Domestic Renewable Heat Incentive

There has been much discussion on the domestic phase of the RHI and recently DECC have begun to manage expectations for delay and significant change. One of the most significant areas of discussion is the linking of renewable heat installations to improvement in the performance of the energy efficiency of housing.

The energy efficiency of buildings is of great importance and wherever possible should be improved. In the UK there is a very wide variety of housing, construction methods, materials, listed status and situation. It is widely recognised that a significant number of houses are “hard to treat” in terms of energy efficiency, in these properties achieving a high level of energy efficiency would be prohibitively expensive. There will be some measures that can be used to improve efficiency in each property, varying according to each house type, and these should be installed prior to any RHI being approved. For example loft insulation and low energy lighting are nearly always possible.

Not only is it important to reduce the quantity of energy consumed but also to decarbonise the source of the energy, these two aims do not always coincide. Biomass is a very low carbon source of heat, which when used in hard to treat properties effectively decarbonises all the heat used no matter what, if any, savings are made.

A good example is a 4 bed rural property that is listed, built of stone with lime mortar with an old slate roof. Solid wall insulation is not viable because it does not allow the walls to breathe. The air permeability will be high, and has to remain so in order to properly ventilate the structure. The listed status means the exterior cannot be altered. Yes, loft insulation and low energy lighting should be installed but after that the most effective carbon cutting measure is a biomass boiler. Should the RHI rules prevent this then the alternative is for the home owner remain on oil heating, with no improvement in carbon or energy saving.

An assessment of carbon reduction would be a more appropriate measure of the positive impact of renewable energy technologies. This would allow the carbon reduction to be recognised independently of energy saving.

Unlike heat pumps biomass offers a completely different fuel source and therefore greater freedom for consumers. Heat pumps are completely reliant on electrical power, and the carbon emissions are a reflection of the grid carbon intensity, around ½ Kg of CO2 against biomass at ¹/₄₀ Kg CO2 per KWh of energy. Biomass can be sourced locally, nationally and globally and is traded by larger dedicated suppliers, independent small mills and local agents. Local jobs are created from forestry workers, fuel processing, installers and equipment suppliers.

Small scale biomass, i.e. less than 25KW or 2 bed houses, is viable and efficient. A good example of this is the Italian wood pellet stove market where thousands of small appliances have been fitted. These stoves are reliable, clean and efficient and on top of this they are also low cost. However unlike heat pumps no significant modifications of existing heating systems are required because the flow temperatures are similar to fossil fuel boilers. This is a major advantage in cutting the cost and making installations far simpler.

In summary small scale biomass is a clean, efficient and cost effective way of reducing the carbon footprint of the UK’s housing stock. It can be combined with some energy efficiency measures but its potential to reduce carbon emissions must not be stifled by too heavy a hand.