Foam Forms Create an Energy-Efficient Concrete House
General Specs and Team
Location: Salisbury, NH
Living Space : 2600 sqf
Cost (USD/sq. ft.): $80/sqf
Design: Rouleen Williams, Al Rossetto, and Online Design
Construction consultant: Al Rossetto
Framing contractor: D&D Construction
Sub-slab insulation: 2.5-in. EPSExpanded polystyrene. Type of rigid foam insulation that, unlike extruded polystyrene (XPS), does not contain ozone-depleting HCFCs. EPS frequently has a high recycled content. Its vapor permeability is higher and its R-value lower than XPS insulation. EPS insulation is classified by type: Type I is lowest in density and strength and Type X is highest. (R-10)
Wall construction: R-24 Logix ICFs (total wall thickness 11 3/4 in. downstairs, 9 1/2 in. upstairs); great room gable is stick-framed with 2x4s filled with cavity insulation plus a continuous interior layer of 1-in. polyisocyanurate.
Windows: Koltech triple-glazed
Ceiling insulation: 16-in. cellulose (R-60)
Roofing: 26-ga. steel roofing
Siding: CertainTeed fiber-cement lap siding
Appliances: Energy StarLabeling system sponsored by the Environmental Protection Agency and the US Department of Energy for labeling the most energy-efficient products on the market; applies to a wide range of products, from computers and office equipment to refrigerators and air conditioners.
Space heat: Propane-fired Buderus boiler; hydronic in-floor radiant heat distribution
Water heater: Indirect Superstor tank
Domestic water pipes: PEXCross-linked polyethylene. Specialized type of polyethylene plastic that is strengthened by chemical bonds formed in addition to the usual bonds in the polymerization process. PEX is used primarily as tubing for hot- and cold-water distribution and radiant-floor heating. tubing
Indoor Air Quality
Mechanical ventilation: Venmar ERV(ERV). The part of a balanced ventilation system that captures water vapor and heat from one airstream to condition another. In cold climates, water vapor captured from the outgoing airstream by ERVs can humidify incoming air. In hot-humid climates, ERVs can help maintain (but not reduce) the interior relative humidity as outside air is conditioned by the ERV.
5 Star + Energy Star rated
An owner-builder finds that insulating concrete forms (ICFs) work well for DIY walls
By Rouleen Williams
My plans to build a dream home took years to bear fruit. I took the first step in 1988, when I bought an 18-acre property in Salisbury, N.H. The lot slopes to the southwest, with a spectacular western view over a beaver pond to Mt. Kearsarge.
It took me 19 years to save enough to qualify for a construction loan. In many ways it was good that the process took so long, because the home I finally built is much better than the one I first envisioned.
I was issued a certificate of occupancy for my new energy-efficient home on March 28, 2008, exactly one year after construction began. Every time I walk in the door I feel grateful to those who supported me or helped me during the home's design and construction.
Designing and dreaming
I spent several years drawing plans and choosing where to site the house. My influences included Craftsman architecture, sustainable building practices, and small house designs. I love the Craftsman style because it is comfortable and inviting. Above all, I wanted a house that looked like it belonged on the site.
A chance encounter
At first, I thought I wanted to build the shell with structural insulated panels (SIPs). One day I noticed that the truck parked beside my car had "SIP" painted on the door. I introduced myself to the driver, who explained that she and her husband were working with a local builder, Al Rossetto. She showed me Rossetto's Fine Homebuilding article and gave me his phone number. I called Al, drove to see his home in Lancaster, and my project was launched.
Al is a knowledgeable and experienced construction consultant who only works with owner-builders. He convinced me that I could act as my own general contractor. He put me in touch with all of his subcontractors so that I had an idea of the price of the various steps in the process. Al agreed with my plan to use sustainable practices and products, and supported my goal of using mostly local contractors.
ICFs, not SIPs
Most of the homes that Al has worked on have a foundation built with insulating concrete forms (ICFs) and above-grade walls built with SIPs. I took such a liking to ICFs that I abandoned my original plan to use SIPs. I ended up using ICFs for the above-grade walls as well as for the foundation.
Building with ICFs reminded me of building with Legos. Although ICF construction is fairly straightforward, we had a few problems when strong winds blew some of the lightweight blocks away.
To facilitate the home's open floor plan, we framed the floors with trusses capable of spanning the full width of the house. As a result, my large basement is free of center posts. Trusses also worked well for the attic, where there is no living space, only insulation.
In-floor radiant heat distribution
A propane-fired Buderus boiler ($6,000) provides space heating for my house. The heat is distributed through PEX tubing embedded in the basement slab and stapled to the underside of the subfloor.
We laid out the PEX tubing for the lower floor in one very long day. The tubing and reinforcement mesh resembled a large sandwich. We laid out 2 1/2-in.-thick EPS insulation over the crushed stone base, then put down a layer of 4-in. reinforcing mesh. Next, we installed the loops of PEX tubing, and finally another layer of the 4-in. grid wire. The tubing was held inside the frame with wire ties. During the concrete pour, we used pieces of tubing to lift the whole sandwich, suspending it above the insulation base so that the concrete would flow under it, with the tubing and mesh floating in the center of the slab.
Under the main floor I installed staple-up PEX tubing. Although this was certainly hard work, anyone could accomplish it. Threading the tubing (which comes in a 300-ft. roll) is like weaving. We first unrolled the PEX tubing outdoors. We laid one end where it would attach to the heating system and brought the other end back to make a loop in each truss bay, taking care not to kink the tubing. It's a challenge to work over your head in a tight space between the trusses, trying to keep the PEX tubing against the subfloor above while avoiding the vents and other plumbing pipes. Some staplers tend to jam; one that worked well for us was a Duo-Fast electric stapler that shot 5/16-in. #5010c staples.
To avoid damaging the radiant tubing, I chose flooring that could be installed without nails or screws: ceramic tile, floating engineered hardwood, and cork. In the kitchen and laundry room, where water might be an issue, I used glued-down cork. The basement concrete floor is finished with an acid stain.
Plumbing and electrical
I used PEX tubing for the domestic water system—red tubing for hot water, blue for cold.
My home's electrical wiring is tucked into channels melted into the ICF foam using a tool similar to one used for the craft of wood burning. A wire loop the size of an electrical box is attached to the tool; when placed against the foam wall, it neatly cuts out a rectangle to receive a plastic outlet box. Even though the electricians were initially skeptical of the tool, it worked well. Cutting channels for wiring was done with an electric drill equipped with a bit the same diameter as the Romex wiring.
To provide electricity in emergencies, my house is equipped with a whole-house propane-fired generator, which cost $3,000.
I always try to save where I can, so I opted not to have air conditioning. I really enjoy living with the windows open and using cross ventilation to bring the outdoors in. On days when the windows are kept closed, fresh-air ventilation is provided by a Venmar energy-recovery ventilator (ERV).
Because my house started out with a lot of indoor humidity, especially in the basement, I thought that I might have to alter the ventilation system. When I asked Al about the situation, he said that there should be no excess humidity. It turned out one of the ventilation grilles in the downstairs closet had been improperly installed. Since that problem was rectified, the indoor air quality has been wonderful.
Insulation and air sealing
Before the house was insulated, I spent a lot of time on air-sealing details. Air-sealing work is much more important to the person who will ultimately pay the utility bill than it is to any contractor. All of the air-sealing work was done by me and my friends and relatives; as a result, I have a very tight house.
Every penetration of the building envelope was sealed with expanding foam: around every ceiling penetration, around every electrical box, around the recessed cans, and every place where wires went through the ceiling and floor.
I would go up to the attic when the sun was on the east side to look for pinholes of light through every truss channel. I worked my way around the attic sealing every spot with spray foam. I did this for several days, with the sun shining on the house from different angles, until I was satisfied that there were no air leaks.
We insulated the ceiling with 16 in. of cellulose (R-60).
I wanted my house to be as maintenance-free as possible, so I chose 26-gauge steel roofing and CertainTeed fiber-cement siding. The siding comes stained in a mahogany color, in 16-ft.-long 4-in. wide planks that look like cedar. The planks are fragile until they are attached to the wall, so the long pieces had to be moved carefully.
The siding was installed with special fasteners that penetrated into the ICFs just deep enough to catch the webbing (1/2 in. under the foam). After much trial and error, we settled on 1 1/2-in. self-starting, square-drive stainless-steel screws purchased from a company in Wisconsin. These screws were so expensive that I had the framers empty their aprons each day so that I could maintain the inventory. Twice I had to order more screws, shipped by overnight delivery, to have enough to keep the crew working.
I used conventional wood framing for the interior partitions. I love having the flexibility to move a wall—for example, a wall that didn't allow enough access to the closet in the master bedroom. Since none of the interior partitions are bearing walls, the change was easy to make.
We finished the walls with conventional drywall. Drywall screws had to be positioned carefully in order to catch the webbing in the ICFs. (Fastening anything to ICF walls is always a bit tricky.)
Building is empowering
By building my own house, I learned that ordinary people can become green builders. Al Rossetto provided a step-by-step program that made it possible for me to have the house of my dreams. I ended up with an airtight house with a fresh-air ventilation system, and I did a good deal of the building myself. I did not know that was possible, but with the encouragement of Mr. Rossetto, it became a reality.
The contractors were unfamiliar with ICFs. After the walls were half-built, rebar and metal strapping protruded from the tops of the concrete. The framers, who didn't realize these were critical wall components, wanted to cut off the protruding pieces of metal to get them out of their way when they were setting floor trusses.
The plumbers put a few unnecessary holes through the ICF foundation, and the electricians hacked away the ICF foam to expose the concrete that they were used to working with. After a few training sessions, however, the contractors all learned to work with this unfamiliar product. I can't say they embraced it—but the end result turned out fine.
Click here to see a video tour of this home.
- Daniel Morrison
- Rouleen Williams
- Toshi Woudenberg
Sat, 01/16/2010 - 10:51
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