INSULATED CONCRETE FORMS - HOW DO THEY WORK?
ICFs are basically very large format polystyrene blocks, comparable to traditional masonry blocks. However, for one ICF block you would need 4-6 traditional masonry blocks (due to the size of most ICFs). The ICF is laid (like traditional blocks) and then braced before being filled with concrete.
This creates a reinforced concrete wall that is incredibly warm (with double the R values of traditional timber frames), incredibly strong and incredibly quiet.
The main benefits to ICF are:
- It’s exceptionally strong – our building code aims to ensure homes last up to 50yrs, yet in Europe there are homes that are 400-500+ years old that are still performing. That’s what we want to be achieving through the use of ICFs.
- It’s super lightweight - this is a huge benefit for getting the blocks to the building site and moving them around in difficult locations. One guy can literally pick up and move packets of these on his own.
- It’s much warmer than traditional construction systems – a timber frame home will have an R-value of 2.2 which drops to about 1.7 with heat loss through the thermal bridging of timber but an ICF wall will give a rating of R3.4 which gives you real saving in heating and cooling costs.
- It’s very quiet – there is reduced sound transfer due to the extra insulation and solid concrete core.
- Cost is comparable to timber framing – in some cases ICFs are actually cheaper than their timber framed counterparts, especially when design complexity is reduced.
Here's how it works...
Lightweight ICF blocks are very easy to get on site, saving significant time and labour costs in the early construction phase.
ICF blocks are designed to stack securely together and are customised on site to suit the building design specifications.
ICF construction is completed by pouring concrete into the cavity.
Once cured, the cladding is fixed. This can be wood, tile, plaster, weatherboards or any other cladding feature desired
Family inside, wet weather outside. The result is a home with triple the insulation values required by the New Zealand building code, and will outlast the 50 year durability requirement for the structure.
Q&A’s on ICF Builds
1- What is ICF?
Insulated concrete form (ICF) is a system of expanded polystyrene (EPS) rigid insulation blocks separated by plastic webbing. It is used as an integrated concrete form to pour a concrete wall instead of a traditional wood plank or plywood form. ICF blocks come in interlocking sections, so a wall system fits tightly together. Once the blocks are in place, concrete is poured, and finishes like drywall and siding are attached to fastener strips embedded in the insulation.
Several steps of the construction process are made quicker because the insulation and fastener strips are included with the ICF blocks. ICF walls are typically between 6" and 12" thick. Wall thickness is often impacted by the soil condition and the amount of support that the overlying parts of a building require.
Insulated Concrete Forms (ICF) are becoming a more common way to build homes. This innovative building material is typically made of blocks of polystyrene foam with space in between to pour a concrete wall. Historically most commonly used for foundation walls, many builders are now taking ICF further and using them for above-grade walls of 1, 2, and 3 story homes.
Overall, ICF homes increase your home's comfort, reduce your monthly energy bills, and, most importantly, reduce your environmental footprint. ICF homes are considered high-performing due to their higher thermal resistance and thermal mass, along with stricter construction standards than are typically required for conventional wood-framed homes.
If you build a high-performance home that is insulated well above code to standards like the Passive House standard, your building will have a much lower energy footprint. That means lower energy bills and even greater sustainability.
2- Is an ICF wall a good insulator?
The short answer is yes, but you need to look a bit further if you build a sustainable, high-performance home. ICF construction has two advantages in terms of the energy performance of the building. First, it seals very well, preventing air leakage through the walls. Second, it has two continuous insulation layers, one inside and one outside, with no thermal bridges. That reduces heat loss.
3- How long does ICF last?
ICF homes have a lifespan of over 100 years, with minimal maintenance required as the foam will not degrade. It is also important to note that ICF homes can add increased protection during natural disasters. These homes perform well in flooding, so they are appropriate for coastal areas. The reinforced concrete also makes them suitable for highly seismic zones. Some builders can even ensure up to a 4-hour fire rating. If you live in an area prone to natural disasters, an ICF home could give you peace of mind.
4- Is ICF used in New or Existing projects?
ICFs are found mainly in new construction rather than retrofitting projects. They are easy to install and have several advantages, including strength, durability, and the ability to be well-sealed and well-insulated.
But just how sustainable are insulated concrete forms? Concrete requires more energy to produce compared to conventional wood-framed construction. However, operational energy also plays a significant role in the environmental impact of a building throughout its lifetime. In this article, we investigate the environmental effects of ICFs by examining the life cycle of this building material.
5- Does ICF need a vapour barrier?
ICF walls serve as vapor retardants and do not need a vapor barrier.