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Buying into biomass

As a sustainable low-carbon technology, biomass has become an increasingly popular option for housing associations. What's more, registered landlords who have installed biomass have seen a reduction in fuel bills for their tenants, making it even more attractive - particularly those operating in rural areas. But for those who have yet to specify a biomass system, how would it work in practice? Here, Jon Cockburn, head of marketing at Heatrae Sadia, tells us more.

Last year housing associations built 50,000 homes. This amounts to 40 per cent of all new homes across the country, and with the government's latest pledge to build a million homes by 2020, it's crucial to consider sustainability when planning new builds.

When building in rural areas, or any location which doesn't have access to mains gas, housing associations must balance the need for reliable power with environmental concerns, and the potential fuel costs to future tenants.

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, housing associations which already run biomass heating systems have reported fuel savings of as much as 40 per cent compared to traditional fuel sources. For tenants who are on strict budgets to ensure they can balance their rent and outgoings, 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 residence?

One option is Heat Interface Units (HIUs), which are increasingly viewed as a sustainable solution that combines maximum safety with easy 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 targets.

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 housing associations, 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, housing associations 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, landlords 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.

Ultimately HIUs offer housing associations a convenient and effective route to designing low carbon and sustainable technologies like biomass into their portfolios.

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