped up to a crawl space with dirt floors and no clearance to the wood joists. The foundation itself only went 8 inches above grade, and was falling apart.

We kept the existing block foundation by repointing the mortar. The bulkhead was demo'd and filled with compacted soil excavated from inside the foundation. Because the crawl space was going to be heavily insulated and air sealed inside the building envelopeExterior components of a house that provide protection from colder (and warmer) outdoor temperatures and precipitation; includes the house foundation, framed exterior walls, roof or ceiling, and insulation, and air sealing materials., I paid particular attention to preventing water intrusion. We installed a perimeter drain to daylight with careful use of gravel and filter fabric.

The old foundation wasn't level or square

As with any project there are unexpected issues that arise. One of these situations was the water main from the street. During the home inspection, we saw that the main was plastic and believed it had been replaced and we would not have to put money into it. However, after demolishing the house we found that the soil was wet around the pipe. It turns out that the plastic was tied to a cast-iron pipe just below the surface, and the cast-iron was rusted through.

I dug out the old pipe and installed a 2-inch sleeve underground, to just beyond the foundation, and buried it with a marker. That way I could proceed with the house and install a water line later.

The foundation is only 20 feet by 36 feet. However, its diagonals were off by 3 inches, and it was out of level by 9 inches. I decided to level the foundation and square the framing. This worked out well. Groton Engineering out of Groton, Massachusetts, did a foundation inspection and explained how to proceed. I built a water level and checked each block individually. As the existing foundation sloped I would cut a block and mortar it in place. By doing this procedure I created a level foundation. Then I added two courses of block on top of that.

The final course was a U-shaped block to allow for a horizontal piece of rebar. This is known as a “bond beam.” I placed a vertical piece of rebar in every other core and wire-tied it to the horizontal length. All rebar was #4. Then I made jigs to hold the 12-inch anchor bolts in place. I placed the anchor bolts before the pour so that I could wire-tie them to the horizontal piece. This also eliminated the air pocket that normally forms by inserting the bolts second. I also poured reinforced footers for posts down the middle of the house.

When I ordered the concrete I bought one truckload. This was enough to fill the entire block wall, and pour a 3-inch non-structural slab. Although the slab was not necessary, it cost the same to buy one truckload of concrete it did to buy only half, so the slab was logical. It also provides some protection from burrowing rodents that might try to find their way in.

Making sure that the air barrier is continuous

Most projects I’ve been a part of think about the air sealing separately from the build. This approach is a mistake, since it doesn't lead to the best air-sealing details. With my home I integrated the air-sealing details into the building process. Inside the crawl space I installed a 16-mil reinforced vapor barrier with double-taped seams. The vapor barrier is mechanically fastened to the top edge of the block wall with plastic clips that are tapped into holes in the concrete.

Then I took a roll of Grace Ice & Water Shield (a brand of rubberized asphalt peel-and-stick membrane), ripped it lengthwise, and capped the foundation. This created my capillaryForces that lift water or pull it through porous materials, such as concrete. The tendency of a material to wick water due to the surface tension of the water molecules. break at the sill and gave me 3 inches of membrane on both sides of the wall which I used to attach my air barrier to. This layer of Ice & Water Shield capped over the vapor barrier on the interior of the crawl space wall, covering the plastic clips (see Image #2, below).

The sill plate was pressure-treated per code; however with the Ice & Water Shield I don’t think this was necessary. Then I added a second kiln-dried plate.

The sill plates on three sides of the house were 2x8s, and on one side was a 2x12. (This is because I had to create a short overhang to create a square house.) If you look down the wall, the sill plate is square, but the foundation is wavy. I verified that everything was square with strings and batter-boards at first, and then double-checked by simply pulling diagonals. The simple rectangular footprint makes squaring easy.

Avoiding thermal bridges

I built a central girder to support the floor joists at mid-span. This is common on most homes. However, I did make a change to help with the insulation. Instead of setting the ends of the girder into beam pockets in the foundation, I cut the beam back by 1 foot to stop that thermal bridge. In order to resist lateral forces on the girder I also turned my last joist into perpendicular joist blocks set into joist hangers. This also provided easy access to the full rim joist for insulating later. The joist hangers were some additional cost, but I saved on the labor of creating beam pockets and shimming the girder.

The joists were 2x10s set 16 inches on center. They only have a 9 foot clear span when all was said and done, but I purchased 20 footers so it spanned continuously from one side of the house to the other. Obviously the joists are larger than needed per code. However, this detail creates a much stiffer floor that I know will never cause an issue with flooring later on, even if I install tile. To me, building the best floor for an additional $250 in material cost, and no additional labor, was an easy choice to make. The platform came out perfectly level and solid.

Double stud walls

Building the walls was relatively easy. I built double stud walls, with the interior and exterior studs offset from one another. The rough cavity is 11.25 inches deep. This was done because I needed a 2x12 in the great room.

A double stud wall is built to the inside, so it eats floor square footage. In my case I could not enlarge the foundation, so I was limited to how deep I could make the walls before the rooms became too small. After working through dozens of floor plans, the 11.25 inch thickness was all I could achieve. However, if I could have enlarged the foundation I would have preferred 18-inch-thick walls.

Sudbury Lumber did a takeoff from my floor plan and sent me all the lumber for the house on one truck. The two long exterior walls are framed with 2x6s, 16 inch o.c., and are 10 feet tall. The gable exterior walls are framed with 2x4s, and all interior walls are 2x4. The exterior wall is structural and picks up the roof trusses. Each stud lines up with the joist and roof truss.

There are two lofts inside the house. The loft floors are framed with 2x10s resting on the interior 8-foot walls, but they also grab the exterior studs to resist outward deflection of the roof (see Image #3, below).

The roof trusses are scissor trusses built and delivered by Quick Build Truss Company. The scissor trusses allowed a very deep cavity for insulation. The average depth of insulation is 25 inches, but tapers from bottom to top. The outside pitch is 12:12 and the inside is 11:12. (See Image #4, below.)

The steep angle allowed a lot of room in the lofts. The trusses were fastened to the top plates with Simpson ties that resist lateral forces better than a twist strap. Each truss lines up with a stud, 16 inches o.c.

The exterior sheathing is covered with peel-and-stick

Exterior sheathing is ½-inch plywood. Instead of using a common water-resistive barrierSometimes also called the weather-resistive barrier, this layer of any wall assembly is the material interior to the wall cladding that forms a secondary drainage plane for liquid water that makes it past the cladding. This layer can be building paper, housewrap, or even a fluid-applied material. (WRB) like asphalt felt or Tyvek, I used Grace Ice & Water Shield (see Image #5, below). This product sticks very well to plywood. In doing so, it air seals every seam and every puncture from nails and screws. I wrapped it around the house starting at the bottom and working my way up the walls and over the roof.

Directly above each window and door I left some paper backing on the back side of the peel-and-stick membrane so that I could lap window flashing up under the higher course. The bottom edge of the Ice & Water Shield was attached to the membrane that was on top of the foundation. This meant that the air barrier was unbroken from inside the crawl space to outside the house and up over the roof.

A particularly nice aspect of installing the Ice & Water Shield on the outside is the ability to easily inspect the air barrier. All I have to do as project manager is walk once around the house. So long as I don’t see any plywood, I know my air barrier is complete.

An exterior vapor barrier

Ice & Water Shield is a vapor barrier, so you should be careful about attaching it to the outside of the home in the same manner as I did because there is a potential for condensation inside the building. Several parts of the system make me confident this will work. First, in every situation I’ve read about or seen of a structural failure due to moisture, the failure was associated with reverse flashing or air leakage. I don’t have either of these.

Also, during the winter I can control the relative humidity (RH) inside the home with my ventilation system (an HRV(HRV). Balanced ventilation system in which most of the heat from outgoing exhaust air is transferred to incoming fresh air via an air-to-air heat exchanger; a similar device, an energy-recovery ventilator, also transfers water vapor. HRVs recover 50% to 80% of the heat in exhausted air. In hot climates, the function is reversed so that the cooler inside air reduces the temperature of the incoming hot air. ). I kept my living environment at 40% RH, which is much higher than most homes in the winter but low enough not to have moisture issues.

I also chose the best insulation for this system, which is dense-packed cellulose. Cellulose manages the moisture in a wall cavity and did not allow any moisture to reach the exterior sheathing all winter.

We tested the assembly this winter with the help of Bill Hulstrunk, National Fiber’s technical manager. Together we bored test holes in my drywall and probed the walls for moisture using a Delmhorst moisture meter with extended probes. The conclusion was that the framing was dry and the plywood was dry. The assembly works for the long term.

Double-pane Andersen windows

When I installed the windows and doors I used a polyurethane caulk on the nailing flanges and then Grace Vycor flashing tape on the sides and top. Then I removed the paper backing from the Ice & Water Shield that I had applied as my WRB and lapped it over the top of the Vycor so that 100% of the house is shingle-lapped without exception. Windows are nailed into the wood frame the same as they would be at any home, meaning that no special details were required. This is one of the reasons I’m a fan of the double stud system.

The windows are wood-framed 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).-clad Andersens. The two south-facing windows are fixed, the four north windows are casements, and the two gable windows are awning. I decided not to install sliders or double-hungs because of the air leakage associated with them.

The windows have a U-factorMeasure of the heat conducted through a given product or material—the number of British thermal units (Btus) of heat that move through a square foot of the material in one hour for every 1 degree Fahrenheit difference in temperature across the material (Btu/ft2°F hr). U-factor is the inverse of R-value. of 0.29. I would have preferred windows with a lower U-factor, but I bought the windows inexpensively as odd-lots. Prior to purchasing them I ran some heat load calculations. My home is heated with electricity produced by a solar array. I had to purchase all the solar panels to make the electricity for the heat. After my heat-loss calculations, I found that the extra solar panels were less expensive than windows with lower U-factors.

I applied this thinking to all my decisions, and found that the least expensive way to be net-zero is not always the most energy-efficient way.

Roof ventilation channels above the Ice & Water Shield

I believe in long-term durability of a structure instead of only building for the initial sale. Because of this I chose a system for the roof that allows re-roofing in the future without damaging the WRB (meaning the Ice & Water Shield).

The way I did this was by purchasing 16-foot 2x4s. I laid the 2x4s on the flat, on top of the Ice & Water Shield, directly over the roof trusses. I screwed the 2x4s in place at the top and bottom with GRK structural screws, and nailed it along the field. This created a 1.5-inch-deep air space. The soffit and ridge vents are connected to this air space, providing ventilation for the underside of the roof deck (see Image #6, below).

I then nailed down 5/8-inch plywood over the 2x4s, and roofed the house with architectural asphalt shingles. When the time for re-roofing comes, nails can be pulled without leaving holes in the air barrier.

A rainscreen gap behind the siding

I created a rainscreen system for the walls by screwing 1x3 furring strips over the studs. Then I trimmed the windows and corners with Kleer brand PVC trim. I made the window and door trim frames on the ground with pocket hole screws. Then I installed the trim frame over the furring strips using a screw-and-plug system made by FastenMaster. This method held all my trim in place while hiding the screw heads beautifully.

Along the bottom of the walls I stapled on CobraVent, which is a plastic sponge-like material, between the furring strips. This will keep the bugs out of the hollow space. I installed James Hardie fiber-cement siding with galvanized 6d ring shanks. It went on easily.

The top of the rainscreen vents into the soffit space. The framing of the soffit is built out on top of the WRB so that there are no penetrations by rafter tails. The soffit consists of a manufactured PVC material with grooves cut into it. I liked it, but thought that the grooves looked a little large for an insect, so I stapled mosquito netting on the back side prior to installing it.

All of this exterior work was accomplished while working off of pipe staging that I rented locally. This meant that nowhere on the house did I leave a hole due to staging systems or ladders that rely on the house for support. Normally, sealing these holes would have been difficult if I were also trying to maintain the lapping of the WRB.

Keeping penetrations to a minimum

Because the air barrier is entirely outside, I was able to schedule plumbing and electrical work independent of my exterior work schedule.

There were a total of ten penetrations through the WRB: a hose bib, the plumbing vent stack, two outside lights, two outside outlets, one data cable, one electrical main, and two HRV vents. This is a far smaller number of penetrations than I would have had if I had attempted the Airtight Drywall Approach, with hundreds of outlets, switches, and pipes.

The plumber (from Spears Plumbing) took advantage of the crawl space by running all of the PEXCross-linked polyethylene. Specialized type of polyethylene plastic that is strengthened by chemical bonds formed in addition to the usual bonds in the polymerization process. PEX is used primarily as tubing for hot- and cold-water distribution and radiant-floor heating. hung from the joists. No holes were needed in the joists. The crawl space can never be finished anyway, so this approach worked out. (The distance from the top of the 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 the crawl space floor to the bottom of the floor joists is 30 inches.)

The electrician worked inside without worrying about air leakage. All interior work used standard outlet boxes. No time or money was spent air sealing the inside. The electrician mounted the panel upstairs and ran most of the wires upstairs.

Electric space heating

The heating system I installed for the first winter was a standard electric-resistance baseboard unit — a single 6-foot 240-volt heater mounted inside the crawl space. It only cost $80 (including the thermostat); it was my whole heating system. I set it to keep the crawl space about 75 degrees, and that warms the floor and keeps the upstairs at 68 degrees. This worked well all winter.

Later, I installed a ductless minisplit heat pumpHeating and cooling system in which specialized refrigerant fluid in a sealed system is alternately evaporated and condensed, changing its state from liquid to vapor by altering its pressure; this phase change allows heat to be transferred into or out of the house. See air-source heat pump and ground-source heat pump. that uses less electricity to do the same job.

Eight tons of cellulose insulation

Except for some polyisocyanurate which I installed in the crawl space, all insulation is dense-packed cellulose. I wanted National Fiber’s brand cellulose because of its all-borateBoron-containing chemical that provides fire resistance to materials such as cellulose insulation and provides decay and termite resistance to wood products. Borate is derived from the mineral borax and is benign, compared with most other wood treatments. treatment, fiberization, and tight quality control. I called the manufacturer to track down a preferred installer for my area and ended up hiring Dolphin Insulation out of Littleton, Massachusetts. Chris, the owner, was easy to work with and excited about the project. In fact, his whole crew was happy to be on site working on such an efficient home.

They stretched Insul-Web material across the face of all the studs and trusses. This is a light netting material that keeps the insulation in place during the installation process (see Image #7, below).

After Chris made a call we ended up having several representatives from National Fiber coming out to the house, excited to see such a deep installation of dense-packed cellulose. The wall thickness was not that uncommon, but the roof installation (at over 2 feet of depth) was. There is just over 16,000 pounds of cellulose in the house (see Image #8, below).

Inside the crawl space I laid out a double layer of polyiso rigid board insulation on the floor and a single layer of polyiso on the walls. Then I built a non-structural 2x4 stud wall to the inside. This was also bibbed by Dolphin Insulation so that the whole cavity of the wall and up into the rim joist was dense-packed. This procedure eliminated any cold corners.

After the cellulose installation was complete, and bag count confirmed, crews rolled the walls flat to the stud face in preparation for wallboard. I strapped the ceiling at 16 inches o.c.; it was a little challenging to push the strapping in place against the packed cellulose. I should have performed the strapping before the dense-pack but after the Insul-web. However, it all worked out in the end.

High-gloss paint reflects light

Wallboard and plaster were installed. I chose plaster because I wanted a smooth ceiling surface.

Then I had high-gloss paint installed on the ceilings. I was cautioned against a high-gloss because the paint can show imperfections in the plaster. In order to make the surface as perfect as possible, my painter applied five coats and sanded between each coat. This came out great (see Image #9, below).

The reason I did this was because I have a low ratio of glass area to floor square footage. I was concerned about daylighting in the home. The high-gloss of the ceiling bounces the light dramatically.

The strategy worked; there are no dark areas in the home. It cost me an extra $500 for the paint and labor to accomplish this. However, I saved money by purchasing fewer windows.

A heat-recovery ventilator provides fresh air

I knew that this house would be airtight, so in order to ensure enough fresh air I installed an HRV made by Venmar. The unit has 4-inch metal ports on the sides. I attached rubber couplings and ran 4-inch PVC as my ductwork. PVC makes a perfect airtight seal at joints, because the couplings and pipe are glued together.

There are two short runs that lead outside, a single supply duct to the bedroom, and single exhaust duct from the bathroom. There is a button on the bathroom wall that steps up the fan speed to exhaust moisture after a shower. This system creates nice cross-flow in the house, and I’m pleased.

A solar electric system makes the house net-zero

I had a 4.8-kw 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. (PV) array with micro-inverters installed on the south-facing roof of the house. The PV array connects to the electric meter on the outside of the house. This prevented more penetrations for wires.

It's very, very tight

I conducted several blower-door tests; the final one was scheduled for after the drywall. A regular blower door could not be used on my house because it does not read below 100 cfm. Instead I built a plywood panel to hold a Duct BlasterCalibrated air-flow measurement system developed to test the airtightness of forced-air duct systems. All outlets for the duct system, except for the one attached to the duct blaster, are sealed off and the system is either pressurized or depressurized; the work needed by the fan to maintain a given pressure difference provides a measure of duct leakage. fan in a window and taped the edges. I used a manometer in the normal manner for checking the whole house. With Ring 3 on the Duct Blaster I could pull an accurate number for the house. It was 22 [email protected] Pa. This translates into 0.09 ach50.

While I conducted this test, the crawl space trap door was open and the outside HRV vents were open. I did not tape them off because the HRV has internal gaskets that close when off. To put this in some perspective, the 2009 IECC International Energy Conservation Code. requires no more than 7 ach50. The new 2012 standard is less than or equal to 3 ach50. The PassivhausA residential building construction standard requiring very low levels of air leakage, very high levels of insulation, and windows with a very low U-factor. Developed in the early 1990s by Bo Adamson and Wolfgang Feist, the standard is now promoted by the Passivhaus Institut in Darmstadt, Germany. To meet the standard, a home must have an infiltration rate no greater than 0.60 AC/H @ 50 pascals, a maximum annual heating energy use of 15 kWh per square meter (4,755 Btu per square foot), a maximum annual cooling energy use of 15 kWh per square meter (1.39 kWh per square foot), and maximum source energy use for all purposes of 120 kWh per square meter (11.1 kWh per square foot). The standard recommends, but does not require, a maximum design heating load of 10 W per square meter and windows with a maximum U-factor of 0.14. The Passivhaus standard was developed for buildings in central and northern Europe; efforts are underway to clarify the best techniques to achieve the standard for buildings in hot climates. standard, which is the most stringent in the world, is 0.6 ach50.

The bottom line: comfort

The end product is a bright and comfortable home. The spaces work well with one another. There is a mudroom when you first walk in with a bench to take your shoes off. The kitchen has plenty of countertop space. The main room has high ceilings, providing a sense that the house has more space then there actually is. There are two lofts which we have not used for anything but storage so far.

During the first winter, I purchased my electricity because my solar panels were not yet installed. There is no fireplace or wood stove, and I was just using the one electric baseboard unit for heat. My stove, oven, and water heater are all electric. There is no propane, oil, wood, or wood pellets on site. Electricity is the only energy source entering the house besides the direct passive gain.

My PV panels have recently been brought online. I’m monitoring the usage and am on schedule to be net-zero in a year. Now I have no heating or energy bills.

[Editor's note: Readers who want to emulate David Posluszny's efficiency achievements should be cautious about imitating his decision to install a vapor barrier on the exterior side of his walls and roof. This approach violates the recommendations of most building scientists. For more information on this issue, see Dense-Packed Cellulose and a Wrong-Side Vapor Barrier.]

David Posluszny is an energy specialist at Dolphin Insulation in Littleton, Massachusetts.

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Image Credits:

  1. All photos: David Posluszny

Oct 16, 2014 6:06 AM ET

Edited Oct 16, 2014 6:12 AM ET.

This is the simplest R-43 airtight wall I have seen
by Kevin Dickson, MSME

It's ironic that this home was posted on GBA the day after BSC published the latest about their "perfect wall".

Compared to the BSC wall and roof design, this "Shirley Wall" is significantly simpler, and should be at least 30% cheaper to build for equivalent performance. Without any petroleum products (that often continue shrinking after installation).

"in every situation I’ve read about or seen of a structural failure due to moisture, the failure was associated with reverse flashing or air leakage." I agree. When condensation has occurred on the inside surface of sheathing, the source of the water vapor has never been proven to be diffusion alone. It has always been because the vapor is being transported by exfiltrating air.

"This is a far smaller number of penetrations than I would have had if I had attempted the Airtight Drywall Approach (ADA), with hundreds of outlets, switches, and pipes." ADA is how Robert Riversong air seals his 12" cellulose insulated Larsen Truss homes. I never liked that approach because of all the damage the occupants will inevitably do to the air barrier without realizing it, and the high number of penetrations.

The air sealing and weather barrier functions are performed by one exterior layer. Again, simpler, cheaper, faster, and easier to inspect. Window installation is conventional (simpler, cheaper, etc.).

The "perfect wall" is very robust and will function properly in nearly all climate zones. The Shirley Wall seems to be equivalent. It apparently remains dry inside the wall cavity even in the worst case when the exterior air barrier is vapor impermeable.


1. The Shirley wall could be risky if the wall has significant air leakage. Therefore, we might want to establish a maximum permissible air leakage rate.

2. I haven't been able to figure out if the Shirley wall is allowed by the IECC 2013 codes. In Colorado, it appears that it will be allowed under the performance path if the HERS rater signs off.

The other heavyweight in wall design comes from Sweden, the USA New Wall:
Again, too complicated. I believe the Swedes evolved to this wall design because they like to prefabricate their walls and ship them complete. The Shirley wall does not lend itself to shipping.

Oct 16, 2014 6:21 AM ET

Water Vapor
by John Brooks

You recognize that an exterior vapor barrier can be risky.
As you may know ... water vapor is not-so-dense ... and water vapor is buoyed UP by the surrounding air.....much like an air bubble is buoyed UP in a container that is partially filled with water.
When I think of water vapor mind jumps to the TOP of the container.
You mentioned that you monitored the RH during the winter and that you probed the WALLS for moisture.
I'm very curious about exactly WHERE you measured the RH and exactly WHERE you "probed".
When I say "where" I am thinking about the altitude.
Did you measure the RH (and temperature) at the peak of the Ceiling?
Did you "probe" the wall near the top of the wall?
How about the Vaulted Ceiling? did you "probe" AT the Ridge?


Oct 16, 2014 6:38 AM ET

Edited Oct 17, 2014 10:20 AM ET.

Wrong-side vapor barrier
by Martin Holladay

I predict that this guest blog by David Posluszny will garner quite a few comments -- especially considering the fact that his cold-climate walls have a wrong-side vapor barrier.

I have decided not to comment on this issue for 24 hours. Tomorrow I will publish a blog on the topic, including a report on Bill Hulstrunk's presentation at the Passive House conference in Portland, Maine. Hulstrunk discussed David Posluszny's house at that presentation.

Oct 16, 2014 10:52 AM ET

by Nate Thames

What's the cost breakdown? Seems like he might have gotten under $100k given the labor he put in, less the solar cost.

I really like that truss setup for the roof. Are there other examples of the dense pack inside a scissor truss out there?

Oct 16, 2014 11:04 AM ET

Response to Nate Thames
by Martin Holladay

David Posluszny has been interviewed several times by reporters, and has written a story on his house for Home Power magazine. He stated that his out-of-pocket costs for the house amounted to $85,000, including the PV array. Elsewhere he said that the house cost about $100 a square foot.

Oct 16, 2014 11:04 AM ET

Reply to John Brooks
by Kevin Dickson, MSME


If you look closely at your photo, it perfectly supports the point I am trying to make above.

Oct 16, 2014 11:35 AM ET

by Malcolm Taylor

Where are the windows? This house sits on what looks to be a beautiful rural lot and has no relationship with its surroundings at all. If you showed it to anyone unfamiliar with energy efficient construction they would notice its failure to achieve any balance between efficiency and other architectural concerns. But for some reason it doesn't occasion any comment here.

This is fast becoming the defining characteristic for similarly built houses. Blog after blog features houses that subordinate everything else to the demands of the building envelope. I'm sorry for ranting, but this one-sided thinking denies a whole range of what it means to be human. Is the solution to our currently inefficient housing to lock ourselves in hermetically sealed containers with no access to our surroundings?

Oct 16, 2014 11:40 AM ET

utility bills
by Jeff Stern

I often hear the statement about no utility bills in a net zero grid tied home. I have a grid tied PV system, and my utility still charges me $10.89 /mo when I'm producing excess electricity. Is my utility somehow unusual? I suspect not but I'm curious to hear from others.

This is an interesting project in terms of it's extremely simple approach and low cost, but from the limited photos the result appears pretty bleak (IMHO).

Oct 16, 2014 11:46 AM ET

Response to Jeff Stern
by Martin Holladay

Net-metering agreements are all over the map. A few lucky homeowners are actually paid a premium for their excess PV production -- if they live in one of the regions of the country that (briefly) offered feed-in tariffs.

Others get to zero-out their bills, but can never receive a check.

And still others (like you) have to pay a monthly service charge, even if they don't need to purchase any electricity.

Oct 16, 2014 11:54 AM ET

Reply to Nate Thames
by Kevin Dickson, MSME


David Posluszny's cost of construction is completely moot.

The cost that matters is how much YOU can build it for.

Oct 16, 2014 1:48 PM ET

Edited Oct 16, 2014 1:52 PM ET.

Respose to Malcom Taylor
by Peter L

I agree with your comments. The home, while efficient, is completely lacking any architectural appeal. It looks like a shed I built a few years ago. I would not want to live in it no matter how efficient it is. As human beings we are not all about function and no aesthetic appeal. Let me ask the guys on the board: Did you marry your wives simply because she was functional or because she was functional and aesthetically pleasing? I would be safe to state that 100% of the men will state the latter.

To remove the aesthetic nature from green home building is to remove the human element. Any architect would cringe at these types of home designs. People need to be connected to the outdoor environment, not locked away in what looks like a barn or some militia compound. If making a rectangle and poking three holes in it for 3 tiny windows is where this is headed, count me out.

Oct 16, 2014 2:21 PM ET

Edited Oct 16, 2014 2:22 PM ET.

Kudos, but...
by Chris Brown

Low material costs, even lower labor costs, low to zero operating costs and unfortunately absolutely zero architectural attention or appeal. I must admit that prior to reading this blog or any of the comments, my initial reaction was: "You couldn't pay me to live in that". As others have already alluded to, is this where we are really headed? Might as well build ourselves teepees, as they are essentially net zero energy abodes. Somewhere along the line some of us have lost sight of the concept of "LIVING". I don't know about the rest of the readers, but actually living and interacting with my surroundings is significant to my well being. It was when I lived on a farm and still is now that I live in suburbia. I can't help but think about some people who answer "I stay over on 4th street" when asked where they live. As for me, I don't want to "stay" anywhere, I want to LIVE somewhere!

Oct 16, 2014 3:01 PM ET

What Would WUFI Say?
by Kevin Dickson, MSME

I will seriously pay $50 each for the first four WUFI simulations of this wall. Post them here, but send me the invoice at kevdickson at Gmail. Com

Oct 16, 2014 3:17 PM ET

Aesthetic appeal
by Todd Stanley

I agree with the comments above regarding aesthetic appeal; the buildings we have treasured most as a society are those that are beautiful. A beautiful building is an object of desire and therefor more likely to be well cared for and preserved throughout it's life. A future owner may not have knowledge of this buildings' status in the world of efficiency and tear it down solely based upon it's appearance; kind of defeats the purpose doesn't it?

Of course beauty is subjective, but in general I think most of us recognize an attractive building just as we do any other object. One doesn't have to be a trained, professional designer to merely draw from our surroundings and generally mimic the attractive characteristics of those buildings, or, heaven forbid, hire a designer just for that purpose alone!

Oct 16, 2014 3:31 PM ET

Missed the Point?
by rjp :

It seems some may of missed the point. Here is a net zero house in Mass. for $85k plus labor. Even down here in Texas, a "tiny house" could end up costing that much. Granted it is small with a 20 x 36 footprint (720 sq ft plus lofts) but it could be progressively enhanced and probably does not have a 30 year mortgage. Add a deep wrap around porch and enjoy the northeast climate.

Oct 16, 2014 3:36 PM ET

Well put, rjp
by Dan Kolbert

What a bunch of whiny pukes. We're sharing our experiences, and attempting to learn from each other. Don't like it? Who cares. Have something to say about the construction details, pro or con or questions? Good.

Oct 16, 2014 3:43 PM ET

Edited Oct 16, 2014 3:46 PM ET.

I'm with RJP
by Martin Holladay

Chris Brown,
David Posluszny built exactly the house he wanted. He paid for it himself and did much of the own work, and he's living in it -- without any energy bills. Millions of families around the world would think that they had won the lottery if they could own such a house.

Can you design a different house? Of course. Do you imagine one with more windows and a nice deck, or perhaps cedar shingle siding? Well, designing a different house isn't that difficult. So build it, and send GBA a guest blog about it.

Oct 16, 2014 3:47 PM ET

It's very, very tight
by w d

Reading David's blog and the comments is just plain fun.

I know a proud papa when I see one. David has done a beautiful job of describing his design and his attention to detail. The enthusiasm beams. I admire the work.

I can't say the photos are my "dream home", but everyone has their own aesthetics. I don't think it's supposed to be a dream house; more of a demonstration design for tight shell techniques.

Meanwhile, I'm wondering: a) Is there just the one door and just the one way in and out? b) Does the heat pump do any cooling in summer? Overhangs seem minimal. c) If we can achieve an ever lower ach50, do we have to worry about an outage with our ventilator? d) Is there a clothes line not pictured? e) Is a screened porch a possibility? f) Imagine an avenue with say 20 or so of the very, very tight design in a row.

Oct 16, 2014 4:00 PM ET

David's design approach
by Martin Holladay

No one has yet commented on David's strategy for making decisions on energy features. He wrote: "My home is heated with electricity produced by a solar array. I had to purchase all the solar panels to make the electricity for the heat. After my heat-loss calculations, I found that the extra solar panels were less expensive than windows with lower U-factors. I applied this thinking to all my decisions, and found that the least expensive way to be net-zero is not always the most energy-efficient way."

Isn't it refreshing to see such a clear, logical analysis? Others may choose to spend more on windows, and that may make sense, but most designers don't even do the analysis.

Oct 16, 2014 4:33 PM ET

Must have different codes up there... eh?
by Armando Cobo

Am I to assume the two lofts are bedrooms? If so, should the windows and stairs or ladders need to meet egress? Any fire scape risk assessment? I would not mind seen finished interior pictures.

Oct 16, 2014 4:34 PM ET

MArtin :
by Jin Kazama

Would you even consider someone to be a "designer" if he forgets to do the calculations ???

Is David's strategy refreshing because it goes on par with your line ?? :p
There is more to it than economics, and we all know that.

David: interesting entry and congrats on achieving your goals on that project!!
Although i see this house more as a "tiny house-like " design, with very minimal architectural thoughts, you seem to have designed using logical steps for achieving your goal and succeeded!!

May i ask a few questions ...

1- What attracted you to aim for NZ house ?

2- What was the total price ( installed ) of the cellulose insulation ?

thanks for sharing your project in such details with us!! :)

Oct 16, 2014 5:04 PM ET

Response to Jin Kazama
by Martin Holladay

Q. "Would you even consider someone to be a 'designer' if he forgets to do the calculations?"

A. Yes. Most designers don't.

Oct 16, 2014 5:18 PM ET

Edited Oct 16, 2014 5:19 PM ET.

by Jin Kazama

What do you consider to be the designer's tasks then ?

Don't you find it alarming that most do not even go through basic calcs?

Oct 16, 2014 7:22 PM ET

by Keith Gustafson

People live in ugly damn houses that are energy pigs all the damn time, and someone got paid to design them.
IIRC moisture damage to sheathing is caused primarily by moisture carried by the airflow caused by shoddy construction, I think he is going to be ok, given his house is tighter than the proverbial mouses arse!

Man. you guys can be rough sometimes

Yes, I would have chosen higher performing glass in somewhat larger amounts, but that would be my choice. I think changing out the door to one of highly insulated glass would be a good idea, and reasonable to do yourself. Not being able to see who is at the door is annoying, but you know what, it is his house and he will get to live there[cheaply] for a long time to ponder it

Oct 16, 2014 7:31 PM ET

Minor comment: you don't need
by Jason D

Minor comment: you don't need gloss finish to achieve good reflection. A bright white paint with a flat finish will just have diffuse instead of specular reflection, but total reflection will be the same or very close. I seem to remember Martin had a blog about white ceilings and/or walls a while back.

Overall a very interesting read. I'm curious how the minimal overhangs are working out.

Oct 16, 2014 11:42 PM ET

Edited Oct 17, 2014 12:08 AM ET.

Reply to Dan Kolbert
by Malcolm Taylor

Dan, I'm sorry if the comments come across as whiny but I do think you are missing the point. We don't come here to share any old experiences. We come to share our experiences of designing and building better houses. Any strategy that only works by leaving out things that people consider essential to a good house can't be considered a successful approach, no matter how efficient.

Let me suggest an analogous situation: Suppose rather than green building we were all here to discuss heathy food. What if the recipies that seemed to predominate suggested we should eat nothing but smoothies made with ingredients chosen to optimize nutrition - even though they looked unappealing and tasted awful. What would be the point of that?

I do want to apologize to Mr. Poslusnzy. Unfortunately we discuss these projects with a critical eye in order to find the right way forward both as individuals and as a larger community. Dissecting people's house in this way, whatever the intent, is a bit rude. I'm sorry, I don't know a way round that unfortunate aspect of the discussion.

Oct 17, 2014 12:16 AM ET

Malcolm :
by Jin Kazama

We are all part of what makes this website interesting.
There is no way to learn without questions ,opinions etc..

Everyone has their ideas and goals, else if we would be all aiming for the same spot
it would be settled very quickly and be boring as hell!! :p

That said, not because fruit/veggie smoothies are superbly nutritious means you gotta eat only that stuff. It's all about balance and compromises, and same it true with everything else.

I would be very surprised if mr Poslusnzy felt insulted in any way from comments here.

His project is very interesting for all of us.

The minimalist design makes it feel as if this was a "test box " or a small cabbin,
that is my opinion. This is something you would expect to see in Alaska or Yukon .

Still does not remove any analytical info we can learn through his shared experience.

Oct 17, 2014 4:23 AM ET

Egress windows, entry doors, and porches
by David Posluszny

Thank you everyone for taking the time to read the article. There have been some excellent comments.

1. There is a back door, plus all the windows in the bedroom are egress.

2. The front door was given to me by a friend, which is why I used it to get closed in. Two months ago I swapped it out for one with a window in it, so now I have a total of ten windows.

3. I can't wait to have a porch. It is on my short list of things to build.

Please understand that I saved my money to buy the land. I saved my money to buy building materials. And in a couple years I will have saved enough to build the porch. (I do have a small loan that will be paid off in two more years.) I'm also saving up to refurbish the garage. It would be great to have those things now, but I would rather not have a 30-year mortgage. So, without energy bills, all I have to worry about paying are my taxes, and water.

Thanks again for reading the story, and hopefully the construction details help a couple of you.

Oct 17, 2014 7:28 AM ET

Edited Oct 17, 2014 9:28 AM ET.

Response to Jin Kazama (Comment #23)
by Martin Holladay

Q. "What do you consider to be the designer's tasks then? Don't you find it alarming that most do not even go through basic calcs?"

A. David Posluszny did not perform a "basic calculation." What he did was to determine the annual kWh savings attributable to upgrading his mediocre windows to windows with a lower U-factor. He then calculated the incremental cost of the window upgrade, and noted the annual kWh production of additional PV modules that cost the same amount as the incremental cost for the window upgrade. Then he compared the kWh savings of the window upgrade to the kWh savings from the extra PV modules.

That's not rocket science, but it is admirable. And if you think that more than 1% of new home designers in North America routinely perform this calculation, you are dreaming.

Oct 17, 2014 9:15 AM ET

What people want
by Dan Kolbert

Malcolm writes "Any strategy that only works by leaving out things that people consider essential to a good house can't be considered a successful approach, no matter how efficient."

Apparently David did not add any more windows than he considered essential. As far as I can tell, we're going through a period of rather dramatic transformation in home design. What people consider essential is not immutable, beyond decent air quality (and even that definition is a moving target).

There are plenty of ugly houses being built out there, efficient or otherwise. I'm all for critiquing them on all fronts. But I'm more interested in the lived experience of the occupants.

Oct 17, 2014 10:09 AM ET

response to David
by stephen sheehy

Congratulations on your accomplishment. Forty years after building my own house, I still smile at how naive I was to think I could do such a thing, with no experience and nearly no money. There's a lot to be said for just doing it. I hope you inspire others to take such a risk. Whatever issues any of us might have with the design or construction details, the fact remains that you have a house to live in that satisfies your needs. Good for you.

Oct 17, 2014 10:21 AM ET

Edited Oct 17, 2014 10:24 AM ET.

Comments all positive thoughts for me...
by aj builder, Upstate NY Zone 6a

David, first and foremost I am utterly amazed... your passion, your detail, your detail, your detail, your goals, money money money... drive down the loan, drive down the size, drive down the monthly costs, exactly what I think is important. And the details, wow, you really used your noggin and a few spread sheets.

And the design is great. What the picture is lacking, is what would persuade others... a future shot with the garage and a garden and the porch and some people a fire pit... a pup... then I think most would say great design all around. Those with 3,000-80,000sqft homes excluded, at least till they get tired of how far they have to go to pee at 2AM.

The last two decades tract houses have 5 extra cosmetic gables that do nothing. I despise them for the look for the intent and to build and roof the darn things! In snow country valleys should be outlawed.

Oct 17, 2014 10:28 AM ET

Edited Oct 17, 2014 10:30 AM ET.

hodgepodge of comments and questions
by David Hicks

When I read that about PV and windows, I said to myself, "yowsa". And I think that was for electric resistive heat, right? Not even a heat pump. On one hand, this is an amazing bit of commentary on the cheapness of PV, something that's well-documented here at GBA. I'm a little afraid that, however, that the way the energy codes prescribes minimum r-value for windows means windows will become luxury items. David's whole-wall performance is far better than a typical wall-of-windows approach that you might see at a high-altitude ski lodge, even though both walls may skate by on code-minimum R-3 windows. Aesthetics aside, daylighting and a connection to the environment are very important in a residence, and I hate to see energy codes make windows into something only the rich can afford, simply because good windows are so expensive. (Don't take this as a knock on David's approach. I hope to do a minimalist, no-mortgage house at some point myself, and I expect to make compromises just as he did.)

If David's still reading these comments, I'd love to see more description of how the interior stud interfaced with the scissor truss bottom chord, and some info on the sequencing there. Did you put the exterior framing up, then the trusses, then build the interior framing? I'm having trouble visualizing how you installed the firebreaks and the insulweb. Also, did you have trouble finding someone to build your trusses? Most of the truss guides I've found on the web say it's pretty common for interior slope to be no more than half the exterior slope.

Oct 17, 2014 11:16 AM ET

#19 Design Approach
by Peter Hastings

It is this pragmatism that seems to characterise a number of NZ practitioners. I'm looking at all this closely in planning my own house and have been impressed and influenced by the work of Damon Gray in BC who has applied this sort of economic metric to his house designs. For those interested, more details can be found at nzbuilders dot com - a company name that neatly reflects not only Mr Gray's interest in net-zero building but his New Zealand roots.

Oct 19, 2014 11:48 AM ET

Edited Oct 19, 2014 12:00 PM ET.

The Reality Of It...
by Peter L

The reality is that this type of building design is less than 1% of the total homes being built in the USA. The majority of people are not going to put energy efficiency over design appeal, that's a fact. This website forum is where die hard green people go to therefore the statements and comments will be skewed towards efficiency over aesthetics. In the real world people will not want to buy or live in such ugly homes. I know the word "ugly" is subjective and maybe harsh but that is reality.

We (the green building movement) will not gain any outside fans by these types of homes. Give people something nice to look at that is functional and aesthetic. Something that keeps them together with the nature and world around them, not closed off by walls with only 2 windows. In order for this movement to get away from being the < 1% we need to think outside of the boring box and maybe compromise a little energy efficiency for something that appeals aesthetically to people.

Two fixed windows? One can't even open a window on a nice spring or fall day! What about in a fire and the door is blocked? Why not operable windows? Yeah, that's a great selling point. Hello folks, welcome to your tomb, this home features 2 1/2 tiny windows that you can't even open.

Oct 19, 2014 2:58 PM ET

Edited Oct 19, 2014 3:01 PM ET.

Reply to Peter L
by Malcolm Taylor

The problem isn't unique to advocates of Lakesideca. In architecture school most of our projects were for our ideal client who, unlike people you meet in the rest of your life, spent his days writing poetry in the perfectly proportioned rooms we provided for that purpose, and didn't mind dressing in public as none of the windows could sustain being covered by drapes without compromising the design.

I agree with you. We are designing for each other, predominantly on large rural sites where the questions usually asked about how houses relate to their community or neighbours aren't so pressing and don't get addressed..

The standard response to this is to say that they are all prototypes, and that the ideas and techniques being generated have application to the wider building community - a sort of trickle down theory - or to claim some moral imperative: that the work is so important that people need to learn to just live with the results. But we went through this in the 70's when the movement started and a whole range of interesting, un-livable houses were built, and as a result the public mostly dismissed the whole thing.

My feeling is that until the new energy efficient houses confront the whole range of other things people want their houses to do there is a real danger they will end up being marginalized in the same way.

Oct 19, 2014 7:31 PM ET

Edited Oct 19, 2014 7:32 PM ET.

Malcolm and Peter L.
by aj builder, Upstate NY Zone 6a

Time to put forth some sketchup plans of designs you feel are worthy both to you, to the public you refer to and to the green group.

Post your designs gents. And also what have you designed? Code only homes? 2% above code? What HERS ratings have all your homes hit??????

Myself I have built two homes not rated but we did downsize the HVAC systems to half my prior work and all is great. The homes follow many ideas, E-W, small north bath windows, larger South, porches on the west ends, insulated well basements, very low ACH, and more.... Hope to build some zero homes someday....

And I still say this home will improve in looks as the owner adds to the project....

Time to post your projects that could be net zero and be loved by your clients... Peter and Malcolm.

Oct 20, 2014 6:13 AM ET

Desirability versus Worthiness
by Peter Hastings

My feeling is that until the new energy efficient houses confront the whole range of other things people want their houses to do there is a real danger they will end up being marginalized in the same way.

If the required improvement in housing is as great as everyone here seems to think, then the solution must involve a significant proportion of the housing stock. To do this the next-generation of (energy-efficient) buildings will have to be desirable to the general public. If they are not, then two things will happen - very few such buildings will be bought and those that are bought will be neglected and abandoned. Neither of these two outcomes is even remotely 'green'. Minor quibbling apart, the technical challenges of making low-energy buildings seem to be solved - although the Big-Endians and the Little-Endians will doubtless continue their schisms until Hell freezes. So the real challenge is one of marketing - how to design low-energy buildings which are appealing and affordable. It is in this respect that the approach described in the original blog (remember that ?) has real merit - applying a cost-based metric in preference to a thermal-efficiency metric in the search for net-zero. De gustibus non est disputandum.

Oct 20, 2014 6:31 AM ET

Edited Oct 20, 2014 6:34 AM ET.

Response to Malcolm Taylor (Comment #36)
by Martin Holladay

You compare David Posluszny's design to the type of designs created by architecture students. But you are missing an important difference: David's design was actually built. More: it was built by a homeowner who loves his house and who wants to live in it.

If I visit a residential development on the outskirts of Atlanta or San Diego, I will be able to choose from a very limited number of designs -- most of them (as others have pointed out) ugly, and all assuming that my family's lifestyle fits certain expectations.

If David's design teaches us anything, it's that there are many kinds of American families, and that some of these families are looking for designs that differ from developers' assumptions. Maybe some people want small houses, or efficient houses, or inexpensive houses, or houses that are simple to maintain, or even houses with fewer windows. Right now, we don't know how many families like that exist -- because developers all over the country are building the same type of (ugly) house.

Oct 20, 2014 1:38 PM ET

by Jin Kazama

This all comes back round again to the fact that there are no serious regulations in building performance in NA .

I assume that you are pointing at Developers who own the land and build "projects " for sale,
( probably what developers mean neway ..the same situation exist here also )
they are there for profits and will build the cheapest house they can with the currenty "looks" to sale.

Unless code is reinforce enough to not allow them that route.

And since it takes money to make money, only the established ones are able to buy large land lots
and there is no more itneresting land available for more reasonable developers.

And then as discussed in recent threads, not enough energy audit once projects are completed.

If in the near future, if most large housing projects are done by "business" developers,
and there is no enforcment of efficiency, how are you supposed to reach levels of efficiency that would impact current global situation ?

Feels like trying to hand push a 1000kg stone.

Oct 20, 2014 8:06 PM ET

Reply to Martin
by Malcolm Taylor

Martin, I've beat this theme to death in a number of threads and come to the conclusion this isn't the appropriate forum to discuss it. GBA excels in providing technical information and developments around energy efficiency. That's quite rightly why readers come here and what their interests are. Widening the debate to include other design issues just seems to muddy the waters. I'm quite happy to stop and I'm sure others are just as happy to see me do so.

Oct 21, 2014 6:11 AM ET

Response to Malcolm Taylor
by Martin Holladay

It's perfectly OK to bring up design issues. Design issues are important, and the debate is healthy.

While the debate is healthy, there is no simple answer to the question of whether David's house is elegant or unattractive.

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