With centralised heat generation, communal heating systems provide an efficient route to providing heat and hot water to high-density homes, e.g. within tower blocks.
In blocks of flats, space heating requirements can be remarkably low compared to in, say, terraced housing, as there are fewer exterior-facing walls in a flat. If we see the flat as a cube, then usually 5 out of 6 of the cube’s faces are abutting other flats, and are thus warm. Generally, only one face is exposed to the elements, resulting in minimal heat loss.
In contrast, hot water usage within flats remains very much in line with hot water usage in any other building type of the same occupancy. For flats built to modern regulations, hot water usage can dominate the amount of total amount of heat drawn by the flat from a communal heating system’s Heat Interface Unit (HIU).
Recovering Heat From Showers
It is widely regarded that at least 80–85% of all hot water usage within the home is used for showering; hence, showering as an activity can be the most energy-intensive activity within a flat, consuming close to 2,000 kWh per year. Typically, no effort is made to recover any heat from the shower waste stream.
The Benefits Of Shower Heat Recovery
The savings from shower heat recovery can be substantial. Given that hot water usage for a 2-person occupancy flat can be 1,700 kWh/year, systems such as the Zypho Slim50 can recover approximately half of this – i.e., 850 kWh/year.
The benefits of such a high level of heat recovery include:
- Reduced demand on the communal heating supply system
- Reduced Carbon emissions
- Reduced bills for the resident
- Better SAP / EPC scores for the flat and building
Point 1, in particular, can have a major impact on the design of the communal hot water system. Lowering hot water demand by ~50% can reduce the power required for hot water boiler systems and the buffer tank capacity needed. These can result in considerable capital savings as well as reductions in operating costs.
Zypho models provide a straightforward method for recovering heat and reusing it within the HIU.
The principle involves running the outgoing shower waste through a Zypho shower heat recovery unit, and using the waste heat to pre-heat the fresh, incoming cold feed. This can then be fed to the HIU cold water input (if it is reasonably close to the shower) or the cold side of the shower mixer.
Unlike older vertical heat recovery units that require complex plumbing between different levels of the building, Zypho offers compact horizontal heat recovery within the flat, very close to the source, with minimal heat loss.
Zypho's Approach
Conventional Approach
A Simple Retrofit Solution
The Zypho Slim50 is a horizontal heat exchanger. At only 50 mm high, it is ideal for compact spaces. When designed in from the start, it simply becomes part of the plumbing, operating passively in conjunction with the HIU. The Slim50 runs solely on mains pressure water and gravity drainage with no moving parts or pumps that can ever malfunction.
Existing Builds
- For existing buildings that have already improved their fabric energy efficiency, significant EPC benefits can be achieved by installing Zypho. As a technology, it is an extremely cost-effective way to gain EPC uplift.
New Builds
- Zypho is a cost-effective way to improve SAP ratings and achieve carbon savings. Lower HW demand means smaller HW plant requirement, leading to capital savings on hot water production and storage.
An Alternative Approach
An alternative approach centres around not using the HIU for hot water production, but instead installing instant electric showers.
Until recently, it was not possible to operate an electric shower with Shower Heat Recovery, so developers tended to score less well when specifying them. However, Zypho has partnered with a major electric shower manufacturer to create a new range of compatible models. This has a significant impact on electrical power demand, reducing it from around 9 to ~5 kW, while delivering the same or even better shower experience.
Having instant electric showers rather than supplying hot water via an HIU means that hot water does not need to recirculate within a building all year round. Heating circuits are only required in winter, meaning the boiler can rest in the summer, with any residual hot water demand met by a smaller boiler or storage system.
