Help & Advice
Is ICF the perfect structure for the modern home? One of our clients recently said that Polarwall construction creates the perfect structure. Perfect is an absolute and nothing is perfect. However any ICF construction does have some advantages over other build type. However, it also has some disadvantages too.
Here is how ICF construction stacks up to other build methods. We review some of the pros and cons of each method.
Energy Efficiency
Energy Efficiency – Most building systems can achieve very low U-values. It is all about the level of insulation. Polarwall’s lowest U-value is 0.03. This is 1/3 of the Artic Region Passivhaus standard. This is a ridiculously low U-value and we have never built at this level (nor even quoted it). Most people take a sensible approach and don’t necessarily want to live with 700 millimetre thick wall.
Design Shortfall
Some building methods do not meet their design targets. A good example of this is traditional build where bricklayers are fixing insulation inside the wall. A brickie is paid by the number of bricks he lays. Consequently, a bricklayer threats proper insulation fixing is often an afterthought. Snots of mortar on the inner wall face push the insulation away from the wall. This creates an air flow between internal skin and the insulation which reduced the effectiveness of the insulation. Brickwork often has small air gaps in the perpendicular mortar joints of the brickwork making for draughts through the wall. This doesn’t happen with ICF construction.
Similarly, a timber structure may be poorly detailed. It may not perform as designed or expected. SIPS panels will usually perform as expected as these are made in factory conditions. They are designed to fit tight to each other thus minimising any potential air gaps. ICF is very similar to SIPS construction in this matter and is difficult for it not to meet design targets. The resulting ICF wall, once concrete is poured, becomes like a composite bonded material. Providing the concrete is probably compacted there will be no air gaps in the wall. Air gaps in any strucutre are not desirable.
Noise Reduction
Heavyweight construction. is the best way to reduce airborne noise within a home. This means that traditional and ICF construction will create a home that is quieter than a timber or lightweight structure. ICF will generally be better than traditional as it is monolithic and should have no air gaps.
Build Speed
Build speed – generally an ICF home is faster to build then traditional brick and block. Rain and poor weather does not stop the assembly of the formwork. However, it is not as fast on site as timber frame or SIPS construction. With factory assembly methods the build time is in the factory.
Structural Strength
In terms of structural strength ICF will win hands down. Traditional build has components locked together by the mortar. An ICF structure is one continuous monolith of concrete which is the strongest of structures. In this country, we do not worry too much about extremes of weather. Perhaps we should worry, The unknown effects of future climate change should be a concern to every house builder.
Non- edible and non-degrading
ICF and traditional construction are not susceptible to termites, fungi, and the infestations that feed on wood. There are treatments for timber that reduce these risks. However, many people have concerns about the impact of such treatments on the occupants of the house. Air quality is an issue with many timber treatments.
Build Costs
For he build cost of a single house the cheapest method is often traditional brick and block construction. The superstructures of other build systems may be 5% to 20% more expensive depending on specification. However, the “fabric that the extra expense on the wall in is more than justified with lower lifetime energy costs. Potential lifespan of the structure is another consideration in the costings.
Environmental Impact of the Build
For many, the concrete used in ICF buildings is a strong negative. There is some justification for this as the insulation is oil based and of course cement production is one of the greatest contributors to climate change. However, things are changing fast. Cement -free concretes are now on the market and we look forward to the changes these will bring to the environmental questions.
Link