City living demands an innovative hot water solution

By Eamonn Ryan

What makes the 158 rental units at the eight-floor 2A Harrison St, Marshalltown overlooking Standard Bank’s head office on Rissik Street, unique is the choice to use a decentralised water heating solution provided by Stiebel Eltron’s instantaneous water heaters.

 

One way of adapting and reusing vacant office buildings is conversion into housing. However, it creates unique challenges, such as long ribbon windows not meant to be separated into units; in this case a massive safe on the ground floor of the premises; and bathrooms situated on staircase landings.

Sink

Instantaneous water systems suit a simple configuration of shower, basin and sink. Credit: Eamonn Ryan

 

Shower

Triumph Taps and Solo Sanitary Ware were selected in respect of taps, mixers and other bathroom finishes. Credit: Eamonn Ryan 

The building is the old Trust Bank building, that is being refurbished by developer Lightwell Properties into 158 accommodation units. “There was a massive safe on the ground floor that took about six months to remove,” says Simeon Kahan, plumber at Pro Plumbing. The project commenced at the beginning of August, with a deadline of two floors complete by 1 October, which was achieved, and the floors already let. The final three floors were in the process of being completed in late November last year, with 12 additional units being built on the roof.

The interior is decorated with face-brick that has been brushed with rhinolite for a smooth, maintenance-free surface. The architect, Greg Katz, also created a community feel through the use of vibrant and colourful common sitting facilities. The location of the building is an attraction, directly facing Standard Bank’s CBD offices – an area Katz describes as ‘a nice part of town’.

The plumber’s perspective

Tight deadlines meant Pro Plumbing had to work hand in hand with the builders to complete the plumbing as each floor was renovated. “It’s a bit crazy working while two floors are already occupied, and it meant we had to have the drainage done beforehand.”

Each floor is a combination of bachelor pads, one- and two-bedroom units, and three to four luxury units on each floor. Rentals starting at a reasonable R3 800 to R4 200 per month and falls into the affordable housing market notwithstanding that the finishes are superior to those commonly found in other CDB developments.

Each unit has a standard bathroom – something of a misnomer considering none have baths, only showers. It has a swimming pool on the roof along with an Astroturf garden and finishes that are of a high quality. “It is affordable housing that doesn’t look like affordable housing – especially when you look at the rest of the ‘affordable housing’ here in the CBD,” quips Kahan.

Pro Plumbing’s brief was to supply the hot water reticulation and it came up with the solution of decentralised water heating, rather than the other available solutions: hot water geysers; heat pump; or solar heating. “It’s a conversion, stripping out the guttering, installing new sewer pipes and PVC. It required a new drainage and entirely new reticulation system, and a smart meterage system with an electronic probe for each unit so that each could be responsible for its own pre-paid billing. The great thing about the smart meters is they are all panelled up and invisible.”

“This was our design, based on the brief from the developer which wanted to bill each tenant individually, giving peace of mind to the developer,” says Kahan. The advantage of this system as opposed to a heat pump for a building, is that the amount of hot water varies considerably between tenants with some benefitting and others losing out – potentially causing tensions. Commercial-sized heat pumps come into their own in large developments with the considerable cost of the heat pump and reticulation system being averaged out over 400 or more units.

The instantaneous water heaters with the advantages for such concentrated living arrangements being its compact size. It’s flow rate of 5-6ℓ is suitable for a single person to have a hot shower or to run a tap, without worrying about running out of sufficiently hot water. This is far more economical than any other system as the water is not heated unless it’s being used. However, it will not be sufficient to fill a bath.

“From our perspective these units are easy to install – you’re in and out very quickly – while with a geyser you have to have sufficient space within each unit, and it has to fall within the SANS regulations when its installed,” says Kahan.

Instantaneous water is much easier to regulate because there’s no tank to store water.

How much electricity (and money) is saved will always be an imprecise measure as it depends on usage and other factors, but Kahan says they are evaluating previous installations “and there are no complaints from the tenants.”
Instantaneous water heating occurs by passing water from the mains cold water system past a thermostatic probe, which heats the cold water.

While Stiebel Eltron was selected for the water heaters; Triumph Taps, Solo Sanitary Ware, and Triumph Showers were selected in respect of taps, mixers and other bathroom finishes; and Geberit for mepla pipes for reticulation. These were chosen by the developer and architect (Greg Katz) as preferred brands, and in the case of at least the latter because they are highly reliable. In the case of mepla piping, says Kahan, there is also less potential for piping theft.

“We only use SABS-approved products to SANS 10400 regulations for piping and fixtures.” A rational design can be done by the electrical or wet service engineer on the project. Because the instant water heaters are still ‘new’ to the South African market, there is nothing in the paperwork to actually work from for SANS.

Pros and cons: the supplier’s perspective

An instantaneous water heating system adds to the efficiency of the building in terms of future running costs as no electricity or water is wasted, explains Kahan. The downsides are that a single phase unit can’t be used for baths, while bigger units (for a family, for instance) require three-phase electricity the same as a commercial building requires.

The building has no other water saving features such as water harvesting or greywater systems, due to the age of the building and tight space available, though borehole water is apparently ‘under consideration’. This will ultimately depend on the cost viability, as the filtration system will be a considerable expense.
The selection of a hot water system depends broadly on two factors: the number of units in a development, and what the water is to be used for. The number of units is similarly affected by occupancy levels: heat pumps are most efficient when used to their maximum. If it is the sort of development where people are away for long times, then the heat pump will not achieve its full potential. In that case, an on-demand system is more effective.

Niel Bosman, technical engineer at Stiebel Eltron Southern Africa, explains that the choice of system is largely a function of the size of the development. “The fewer the number of units, the higher the price would be per unit/tenant in the case of a centralised heat pump system because of its fixed costs. A centralised heat pump system consists of the heat pump itself, storage capacity, ring main system, lagging of pipes, the plant room itself – whereas with a decentralised instantaneous hot water system all you need is the cold water connection with the water heater connected to the DB directly.

“An instantaneous water system definitely works better than an integrated system, where the need is for a simple configuration of shower, basin and sink.

“With regards to the installation, the instantaneous water heaters will be done according to SANS 10254. Their installation is much simpler than a geyser, as they do not have any storage capacity. So, no drip tray, TP valve or vacuum breakers required. As for SANS 10400 XA, the instant water heater is quite new to the market and was not included/considered when the standard was written,” says Bosman.

“Thus, the use of a rational design is required by the professional in charge of the energy efficiency of the building. Due to the lack of storage capacity and the short pipe runs, the energy efficiency/power consumption of the instantaneous water heater is a lot better than that of a geyser or in this case, even a split heat pump system,” he adds.

 Features:

  • Microprocessor control with inlet and outlet temperature sensor for accurate temperature delivery
  • Selection of temperature (40, 50, 60 °C) up to maximum output for maximum convenience.
  • Manually adjustable flow limiter in cold water inlet (can be adjusted by the contractor) for greater energy savings.
  • LED ON indicator on the appliance cover provides clear information about appliance status.
  • Installation on finished and unfinished walls is possible.
  • IP 25 for greater protection against water ingress (hose-proof).
  • Tubular heater made of copper for a longer service life.

The architect’s perspective

“There is huge demand for housing in CBDs, which is fuelling the trend to adapt and reuse existing buildings – a form of recycling reflecting an urge towards sustainability to reuse rather than demolish. It’s an ethical solution,” explains Katz of Gregory Katz Architecture, the architect on the project.

“There are a number of challenges to adaptation, but also advantages. In this case, a good starting point was the fact that the structure had an H shape, which was conducive to good natural lighting, but the building also had the ribbon-window design of the 1950s and 1960s, where there was no break between windows. This made it tricky for fire control purposes to separate the structure into individual units, but also enabled us to be more creative in finding a solution.” That solution was to intersperse clear glass with Georgian wire glass, thereby creating an interesting façade set at a 45-degree angle so as to create a bay window feel.

“The idea of the community feel is that residents ‘take ownership’ of the building. High density urban living is not yet common in South Africa, and so the design has emphasised more congregating spaces so that each floor feels like a unique community. For instance, the basement has been renovated to provide a mix of retail and accommodation, with a creche. We have used every inch of space,” says Katz.

 

Developer

  • Nightwell Properties

Professional team

  • Gregory Katz Architecture

Contractor

  • Pro Plumbing

List of suppliers:

  • Geberit – piping
  • Gyproc – Rhinolite
  • Triumph Taps, Solo Sanitary Ware, Triumph Showers – mixers, taps and sanware
  • Stiebel Eltron – water heaters

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