Just a short stretch down the road from me there is a recently constructed house - well, it's now about 2 years old I guess. It has always caught my eye because it is unlike most of the buildings you see in New England, the ubiquitous white two-story Georgian-style Cape Cods or the occasional asymmetrical Saltbox house. This new house had different proportions, it was partly round and partly rectilinear, and clearly had been built, mercy-sakes, with passive solar orientation - the north wall of the place was even earth-bermed. Shocking! It was obvious to me, upon glancing at the structure, that the builder was someone who was actually thinking outside the, er, box.
I could clearly see that someone had built the house with an eye to 'green' and thus I had a certain interest in finding out a little more about the place and its builder. A few weeks ago I decided to pull in to the driveway of the place to see what was what. I met the owner, who turns out to be a local contractor, long-established, and he was quite enthused to show me his place and tell me all about it. I ended up staying for more than a couple of hours in fact.
The contractor had spent most of his career doing the regular sort of stick framing with 2x material, OSB, vinyl siding and sheet rock that you find pretty much anywhere. This building however was a point of departure from that rut, and was heralding, for the builder at least, a new approach to construction. He wasn't going back either. This approach, about which he extolled the virtues for as long as I was willing to hear, was building a house, from foundation to roof, using Insulated Concrete Form construction, ICF for short. I thought that today in my blog I'd begin to address the topic of ICF use in construction, and to relate some of the claims that are made for it and to share my opinions and conclusions, after having done some further research into the matter.
For those with a high-speed computer connection, I'll link a time lapse video showing how typical ICF construction works.
Like, ahem, all good things in life, ICF's as a system can be said to have gotten its start in Canada in the mid sixties. The first Canadian patent being issued to a German immigrant named Werner Gregori. He got an idea about changing the way people formed up concrete, which, at he time was largely by means of steel pan forms and disposable wooden forming. The disposable wooden forms are wasteful obviously. The metal pan forms are stout, however they suffer from the drawback of being heavy and cumbersome, which means that heavy machinery is needed to move them about the site and both machinery and forms take up a lot of space during that process. Further, metal pan forms are not easily adapted to designs that call for anything other than flat walls and 90˚ corners. Gregori understood these issues and set out to design a form that was lightweight, easy to manipulate and modify, and which could be used to easily form a wide variety of shapes. Thus, in short, his intention, the driving concerns, was to create a forming system that was going to improve productivity. As always in North America, the drive of innovation is almost always a drive towards increased economy.
Gregori's solution was to use a form made of expanded polystyrene - the forms are light and easy to place, and would be left in place after the concrete pour, so labour costs would be reduced. ICF's then are hollow blocks or panels made of plastic foam that can be stacked into the shapes of building walls. The center of the form is then filled with reinforced concrete. This produces a sandwich between the high strength concrete and the light insulating foam. Gregori's system was dubbed Foam Form.
Of course, like many new ideas which are introduced, traditional concrete crews ridiculed the idea of pouring straight concrete mix into anything except steel forms and Gregori had a long struggle to gain any modicum of acceptance for his concrete forming technique. In fact, he ended up going back to Europe where he found he had better success in finding people open minded about his product. Europe after all has a long tradition of building with stone and brick walls, and wood is more expensive for house framing than it is in North America, so he had an easier sell from those angles. Over time, ICF's gained a foothold in the European market, underwent many innovations in Germany and France, and eventually crossed the Atlantic once again to a somewhat warmer reception.
I say somewhatwarmer as a bit of a play on words. You see, though ICFs were created as a replacement for steel forms and to increase productivity, many people with ICF basements noticed how much warmer and drier the spaces were than the conventional concrete formed basements. Further, ICF walls didn't suffer from cracking as is somewhat common in conventional concrete, nor did the ICF floor-wall systems require expansion gaps to be built in - these expansion gaps being notorious as a place for water and air infiltration in conventional concrete structures.
By the mid 1990's ICF use began to be employed for more than just foundations - entire walls, one and two story and higher, were now constructed using ICF methods. This development is that of a wall and floor system that form, literally, a continuous envelope. Today, more than 40 years on after Gregori's Canadian patent of 1966, there are dozens of manufacturers of ICF systems and ICFs are being employed for floor and even roof construction these days. Though wood-frame construction still accounts for some 90% of the N. American market, ICFs are gradually gaining a decent foothold, and have some 7% of the market at present.
During my visit with the contractor down the street, he touted many advantages to ICF-constructed homes, among them (and I'll expand somewhat upon each point):
-Higher R-value. A conventional 2x6 framed wall may have pink fiberglass insulation rated at R-19, however due to thermal bridging through the studs themselves, which are only about R-7, the net value of such a wall is typically only R-13. An ICF wall, depending upon which thickness is used, can vary from R-22 up to R-50. So, comparing apples to apples, the thinnest ICF wall outperforms a conventional stick framed wall in thermal efficiency by some 70%.
- Simplicity. A modern stick framed wall system is a complex sandwich of many parts, and in common practice these components form sub-contracted portions of the work. Thus there is a framing crew, a sheeting crew, an insulation contractor, a vinyl siding contractor, the boys with the sheet rock, the house-wrap with Tyvec® is another step, and of course the plumbing and electrical people need to get in there after the frame is up with sheeting. With a conventional concrete foundation underneath the stick framed structure, there is also a concrete forming sub-contractor involved, who needs to make two visits to the site (set up and removal of forms), along with the concrete company. With ICFs however, the forms are set up plumbed squared and braced, in very short order I might add, and the walls are poured. The forms can be placed in a day and the concrete poured on the next day. The walls are braced with steel which can be re-used on the next job. In one step the insulation and moisture barrier are complete, and each is ready to receive any finishing system, be it stucco or siding on the exterior, or sheet rock or wood paneling on the inside. Electrical and plumbing or fairly easily fitted into the foam cladding using simple methods, and modern ICF systems have pre-formed channels in the foam of floor blocks for routing electrical and plumbing circuits.
-Low sound transmission. Studies show that a conventional wood framed house dampens sound transmission by 50 times, whereas a ICF-walled house dampens sound transmission by 400 times, which is eight-fold better performance.
-Durability. A modern stick framed house is likely to be a 50-year proposal at best, then scraped off and dumped in the landfill. A concrete house will last much longer. The contractor I spoke with gushed that and ICF house would last "a million years" and said that, "you know, the ancient Romans built with concrete and that's still around..." Well, I'll take up those claims and their implications soon enough, but I think it certainly is accurate to say that an ICF house will last considerably longer than a conventional wooden stick built house.
-Mold and Insect Resistance. Mold is not uncommon in stick framed walls for there is both moisture present in the wooden components themselves, which may evaporate and then re-condense inside the wall cavity, and if the moisture barrier system is not perfectly installed, there are numerous places where moist interior air can find its way into the wall and condense. Water vapour condensing in the wall cavity can result in rot, mildew, and deterioration of the studs and wall over time. The mold which leads to wood damage then sets up an environment which is more attractive to certain insects, namely carpenter ants and termites. These insects either employ wood as a food source or as an easily-tunneled medium in which to build their nests.
ICFs, especially of the panel-formed type, have a continuous barrier of concrete which is neither a food source to insects nor can be penetrated by them. Although the EPS foam is not a vapour barrier as such, it still is a closed cell foam and thus allows for diffusion of moisture and water. The poured concrete forms an effective vapour barrier, though concrete itself can wick water very readily if it becomes in contact with water, which could happen through damage to the foam.
So, lots of pros being touted here for ICF construction. Does this mean I'm sold on the system? Is it the Holy Grail? Am I now a paid hack for the ICF industry? Well, no, I'm not quite in the employ of the ICF contingent, nor do I plan to be, and I'll get to addressing those other issues in my next post. In it, I'll take a closer look at the situation with ICF construction methods and materials, with the long-term lens in place, and with a look to environmental issues comparing ICF construction to other methods. There are pros and cons with everything of course.
Put it this way though, given the choice between a stick built house and an ICF house, I would choose the ICF house. Further, given a choice between the timber frame wrapped with structural insulated panel system (trimberframe + SIP) currently in vogue in North American timber framing practice, I would choose the ICF system over that without second thought. I do think there are yet 'better' ways to go than an ICF house though. 'Better' from my perspective at least. I'll get to some of the reasons I draw those conclusions in the next post.