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Fuel for thought

For homes located in rural areas, mains gas power is not always an option. When it comes to local authority housing, it is vital that the alternative energy source selected is as cost effective as possible to support tenants and combat heat poverty. Biomass fuelled High Interface Units (HIUs) combine cost efficiency, easy maintenance and low carbon credentials to create the perfect solution. Jon Cockburn, head of marketing at Heatrae Sadia, explores the benefits.

When building new homes or managing existing stock in rural areas, or any location which doesn't have access to mains gas, local authorities must balance the need for reliable power with environmental concerns and potential fuel costs.

An increasingly popular solution is biomass fuel. Although biomass is often used as a by-word for plant derived energy, it actually applies to any biological material gained from vegetables and animals, and in Europe is most likely to mean wood and energy crops.

A recent report estimates that UK-grown biomass could cut the cost of meeting the UK's 2050 carbon targets by over one per cent of GDP - an important consideration when choosing an environmentally responsible fuel source.

Additionally, properties which already run biomass heating systems have reported fuel savings of as much as 40 per cent compared to traditional fuel sources. For cash strapped tenants on low incomes, a reduction in energy costs on that scale can make a huge difference.

But what's the best way to build a biomass system into a multi-occupancy council managed residence?

One option is Heat Interface Units (HIUs), which are increasingly viewed as a sustainable solution that combines maximum safety with fuss-free maintenance. They can be used to provide central heating, and sometimes domestic hot water, to individual properties within a multi-dwelling development (such as a block of flats or apartments, or a larger district heating scheme) served by centralised heating plant.

Centralised plant significantly reduces the time and costs involved with boiler servicing and maintenance, and the problems associated with supplying gas to multi-dwelling buildings, decreasing the risks linked to gas distribution pipework and costs. It also eliminates the need to fit numerous flue terminals or condensate drainage systems, reducing the capital installation and whole life costs as a result. If there are no other gas appliances in the affected properties, centralised plant could even negate the need for individual gas checks.

The incorporation of low carbon or renewable technologies - such as biomass - can become simpler and more cost-effective when paired with this kind of system. The diverse thermal loads offered by multi-occupancy accommodation presents an attractive demand profile against which biomass technologies can be operated to maximise the benefits, helping designers and specifiers to meet zero carbon.

Serving multiple dwellings with centralised heating plant requires a way to manage temperature control and monitor each household's energy use to ensure correct billing. In the case of HIUs, the amount consumed by an individual household is recorded by a meter.

Meter readings can be carried out remotely, making HIUs a very attractive option for local authorities, who can then bill their tenants. Metering can also be a positive incentive for occupants trying to lower their energy consumption, and can help to reduce fuel poverty among vulnerable groups.

A controller monitors and regulates the heating and hot water system in order to optimise performance, working with a room thermostat. Units come complete with a factory set of 55ºC for domestic hot water and 60ºC for the heating circuit, standardising usage for tenants. A two speed pressure independent controller output prevents overshoot of the temperature set point, ensuring more stable control of temperature, and an integral pulsed bypass function kicks in during periods of no heating to ensure that the HIU is quick to respond when it is eventually used.

HIUs can be installed within each individual dwelling, or in the dividing wall between each dwelling and the 'landlord' space for easy access for inspection and maintenance.

As a matter of course, council planners should ensure that HIU installations are electrically, as well as hydraulically, safe.

Currently, fixed wiring installations in new build properties are required to comply with Part P Building Regulations, and management regulations for multi-occupancy properties require landlords to arrange for a qualified electrician to inspect and test fixed electrical installations every five years. However, while this would cover the ring main from the fuse box - up to and including the sockets and fused spurs - it does not cover the HIU itself.

Meanwhile, there is no legal obligation to carry out a portable appliance test (PAT) in residential rented accommodation*. While the Electrical Safety Council recommends PAT testing to ensure that landlord supplied appliances are safe at the point of letting, the HIU wouldn't be included as it doesn't fall under the definition of a portable appliance.

Therefore, to ensure electrical safety, councils should look to independent third party approvals of the HIU in order to be sure that they comply with electrical industry standards and regulations. For example, the NEMKO mark demonstrates that the product has been assessed for conformity to electrical safety legislation by a competent body.

Equally, independent testing for water fittings ensures that products are suitable for potable water use, guaranteeing that they are safe to use and will guard against contaminating potable water supplies. Here, the industry standard third party certification is provided by WRAS or KIWA.

HIUs provide an ideal route for councils looking to incorporate money-saving, sustainable technologies such as biomass into their portfolios, while having a positive impact upon their tenants.

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