We first came across ICF (insulating concrete formwork) over 20 years ago and, like many wanna-be self builders, were bowled over by the idea of building a house out of polystyrene Lego-type blocks. The benefits: it’s fast, lightweight, plus we really could build the house ourselves, with a little help. That’s not to mention that they create an airtight home with excellent thermal performance.

Now, faced with the reality of a project, we began looking objectively at the costs versus the benefits. Also, because we are selling at the end, we had to decide if any higher costs will translate into profit, otherwise the decision would be hard to justify.

We carried out a cost comparison exercise of more traditional brick and block versus ICF. In addition to the shell build materials and labour, we also factored in differences with external finishing, ancillary costs and the knock-on impact to services and the interior fit-out.

With ICF, we could do a lot of the work ourselves and it would be quicker to build the shell of the house as we had less complicated construction details to get right. Plus, the ancillary costs (e.g. for scaffolding) would be lower. The special monocouche render for ICF is more expensive, but there is a big saving with (potentially) not having to install gas, as electricity alone should be sufficient to heat what would be a very thermally efficient house.

Brick and block is cheaper when it comes to materials but will incur higher skilled labour costs, and the shell will take longer to build.

Would brick and block houses be more saleable, however? This was a question that sparked lots of debate with Nicola and Russell, our build partners. Having checked with the ICFA (Insulating Concrete Formwork Association) we know that the CML (Council of Mortgage Lenders) categorises ICF as a standard method of construction, so there should be no issues with buyers getting a mortgage.

But what about not having gas; some people prefer to cook with gas. We think induction hobs now are a better, safer option. Gas central heating is familiar but imagine not having a boiler to service once a year and radiators that have to be bled. Electricity is cleaner, safer and with solar panels on the roof and high levels of insulation, the cost for running electric panel heaters would be minimal.

Our conclusion: good marketing. We will have to explain the benefits and most buyers’ ears will prick up at the prospect of lower fuel bills even if they are not interested in the brilliantly engineered polystyrene blocks that sit behind their plastered walls.

The sale price of the houses will be the same and, as ‘self developers’, we would be providing progressively built properties to the market that cost pretty much the same to build — keeping both head and heart satisfied with our decision. It had to be ICF.

We’ve had speedy and helpful service from the providers we’ve approached for quotes, including Logix and StyroStone, and are convinced of the benefits of the latest Neopor blocks which use graphite to further enhance the insulative properties of the foam.


Charlie (shown) and Tracy visited the National Self Build & Renovation Centre in Swindon to investigate ICF

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