Saturday July 6 from 10 am to 6 pm: The house is taking on a handsome look as wood siding and soffit go up piece by piece. When we fire up the saw, we’re running on clean energy—the solar panels are now hooked up to the grid. Inside, you’ll still see the skeletal structure of the double stud walls and the barn-like open space. Wait till next month, and each room will be defined by their stud walls. I’m just back from the Midwest Renewable Energy Fair where I gave a talk on our progress and plans for a new vision of suburbia. Come see what we’re doing, ask me questions, and tell me what you’re looking for in a modern home!
Friday-Sunday June 21-23: Have you been wondering what you can do to reduce your carbon footprint? Would you like to help build a straw-bale wall? Get a good look at the latest electric cars? Learn how to raise chickens? Can you picture yourself eating pizza from a outdoor wood-fired oven? Listening to live music while lounging in the grass? If so, you can’t go wrong at one of my all-time favorite events: the Energy Fair in Custer, Wisconsin.
I’ll be giving a talk about building Spring Green’s first Net-Zero Energy house on Sunday at 10 am called “Follow the Build-Part 1”. Here’s the link to my presentation:
I hope to see you there (or at the beer tent).
June 3-5: At last I was ready for insulation. For good reason, the type of insulation, where to install it, and how to install it is of obsessive interest to green builders like me. Other building materials might be the same, but insulation is where we veer off. I chose dense-pack cellulose because there’s no other insulation that takes less energy to produce, uses more recycled content, and is less toxic to people and animals. Not counting direct-from-the-earth materials like straw bale, straw-clay, cordwood, log, and cob.
Yes, I did consider straw. But for my subdivision house geared to taking super-insulation and net-zero mainstream, I’ve heeled close to convention. All I’ve done is make deeper cavities and prioritized initial cost over operating cost.
There aren’t many contractors set up for this kind of work. Wallace Kennedy and sons of Accurate-Airtight Exteriors arrived from Madison to install what turned out to be the most number of bags ever for a dense-pack job. Wallace packed 238 bags in my 22 inch deep truss cavity, for a total R-80. That’s double code minimum.
The insulation comes from Champion Insulation in nearby Fond du Lac. It’s made from wood fiber paper stock and claims 85% recycled content. By weight, it’s 84% cellulose, 14% boric acid, and 2% starch—all benign materials that pose no threat to the environment. It doesn’t cause skin irritation like fiberglass, and has little or no smell—though breathing the dust should be avoided.
Cellulose reduces sound transmission, and when dense-packed resists air movement, fire, pests, and vapor diffusion. Because it’s hygroscopic, it can take on and release moisture from surrounding materials like sheathing. This protective characteristic makes it especially favorable in double-stud walls. The added borate aids in resisting mold and insects.
Cellulose is a “low embodied-energy” material. That’s the energy it takes to source its ingredients, manufacture and transport the product, and dispose of the product at the end of its useful life. Side-by-side comparisons with other insulation types are hard to come by. Cotton, wool, and cork are more energy-intensive and cause some pollution, while fiberglass, mineral wool, and all the foam insulations pose significant risks.
It took the crew 3 (monotonous) days to complete the job. Wallace stayed on hose, while the younger men fed the blower machine. By the end, the vapor retarder at each truss bay was sealed up—ready for the 12” strip of drywall that will complete the airtight lid of the house. I’m grateful for their conscientious work!
May 24-29: Time was running out. I wanted to have things looking nice for my June 2nd Open House, but I could tell after just a few hours of scrubbing that getting the slab ready to seal was going to be a long and grueling ordeal.
During the planning process, I made the decision to go with a “raw” concrete look: no stains, no stamping, no pattern cuts. No grinding or polishing to reveal the aggregate. No faux finish and no visual tricks. Above all: honesty of material. A simple matte finish would save money that could be put towards fabulous area rugs. Plain with a touch of luxury would suit my style.
I’m not one to rush out and buy expensive equipment or take a chance on a rental that may or may not get the job done. I also don’t like to hire out if it looks like something I can do. All it is, is work. Stubborn stick-to-itiveness and shear parsimoniousness has made for many a long day.
The slab was well-cured after 6 months and it was finally up to temperature. Over the last several weeks, I watched as my borrowed infrared thermometer read out 40, then 50, then 60 degrees. I had my plumber install a hose bib and the Village hook up a meter. I broke down and bought a shop vac and a stiff push broom. I watched a couple of YouTube videos about how to apply muriatic acid (it micro-etches concrete and prepares it to “grab onto” a sealer), and invested in a spray bottle, rubber gloves and a mask. I was good to go.
By sections, I scrubbed the slab 3 or 4 times (just water, no soap). When the water finally vacuumed up mostly clear, I applied the prescribed dilution of muriatic acid and watched it bubble & mist. I rinsed 2 or 3 times then let it dry for a few days before brushing on a test patch of sealer where the cabinets will go.
I chose ECOS Paint’s “Concrete Sealer”, a zero VOC, no odor, water based acrylic product that was easy to use. It carries the “Red List Free” label from Living Future Institute for not containing any of the worst-in-class materials prevalent in the building industry. I hoped to save time by rolling it on with an 18” wide paint roller but quickly saw it left tiny bubbles. I switched to brushing it out on hands and knees.
Two coats got me an interesting finish that I kind of liked but told a friend that “10 out of 10 people will find this unacceptable”. My prediction was way off: at my Open House, many people commented on it and likened it to a natural stone floor. The finish seals out water (I tested it), but took to the concrete in a mottled way. Some areas are shiny, others are dull. The look is growing on me! What do YOU think?
May 20: Sometimes, conventional wisdom should be questioned. In this case, it’s the conventional sequence of residential construction. Today, the drywall crew arrived to “hang the lid”—builder speak for installing ceiling drywall.
In my quest for a super air-tight house, I decided to eliminate all electrical and mechanical penetrations through the ceiling and to insulate it and drywall it before framing out interior partition walls. While it takes separate set-ups for each crew and some flexibility in scheduling the next phase, it does make the actual job easier and faster.
Drywall is relatively cheap and it’s common to add a few sheets in case of a miss-cut, but I wanted to reduce waste. I also wanted to try out a product called Insta-Back that eliminates the need to cut drywall back to the nearest truss. I came up with a plan that saved 4 sheets of drywall, reduced the number of seams to be taped, sped up installation, and left me with a manageable pile of scraps at the end.
My plan called for cut sheets at the perimeter only and full size sheets in the field, run past their truss supports. All lengthwise seams are factory. Butt seams are joined by Prest-on’s “Insta-Back” drywall clips that promised a “bump-free” joint with a 1-2 degree taper, similar to a factory joint.
Adam Esch of Esch Drywall appreciated the wide open space to roll his scaffold and did a great job. But I could tell he wasn’t too impressed with the clips. Later, I went back through with a level and determined that of 20 butt seams, only 2 had the requisite taper, while most simply held their own by laying flat. I’ll have 3 or 4 bad joints to deal with. At this point, I’m not sure if the problem can be blamed on the Insta-Backs, or the adjacent trusses. For the walls, I may try another product.
I chose 5/8” thick USG’s “EcoSmart” panels for their long list of green credentials and green certifications. The upcharge was under $20. The panels are significantly lighter and use less water in the manufacturing process. The ingredients are so benign, I tossed scraps at the edge of my lot to decay into the soil.
We left a 12” gap down the center of the ceiling at the request of the insulator. He’ll use the gap to snake his hose into the truss cavities. Later, we’ll fill the gap with 1/2” thick drywall for a smooth connection to the factory seams. Here’s hoping drywall mudding and taping will go well, because I’ll be tackling it by myself!
May 18-19: The latest buzzwords are “smart & sustainable” and I’m saying them but thinking ruefully of all the things builders and industry get wrong and have to walk back in say, a couple of decades. It was on my mind while on a ladder while wrestling with a 50 foot long roll of so-called “smart” vapor retarder.
Today’s homes are much more vulnerable to mold and decay than older homes because they’re slow to dry out if they get wet. We pack wall and ceiling cavities with insulation, and cover surfaces with materials that trap or retain moisture. When driving rain sneaks past cracks & crevices and soaks in, a day or two of sunshine isn’t enough to make things right.
Inside, a family of four can create 2-3 gallons of water vapor a day when cooking, bathing, and washing—and all that moisture can find an exit through a hundred sloppy construction holes.
An older home is like a wood box. A new home is like a wood box lined with sponges imperfectly wrapped in plastic.
Since the 1970’s, building codes in cold climates have required a vapor retarder installed on the “warm side” of a wall or ceiling. It can be old-school kraft paper that comes with fiberglass batts, but is usually 6 mil polyethylene stapled to the face of the studs and covered with drywall. Poly is a Class I Vapor Barrier, practically impervious to water vapor. Kraft paper, once maligned as too loosy-goosy, is now considered “smart”. It’s a Class II Vapor Retarder, which means it can stop some but not all vapor.
The problem is that with the advent of air-conditioning the “warm side” of the wall in summer is on the outside. How this obvious truth could be overlooked (and why Wisconsin’s building code is still stuck in the past) is hard to fathom, but the building industry has stepped in with a new product—and this is how I ended up on a ladder, wrestling.
CertainTeed’s MemBrain is a 2 mil polymide film that alters its physical structure (!!!) when the relative humidity changes—shifting from Class II to Class III. Water vapor can pass through when humidity is crazy high (60%), but stays “shut down” when humidity is in the normal range. So in winter, MemBrain works like a normal vapor retarder in that it stops warm, moisture-laden inside air from entering a wall or ceiling cavity and condensing on the cold surface of the sheathing. However, should the cavity become seriously saturated, MemBrain will “open up” and allow drying to the inside.
In summer, with air-conditioning running full tilt, MemBrain will stop the warm, moisture-laden outside air from entering the house. But should the cavity become overloaded, it has a chance to diffuse its vapor to the dry air of the interior. Picture a downpour followed by sunny skies. Wood, brick, stone or cement board siding becomes saturated. Solar heat drives the moisture into the building cavity. If traditional poly is used behind the drywall, that moisture will condense and saturate the insulation. With MemBrain, the moisture can pass through.
But many building scientists and high-performance builders say a vapor retarder isn’t needed, except in extremely moist situations like pool rooms and greenhouses, or in homes up north where air-conditioning isn’t used. They argue that vapor diffusion through drywall is minuscule compared to bulk vapor drive through sloppy holes. What’s needed instead is an interior air barrier. Drywall is fine, as long as it’s well-sealed.
Martin Holladay of Green Building Advisor makes an exception for double-stud walls like mine. Because super-thick insulation keeps exterior sheathing extra-cold in winter, the chance for moisture accumulation is greater than in a conventional 2×6 wall. He recommends a vapor-open sheathing like fiberboard or exterior-grade drywall in addition to siding installed on a ventilated rainscreen. Both measures speed drying to the exterior. The other option is to slow moisture diffusion from its source by installing a smart vapor retarder.
My sheathing is plywood, which is more forgiving of moisture accumulation than industry-standard OSB (oriented strand board), but less so than fiberboard. I’ll be installing my siding on DuPont’s DrainWrap, a crinkled version of Tyvek that accelerates drying, but not nearly as well as a dedicated rainscreen. Holladay would say that in my case, a smart vapor retarder is cheap insurance.
While my wall is moisture-forgiving, I’ll bet most of the homes in my neighborhood (built over the last 20 years), are a “moisture sandwich”. Typically, the walls are 2×6 frame with fiberglass insulation and a poly vapor barrier under the drywall with 1 inch of foam over the exterior sheathing. Sheet foam is a good solution for increasing the R-value of a conventionally framed wall, and it really reduces “thermal bridging” but it comes at the cost of trapping moisture. Both foil-faced polyiso and pink or blue XPS are Class I vapor barriers on par with poly. If this wall gets wet, it will likely stay wet for a long time.
My vapor-variable retarder might be cheap insurance, but it’s not cheap. I tried hard to find kraft paper (not attached to a fiberglass batt) that was labeled a Class II vapor retarder, but no luck. I looked at vapor retarder paint, allowed with special permission in Wisconsin, but only found the usual toxic mixtures.
Installing MemBrain wasn’t really too hard. It was more durable than I imagined it might be, and held up to hanging and stretching without tearing. I lapped seams by 12 inches and sealed the perimeter with ChemLink’s DuraSil, a non-toxic, low odor silicone adhesive. In this way I achieved both a continuous vapor retarder AND a continuous air barrier.
Some type of vapor-variable retarder is the only option I’d consider for a smart and sustainable home—given the current level of building science and available technology. But it’s not a hill I want to die on: what will progressive builders be doing in 20 or 50 years? Will my so-called high-performance assembly look antiquated?
May 15: There’s a lot of confusion out there about how tight is too tight. Some builders say a house “needs to breath”, and that sealing every gap is a waste of time. This is how I see it: we all want fresh air. Some of us with allergies need filtered fresh air. What we don’t want is “fresh air” filtered through the building materials in our walls and ceilings. If we leave gaps we are:
1. Wasting energy (losing heat in winter, coolness in summer).
2. Allowing moisture-laden air a route into walls and ceilings, where it can condense on cold surfaces, creating a breeding ground for mold and mildew.
3. Allowing dirty or polluted air a chance to dump dust and allergens into walls and ceilings, or directly into the indoor air.
4. Creating a pathway for insects, or worse—rodents.
In the summer, I can open windows. But in the winter, I’ll need a mechanical system to bring in fresh air and exhaust stale air. Later, I’ll explain the quiet, energy-efficient ducted heat-recovery ventilator (HRV) that will be installed.
Just as I did for exterior air-sealing, I took an enthusiastic approach to interior air-sealing. I used canned spray foam to seal window and door rough openings. It was easy and fast. I’m a little worried about reports I’ve read that foam can crack and separate from it’s wood substrate over time. A bead of caulk or a run of tape over the foam would be prudent, but I haven’t found a way to do that in my particular situation. Where spray foam wasn’t appropriate, I used caulk or tape.
Foam in all its guises is one of the worst building materials for carbon footprint. I chose a low-pressure polyurethane foam called Handi-Foam. It’s a Green Guard Gold product certified for low chemical emissions and is non-toxic when cured.
The electrician has run a few pipes. I sealed those with DuPont’s FlexWrap EZ, a butyl-based peel & stick tape that’s a breeze to install.
With air-sealing complete, the moment of truth arrived—my first Blower Door Test. I’ve arranged for energy auditor Jim Kjorlie of Kjorlie Design Services to come out and test my house three times: before insulation, after insulation and before drywall, and finally upon completion. With his help, I hope to be certified through Focus on Energy’s New Home Program.
Blower Door tests aren’t too common around here, but in neighboring states where stricter energy codes have been adopted, they’re required. Jim set up a large fan in the front door, turned it on, and brought it up to speed. The idea is to depressurize the air to simulate a 20 mph wind bearing down on all sides of the house. Drafts can then be hunted down. Gauges and gizmos spit out numbers—and you either “pass” or “fail”. Here’s how I did, expressed in air changes per hour (ACH)—literally how many times the volume of air in the home is changed out with fresh air each hour:
Wisconsin Code (2009 IECC national code) =7.0 ACH
Focus on Energy New Home Program =3.8 ACH
Test #1 =2.6 ACH
It’s good, but I was hoping for better, like 1.0. Jim went around with a “smoke stick” that detects leaks by showing a trail. Tell-tale puffs shot out at the base and top of the patio door—the usual places, he said. He suspects that the fiberboard vent chute—which comprises 40% of the interior surface area is much more air permeable than the plywood sheathing on the walls. He suggested I find air-perm ratings for both materials, but so far I haven’t found any definitive information.
I’m stoked to bring that number down, so stay tuned for Test #2!
Sunday June 2 from 10 am-6 pm: Progress continues at Spring Green’s first net-zero energy home. Since our last Open House, we’ve completed the roof vent chute, installed the PV solar panels, drywalled the ceiling, started interior wiring, conducted our first blower-door test, and sealed the concrete slab. You’ll still see the skeleton double-stud walls. Look around, meet new people, enjoy refreshments, and ask me questions! Find us one block north of the High School at 770 North Westmor Street. For more information call or text Amber at 608-935-9020.
April 18-28: Icicles sparkling and draping from a roof on a vacay-snow-day is a beautiful sight, but when you know more you see trouble. You see heat loss, hidden pools of water, and stained ceilings.
My super-insulated, super-airtight, super-vented roof will even out and slow down snow melt. Warm moist inside air won’t find a route through and condense on cold surfaces and soak insulation. If I worry about sealing up every single little-bitty gap now, I won’t have to worry about mold, mildew, or rotting structure later.
A flat ceiling is easy to insulate and easy to ventilate. A sloped ceiling like mine takes extra steps. I’ll use eco-friendly cellulose, made from recycled newsprint. But there are two hurdles: it settles and drifts unless “dense-packed” into a cavity, and Code requires it be top-vented to allow any moisture migrating from below a route of escape. The usual solution is a manufactured “vent chute” made of cardboard, plastic or foam—but dense-pack would crush it.
I ordered up a few bundles of 1×2’s and a stack of fiberboard from the lumberyard and had on hand a case of low-VOC caulk (ChemLink NovaLink 35) from Green Building Supply. We air-stapled the 1×2’s to the sides of the top truss chord, fitted in rips of fiberboard, then went back to caulk the gaps and tape the seams. This left us with a 3 inch deep continuous chute separating the roof from the insulation. Any warm, moist air that migrates through will be whisked away, through soffit vents we’ll install in a few weeks.
Fiberboard is an old-school building material and nowadays, a special order. It’s used for wall and roof sheathing, for insulation (R-2.5 per inch) and for sound-proofing. It’s classified as non-hazardous and is recyclable if you can find a facility. It’s made from recycled wood fibers, wax, and usually has a black asphalt coating on one side. It’s vapor-open and sturdy. I could have used OSB (oriented strand board) for slightly less cost and but greater environmental impact. We found the fiberboard easy to work with and not too dusty.
We did a pretty good job with waste, although there were the inevitable cut-offs and caulk tubes that had to be landfilled.
April 20 noon-5 pm: We’ve made some good progress on Spring Green’s first net-zero energy home. Take a tour, snap some pictures, ask questions. You’ll see the skeleton structure and what double-stud walls and raised-heel roof trusses look like. Admire the views through the recently-installed windows and ask about their energy-efficiency backstory. Have a look at the still-to-be-trimmed-out galvalume standing seam roof. Find us one block north of the High School at 770 North Westmor Street. Bring the kids, stay for s’mores. For more information call or text Amber at 608-935-9020.
March 29-April 14: My favorite thing so far is the 12 foot wide patio door we installed on a glorious spring day. It’s what’s going to open the living room up to my garden and help heat the house in winter. I chose a Marvin aluminum clad wood slider, with a heavy-duty fiberglass sill. Thank goodness for my crew of Very. Large. Men.
I prepped the sill by securing the under-slab vapor barrier to the edge foam with caulk and measuring out a length of 5” EPDM sill gasket. The patio door sill will sit directly on these materials, completing a continuous thermal-barrier, air-barrier, and vapor-barrier to the exterior.
Mark of Bear Paw Design & Construction and “the boys” hustled the thing into place.
Here’s Mark finessing the gasket, bathed in sunlight. “Passive Solar” was the buzzword of the 70’s that got me excited about architecture and back to school to take a drafting class. Since then, the idea that south-facing windows can serve as heating appliances has been disparaged. Those early, hippie homes with their wall of factory-seconds windows skimped on insulation and leaked like a sieve. They overheated during the day, and without thermal curtains lost all that heat at night. We now know that thick layers of insulation and a double-down on air-sealing are far more important than trying to capture solar energy.
Many high-performance builders shooting for net-zero are building conventional-looking homes without regard for window orientation. Even so, I’m inclined to cling to my roots. My design follows the recommendations of Dan Chiras and his seminal book The Solar House which balances “solar glazing” to “thermal mass”. During the winter when the sun is low in the southern sky, sunlight will stream through my south-facing windows and patio door and its heat energy will be absorbed by my concrete slab. There will be some lag. Some days, it will be cloudy. Other days, the house will get too hot. Thermal mass is slow—it’s slow to absorb heat and it’s slow to release heat.
Here’s where I divide company with the mainstream—I don’t need and I don’t want to live in a thermostat-controlled environment that never, ever varies. I’ll live in a house that responds to our flight across the sky and I’ll save energy by accepting indoor air temperatures that climb to 80 degrees on sunny afternoons and drop to 60 degrees overnight. So it’s slippers for me.
One of the most-asked questions I get is if the slab is heated, meaning with PEX hot-water tubing run through or under the slab. Heated slabs are wonderful. They’re warm to the touch and can carry a well-insulated house through most of the winter with supplemental heat turned on only for the coldest days. But because thermal mass works slow, the PEX system really should be left on continually—leaving very little absorptive capacity for incoming solar. And because it’s slow it can’t respond to a sudden change of weather. Most homes need a backup heating appliance that ideally also supplies air-conditioning. So while wonderful, heated slabs are more expensive than unheated slabs because you’re investing in two—not one—mechanical systems.
To satisfy my curiosity, I ran my design through modeling software REM-Design. Per recommendation, my “solar glazing” is 12% of the area of my “thermal mass”. When I remove the slab, annual heating costs increase by 3.5% and surprisingly—cooling costs rise by 9%. Southern Wisconsin is hot in the summer, but has enough temperature differential between daytime and nighttime (about 20 degrees) to power up the “thermal flywheel” effect. While overhangs will mostly shade my south windows from the direct rays of the sun, August heat will warm the slab during the day. If I keep the windows open and there’s a breeze, that absorbed heat will flush out and by morning, I’ll feel a nice cool underfoot.
Besides the cooling effects of the slab, windows placed for cross-ventilation in each room will keep the air-conditioning off most of the summer. Casements or the patio door can be cracked open a little or a lot to funnel prevailing Southern breezes out North-facing awning windows. High windows enhance the “stack effect”, naturally drawing warm air up and out, all hurried along by the sloped ceiling. The speed of the air can be increased even more when the area of opened window on the windward side is small compared to the area of opened window on the leeward side. Awning windows are perfect for passive ventilation because they can be left open all summer long without any worry about rain.
I chose Marvin Integrity All-Ultrex windows for their rot-proof, maintenance-free finish and long-term durability. They’re less expensive than Marvin’s wood aluminum clad windows but more expensive than common vinyl windows. They’re made from pultruded fiberglass, which takes 39% less energy to manufacture than vinyl. And because they’re 60% glass (silica sand), the frames expand and contract at nearly the same rate as the glazing, making the units less likely to break seal.
Window glazing comes in a dizzying combination of features that effect energy performance, and I gave them all an equal run through REM-Design. Turns out, the most commonly available is also the most cost-effective. I chose “dual-pane, low E2 with argon” which is rated for year-round comfort in Northern and North-Central states. The equivalent R-value is 3.4, the same as one inch of cellulose or fiberglass insulation—not too impressive. There are several (mostly Canadian and European) window manufacturers that make up to R-10 windows, but they are far outside my budget.
Other high-performance builders in our climate zone upgrade to triple-panes and low E1 coatings where south-facing. If I did the same, I could save $59/year in operating costs. However, the package would cost me $2,785 extra or about 28% more. Even when amortized over the expected service life of the windows (30 years), the triple-pane windows never pay for themselves.
The argument then comes down to comfort. It’s true that dual-pane windows are colder and more prone to condensation problems. If you’re sitting next to a cold window in the evening, you’re going to feel a chill as your warm body radiates heat to the cool glass. And you might experience a waterfall-like spill of air and be tempted to turn up the thermostat. Curtains or thermal shades are the answer here, or to paraphrase Frank Lloyd Wright: “move your chair”.
I saved money and resources and kept to budget in another way: my home doesn’t really have many windows. If my design answers the need for natural light, views, and cross ventilation—it works. If the windows are well-proportioned and well-placed to create a harmonious whole with other architectural elements—I have style. But the biggest savings of all: the house is small.
Installing the windows was a satisfying step for me. I chose DuPont’s Tyvek system of flashing products. While it can sometimes seem like you’re wrapping a Christmas present, tape and Tyvek are stronger and long-term more reliable than old-school caulk and tar paper. The products had a quality feel and were easy to use.
I used FlexWrap NF, StraightFlash, and FlexWrap EZ—all butyl rubber flashings that are solvent- and VOC-free. They can be installed in cold weather on cold surfaces, are self-healing, and don’t off-gas. There’s no waste except for the peel-off paper backings. With windows in, the house is warmer and a better place to be.
March 29-31: Spring construction got off to a big start when Mark Morgan of Bearpaw Design & Construction arrived with his sons to install the metal roofing. The pre-cut-to-length roof panels flew on and by Sunday afternoon the work was nearly done—all except for the “gingerbread”. That’s Mark’s term for edge and ridge trims.
We had a good rhythm going with Mark cutting and bending panels at a workbench, Nate carrying and sliding them up to Joel who screwed them down, and me filling in where needed. My work included peeling off the shrink-wrap that protected each panel from the next. I grew more and more dismayed as trash bag after trash bag filled up. Technically, plastic like this is recyclable but the reality is different. Do any of you know a facility?
The panels came drop-shipped in large wooden crates (wrapped in more plastic). The 2x material isn’t good quality and some of it will split when I bang it apart, but I plan to reuse what I can for blocking and bracing. The rest will be firewood. My sales rep recommended I order two extra panels in case of a miss-cut or the wind taking one but we had no mishaps. Mark will take the extras for his shed and I can take scraps to the local recycling place.
The roof is standing seam steel with a galvalume finish that comes with a 25 year warranty. Most estimates put its lifespan at 50+ years, a nice match to the lifespan of the PV (photovoltaic) panels that will cover a third of the house roof. An installer I spoke with told me that to take down and put PV panels back up for a re-roofing job he’d need $2000—-a cost best avoided.
Metal roofs aren’t very common for homes in our area. They’re more expensive, so to recoup your costs you need to be in the house a LONG time or be confident there’s resale value. Many people find them too stark, too commercial-looking, or too modern-looking and in some cases I agree.
I chose galvalume instead of a painted finish because I like the way it looks and it goes with the casual, contemporary style of my house. You can get steel in lots of colors but unless it’s gray I think it looks cheesy (think Pizza Hut). The galvalume fits my aesthetic because it will take on a weathered patina much like a well-used cutting board. The more common choice—asphalt shingles—wouldn’t meet the long-term durability and low-maintenence goals I set for this project. They last only 15-20 years and while in theory can be recycled, usually end up as landfill. Steel is recyclable at the end of it’s useful life. But to honestly evaluate the “green credentials” of various roofing options you’d have to compare their embodied energy—a moving target that only a few scientist-types have attempted. It includes the energy to extract, to transport, to manufacture, to install and maintain, and finally to dispose of.
With the roof on, I can now turn my attention to windows and doors!
Noon to 4 pm: You’re welcome to stop by and see my house under construction in Spring Green, Wisconsin. The walls are up and the roof is on so you’ll see what double-stud framing looks like and how the raised-heel roof trusses create space for an extra-deep layer of insulation. If you’re curious about what a smallish (1200 square foot) home feels like or want to learn more about super-insulated, passive solar, net-zero energy design I’m there to answer your questions. We’ll have a little campfire and refreshments too!
March 2, 2019: My house is a throwback to 1955. That’s the last time the average new home built in America was 1200 square feet. By 2014, the average new home ballooned to 2657 square feet—even while families got smaller. Today 62 out of 100 households are just one or two people.
I meet people all the time who want to down-size. As an empty-nester myself, I can relate. A big house is too much work. It takes a lot to heat and cool. Steps can become a problem. Older homes need updates and don’t adapt well to modern lifestyles but newer homes are big and boxy and lack character. Living in the country is nice but can be isolating and you’re forever driving back and forth to town.
As a designer who’s listened to hundreds of families describe the good and the bad of their living situations, and as a builder who wants to make a difference, I see an under-served market.
At first, I didn’t think I would be able to build the house I wanted on the lot I wanted. Like most subdivisions, mine has Covenants—certain minimum requirements laid down by the developer to insure a sort-of uniformity to the neighborhood. The minimum size for a one-story home was 1500 square feet.
Turns out, rules are negotiable. My Offer to Purchase was contingent on approval to build a 1200 square foot home. As soon as it was accepted, I hit the drafting board.
Whittling down a wish-list takes some time, a little work with a tape measure, and a bit of inspiration. Of course, not everyone will make the same calculation I did, but here’s what made the cut and what didn’t:
NO HALLWAYS: Eliminating hallways is hard to do in a large home but pretty easy to do in a small home. Each bedroom is on either side of the great room, not lined up along a bedroom wing. The kitchen is a galley with standing space doing double duty as the main circulation route. The laundry is a smallish “room” that you walk through to get to the bathroom and bedroom.
NO CLOSETS: Instead, there are built-in cabinets for coats, clothes, pantry, and cleaning supplies. This saves space usually taken up by 2×4 wall framing.
NO STAIRWAY: There is no basement and no second floor. Instead, there’s a narrow ladder-stair to attic-like space for bulk storage.
NO DINING ROOM: A nook off the Living Room is convertible to informal dining, homework, crafts, games, or TV area.
NO FOYER: Instead of two rooms—one for guests and the other a mudroom, there’s a single way in with a place to hang coats and drop boots that does double duty as the main circulation route.
NO LAVISH MASTER BATH: Each of two bathrooms is a modest size with a tiled walk-in shower. There’s no tub.
YES WINDOWS: The number of windows is modest, but their size varies from small view-port to over-scaled, adding drama and bringing attention to particular views. Each room has windows on two sides to balance light and draw in fresh air. Each bathroom has a window.
YES VAULTED CEILINGS: I splurged on volume but keep things cozy by layering in wood beamed ceilings over the kitchen, entry, and bathrooms. The rooms feel bigger and airier and more spatially complex. Diagonal views both up and out extend views and expand space.
YES OUTDOOR LIVING SPACE: There’s a breezeway-style porch for summertime dining and lounging and a walled garden/patio for campfires and watching the stars, both just steps away from the kitchen. I’ll live mostly outside 6 months of the year!
December 10-21, 2018: Watching the crane swing the roof trusses in place was a thrill, and once all were set into place the house began to take on a shape you could feel.
Manufactured roof trusses are an economical choice and at 24” deep can clear-span the width of my house. The deep cavity provides a built-in space to fill with insulation (more on this in a later blog post).
The style of my house calls for deep overhangs and generous rakes. Like the brim of a hat, the eaves will deflect rain away from the walls and provide the shade I need to help keep the house cool in summer. I used Sketchup, a 3D modeling software to visualize my design. I played around with thickness and depth of eave to get the look I wanted, and dialed in day of month and time of day to find out where shade lands on the Summer Solstice, when the sun is highest in the sky. I found out I needed a 30” overhang to get full shade on my south-facing windows. On the Winter Solstice, when the sun is lowest in the sky, the windows are in full sun, capturing free heat energy.
The problem is that mid-June isn’t the hottest month, and December isn’t the coldest month. To optimize shade, I should look at July which weather data says has the most “cooling degree days”. To optimize passive solar heat gain, I should make sure my windows are in full sun in February, the month with the most “heating degree days”. I found that cutting the overhang back by 8” gave me full sun on February 15th , but exposed the windows to way too much sun on July 15th. (Note to fellow building science geeks: also play around with truss heel height, wall height, and window placement).
To build a strong, wind-resistant overhang, I upgraded the truss “tail” (top chord) from the usual 2×4 to a 2×6. For each rake, I specified two dropped top chords supporting 2×4 flat “lookouts”. These cantilevers were then reinforced with 2×4’s on edge.
Instead of the usual 2×6 “sub-fascia” covered with a 1×6 “finish fascia”, I kept things simple and straightforward with a 2×8 cedar fascia screwed directly into the truss ends. Cedar is naturally decay-resistant and needs no paint or stain. In this way, I haven’t “sandwiched” materials that might get wet and stay wet, hiding rot from view.My overhang is what’s called a “boxed-in eave”. You see it on farmhouses around here that retain their vintage forms, although their roof edge would have a “square cut” not a “plumb cut” like mine. I’ll need the plumb cut to attach the large gutters I have planned.
Newer homes or remodeled older homes usually have “soffited eaves” that while practical, can look awkward. High-end newer homes or Arts & Crafts homes sport “exposed eaves” which I love but are considerably more complicated and expensive to build.
Each roof truss was secured to the wall framing with a Simpson truss screw instead of the usual hurricane anchor. It’s simpler and faster and can be installed from the inside. I upgraded the nailing protocol for the roof sheathing to match the wind-resistant specifications I used for the wall sheathing. For underlayment, the crew rolled out a double layer of Titanium UDL 25—a synthetic air, water, and vapor barrier—and attached it with cap nails. It’s rated to perform up to 240 degrees, a requirement where PV (photo-voltaic) panels are installed.
It’s become common practice to roll “ice & water” peel-and-stick membrane at the lower edge of a roof as a hedge against ice dams. I’ll save the expense because my roof will have:
1. uniform heat loss across the entire roof area (insulation doesn’t thin @wall)
2. minimal heat loss with 20 inches of dense-pack cellulose
3. minimal heat loss because of air-sealed ceiling cavity
4. vent chute above insulation keeps underside of plywood sheathing cooler
5. metal roof promotes snow shedding
December 21st was a pretty sweet day because the crew got the underlayment down even as night was falling and we enjoyed a beautiful sunset. It was our last day before the holidays and as it turned out, our last day. Winter arrived and hasn’t let up. We’ll be back in March……for sure by April!
December 10-21, 2019: While my crew was busy framing the eaves and laying down roof sheathing, I tackled the exterior air-sealing.
Stopping air from whistling through random cracks is an essential step to meet my net-zero goals. Taking the time to caulk and tape each and every joint adds up to energy savings. It also makes a home more comfortable by eliminating drafts, cold spots, and uneven indoor temperatures. I can be confident that my house will last for the long haul because moisture-laden and dust-laden air can’t enter the wall and roof cavities. My insulation and framing will stay dry, which means mold, mildew, and wood decay can’t take hold. And a not-to-be-taken-lightly side benefit: carpenter ants, cluster flies, Asian beetles, and mice are stopped cold.
With all these benefits, you’d think exterior air-sealing would be standard practice in residential construction—but you’d be wrong. Sheathing seams are left untaped. Builders assure themselves that a layer of housewrap is enough to ward off wind and rain. But from what I’ve observed, it’s often hastily tacked up. Seams are sloppy and mechanical penetrations are haphazardly sealed. Siding covers all sins and buyer beware!
Several visitors to my building site have been surprised to see my use of plywood sheathing—not the more common OSB (oriented strand board). Plywood is a reliable air-barrier and can tolerate some saturation. OSB has been found to leak air when pressurized during blower-door testing (more about this in a later post), and is more vulnerable to decay when repeatedly wetted. A good alternative to stock OSB is Huber’s ZIP sheathing which has a factory applied coating that replaces housewrap.
Plywood scores worse for efficient use of wood resources (it requires larger diameter trees and generates more waste), but it uses less glue than OSB. It’s also more expensive: I chose 5/8” 5-ply fir, a significant upgrade from code-minimum 1/2” OSB. My decision to use plywood came down to its durability, and the advice of many building scientists who say it’s the “least risky” choice for thick double stud walls like mine. When packed with 12” of insulation, the plywood sheathing will stay cold—much colder than in a thin wall that rapidly loses heat to the exterior. The plywood can become a “condensing surface” (like window glass) if the drywall is breached and moist indoor air finds a convective pathway.
My first step was to caulk seams wider than 1/4” and tape narrower seams. I chose the same caulk (ChemLink M-1) I used for the under-slab vapor barrier where it seals to the top of the foundation wall. It’s a waterproof, non-shrinking, low VOC sealant that can withstand joint movement in excess of 35%. It was very easy to work with and had no apparent odor. The tape is 3M’s All Weather Flashing Tape 8067, selected for its good track record.
Caulk and tape are more reliable than foam products because they remain flexible. They hold up to thermal expansion, structural settling, lumber shrinkage, and wind stresses. Foam is brittle. It can pull away, leaving hairline cracks that link outdoor air to indoor air.
At the bottom of the wall, I folded up and taped the under-slab vapor barrier that I had let run long (see blog post “Sills & Slabs”). Now married to the plywood sheathing, it completes the continuous air barrier at this critical juncture.
At the gap between the truss tails and the wall sheathing, I used DuPont’s FlexWrap EZ, a flashing tape that takes a curve. Later, I’ll use it for mechanical penetrations. On the inside, a “vent chute” will complete the air-barrier at the top of the wall (more on this in a later post).
My next step was to roll out the housewrap. A few green builders swear by old-style tar paper (asphalt impregnated felt), but most agree that synthetic products tear less and hold up better under repeated wetting. They are also lighter and easier to install. Known to the trade as “Weather Resistive Barriers”, a good quality housewrap is wind-resistant, waterproof, and vapor open.
I chose DuPont’s Drainwrap which has a slightly crinkled surface to facilitate water drainage behind the siding. With help from friend Bob Rowen, we got a nice tight fit around corners and secured it with caps. Simple stapling wouldn’t hold up in my windy location. We kept clear of window and door openings.
The caulk/tape/housewrap method takes patience and many steps. There are other ways to air seal including sheet foam, spray foam, fluid-applied membranes and peel-and-stick sheets—all more expensive in material but may come with a savings in labor. What I’ve chosen is simple, readily available, and easy to execute or adapt when future changes are made.
When spring comes around we’ll install a combination of vertical wood and horizontal cement board siding. Siding is the first line of defense against rain, wind, and snow. Any water that sneaks past will hit the housewrap and drain down. If the housewrap is breached, the plywood can take the blow. Each layer deflects water and wind, and does so while staying vapor-permeable. Any moisture that’s absorbed can eventually evaporate. The wall can dry to the exterior when the sun comes out and warms surfaces. Or it can dry to the interior when the indoor air is warmer and drier than the outdoor air (more on this in a later post).
I hope what I’ve described here makes sense to you whether you’re a fellow builder or a homeowner. Please let me know if you have any questions or insights of your own on the fascinating topic of air-sealing!
December 16, 2018: Everyone is welcome to stop by and have a look at Spring Green’s first net-zero super-insulated home. I’ll be there to show you around and explain anything you might be curious about. My POEM HOME is at 770 Westmor Street, one block north of the High School and on the same side of the street.
November 30-December 10, 2018: Framing is underway! The wall panels arrived from a factory up north, along with the roof trusses. A large flatbed truck off-loaded them onto a flat area I had the excavator prepare next to the curb.
My crew, brothers Pat and Jamie Rogers, immediately set to detaching the stacks from their shipping lumber. By noon, the crane arrived from Dodgeville and the first panel became airborne a half hour later. By 3 pm, all but the east wall was set and secured.
Most homes in our area are built on site, stick by stick. The promise of prefab homes has long been held out as “the future of home construction”. I’m not sure why it isn’t more commonplace. In my 32 years as a home designer I’ve only collaborated on two. But I decided it was a good bet for this house.
One reason is that my salesman at Tri-County Building Supply in Spring Green was experienced with it. Jim Barnicle became my partner in reviewing the shop drawings supplied by the factory to make sure they lined up with my blueprints. The idea is to think things through on paper instead of on-the-fly at the job site. I wanted to apply the principals of “advanced framing”—-using as few studs and headers as possible to reduce waste and structural redundancy while also providing more room for insulation. This protocol is promoted by building scientists and “green builders” like me but isn’t well known or well accepted.
Prefab homes—or in my case panelized components—are built in a climate controlled facility and are erected in days, not weeks. The wood isn’t exposed to the weather as long so it stays dryer and straighter. The factory is incentivized to minimize waste, and spares me the work of stacking, saving or dumpstering cutoffs. What’s the downside? The cost and energy to transport and erect the panels. Renting a crane is expensive. This one is $170/hour and it’s not always easy to stage a project for fast action. Sometimes, it idles.
The next day, my crew set the interior wall panels, finished the house shell and got the garage up. We called the crane off for the next day to fiddle around with details but brought it back the following day to set the roof trusses.
My plans call for a “double stud wall” and “raised heel trusses”. The exterior walls are 2×4 studs spaced 24” inches apart (instead of the usual 16”) with a matching 2×4 interior wall to create a 12” deep cavity for insulation. The roof structure is 24” deep, to accommodate up to 22” of insulation. The sheathing is 5/8” 5-ply plywood—a premium choice over the usual 1/2” OSB (oriented strand board). Thicker sheathing is stronger and less likely to bow across the wider spacing. Plywood is better than OSB at taking on and recovering from any water or vapor intrusion and is more airtight.
The idea is to go above and beyond code minimum for long-term energy-efficiency, durability and occupant safety. I specified an aggressive nailing pattern and other structural upgrades, based on the American Plywood Association’s protocol for wind-resistant construction. Their research shows that when homes are carefully constructed, they can withstand—with minimal damage—95% of tornadoes. This comprises EF-0, EF-1, and EF-2 tornadoes. We don’t exactly live in Tornado Alley, but most of us around here remember the EF-2 tornado that tore up homes and a wide swath through our beautiful Governor Dodge State Park in 2014. Here’s a map showing the incidence of EF-2 and stronger tornadoes.
Rough framing has got to be the most glorious stage of new home construction. Plans on paper become three-dimensional forms you can finally walk through and feel. Elevations sketched with nicely proportioned windows finally become picture-perfect views. Here’s sunset from the west bedroom (with pond).
November 5-9, 2018: We got a pretty good foundation pour, but there were a few rough spots. Carpenter Lew Lama used a grinder to smooth out the top of the wall for the sill plate and leveled a few areas with a cement patching compound called Rocktite.
Our next step was to lay down the vapor barrier. I selected Tu-Tuf #4, a sturdy, tear-resistant white polyethylene that handled easily. We sealed seams and penetrations with 3M 8067 tape—an extremely sticky and tenacious product that earned my confidence.
The vapor barrier is to do double duty as an air barrier. We ran the sheet long over the foundation wall, where it was bedded into a bead of Chem-Link M-1, a low VOC sealant. Later, it will be taped to the exterior wall for a continuous barrier against air, moisture and bugs.
We then laid out and cut the sill plates to length. I chose western red cedar instead of the usual pressure-treated southern yellow pine. The building code requires that any wood in contact with masonry (like a concrete wall) be treated with preservatives or be naturally decay-resistant. Cedar is more expensive, but eliminates any concern about inhaling chemical-laden dust, residue on the skin, or leaching into the soil. Pressure treated wood comes with an environmental cost, and disposal is a problem—-the only option is landfill. The cedar I ordered from the lumber yard (from Idaho), was a joy to work with—dry and straight.
So far, the product I’m most excited about using is Conservation Technology’s EPDM gasket we stapled under the sill plate. It’s a super-robust alternative to the thin “sill sealer” (closed cell foam) used almost universally in residential construction to seal the air gap between an uneven foundation and a wily wood plate. It was fast, easy, and effective. We overlapped the ends about 1” at plate seams for a continuous seal. It compressed to 3/16”, providing a capillary break to any moisture rising up through the foundation wall. We secured the sill plates with Tapcon screws—just a few per board to hold the assembly in place for now.
Finally, we were ready for the excitement of big trucks and the smell of wet concrete. Contractor Josh Spurley of JMS Concrete in Spring Green arrived with his crew to pour the garage slab and the next day, the house slab.
The following day they came back to saw control joints. Curing tarps were secured and with great pride and relief, the first POEMHOME is officially out of the ground!
November 2-3, 2018: Crew members Lew & Nino Lama arrived to help me lay foam board on top of the gravel bed. We started with the garage, with one layer of 2” XPS (extruded polystyrene). Of all the common materials used in modern construction, XPS is about the worst for environmental impact. It leaves an ugly trail of pollution from extraction to manufacture to disposal. The only material that could be considered worse is SPF (spray polyurethane foam).
For under-slab insulation, there are few alternatives. I could have bought “Insulfoam type IX” EPS (expanded polystyrene) for about the same price—or Roxul mineral wool for about 4 times the cost. EPS has material properties almost as good as the Owens Corning “Foamular 250” XPS I installed, and acceptable for my application. Most building scientists agree that EPS is more benign than XPS, though side-by-side comparisons are difficult—formulas are proprietary and manufacturing methods vary. Demand from green builders is starting to change the marketplace, and so too is regulation—-Europe is far ahead of us in outlawing HFC’s (hydro fluorocarbons), a “high global warming potential” chemical used to manufacture XPS.
A more tangible environmental impact is how readily cut-offs and scraps can be recycled. While Owens Corning and Insulfoam both claim their product is recyclable, neither company offers a take-back program, and finding a facility within reasonable driving distance has so far eluded me.
My decision to use the XPS finally came down to convenience—it’s stocked by my local lumber yard. I also like that it’s certified by “Green Guard Gold” for low VOC’s (volatile organic compounds—toxic chemicals that pollute indoor air). In my application, the foam won’t be exposed to the interior, but the certification is at least somewhat reassuring. This product also contains a minimum of 20% pre-consumer recycled content.
Insulation under a garage slab isn’t necessary but I think it’s worth the extra cost (in money and environmental impact). If a future homeowner wants to set up shop, the slab will be more comfortable and save on heating. In spring and summer, when warm moist air hits the cooler slab, the insulation will prevent “sweating”—condensation that could cause rust or mold/mildew under and around equipment stored there. We installed one layer of 2” XPS on top of a layer of gravel and taped the joints with 3M 8067 tape—this combination makes a continuous vapor barrier under the slab.
To eliminate any thermal break, we placed one layer (2” XPS) around the slab perimeter and where the future overhead door will meet the slab. To protect this vulnerable edge from damage and UV degradation, I special ordered a galvanized steel channel. The channel installed like a charm and was taped to the foam, with help from friend Marken D’elene. Here’s how that detail looks (NOTE: a future owner will need to insulate the frame wall and build a kneewall from slab to sill plate to complete the thermal envelope):
I knew I wanted a thicker layer of insulation under the house slab—but how much was enough and how much was a waste of money? Code minimum for my foundation configuration is R10, or 2”. To make an informed decision, I used an energy modeling program called REM Design.
I was surprised to learn that creating a “tray” of foam for the slab to sit in was more effective than running sheets of foam down the inside or outside of my stem walls. I also learned that increasing the thickness of the tray edge was far more effective than adding more layers of foam under the slab. The energy model gave me the heat loss for each scenario, and after I figured in material costs, I settled on an R20 edge with R20 under the slab. Here is my detail:
In order to minimize waste—and to avoid having extra sheets lying around the job site getting banged up—I prepared a “sheet foam cut list”. I spent a couple hours in the office with “Sketchup” drawing software, to come up with an optimal arrangement that staggered the upper and lower layers, calculated how many rips of edge foam to make, and showed where scraps could be utilized. I like to think it saved us time on-site and saved on landfill waste.
The first layer of edge foam was placed inside the concrete forms before the walls were poured. This left a 6” wide stem wall—just enough to fasten the sill plate.
It worked really well except where the skid steer continuously drove over the wall, forcing sand between the foam and the concrete. Here’s a picture of that compromised section, which we removed and replaced with a fresh rip of foam:
The mechanical protrusions were challenging to cut around, but a good tight fit was finally accomplished. Gaps in each layer were filled with a Green Guard Gold certified spray foam called “Handi-Foam”.
Each step of the way, I am recording not only how much material we use, but how much waste we generate. According the the University of Wisconsin Extension, construction debris make up 20-25% of Wisconsin landfills. Building an average 1500 square foot home generates 3 tons of waste (let’s assume that’s on-site). A quick internet search finds that a 20 yard, 3 ton dumpster measuring 17’x8’x5′ can be rented for $375. That’s really not a lot of money, so it’s easy to see why it’s more expedient for the average contractor to dump instead of deal with the inevitable waste generated for each task.
POEMHOMES is all about building smaller and smarter, with minimal resource expenditure. A key goal is to take the time to sort and responsibly dispose of waste. The cardboard box the Handi-Foam came in went to recycling. The 4 aerosol cans it dispensed from regrettably went to the landfill. With better planning and more finesse, I could probably cut down to 2 or 3 cans. I’ll continue to try to find a supplier who has more eco-friendly packaging or who offers a “take-back” program. I can also continue to find a better product or a better (still affordable) construction method that eliminates the need for spray foam in the first place.