Building Science Summer Camp

One of the big advantages so far to being part of the Green Building Advisor team is that I finally got invited to Joe Lstiburek's Building Science Summer Camp this year. This is an invitation-only gathering of 200 of the top building scientists in America. Of course I didn't get invited as a scientist but as a member of Peter Yost and Dan Morrison's new Green Building Advisor project, so technically I was there as a "journalist". But the experience was absolutely amazing none-the-less.

Me and Joe Lstiburek at "The Club House"

Summer camp is largely an indulgence-of-curiosity project for Joe. He just looks at the Building Science community and asks himself "who is doing interesting research these days?" and calls them up and offers them a chance to speak about what they are passionate about. The talks can range over a pretty wide area. We had a guy from Johns Manville talk about how the fiberglass insulation of today is different on a micro-structural basis to the fiber glass of five years ago and why that matteres. We had Pierre-Michel Busque talk about water envelope penetrations in Western Canada and various pressure assisted rain screen strategies being used successfully to keep walls dry. And, we had Ron Anderson from the National Renewable Energy Lab talk about the work they are doing in the reconstruction of the tornado ravaged town in Kansas to value engineer advanced energy performance into the new homes that are going up there. He says they have found a way to get to 58% better than code at neutral cost, balancing energy savings against increased mortgage costs, and that with a 40% increase in fuel costs they can get to 90% better than code at neutral cost.

BSC summer camp lecture for 200 from 8:30 am 'til 3:30 pm each day.

After the lectures we all would reconvene at Joe and Betsy's house for feasting and drinking and science discussion and debate until late in the evening. There was a significant contingent of folks from Alaska, where they are really getting hit hard by the global warming problem. As the temperatures rise the pack ice that used to protect the out islands in the polar seas is coming in later in the season so the shores, which are a composite of sand and permafrost, are getting exposed to fall storms that they never experienced before, and the islands are just melting into the sea. I spoke with people who were working on the social and logistical challenge of trying to relocate entire villages of people onto the mainland. While building durable, healthy, "green" and energy efficient housing for these people who have been living a subsistence life on remote islands is enough of a challenge the social implications are very knotty. Many of the elders would just prefer to sink into the sea with the rest of their way of life. The ethical and moral complications are mind boggling and the folks who are working on them are awe inspiring. To bring home the reality of what they are dealing with, they brought along a gift from the community, raw bow fin and beluga whale and seal jerky with seal oil dip. I couldn't bring myself to sample the seal oil, but the raw bow fin was quite good. The rest may be an acquired taste…

Me and Betsy Petit, day three of Summer Camp.

I was welcomed to "the club house" by Betsy Petit a renowned architect and writer/ speaker who shares the place with her husband Joe Lstiburek when it's not being used as summer camp HQ and runs Building Science Corp with him. The house is a 150 year old Massachusetts farm house that they renovated into a very energy efficient building. You can read about the process at Joe calls himself a "Building Science Insultant" and is known for his colorful language and lack of tact. Betsy takes it all in stride.

The summer camp house band has a great band leader, Rick, who keeps all the guitarists, bass players and drummers in the crowd sorted out and makes sure they all get a chance to play their best while rocking the house all night long & reading lyrics from a Blackberry propped up on the piano.

Most of the presentations were really interesting but one by Henry Gifford was particularly earth shattering. Recently the USGBC had published a report from the New Buildings Institute that showed the LEED certified buildings perform 25% better than non-LEED certified "CBECS" buildings. Henry is a building efficiency expert in New York city, and he thought he smelled a rat because he sees these all-glass LEED buildings going up and he, at least, is sure they don't perform that much better than the CBECS average. So he downloaded the data and discovered they were comparing mean data for all age CBECS buildings to median data for new LEED buildings . He made some adjustments so they were comparing mean to mean for equivalent age building and was able to demonstrate that the new CBECS buildings were using 81.6 thousand BTUs/year/sq ft and the LEED buildings were using 105 thousand BTUs/year/sq ft so not only were the new LEED buildings not performing as well as the "normal" comparison buildings but
they were actually performing 30% worse. Of course LEED buildings tend to be very high budget, and high profile buildings with a lot of glass etc. but the point he was making is that the science may be good, but until we go back and test the work we are doing we're not doing building science, we're doing building theory (and getting pretty close to religion if we just take things on faith.) Read Henry Gifford's report!

This was a great set up for Peter Yost to step in and announce that Building Green Inc. publishers of Environmental Building News is forming a Partnership with Taunton Press, publishers of Fine Homebuilding Magazine to form Green Building Advisors and one of their (our) initiatives will be to support third party auditing of existing green certified homes (I'm starting with four of our recent homes as part of the first wave of the study). It's an exciting project to see how the theory really works out over time as compared with other excellent builders across the country, if a little intimidating.

Not to be out done, Sam Rashkin from Energy Star got up to announce the latest "version three" release from Energy Star and their newest "Advanced New Home Construction" program. The version three builds on the 2006 enhancement of the Energy Star standard to add new ventilation, humidity control, water management, thermal bridging, HVAC installation testing, radiant barriers, and overall size limitations. Sam is a guy who likes to knock at bee hives with a stick and his announcement that energy star for homes was going to get a whole lot harder and that homes with more than 1,200 sf per occupant were going to be disqualified from the program in version three set the whole room to buzzing.

He went on to show what would be required to meet the Advanced New Home Construction standard; 50% better than code, triple glazed windows, super HVAC, and no more than 1,000 sq ft per occupant and even I was thinking this will work at $10/gallon maybe but America's not ready to go there yet. Saying "no more Hummer Houses" is one thing but this feels like he's taking Energy Star away from the market. It's a very interesting time to be part of the green building movement.

Recently I spoke with one of my more eccentric Yankee cousins, Appy Chandler, who mentioned that I really needed to go visit my cousin Bob Ferris, who was also an environmentalist and a green building proponent. He was sure I must remember him, he's the guy who used to train trumpeter swans to migrate by getting them to follow behind him in an ultra light aircraft and restored wolves to Yellowstone Park. I had no idea who he was talking about but agreed that I needed to meet him. Appy said that now he's the director of a place called Yestermorrow Design-Build School up in Warren, Vermont. This is a place I had been hearing about and been fascinated by for the almost 30 years that it's been gathering the most outrageous architects and building system innovators and teaching people about many different ways to build homes. Appy put us in touch with each other.

Bob Ferris next to a cob built bread oven with the Yestermorrow lower campus behind him.

Of course Bob is an open and friendly person and he immediately invited me and Beth to come up to visit with him and his wife, Carlene Ramus, who is a green architect and landscape designer. Beth had another obligation so I made the trip solo.

Carlene Ramus enjoying the view from a cob structure under construction on the Yestermorrow campus.

The view of the main studio building from the "upper campus".

The Yestermorrow campus is on 35 acres of heart-stoppingly beautiful land that used to be a tennis camp in the Mad River Valley in Warren, Vermont. The "lower campus" is the old camp building which has the dormitory, cafeteria, woodworking shop, design studio, and library. The "upper campus" is a hillside with a creek, tent sites, and many experimental buildings that have been constructed over the years by the students. Not all of these experiments were successful and not all of the buildings have been maintained, but walking through the woods is an educational and inspirational experience.

The gate to the upper campus. Cob walls and green roof.

One of the first things we saw after our tour of the main building was the gate to the upper campus. One of the interns had hand-knotted a hammock and hung it in the gate to make a cool and relaxing space along the, now diverted, path from the hills to the main campus. Bob explained that this was an early example of straw bale construction and had been built with a plaster that was too rich in cement and wouldn't allow for natural breathing of the straw bales. The bales had as a result gotten moldy inside and the cement has cracked. Newer stucco formulations are breathable and self-healing. Living proof that this stuff is harder to get right than it looks and that it's worth learning from people who have been doing it for a while.

Just around the corner from the gate to the upper campus is another essential structure that provides comic "relief". The path approaches from the side and my first view was from so close that I didn't get the joke until I got home and looked at the photo. The zipper is the door knob to this open air privy. Perhaps next year they'll build a roof with a giant belt buckle. Designed and executed by an intern with no review from the staff. There is a culture of trust and empowerment here that is pretty amazing.

The pine cabin, built by the women's construction class.

Empowerment seems to be a theme here. One of the more popular focuses is a women-only construction curriculum and Bob is especially eager to point out all the amazing projects built by women-only construction teams. Many of these folks are here gaining the knowledge to go back and build, re-model or GC their own homes. They are motivated to learn and come away ready to make the sawdust fly.

A half timbered cabin built by one of the pro classes.

Professional builders and designers also have a place here. This half timbered cabin was built by a group of skilled woodworkers who came here for an advanced class on timber framing and cob construction. It has a wood stove and a sleeping loft and is a very sweet miniature of a home hidden up here on the hillside. (I'm looking at the terrain and thinking about all the work just to get these materials to the site.)

A wheel chair accessible tree house.

Another pro class conceived and built this wheelchair accessible tree house. Yestermorrow is a great place for architects and designers to come as an antidote to the grueling reality of a traditional architecture practice or for young architects to use as a transition from the theory of design school to the reality of nails and bricks.

From the inside of the tree house, the split knee arch and the structural yurt cable, things you might not have covered at architecture school.

"Let yourself be silently drawn by the stronger pull of what you really love" Rumi

This is a place where it is truly okay to build just because it's the only thing you really feel capable of doing. It celebrates the joy of getting dirty in the pursuit of something beautiful that will give graceful shelter.

It's alive! A current natural building class project incorporates recycled grain bags filled with dirt and tied together with barbed wire for a foundation and cob walls with an innovative roof structure and a high tech roof membrane.

In recent years Yestermorrow has become well known for their "natural building" curriculum. With the new realities of global warming and the energy crises it hopes to reach out to the green building community and expand the curriculum to address the educational needs of green and high performance builders and designers. It has the potential to be a meeting ground for many different building approaches. As I was leaving I ran into Robert Riversong, one of the faculty, whom I have had lively debate with on Fine Homebuilding's on-line construction forum. He and I have fundamental disagreements about construction and business best practices. We shook hands and I introduced myself and we smiled and enjoyed each others company for a little while in the afternoon sunlight. In the end we agreed that, while we may differ in approaches to the details, we are both passionately committed to seeing better homes evolve to meet the new world. Even Martha Stewart would agree "it's a good thing."

Have a low-carbon summer feast

Summertime is all about getting together with friends and enjoying good food and drink in the great outdoors. The choices we make can reduce our impact on that outdoors and global warming without getting in the way of our enjoyment of the event.

We’ll start with the beverages since that’s where the guests (and hosts) will likely start. I was interested in finding out what was the most environmentally benign beverage and called my local recycling coordinator who wasted no time in telling me that tap water was my best choice. So I refined my query, I had heard that recycling 30 beer cans saved the equivalent of a gallon of gas - how many beer bottles, I wondered, would be equivalent to 30 beer cans. He did some research and we ran the numbers and it turns out that 385 beer bottles has the equivalent embodied energy of 30 beer cans. He pointed out that there was some minimal adjustment needed to account for the transportation cost of imported beer so this calculation was most accurate if applied to domestic beer in both bottles and cans. Ah-ha! I said, this gives me an environmental rationalization for buying that nice local microbrew! Maybe even to buy it in kegs and keep a kegerator in the garage! Actually he replied, the kegorator idea is a no go due to the carbon footprint of the refrigerator (regardless of the impact of the increased beer consumption) However, if you consider that there are 22 shots of bourbon in a bottle that likely has the embodied energy content of two beer bottles this gives you an environmental justification for drinking bourbon on the rocks or mint juleps. If a single beer can equals 12.83 beer bottles it is equivalent to six bottles of bourbon in terms of its carbon footprint. As a dedicated environmentalist I found his logic irrefutable.

But what about the kids? We needed to get them off the cans and plastic bottles that impart bisphenol-A into soft drinks, but “let them drink tap water” was not going to fly. We decided we’d have less of an insurrection if we made up a sun tea and fruit juice concoction. (And the cost works out to our advantage as well.)

The main course? Certainly not pork barbeque, though as a North Carolina boy I run the risk of getting my tires shot out for saying so, I’ve seen first hand the environmental cost of factory pork farming and one of the major precepts of sustainable cuisine is to eat less meat and more local vegetables. Lamb, even that shipped from New Zealand, has a low embodied energy content in comparison to grain fed pork and beef. Of the factory farmed meats, chicken has the lowest carbon footprint overall considering both embodied energy content and methane production. We can make points on both carbon footprint and embodied energy content by preparing meat and vegetable shish kabobs on the grill with range fed lamb tips or chicken thighs and local farmers market vegetables and Yukon gold potatoes. In general our goal is to reduce meat portions to less than ¼ lb per person by filling in the plate with delicious local vegetables and starches.

For the sides we’ll keep the theme going and instead of hitting the local grocery for tubs of coleslaw and potato salad we’ll sauté up some summer squash and onions and make up a great green salad with ingredients from the farmers market.

As for dessert I’d say the best thing to do is ask the kids what they want and make it happen. It is summer after all.

The Menu

Canned BeerMint Juleps or Bourbon on the rocks
Canned Soft drinksIced sun-tea sweetened with fruit juice
Shrimp cocktailSalted nuts, cheese and toast, carrot sticks
Barbequed pork sandwichesLamb or chicken shish kabobs with local vegetables and quartered Yukon gold potatoes
Cole slaw and potato SaladFresh local salad with vinaigrette dressing

Dessert, whatever the kids want!

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Digital Take-Off

One of the biggest advantages of working with a design-build company such as Chandler Design-Build is that we have a track record of building our own designs and we have a data base of the cost breakdown on the houses we've built in the last eight years. So when clients ask us what something is going to cost we have comparable data somewhere in our system that can give us a good idea of what it's going to be. The issue is generally just the effort of measuring up and inputting the data and assumptions on ever-changing 1/8" scale pencil drawings we are working with in the preliminary stage of the process.

In the past that meant poring over the drawings with a scale and making guesses as best we could. While there is still a lot of "educated wild ass guessing" involved, we have recently added a tool to our system that improves both speed and accuracy.

It's called "Digital Take-Off" and it's one part of a design and construction management system from Digital Canal Corp. In many ways it's similar but superior to an older piece of software called "PlanSwift" that other builders may be familiar with.

The screen shot above shows what the interface looks like. I've just imported a digital photograph I've taken of a plan Beth is working on. It's drawn on a piece of thin trace (you can see the drawing below it on the table bleeding through) with no dimensions or indications of finishes or construction; it's got loads of offsets and 45 degree angles. To bring it into the computer I just lay it on the table and shoot a photo of it and drop the image into the client's folder in our computer.

The next thing I do is take a distance that I know on the plan, in this case the width of the living room and, to "set the scale," I drag my mouse across the distance I know. It asks me to type in the known distance, 22 ft. here, and the scale is set for the entire drawing.

I've set the tabs on my software to correspond to the questions my estimating worksheet asks me; Heated SF down, up, ext wall perimeter, interior wall cumulative length, number of windows and such. Pulling to the "Heated space down" tab, I drag my mouse around the perimeter of the building.

Once I have the shape I want I click the plus sign and I get an accounting of the area, (too big, we're trying to keep it under 3,000 sf) perimeter and other information that I can either cut and paste into my estimating software or export to Digital Canal's estimating package, Bid Builder, which is part of their software suite.

As I click through the tabs they prompt me to remember to measure, count, and export all the different elements I'll need to prepare a preliminary estimate for the house.

When counting items such as windows or fixtures it leaves a mark so you will know if you've left anything out or counted anything twice. Right clicking allows you to undo the last few points you've selected. It has a roof pitch converter so when you want to figure out how many roof shingles to order you can enter the pitch of the roof and it will tell you (you still need to add for ridges and valleys) Once the house is under construction the software will help with lumber and flooring take-offs and even figure rafter lengths and counts for you.

I bought Digital Take-Off at a special price the last day of the international builders show and they immediately assigned me a sales rep who has since sold me on "special deals" for their CAD software, Solid Builder, and the estimating component, Bid Builder. I'm not sure what the regular price on any of these items is since they are always doing specials. If this is something that would help with your building projects call Monty Alexander at 800-449-5033 ext 139, tell him I sent you. I have their CAD software which I got to replace Chief Architect and have started experimenting with it and will post about that here soon. He also made me an offer I couldn't refuse (thanks Monty) on Bid Builder so I'll be diving into that sometime soon as well.

Table Framing

I've been building custom homes for over 30 years, and I've framed more than my share with a crew, swinging a hammer myself back before we had these new fangled nail guns. Along the way I've grown somewhat particular about how I like things done and I've worked off and on with the few framing crews who could wrap their brains around what has come to be known as Advanced Energy Framing advocated by Joe Lstiburek (pronounced Stee-brick). As I've gotten increasingly involved in the green building movement I've searched ever more vigorously for a better way to build homes especially when it comes to keeping the framing dry and reducing lumber waste and impact on the landscape at the building site. Here's why I've settled on Table Framing as a solution that fits my business.

There are a number of new wall alternatives on the market these days. I like the thermal performance of Structurally Insulated Panels (SIPs) but worry about their performance in a hurricane and I like the simplicity of being able to fill my walls with pipes and wires at will and add the insulation later. Insulated Concrete Forms (ICFs) are a really fabulous innovation and I'll probably continue to use them extensively for high performance foundations and for all our radiant slab applications but I do worry about the embodied energy content and cost of the concrete and steel and I'm, again, not thrilled about the need to remove the insulation (and concrete in some cases) to install pipes and wires. Aerated Autoclaved Concrete (Hebel) block is a fascinating material but many people have expressed concerns about it's permeability to water vapor and its lack of compressive strength. I look at the flashing systems used to install windows in AAC and have serious concerns about moisture intrusion. I'm personally appalled that anyone can seriously advocate steel framing as a green building system when we have so many better uses for recycled steel and wood is such a renewable and low embodied energy content resource.

So I keep coming back to wood Advanced Energy Framing, its economical cost, renewable source material, ease of access for wiring and plumbing and most importantly the ability to wrap the house with a durable and repairable water repellant membrane to manage moisture intrusion. I think it is the best of a number of imperfect alternatives. But I've been frustrated by the slowness of the site building process and the willfulness of framing crews who revert to the old "more wood must be better" way of building and end up wasting materials and time.

Table framing the walls off site minimizes lumber waste (computerized cut lists optimize lumber utilization and what little waste is produced at the plant is converted to wood I-joists and used in the next house) Building the walls indoors on a special table made for the purpose means all the walls are square and tight. Floor plates are marked by a computer pulling information directly from the blueprints, minimizing errors. Nail patterns are better managed and generally exceed code specs. When we ask for 3 nails in a 2x6 we generally get four. Code asks that plywood sheathing be nailed 4" oc at the edge and 8"oc in the field, we generally get 3" and 6" and the nails are placed by a computer driven auto-nailer. It's not dependant on the attitude and conscientiousness of the worker in the field.

But the biggest advantage I see is that I can build homes in densely wooded sites without needing to stockpile and protect large stacks of lumber on the job and without needing to manage all the piles of cut off lumber ends so my sites stay cleaner and safer and the jobs get a huge boost of speed with roofs going on faster and the interiors of the homes therefore being subject to much less weather damage.

I participate in third party green building certification through the NAHB and that system awards me points for lumber optimization and scrap reduction and for not beating up the jobsite environment. Take a look at the following images and you'll see what I mean about the speed and quality of construction. These images were taken between Thursday 3-13-08 and Wednesday 3-19-08. Six days from subfloor to tarpaper on the roof. By working off site we can schedule the walls to be built while the floor is being installed and have the roof trusses built and ready to go up as fast as the wall panels can be tilted up and made ready. We cut weeks off the build time and improve quality at no additional cost.

Table framing is not any less expensive than on site framing and it's not possible for every house but the improvement in quality and speed and reduction in lumber waste make it a better value from my perspective whenever we can make it work.

3-13-08 8:53 am. Thursday Morning, Builders First Source drops off the wall panels at the job

Table framed walls arrive on the truck. Nail spacing exceeds code. Cuts are amazingly straight and square.

8-13-08 4:22 pm. Thursday afternoon. All exterior walls up and braced and ready for interior wall delivery

3-14-08 9:43 am. Interior walls delivered and set, walls straightened and ready for roof trusses

3-14-08 1:14 pm Friday afternoon. Roof trusses delivered and begun to be set. The small scrap pile in the foreground is the total of floor and wall framing scrap.

10-18-08 10:48 am. Tuesday morning. Roof framing and sub-fascia installed and roof sheathing underway.

3-19-08 3:52 pm. Wednesday afternoon. Roof largely dried in and specialty hip framing getting wrapped up


After the I-joists were hung from the mudsill and inspected we got to try working with a material that we've been hearing about for a long time but until now had not had an opportunity to try. Warmboard is a subflooring material that is 1 1/8" thick and has grooves for 1/2" PEX tubing routed into it in different patterns corresponding to different ways you might wish to lay out PEX to heat a floor. In terms of raw cost per sq. ft. it cannot compete with a radiant slab but it has some interesting properties that make it far superior to all other staple up radiant options and in some jobs superior to radiant slab a well. This was one of those projects where it really did make sense.

This project will have 2,300 square feet of heated space so we needed 83 four by eight panels which, including shipping, cost $17,325.04 delivered to the site. By comparison 83 pieces of advantech sub flooring with staple up tubing would have cost us much less but would not have given us the advantage of being able to use oak flooring with antique rugs and still heat the house with our choice of solar, wood, or propane derived BTUs.

If we had used regular plywood under the oak and stapled up ½" pipe underneath we would have had much slower heat transfer to the home than the tight contact aluminum sheet we get with the Warmboard. To compensate for this we would have had to kick the heat in the pipes up to 140 degrees which would have meant that the "cooled" water returning to the heat exchanger from the floor would still be at 120 degrees. This return temp is too warm to effectively heat with solar and even presents efficiency issues with a Rinnai demand water heater (it's harder to heat water that is already hot). We expect the cooled water returning from the Warmboard to be barely warmer than room temp which makes it ideal for use with solar panels and optimizes efficiency with the wood fired boiler and Rinnai demand water heater that will be our back-up energy sources after the solar.

The Warmboard folks provided right and left turn full and half sheets, straights, fillers, and an elaborate schematic showing exactly how each board fit in the scheme. When we were finished we had used every piece and had one straight and one filler left over. If we had come up short it would have been a week or more back order from their distribution facility in so I was pretty content to have a couple sheets left over even if they did cost about $207 each. It took us a day and a half to install all the sheets and another half day to rout out all the special grooves.

The next project was to install the pipe and again the Warmboard folks had provided a lay-out and calculated the length of each run and identified the locations of the manifolds. We used 3,000 feet of pipe for this project which added $840.00 to the cost of the system. We glued the pipe into the grooves with silicone to keep it from making noise as the warmth hits the system and rolled it in with a lawn roller as we set it out. This took a little over a day with all the constant vigilance to keep the grooves clear of dust and debris.

Backing $10,000 worth of Warmboard into the job site.

Warmboard cuts just like regular plywood but throws up aluminum chips that you really don't want to get in your eyes so safety glasses and a cap are not optional.

The folks at Warmboard provide an installation plan and, at $207.00 a sheet, you can't afford to make any mistakes. We had to pull up one sheet at the outset and decided to assign one person to be in charge of the plan. At the end of the job we had two sheets left over...

The stuff goes down like regular ply except that it weighs over 100 lbs per sheet. I thought it was smart that they marked the pipe locations on the underside of the sheets so if we need to cut or drill in it after the finish floor is down we have at least a chance of missing the pipes.

Toilets and other items that would necessitate re-location of pipe are located and grooves get routed in ahead of time to allow the pipe to dodge the hazard.

Additional grooves get added to link floor sections and accommodate for all the bays in this design.

We made a spool out of left over plywood and 2" electrical conduit to allow the 1000 foot coils of PEX to roll out evenly from between a couple of ladders. Vacuuming out the grooves was critical and tedious.

A very thin bead of silicone is laid into the grooves and a lawn roller filled with water embeds the pipe into it very quickly. On the tight turns we screwed nail plates down over the pipe to keep it from popping up. The manifolds will be in walls 36" above the floor to allow air bubbles to accumulate and be expelled from the system through air vents.

The final project was to pull all the manifold tails back under the floor and pressurize all the pipe to 100 psf before the walls went up. Since the walls were table-framed off site there was little assembly done on the deck and the walls were up in a day and a half so wear and tear on the pipe was minimized.


Warmboard is generally installed with PEX-AL-PEX tubing, a type of tubing that was originally developed to provide an oxygen diffusion barrier so radiant heat installations could be used with old-fashioned cast iron boilers and pumps. This tubing combines a thin, flexible aluminum core with an inner liner of PEX and an outer wear layer of PEX and a waxy lubricant. It has doesn't have the annoying "memory" that PEX has which makes that product want to spring back into the roll shape it came in. You can shape it to any shape you like and it will pretty much hold that shape. It also has a far lesser coefficient of expansion than pure PEX does which makes it less likely to wiggle and squeak when a slug of hot water hits it in a radiant floor application.

But PEX-AL-PEX gets stiff in cold weather and doesn't feed easily through holes and over obstructions. And it's significantly more expensive than plain PEX. (For this project it would have been $1,400 more.) PEX-AL-PEX pipe uses proprietary sleeve and ring fittings and any scrap shorter than 200 feet generally ends up in the landfill as we don't use this type of pipe in potable water supply piping. PEX pipe is the same pipe we use with potable water installations so it uses the same crimp fittings we already have and 100% the scrap pipe can be immediately recycled into the same house.

When plain PEX is installed in a radiant floor application such as Warmboard it must be continuously embedded in a 1/16" to 3/16" bead of 100% silicone caulk in order to bond it to the aluminum to prevent it from slipping and "popping". The pipe is pressed into the silicone with a heavy weighted roller so that it displaces the air between it and the aluminum which enhances heat transfer. This process has the potential to be messy and prone to operator error in that too much silicone will keep the pipe from sinking below the surface of the board and too little can lead to a noisy floor. Still, it really is no more difficult or time consuming that wrestling with the stiffer pipe and I chose to use this system based on the enhanced contact between the pipe and the aluminum combined with the cost savings and my prejudice against the stiffness and proprietary fittings of the PEX-AL-PEX.

We'll install the Rinnai water heater and the flat plate heat exchanger and get the system up and running to dry out the Warmboard before we start installing the hardwood and tile flooring. At this point we have the system pumped up to 100 lbs so we can rest assured that there is no hidden damage to the pipes.

Get the details from the Warmboard installation manual for PEX tubing.

Inset I-Joist Installation

This house is being built to accommodate aging-in-place design principles so one issue we wanted to achieve was a step free access from an entry that was to be a slab on grade patio.

Our solution was to hang the floor framing inside the ICF foundation using top bearing joist hangers.

The engineering team at PolySteel specified that we had to remove the foam from the top 8" of the area under the joist hangers to provide good support for the 2x10 mudsill.

We tacked 12" galvanized flashing to the bottoms of the treated mudsills and then tacked sill seal gaskets to that so there would be an air tight fit between the flashing and the top of the PolySteel. The top sill is strapped down every four feet with hurricane straps and the I-joists are isolated from the foam and concrete with galvanized steel patches to help keep termites from tunneling into them. (This is in addition to a low toxicity soil treatment and borate based insecticide mixed into the foam at the PolySteel factory.)

We ordered all the Joists precut to within about eight inches of their final length. The scrap would have fit into a single trash can.

With all the pieces precut at the supply house the floor was framed and ready for inspection in a day and a half. It fits into the concrete foundation like a cork in a bottle.


We’re getting started on the Rockwell Residence which will be our entry in this spring’s Green Home tour. It’s pretty extreme green for us, so I’ll be writing about the progress as it goes forward. We’ll be using Insulated Concrete Forms from Triangle PolySteel to do the sealed crawl space walls. There will be a unique dropped I-joist floor system to help the building sit low on the site and make the front door handicap accessible. The walls will be panelized and the roof will be a Cantilever Truss System so the exterior soffits will be the same elevation as the interior ceiling to help let in more light. The Sub-flooring will be WarmBoard heated by a combination of the solar hot water, an outdoor water furnace, and a Rinnai demand water heater.

Chapter one The PolySteel Sealed crawl…

The forms come off the truck.

The forms are so light we were able to carry them down the dirt driveway by hand.

Soil conditions were some of the worst I've seen. Giant granite boulders and soft black muck. The footings were engineered by by a soils engineer with extra concrete and steel. We built forms to get above the stone and mush and lined them with black poly as a capillary break to help keep moisture from wicking up into the concrete and into the crawlspace.

Once the footings are poured we laid out the shape of the foundation on the concrete with string and glued the first layer of forms to the concrete with spray foam. Brennen went around with a hammer drill and a 24" long concrete bit and set all the ½" by 18" steel pins to lock the concrete to the footings.

Steel in the forms.

Once we had the forms stacked up to finished height we tied in the rebar for the top course bond beam and the bent up the vertical steel and tied it all together.

Once the forms are set and loaded with steel we attach 2x10 bracing to the forms with long screws into the steel embedded in the foam. Then we braced down to grade and aligned the forms to the lay-out.

The day of the pour we were racing to beat an impending thunderstorm, the storm won but we were able to pour in the rain because we were pouring on top of concrete. Still it was cold and wet and concrete went everywhere. Here Bradley Yoder, our coach from Triangle Polysteel, shows us how it's done.

As the pour went on the rain subsided. We vibrated the concrete down into the forms and shoveled more and more into the top to keep them full. It was good to have a big crowd, and a special pleasure to have the home owner, Paul Rockwell, lend a hand in the big push.

Here Paul is running the hose from the concrete pump while Matt and Brennen vibrate the concrete down into the forms.

The next day, strippjng the braces and getting set up for the I-joist floor framing.


Chandler Design-Build Creative Construction

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