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More and more front gardens in housing estates are adorned with an outdoor heat pump unit: good for the climate, hopefully, but aesthetically problematic. Why are the boxes needed at all, what design strategies are the manufacturers pursuing? And could this have been avoided?

By Martin Krautter

The heat pump hums “Ommmmmm” quietly, so it has to keep a safe distance from the neighbours. © Bosch Home Comfort

No effect without side effects is a principle of pharmaceutics. This statement can be generalised to technical progress, as necessary changes towards a more sustainable lifestyle also have side effects, not least of an aesthetic nature. The most recent example of a development that is only just beginning to have a broad impact: The use of heat pumps instead of fossil fuelled oil and gas heating systems. The German government is stepping up the pace with the Building Energy Act and setting guidelines for decarbonisation in the heating sector. The market is expected to regulate further developments, and it currently clearly favours the electric air/water heat pump, which is becoming a mass product and thus also an object of industrial design.

Applied Thermodynamics

Nothing against heat pumps in general. Their principle: instead of generating heat energy locally through irreversible material conversion (i.e. combustion with the release of greenhouse gases), it is simply transported from the environment, where it is available in abundance and unused, and concentrated where it is needed – namely in our living spaces – with a fraction of the energy input. So this principle is ingenious, and it is also indispensable if we take climate protection seriously. Of course, it is not new; we have been using it since Linde’s refrigeration machine in 1874, not least in every refrigerator and every air conditioning system.

Brick idyll in German housing estates – the appearance is increasingly characterised by the outdoor units of air-to-water heat pumps alongside carports and hunter’s fences. © Bundesverband Wärmepumpe e.V.

It’s just that we usually hide our fridges behind fitted kitchen fronts and don’t put them in front of the house without a bulky waste collection date. However, the evaporator units of air/water heat pumps are increasingly making their way into front gardens across the country, where they threaten to become a design problem. The purpose of the bulky boxes is to extract energy from the ambient air. To do this, they typically contain the evaporator, a heat exchanger between the refrigerant and the air. There is also a fan that shovels this air onto the evaporator, as well as the compressor, the mechanical heart of the heat pump. As a design task, these so-called outdoor units are extremely thankless, as there is nothing to operate, see or understand. Any reference to people as users, beyond the one-off installation and sporadic maintenance, is missing. These are units that simply want to hum along undisturbed. If architects have the opportunity to do so, for example in commercial construction, they do the only right thing: they hide these machines, for example out of sight on the roof of the building.

The Problem of Placement

An option that homeowners usually cannot take. On the contrary: distance rules in some state building regulations make placement more difficult. This is because both neighbours and the residents themselves must be protected from the low but still perceptible operating noise. At the same time, optimum function requires an unobstructed air flow. Too much distance from the building, on the other hand, makes the connection complicated. As a result, the expensive devices quickly end up in the front garden between gravel and box trees, where they not only enhance the street view, but also increasingly encourage criminals to steal them.

Well camouflaged: WP outdoor unit, clad with typical architectural materials such as wood. © Glen Dimplex

Design Strategies

What strategies are the various manufacturers currently pursuing in the design of these devices, which are so unexpectedly beginning to characterise the soft landscape of our housing estates? In this field, too, there are still companies without any design aspirations at all: they build generic, colour-neutral boxes made of sheet metal and plastic, with fan grilles, lettering and fastening elements seemingly randomly distributed across their surfaces. Other brands are apparently banking on the “fancy” heat pump in front of the house soon replacing the SUV as a status symbol. They design expressively and with self-confident branding, often supported by pop culture testimonials on the marketing side. Another strategy relies on camouflage, for example through cladding made of typical architectural materials such as wood or discreetly tinted aluminium – or an angular, simple design based on architectural forms. The appliances from a manufacturer in the Ulm area even refer so obviously to models from the design history associated with that region that you would think Hans Gugelot was still engaged as design consultant.

Simply omit the scale and buttons from the Braun “G11” radio and there it is: The Ulm heat pump. © Weishaupt

It Would Also Work Without It

But none of these strategies can ultimately conceal the sheer volume of these appliances. Design or not, it seems that the boxes on four wheels are now being joined by another box in front of the home – as a reminder of the heating revolution. Could this have been avoided? Possibly, if our society, under pressure to act, were to look more closely for collective rather than individual solutions. Of course, there are heating solutions that work without a box in the front garden: District and local heating networks, geothermal heat pumps or smart combinations such as local low-temperature networks – these distribute lukewarm water, say from the waste heat of a data centre or from a central geothermal borehole in the neighbourhood. This in turn allows compact heat pumps in houses and flats to be operated very efficiently. However, the prerequisite for such solutions is agreement with neighbours – a lot to ask, I know – as well as a public administration that does not bureaucratically slow down such projects. Other European countries, particularly the Scandinavians, are once again further ahead in this respect, and the component of municipal heating plans in the new Building Energy Act at least points in this direction. “Design”, postulated the Swiss sociologist and design theorist Lucius Burckhardt over 40 years ago, “is invisible”. Let’s hope that this thesis is confirmed in the long term when it comes to heat pumps, too.

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