Energy Efficient Homes with an Insulated Concrete Form System

A simple ICF block is just a mold to hold the concrete without special features or engineering. A system is designed to meet special requirements, it is interlocking in any direction and should be a complete building solution. The main concern is the shell form of the structure including exterior and interior walls and the ceiling or floor for the next storey or roof in case of a flat roof structure. The German Isorast System is such a "System" and goes far beyond the normal expectation of regular ICF forms. There are over 60 main elements to fill the gap between ICF molds filled with concrete and a complete closed, interlocking and thermal tight shell building solution for any design or static requirement and up to 10 storey building projects.

System features and requirements for to build passive homes, solar homes, low energy homes or zero energy homes:

- Insulation properties are different if you build in hot (tropical) or cold climate. Under hot climate condition the block size (width) can be less as for building in cold or extreme cold climate. For example, a 43 cm (17 inch wide) block with a total of 29.5 cm (12 inch) insulation, ext. and interior, opens the door for a passive home* built in Alaska. *A passive home is a house without active heating system. Usually waste heat is used and circulated via air exchanger. This can be heat from cooking, the shower, candles, a fire place or even people. One person produces about 100 Watt of heat!

- In hot climate a block size of 31 cm (12 inch) or 25 cm (9" 7/8 inch) is absolutely efficient to keep the house cool, except for cooling purpose one would need the bigger block with thicker insulation.

What we see here in the picture is a 31 cm (12 inch) wide block for exterior walls. In the "raster" grid end pieces slide in to close the wall at the end or for openings like windows and doors. No framework is needed. The exterior wall part is thicker (11.75 cm / 4" 6/8), the interior part is always the same with 5.5 cm (2" 2/8) of insulation. The increments for cut's are as small as 6.25 cm (2" 7/16) which makes the system much more flexible for any dimension or design. When a standard block of 75 cm (2.46 feet) or 150 cm (4.92 feet) in length is cut at the cutting line (increments of 6.25 cm) there is no waste! Every cut off piece can be used in another location. The end pieces will always fit perfectly. Cut off waste, what we see in other ICF forms, means throwing away money.

- What is the best ICF wall good for when the heat, cold, leakage comes from the top cover?

This is another important issue to build energy efficient or passive homes. Conventionally there is a ceiling made out of drywall and on top of it some kind of mineral wool insulation. For passive home or low energy homes this is not sufficient. Weather changes and humidity (cold/hot/rainy) fill up the insulation layer with moister and the original insulation value goes against Zero. Spray foam solution are some degree better, but there are often gaps and spaces not filled completely, hard to reach or they just have air inclusions and it requires special spray equipment. The perfect solution is of course high density styropor (Neopor), but it must also cover beams or other load bearing elements. This is the point when we come to the Isorast Floor-Ceiling solution.

To make the structure more energy efficient the structure must be air tight, completely sealed. The myth that walls or a structure must breath is just a myth of the old school thinking. No wall is breathing when properly installed, not even a wood wall. But please keep in mind the word "breathing" - it is something important I will address later.

What means Floor / Ceiling System?

That's the two-in-one solution of the Isorast building system. Patented (15), extraordinary in design, engineering and accuracy.
The system consists of three components:

A) the light weight floor beams (only 9.5 Kg per meter)
B) the insulation panels made out of high density foam (27 g/l) with fire retardant like all other elements.
C) Concrete plus additional horizontal steel reinforcement between beams if a higher load is required.

The floor / ceiling system is easily installed in one day with a 3-4 man crew. It serves as ceiling and roof if it is a flat roof construction or as ceiling-floor if it is a multi storey construction. The first insulation element slides in the beam, when the row is complete the beam is closed (left move) and all elements interlock with the exterior wall, done. Next row and so on, the last row is an end-element and comes in different sizes to fit in the last, closed beam. The system layout is specified in the floor layout plan and the accuracy is on the millimeter. The breaking point of one single insulation element is minimum 3.3 kN, in a completed row already min. 5.5 kN (= 550 Kg or 1.210 lb) without concrete.

When the system is in place it's time to poure concrete. First, in the beams - to fill up the space underneath. All beams have a bow upwards. Through the weight of the concrete (only in the beams first) the beam is straighten up after 1 hour. When this is done the entire floor can be poured until completion. It's 100 liter concrete per square meter. Regular walls take 121.5 liter / m2, fire walls 140 l/m2. This is extremely "material efficient" - with the least material to accomplish the highest strength.

As soon the floor system is installed and poured the entire structure is completely closed and sealed. All interior-, exterior walls and the floor system interlock and have a solid concrete connection in any direction. There is no gap, no tie beams are necessary, no framing for holding the walls or closing window / door openings. The house is complete and ready for finish work like stucco (ext.) and plastering (int.), window and door setting, connecting the integrated plumbing and electric.

As soon the foundation is finished and the material is on the building site the erection of the walls begins.

At the first day we lay only the first 1 or 2 rows all around including interior walls. This is the most important step for the entire structure. The first row must be completely leveled, horizontal and vertical. It is important to watch the accuracy of the foundation closely. If there are any differences more than 0.5 cm (2/8), eventually small wedges can be placed under the elements to level horizontal for the moment. To see if the foundation is straight we put some water on it to see if you we have puddles and than mark it. When the entire floor plan layout is in level, just shoot a laser beam from diagonal corner to corner.

The next step is to mix some concrete and put it in the forms by hand here and there, especially where the wedges are and on corners and let it dry overnight. Nothing else is done on the first day. The concrete is just to attach the forms and hold them in place. For perfect accuracy we put a longer block temporarily over door openings as second row, just to hold the wall in place. When the concrete is in we shoot the laser again to make sure everything is in perfect level.

By the way the bigger forms, 12 inch+ (31 cm in the picture) are pretty self leveling and you will see gaps if there are any. The wedges are for the moment until the concrete is dry and hard. On the following day nothing can move anymore and we are ready to stack the forms together in a lego like fashion.

This is the time when the fun begins

It was raining over night, everything is wet but this is absolutely no problem. All forms are 100% water resistant, we don't use any wood and we can start putting them together now. When it is a small house (up to 1.000 sft) the erection process could be done in one day. But it's better to take some time to think because it goes up so fast and we don't wanna forget a window opening or the pipes for water and electric.

On this picture we have the pipes for the kitchen ready and left / right outlet boxes. To install the pipes in the wall before it's poured takes a little bit more time but it's well worth it.

That's the last row. It looks like an "L" and has steel clamps in to hold the 6 mm bars and the floor beams, exactly in the middle of the concrete cell. So that the concrete from the floor can float into the exterior wall cell to build a solid Floor-Wall connection. The places (place holder) for the steel bars are calculated and engineered for highest strength as part of the Isorast system. There are also 4 place holder for re-bars in any form element. Depending on the static calculation for the wall, 1-2-3 or 4 re-bars (6 mm or bigger) can be inserted in the wall elements, usually every second row. If the wall is used for a pool or basement for example steel bars must be placed in every row, up to 4 bars. When the wall is finished the vertical bars will be easily inserted and stay perfectly straight between the horizontal bars. In the corner of the picture we can see two PVC pipes for the electrical wires. So when this step is done and the floor system is on, the shell or the main structure of the house is finished. Completely closed with a flat roof - never leaking. If it's a multi strorey building, the installation steps will be repeated.

Everything looks clean, all windows- and door openings are in, plumbing and electrical pipes, outlet boxes are in, end-block (L-block) is on, steel is in - we are ready to poure the entire structure. With a smaller truck concrete pump this will be done more peaceful and relaxed than any kind of boom pump.

Why?

The flow speed is adjustable and the pump can be stopped remotely very easy. It will just take a few hours. First, beginning at the windows - 1/2 hour waiting, coffee break or lunch - and then at full wall hight until every wall is full. A vibrator or any kind of shaking equipment is not needed as long the concrete mix has the right consistency. (not to thin not to fat, slum grade 4-5, aggregate size 4-8 mm, 4.500 psi or better). In every block are "flow-wedges" to support the concrete flow into the next open cell. It is filling up like a pyramid.

I mentioned earlier that walls don't breath, except we have gaps, cracks or air leakage - but this is something we don't want to have in a low energy home. So the conclusion, all walls and the ceilings must be air tight. For ventilation we use windows or air exchanger that's healthier.

When we use clay plaster for the interior finish, than we can say we have a kind of breathing wall. It's not breathing to the outside, but internally. Clay is natural, brings energy in the room, clay takes out dust and odor and is self-regulating the room humidity between 50%-55%, which is very healthy. Clay reduces magnetic pollution (cancer). So to speak when we want to live in an Eco-Home, there is no way around Clay. After a mineral based grounding substance, the clay can be sprayed directly to the Isorast wall. Allergic and asthmatic people say the clay helps them to cure their disease.

Clay plaster is widely available in many parts of the world and it comes in many different colors and textures. Clay looks just gorgeous.