This podcast series is excerpted from a two-day class called “Building Science Fundamentals” taught by Dr. Joe Lstiburek and Dr. John Straube of Building Science Corporation.
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PVC Form-A-Drain is a new product I ran across on while researching my page on basement foundations. The
system is composed of a hollow PVC drains shaped like a rectangular tube. The drains serve as the concrete forms for the footers for the basement or crawlspace foundation and I suppose even for slab-on-grade foundations. The systems has corners to join the straight sections and outlet systems to connect to 4″ round PVC perforated or solid pipe to drain the water away from the foundation.
Foundation Perimeter Drain and Footer Concrete Form
In addition to acting as a perimeter hydrostatic water drain, it can also serve as an evacuation vent for radon gas. This is what caught my attention first and foremost. You get three functions for the labor cost of a single installation. For me that made this something to give serious consideration to.
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Tweet ThisMany people have a negative view of concrete as a building material that supports green building objectives. It is true that concrete does take a lot of energy to produce and transport (to smaller sites where on-site batching is not feasible). Concrete does consume water during the manufacturing process. But those are narrow views that do not hold up under critical examination.
LEED sustainable design principles have five disciplinary focuses:
- Sustainable sites
- Water efficiency
- Energy and atmosphere
- Materials and resources
- Indoor environmental quality
Concrete is recognized as a green building material in terms of qualification under LEED certification principles. The five ways that concrete can help support green building objectives:
This is a video that explains how concrete fits these principles:
- Concrete creates sustainable sites.
- Concrete enhances energy performance.
- Concrete contains recycled materials.
- Concrete is manufactured locally.
- Concrete builds durable structures.
For residential construction, the main guiding principle for design over the last 60 years has been on affordability. Trying to match the overall cost to produce the home to the ability of the local market’s economic base to afford the home.
This led to design decisions solely focused on initial costs that did not account for life cycle analysis that would dictate different decisions if the installed and operating and maintenance costs were analyzed over a specific life cycle. If fact, not one has ever sat down and really focused on what is a reasonable economic life cycle to build to when it comes to residential structures for the mass market.
There have been some studies, but the market has never really focused on this previously in establishing a target sustainability for building homes to. The focus has been on costs, profit to the developer, profit to the builder and profit to the financing entity. to be fair, there are so many layered costs dictated by housing regulation, that has made it almost an impossibility to make these considerations very high in priority. Part of that is attributable to the structure of regulations that deal with the development of housing for the larger market.
But, getting back to concrete. Because it creates very durable structures, first and foremost, lands it in the sustainable category. It would be hard to argue that building a home that lasts 2-300 years is not worth the expenditure of resources required to build that home. Properly built and maintained, this is definitely an achievable goal, we have examples all over the United States and Europe towards this end. One thing about concrete is that it is not a very friendly DIY material to work with. The skills, and equipment necessary typically exclude it as a DIY project.
Next, final production of concrete occurs close to the site of installation, again this is in conformance with LEED principles. Concrete can also contain recycled concrete as an aggregate although there are greater opportunities to expand this practice. The highest profile example of large scale concrete recycling back into a redevelopment occurred in the late 90’s and early part of this decade in the redevelopment of Stapleton International Airport from the main airport in Denver into an urban mixed use suburb. All of the concrete from the runways was recycled back into this and other construction projects in the Denver urban landscape.
To be sure, there are new technologies and ways of thinking, such as precast panels used as basement walls.
Precast Concrete Basement Walls
So analyzing concrete as a sustainable material is perfectly valid and in the case of residential foundations and homes built in high-risk areas (Florida and coastal hurricane zones) certainly support green building objectives. There is no currently available material that can offer the durability of concrete under the stresses of soils that are subject to expansion forces that can destroy a foundation. Building a foundation that can be viable for 2-400 years allowing the recycling of the basement over that lifespan, further establishes the viability of concrete as a green building material.
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Tweet ThisInsulated Concrete Forms are a modular structural building system that mimics the Lego concept of pieces that fit together to make a larger structure. The forms are made of either Expanded Polystyrene or Urethane based products. By themselves they will not burn, have been found non-toxic and emit no gasses in place.
Typical Properties of Plastic Foams
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As part of a system, there are provisions made to support the rebar necessary to hold the concrete together after the pour and to support the attachment of siding and interior drywall for direct attachment of these finishes to the system. Many times, the exterior finish will be a troweled on stucco type finish that will add additional fire resistance to the structure. As the structure is reinforced, solid concrete, the structures have a high resistance to windstorms (hurricane and tornado) and to seismic events. The structure is also fire resistant.
Insulated Concrete Forms Efficiency
Since the systems are engineered, they tend to maximize the efficiency of the concrete needed to support a residential structure and eliminate to typical overuse of concrete for the limited loads involved. A standard formed concrete foundation will have a full 6″ thickness of concrete wall where as an ICF will have 4″-12″ of solid concrete depending on the load you need to engineer for, but you can select that which maximizes the resources for the needs of your specific project.
In addition to having excellent strength characteristics, the insulating qualities of the foam and the solid, construction reduce air infiltration to minimal levels increasing the energy efficiency of the system. The structures also are impervious to attack from insects or mold and are much quieter in urban environments. There is much to recommend them.
Insulated Concrete Forms As a DIY Project
ICF With Corbel
While Insulated Concrete Forms are a project you may undertake as a DIY home building project, get well educated in advance. Because they are the core structure, there is no room for mistakes in planning, and construction of the system so you need to take advantage of all the expert advice you can find from ICF manufacturers and ICF contractors. You would be well advised to hire a professional ICF contractor if you have any doubts as to your ability to do this project, make sure at a minimum that you hire a qualified Engineer or ICF contractor to consult with and most importantly to inspect the forms before you pour the concrete. In many jurisdictions you may be required to have a licensed Engineer inspect the forms before the pour anyway. Spending a few hundred dollars for expert advice could save you thousands of dollars down the road.
The ICF forms are lightweight and assemble like blocks or are sheets that are tied together with pre-designed form ties. The blocks may be simpler for the DIY home builder while the sheet systems can be faster and offer a cleaner surface to stucco over. The system you select will determine the overall complexity.
All of the systems rely on steel reinforcement to tie the structure together, add tensile strength and to distribute temperature stresses throughout the wall. In very cold climes, often times you will see another wall re-framed to the interior to increase the available cavity for adding to overall u-value with sprayed in Icynene foam or standard fiberglass batts and to proved access to install mechanical and electrical systems. Additionally, ICF structure act as a heat sink in the winter, storing heat energy. and can act as a barrier to the transmission of heat energy in the summer months.
Green Aspects of Insulated Concrete Forms
There is some controversy over whether or not concrete supports green building objectives because of the energy intensive nature of its production. But ICF’s have been recognized for LEED points on the basis of their insulating capability and when fly ash is used in the concrete they are an excellent example of recycling waste to produce a high strength structure with maximum durability, another LEED characteristic. The structure will last a long time, with lower maintenance costs, reducing future impacts to the environment from having to rebuild the building say 100 years hence.
This system is becoming very popular here in Florida for their Resistance to storms, fire and for their superior thermal performance compared to CMU. They are certainly a very viable system for you to consider for your DIY home building project.
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Tweet ThisHome Building starts with the foundation. The foundation of your house is…. well your foundation. If your foundation was laid out wrong, or you are having problems with water or expansive soils around your foundation, you will see them manifest themselves in other areas of the structure. Whether your project is DIY, or you have hired a building contractor, you need to understand the terminology and the pitfalls of each foundation type to make sure you cover all the issues and account for the proper handling of water infiltration and Radon infiltration.
If your foundation does not have an adequate waterproofing system to drain excess water and you do not have a sufficient water barrier on the exterior basement walls, you will have a damp or soggy basement and subsequently, this will lead to mold. In basement foundations, water infiltration is controlled with perimeter drainage systems tied to either a sump pump or daylight drain and a waterproof membrane either sprayed on or mechanically affixed to the perimeter walls.
Perimeter Perforated Drain system - DIY Green Home Improvement
Although basements are popular with a great many people, they are not always feasible. In Florida, Georgia, Mississippi, Texas, etc. – sub-surface water is too close for portions of the year to control the possibility of water infiltration to the basement. So in these areas the preferred foundation has become the slab-on-grade.
Slab-on-grade is a foundation where you pour a mattress of concrete (usually with thickened portions at the perimeter and at interior load bearing locations). These are typically 4-6 inches thick and are both very economical and reliable and the easiest to control water issues with. They are preferred when dealing with low-bearing capacity soils and areas with water tables close to the surface (less than 10 feet). You will notice if these are the predominant type of foundation in your area. just look at the building lots in your area when construction begins and you will see what type of foundation is there.
Another issue with basement foundations or crawl-space foundations is the bearing capacity of the underlying soil and the expansiveness of the soil. Expansive soils expand as the take on moisture. If not accounted for, they can destroy a foundation is short order because of the pressures they exert on the concrete. They require special attention to drainage , backfill and sometimes the addition of caissons drilled into rock to support the walls. The caissons are drilled down to rock and the walls are supported on the caissons with a void form underneath to allow for expansion of the soils. In any event, most basement foundations will have a concrete slab for the floor.
Concrete Void Form - DIY Green Home Improvement
Another issue that is important to the safety and health of your family is to plan to mitigate Radon. Radon gas is now recognized as a very serious threat to the health of those who endure long-term exposure. It has been linked to lung cancer and other serious illnesses. It is also present in about 80% of the country. So you need to incoprorate systems to mitigate its presence in the foundation. We will talk about this in detail later.
Lastly, if the foundation is not laid out square, you will have problems with framing the upper portions to a square condition and thus problems with interior finishes etc. It is important to pick a competent and diligent concrete contractor to build the foundation and it even more important to have an engineer design the foundation to ensure that the proper type of foundation is put in place on the site you have chosen. If you do not sufficient expereince and skill to perfrom this project, it will be best to leave it to a pro. It is highly likely, given the need for concrete forms, that you will not be able to justify tackling the foundation as a DIY project. Visit the American Concrete Institute for further information.
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