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.
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.
PEX or PEX-AL-PEX?
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.
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.
At the press conference at the International Builders Show the press kept on challenging the NAHB spokesmen about the differences between LEED for homes (known as LEED-h) and the new NAHB National Green Building Program (NAHBgreen). The responses centered on the word “mandate” but the definition of that seemed to float between referring to governmental mandates that all construction be “green” and issues with the number of mandatory items required for a home to pass LEED-h minimum standards. The alleged cost of these programs was also a source of great confusion and rancor. During and after the conference I kept reflecting on how wrong headed all the tension between LEED-h and NAHBgreen is and how it distracts us and keeps us from getting our message out which is all about transforming the market and the way people build and buy homes and the decisions we all make about remodeling and maintaining the homes we have.
Let’s get one thing very straight here. LEED and NAHB are on the same side. We are both focused on helping the market shift to recognize energy efficient and resource efficient building systems that result in well maintained houses that are healthier to live in than the status quo and use fewer materials to build and less fuel and water to live in and last longer.
There are significant differences between the two programs. LEED-h is focused on serving the “Top 25% of the Most Environmentally Conscious Builders in America”. It is a green building program for high end, high performance homes and, as such, its requirements are very rigorous and the standard of proof in terms of third party verification is very stringent and therefore more expensive. The “NAHB National Green Building Program” is aimed at every builder in America not just the top 25% of the greenest builders in America. Its standards of proof are designed to make the program meaningful and verifiable but not onerous to participate in from the builder’s or the verifier’s perspective. A pre-construction plan review, two site visits and a paper trail showing receipts and photographs of systems implementation are all that are required. Third party oversight and “consulting” are minimized. The system is designed to make it easy and inexpensive for builders to step up to green building best practices. In that builders are going to be using the Green Certificate as a marketing tool when they sell their products, the documentation has to be stringent enough to stand up in court if the builder is accused of “green-washing” by cheating on the certification.
I have been having all my homes scored to both LEED-h and NAHBgreen as well as to the North Carolina version of the NAHBgreen system that our state has modified to fit our particular climate and humidity and water conservation challenges. But I’m an NAHBgreen builder because I want to be part of improving the way America builds homes and I believe that NAHBgreen has a better chance of creating a market shift than LEED-h does.
If we want to make a difference we need to be able to build green homes for school teachers and factory workers and cops and the real life beer drinking folks who make this country work. Not just for the movie stars and Prius driving, granola crunching, chardonnay sipping, crème de la crème.
Ed Begley and Brad Pitt need homes too and I’m thrilled to think that they are building structures that push the envelope for zero carbon footprint LEED-h platinum excellence. But I spent some time talking with LEED-h builder Steve Glenn in Los Angeles the other day about how much it costs him to build one of these super-green homes and he’s looking at $400 per square foot for construction (not including land costs.) His cost for LEED-h certification is $5,000 - just for the report card! Maybe people in LA can afford that but I would have a pretty hard time selling it in Carrboro, North Carolina. My cost for LEED-h certification is only $3,000 here in NC for the same report card that Steve pays $5,000 for in LA but the NAHBgreen report card is $150 here and across the country.
If we care about making green building affordable and accessible then we are going to need a program that has an affordable level of entry and is accessible to the average builder. NAHBgreen is that program. But that doesn’t make us the enemy of LEED-h. They provide a very challenging program with a stringent verification; NAHB provides a very welcoming program with a lot of peer support and encouragement for new builders taking the first steps towards Energy Star and Green certification. The market is big enough for both programs and it’s going to take both to move our country away from the crises of out-of-control consumption we are in.
Builders and developers worry about government mandates and their concern is justified. Our local Orange County NC County Commissioners have made it clear that they want every home and building built here to be Energy Star and Green Certified in two years. The local Home Builders Association has made it clear that we will not buy in unless our National Green Building Standard is one of the definitions of green that are accepted by the county. Imagine if they adopted the LEED-h standard instead, and only the top 25% of the most environmentally conscious builders in America were allowed to build here. A move such as that would have a devastating effect on affordable housing in our county.
When I talk to builders about LEED vrs NAHBgreen, I find it is useful to compare it to a religion. In all too many ways it is an apt analogy. The LEED-h providers are like the high priests and priestesses of green, up in the fancy stone church on the rich side of town. The NAHB crew are the folks in the revival tent down by the river. You don’t need to take a bath and put on nice clothes to come to our church. But we’re both preaching from the same gospel. “Listen up Builders and Architects of America, there’s a better way to build homes that doesn’t cost much more but saves energy and water, and lasts longer, and makes for much less warrantee expense, and it’s a better way to do business, and it’s easy to get involved.”
The enemy is not the high priest mumbling in Latin up on the hill. The enemy is those who are still building inefficient, drafty and leaky, minimum standard homes that waste energy and water and cost more to maintain and will have a shorter life span than homes built with existing green building systems. But the goal of our program is not to attack those builders either, just to bring them into our tent and show them how easy it is to join our congregation.
Here are a few more of the best of the gleanings form my time on the floor
Beth and I love the designers at MTI so I made a special point of seeing what they are up to.
There are a lot of people designing tubs and showers and Kohler generally snaps up the top designers yet here is this little company coming out year after year with cutting edge brilliant stuff at a great price point. Their free-standing Osiris bath tubs (with the wide flat lip for wine glasses and paperback novels) have become almost standard equipment in our master bathrooms, a huge amount of luxury at an amazingly low price (considering what it would cost with a different label) and they nailed it
again, on several products!
Clearly the sexiest bathtub I’ve ever seen is their new Elise tub made from some solid surface material that resembles Corian, a luscious matte finish totally unlike any acrylic whirlpool tub. Pretty expensive in comparison to the Acrylic tubs but just gorgeous and they come with several matching vanity sink options.
But they still do the whirlpool tubs like the Osiris but made them better 
by adding electric radiant heaters behind the shoulders. This is a thin, low-voltage heater that they embed in the tub before they put the gel coat on. Lean back and the area behind your back both above and below the water line is warm like a hot rock on a sunny riverbank. They did the same for the seat (and even floors) in their new line of showers so when you sit down to shave your legs you don’t have a clammy plastic seating experience. And even they make the matching heavy frameless glass shower enclosures to save
another trade from having to measure and fit.
They’ve also addressed the issue of germs growing in the plumbing of a whirlpool with new technology and come up with a big challenge to Jacuzzi’s lock on the shower floor market with their new teak wood shower receiver. It is an acrylic shower floor that pairs easily with tile or glass wall treatments but has a teak duckboard floor that covers up the
acrylic floor creating the appeal of a casual wood floor with the leak resistance and low maintenance of an acrylic floor. I haven’t seen the documentation but I think it’s safe to assume that when a company sweats the details as much as these guys do the teak is likely to be FSC certified sustainably harvested.
Finally, a very pedestrian product that solves a very common problem.
We do a lot of stucco applications on chimneys and ICF walls and veneer stone applications that all require galvanized wire mesh to attach the stucco or thin set to the substrate. This stuff is very unpleasant to work with and can lead to moisture migration into the wall. Spider lath is a plastic stucco lathe with rubber gaskets that you nail through to attach it to the wall so you will not have leaks through the fastener penetration and it comes in a 4’ x 20 foot light weight roll that is very easy to work with and corrosion proof. It solves a difficult problem in a very elegant way.
The classes at the IBS were great but having been to a few shows already I knew who the really good teachers were and I spent a lot more time on the show room floor than I have in times past. I skipped all the silly games, although the value of all the prizes given away was said to be in excess of a million dollars and the attendance was down 10% to only 192,000 so the odds would have been fairly good. I should have brought my mother-in-law who would have made a full time job of entering all the contests and would have undoubtedly come home with some really great stuff. But I was solo other than hanging out with Dan Morrison and all the good folks from Fine Homebuilding and Environmental Building News so here are the best of the gleanings form my time on the floor.
I've been a Bose fan for years and these may not have been quite as crisp as that but I would definitely put them in my own house.
Many of my clients already have a serious investment in home audio and video components and a collection of music on PC and MP3 players and just want to find an affordable way to integrate the many parts into a unified system. The Hi Fi by Hai (sorry about that name fellas) is a system that connects all the various stuff you already own into a central system while allowing you to leave them distributed all around the house. The tuner in the living room can feed the news to the speakers in the kitchen in the morning, the computer in the office can now feed tunes to the kitchen in the afternoon and the game on the TV can feed audio to the kitchen in the evening. It's a great idea. As with all this electronic stuff I want to see it work in real life before I completely but in but this does look like a great solution to a persistent problem. Plus the system uses the energy efficient Class D amplifiers that use much less power and virtually no power on standby. This is NOT and audiophile solution like the Bose home audio but works with the audiophile equipment you already own to project good quality sound throughout your home.
The classes at the IBS have been extraordinary this time. Wednesday afternoon I went to a panel discussion featuring Peter Pfeiffer, one of my favorite architects from Austin Texas, speaking on “Real, Relevant, and Do-able Green Building Techniques.” I got to ask some questions that have been bugging me about the efficacy of radiant barriers and air gaps in spray foamed roofs and walls. (Peter is in favor of them in roofs but not so much in walls.) There still seems to be not enough hard information about the opacity of spray foam to radiant heat.
The next day started out with a long talk from Bill McDonough on the evolution of “Cradle to Cradle Analysis” and ended with a panel discussion Entitled “Greenwash or Green Integrity” featuring Ron Jones who is a great green motivational speaker and a person I have gained a lot of respect for through his role as chair of the NAHB-ICC National Green Building Standards. He’s sort of the Barak Obama of Green. He manages to find a way to state what we all know in our hearts to be true in a way that makes us feel encouraged about ourselves and the green building movement. He puts ideas together in a way that builds consensus and enthusiasm and that’s worth a lot right there.
The next morning found me in a class lead by Scott Sedum on business management and reducing the wasted effort in the building process that was really provocative and beneficial. He’s a great presenter and a very organized individual. He sent everybody home with a CD of his writings and ways to improve their businesses. If I incorporate even one of the good ideas gleaned from that class, my business will be better as a result.
I spent a good part of that day roaming the IBS floor picking up new product information especially in the low-rent “South Pavilion” where all the new businesses had their booths. But at 3:30 in the afternoon my long time Building Science hero Joe Lstiburek was presenting on “Managing Moisture in Residential Building Envelopes" and I finally got to meet the man himself. In the early 1980’s I happened to come across an article Joe had written that showed the results of thermal imaging they were doing as part of the Canadian R-2000 program and first came across the term “Building Science” and knew what my life’s work would be. I have followed Joe's writing and his website www.BuildingScience.com ever since and his research has deeply influenced the way I build houses.
Of course I had a lot of questions to ask about rain screens and sealed crawlspaces and radiant heat penetration of spray foam in roof applications and eventually he said “I’ll answer any questions you want, but it will have to be over a cold beer at the bar at the Peabody Hotel, and I’m buying.” So we went to the hotel and drank beer and talked about building science and he answered all my questions, and raised more of course. I was too shy to ask for someone to take a picture of me with my hero but here he is during the question and answer period. The look of concentration on the faces in the audience gives you a sense of how respected his thoughts are among builders.
