CIBSE Case Study Barking Bathhouse

Article from the October 2012 Hotel and Leisure supplement of the CIBSE Journal by Alex Smith.

Hackney designers Something & Son have built a health spa using just one chiller and a single immersion heater. Alex Smith looks at the pared-down approach to services at the pop-up Barking Bathhouse in East London.

The bathhouse has returned to Barking. Nearly 30 years after the closure of the town’s Victorian baths, Hackney designers Something & Son have created a flourishing health spa in the heart of the town.

Hundreds of visitors have found rest and recuperation at the Barking Bathhouse since it opened this summer. The 250m2 bathhouse includes a sauna, ice room, treatment rooms, relaxation yard and a cocktail bar serving up healthy elixirs under the trailing vines of a cucumber plant.

The facilities may not be unusual for a suburban health club – but Barking’s bathhouse is a pop-up project with planning permission for just two months, meaning the normal rules for designing spas have been ripped up and thrown in the Jacuzzi.

‘It’s a temporary building and it has a very small budget,’ says Something & Son’s Paul Smyth. ‘Building services that may have been suitable for a building with a 30-year lifespan were not suitable here. There would have been no payback on investments such as solar thermals.’

The bathhouse could not be connected to the gas mains because of the tight budget, which meant the team was constrained by how much energy the building could use. Smyth realised the only way the spa could work was if he could design out the energy loads. He approached this in two ways – using Passivhaus principles to create insulated envelopes to minimise heating and cooling requirements, and by getting visitors to understand that a blissful sense of wellbeing doesn’t have to be associated with profligate use of energy.

‘We are questioning people’s perception of what is comfortable,’ says Smyth.

‘When people go on holiday they remember the simple, such as a massage in a mountain hut, or a plunge in an Alpine river. They don’t recall swims at the local leisure centre. We want to recreate that here.’

On colder days, Smyth says he wants guests to feel cosy by using hot water bottles and drinking mulled wine. Guests experience the elements in the relaxation yard and the gravel bays, which are both open to the sky – trees planted in the relaxation yard offer shelter from London’s weather. ‘A little bit of rain usually sends people running inside, but here people lie out it in,’ says Smyth.

Without a connection to the gas mains, limitless access to hot water could not be taken for granted and Smyth had to find a way of limiting its use.

‘For the number of people using the spa we needed three shower units, but a normal power shower is 2 to 6 kW and running four simultaneously would mean a very high peak load.’

To reduce peak load, Smyth opted for a single shower run off an electric immersion boiler. This was complemented by three bucket showers, which were refilled from the same boiler. As the buckets would only be filled intermittently, the use of hot water was limited and the peak load low.

‘It was a good way of restricting the water supply,’ says Smyth, who noted that many people opted for a cold bucket shower anyway after the heat of the sauna.

‘Meeting higher peak loads would have meant ‘the cost and hassle of needing a three-phase electricity supply’ says Smyth. ‘By downgrading to a single-phase supply we saved on the cost of cabling.’

Anybody familiar with the fishing net huts of Hastings will recognise the bathhouse exterior’s painted black weatherboarding, which has been nailed onto plywood.

The black boards helped rooms retain the day’s heat. In one room, inspired by pebble beaches, mounds of gravel trapped more heat, which helped the space retain warmth into the evening.

As a Passivhaus certifier, Smyth understands how the building’s fabric and orientation can be used to maximise solar gain. The gravel bay faced south to increase solar gain, and special attention was paid to the insulation of the ice room.

‘We wanted to create the experience of an ice house using less energy than usually required,’ says Smyth (see below). He increased the insulation of the door, wall and floor of the chiller from the recommended 19 mm to 300 m. ‘We insulated the room ourselves to make sure the details were right.’

Smyth believes that over reliance on building services means not enough effort is made in the thermal design of buildings. ‘It’s ridiculous,’ he says. ‘People end up overengineering the space to compensate for the lack of insulation in place.’

Insulation was applied to the walls of the ‘store rooms’ where the treatments take place, and insulation ensures the sauna maintains a constant temperature of at least 60 OC with minimum intervention from a 24kW wood-burning stove. On an average day the sauna, which can accommodate eight people, uses ten 20 cm logs. These are sourced less than a 45-minute drive away.

Something & Son chose to build a hatch into the sauna roof, in case the room overheated and to provide further temperature control. ‘The stove manufacturer said the boiler would be suitable for rooms between 15 and 30 m3,’ says Smyth ‘and with such a wide range we didn’t know what temperature our room would reach so designed in buffers.’

In case the sauna temperature fell, Smyth also built in a roof space where more insulation could be installed.

The only other issue Smyth noted was the boiler’s two-hour start-up time. ‘We would be better to throw a couple of logs on to keep it going through the night,’ says Smyth.

Something & Son has successfully applied to extend the life of the Barking Bathhouse from mid-September into the winter months. The colder months will be a real test of Somebody & Son’s approach and whether users will respond to chillier days by putting a blanket over their knees, or by going back to their centrally heated homes.

Smyth is excited by the challenges of making the bathhouse work during colder months. ‘We will change the character of the spa. We will put a fire pit in the gravel bays and hot drinks will be available.’

Some extra insulation will be necessary, especially in the sauna and the store rooms, which currently has no insulation in the ceiling. ‘We need to take measures to ensure that people don’t pop down to Argos to buy a heater if it gets too cold,’ says Smyth.

Smyth says being a temporary project on such a tight budget has allowed Something & Son to be more experimental. ‘We’re not having to design to guides. A temporary project gives you a bit more room to play.’ ‘We have returned to the days before affordable electricity, where straw bales were used to insulate rooms filled with large blocks of ice.’

With his Passivhaus background and restrictive budget, it’s not a surprise to hear that Somebody & Son had ‘taken a light touch to building services.’

But Smyth says there were services he would have considered, if he had the funds. He would have liked to have recovered the heat from the chiller unit to use elsewhere and would have experimented with a mechanical ventilation heat recovery system for the ice room. Solar thermal panels and a rainwater system were high on the wish list.

The bathhouse is part of the cultural Olympiad. It was originally supported by the Arts Council, but now pays for itself. ‘It started with a grant but it’s currently a going concern. We are always keen to design a business as well as a space,’ says Smyth.

Something & Son’s services strategy is clearly helping the bathhouse wash its own face.

A fire pit will be built into the gravel bays area during 'winter mode'

[edit] The ice men cometh

The ice room is effectively a huge freezer, with highly insulated walls. Something & Son cut expanded polystyrene (EPS) into a 300 mm blocks themselves to ensure that insulation was continuous. Another 100 mm layer was applied to the external façade to prevent thermal bridging.

Part of the cooling strategy was to create a thermal store for the coolth generated by the chiller. To do so, Something & Son came up with the ingenious idea of covering the walls in ice.

They made 12x12 cm tiles of ice and put them in horizontal silicone trays. As the room warms, ice melts into the angle, and then into channels in the corners of the room. Water collects in large containers, which act as another form of thermal storage (as well as giving guests another means of cooling down).

‘Storing the coolth in the ice room was key to reducing cooling requirements,’ says Smythe. ‘As a result we got away with using a smaller chiller.’

The chiller used for the ice room was a standard through-the-wall monoblock unit, which Smythe expects to sell to a shop when the project comes to an end.

It remains at around -1 OC during the day, dropping to -6 OC over night.

There was one problem with the chiller – it kept trying to defrost when the temperature fell. ‘It’s typically used at 0 to -0.5 OC so, when it goes as low as -6 OC, it would automatically defrost’ says Smythe. ‘We’re putting it under unusual conditions.’ Smythe says he couldn’t find anything on the market that was suitable for the ice room. ‘We had to keep turning the chiller off and back on again to disable the defrosting,’ says Smythe, who was keen for the frost to form for aesthetic reasons.

The designer was pleased with what had been achieved on such a limited budget, but there were a couple of regrets.

‘We would have liked to have spent more time insulating the eaves and junctions and making the building more airtight,’ says Smythe, ‘but the timescale was so tight at six weeks’. ‘We also realised we were wasting energy keeping drinks cool in the bar fridge at night. We’re thinking about wheeling them into the ice room but need to find a suitable trolley.'

This article was created by --CIBSE 14:43, 29 July 2014 (BST)

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