The house paints that promise much more than colour

The door of Juan Botero’s apartment in Houston, Texas is made of wood – with a classy, walnut-like finish.

But, for Halloween, he planned an eye-catching change. “I’m going to paint my door orange,” Mr Botero, founder and chief executive of Colombia-based Glasst, told the BBC last month. And he has kept his promise.

However, the move is not as drastic as it sounds. Mr Botero’s firm, an “innovation company”, has designed the paint to be removable – once dry, you can peel it off like plastic wrap. If it works as intended, it shouldn’t leave behind any marks or residue.

Mr Botero had the idea for the product, called Unpaint, about five years ago and, initially, his investors weren’t keen. “They said I was crazy,” he recalls. Nevertheless, he insisted: “People are looking for customisation in their lives.”

Glasst is just one of many firms that claim house paint can do more than look nice. Various products now on the market, their makers promise, will save you money, keep you comfortable during heatwaves, or transform your relationship with the walls of your home. But is it all too good to be true?

Unpaint is due to launch in the US this November, and Mr Botero is convinced that there is a market for the stuff. He argues it will appeal to people living in rented accommodation, who can’t make permanent changes to their decor.

Glasst, unsurprisingly, declines to share details about how it makes the paint, but Mr Botero says it is a resin from a renewable source. I ask if he means trees and he confirms.

Peelable paint already exists for car bodywork, but getting such a product to work reliably on softer home interiors is more challenging.

There is a risk of damaging your existing, underlying paint when you eventually wrest Unpaint off your walls, but, if the permanent paint below is in good condition, this shouldn’t happen, says Mr Botero.

It does have an odd texture: “A little bit rubbery," says Mr Botero. Plus, it is easier to scratch than water-based emulsion.

Bringing the product to market hasn’t been easy. Glasst posted a video about the paint to YouTube two years ago, but the launch was delayed until this year “to align with the correct funding and resources needed,” says Mr Botero.

He mentions that Glasst is working on other coatings with unusual properties – including “Thermglasst”, an insulating resin due to launch next year. Mr Botero claims that less than a millimetre of this coating will provide the same insulating effect as 40 millimetres of foam.

There’s no independent validation of that claim just yet, but there are already a range of insulating paints on the market that promise to reduce your heating bills and, it is fair to note, they have not always performed well in scientific evaluations.

In 2019, Richard Fitton of the University of Salford and colleagues published a paper, external in which they investigated the efficacy of six thermal paints available on the UK market at the time. In short, they found that claims that such paints could reduce heating bills by up to 20% or 25% were impossible to validate.

First, the researchers coated boards with the paints, which allowed them to measure the coatings’ thermal resistance, or insulating values. Then, the team calculated the reduction in heating costs you would expect after applying each of these paints to the interior of a typical Victorian terraced house.

The biggest cost saving measured was a mere 2.9%, and, given the price of the paints in question, homeowners would potentially have to wait centuries or even up to a millennium – at 2019 prices – before they would recoup the decorating fees in terms of reduced heating costs.

“If someone brought me a paint that could save me 25% of my energy bill, it would be on my wall by the weekend,” says Prof Fitton. He adds that he is currently working on a follow-up paper to the 2019 study, and would also be open to testing Thermglasst, or any other insulating paint, in the future.

Paints that help to keep your house cool might be more effective. For years, researchers have pursued the idea of improving the reflectivity of paint on exterior walls or roofs, since this could help keep buildings cool on hot, sunny days. Such weather is becoming ever more common due to climate change.

The principle is as old as the hills – consider the white painted houses of the Mediterranean. But paints designed to be significantly more reflective than standard white paint could heighten the effect. i2Cool in Hong Kong is one of several firms marketing such a product at present.

In their case, the paint contains tiny nanoparticles inspired by the extremely reflective body of the Saharan silver ant, external – which must naturally cope with baking sunshine.

Martin Zhu, chief executive and co-founder, says the paint made by i2Cool was tested on the roof of a shopping mall in Hong Kong – but only on one of its two buildings, in order to find out whether there was a noticeable effect in terms of reducing the costs of running that building’s air conditioning (AC).

“We used a power meter to measure the energy consumption of the AC system,” says Dr Zhu. The cost of running the AC duly fell in the painted building, by 40%, he adds.

Dr Zhu first began working on the paint while a doctoral student, and he mentions that early versions made around 2017 contained silver, which made it very expensive – more than $100,000 just to cover a small area. Years of development later, it now costs around $10 per square metre of coverage. It also now comes in a variety of light colours, including grey, yellow and green.

Researchers have noted that highly reflective coatings for passive cooling applications need to be resistant to dirt and soiling, for example, to avoid their efficacy dropping overt time. And glare from ultra-reflective roofs risks heating up nearby darker structures, a 2020 paper suggested, external.

The paint from i2Cool does not contain heavy metals and uses a water-based emulsion, and while it is not biodegradable, it can be recycled, says Dr Zhu.

The company’s latest major project is the Dubai Mall. The roof of this sprawling complex – the largest mall in the world by total area, external – will eventually be fully coated with the paint. A 1,000 sq m section has been completed to date.

While not yet available in Europe, that could change, says Dr Zhu. “We are discussing with some distributors in the UK,” he says.