Frequently Asked Questions

In most cases, yes - over the mid to longer term. There is obviously the initial capital expenditure to factor in but the ongoing running costs will be undoubtedly cheaper than those of current conventional energies. However it is impossible to predict accurately what the cost saving will be because of the unknown future pricing of gas or oil but it is fairly safe to expect them to rise.

As well as reducing annual fuel bills, an investment in renewable heat and power generation will also add value to a house. There is now strong evidence that house buyers are increasingly aware of the fuel costs involved in heating a home, and are prepared to pay more for houses that have lower operating costs.

A meaningful payback period can only be calculated if future gas and oil prices are predictable, but the volatility of the last few years demonstrates amply that they are not. Some commentators are prepared to base their payback analyses on a simple extrapolation of current prices, but set against a rising trend in prices this will consistently overestimate the payback period.

The important point to note is that once installed, there are no running costs for solar systems, very low costs for geothermal systems and for those areas where wood is plentiful, biomass is likely to be much more cost effective than relying upon imported gas or oil.

Heating requirements can be assessed using the Standard Assessment Procedure for Energy Rating of Dwellings (SAP 2012). The heat loss coefficient for the building envelope, including doors and windows, is derived based on the fabric heat loss, thermal bridging and ventilation heat loss. From this the peak heat load is calculated.

Before we can specify a biomass boiler or a heat pump we will need to carry out an MCS heat loss analysis. This gives us a peak heating requirement for the building and also room-by-room heat losses for design of heat emitters (UFH, radiators etc). This analysis also gives us a recommended flow temperature for the heat pump to work effectively.

Energy needs are often most cost effectively addressed by strategies that minimise energy consumption. Improvements to building fabric and reduced ventilation are the highest priorities along with low energy appliances and light bulbs. The next priority is to make use of any locally available clean or renewable sources of energy. In Kent these will typically be solar (thermal or PV) and biomass (wood/pellet stoves or boilers). Finally where fossil fuel use cannot be avoided, higher efficiency appliances should be used, e.g. condensing boilers.

A solar combi system provides both hot water and space heating to meet a building’s energy needs. The pitch and orientation of the solar collectors are set to maximise the winter heat gain and to minimise overheating in summer. Typically the collector area will be greater than is used for a standard solar hot water system.

The collectors will be linked to a heat store (aka thermal store) which replaces the traditional hot water storage cylinder. This heat store supplies both hot water at mains pressure as well as heat for the central or underfloor heating. An auxiliary heat source such as a boiler or a wood stove can be used to supplement the solar collectors during periods of peak heat demand.

Solar combi systems can be used effectively in well constructed modern houses where the heating requirement has been significantly reduced through a combination of airtightness, insulation and minimal thermal bridging.

During the summer a solar hot water and/or heating system can receive more heat than is needed to supply heat loads. Traditionally once the solar collector has reached this state it is allowed to stagnate at temperatures which can be 230°C or more for evacuated tube collectors, with high temperature steam forming in the upper pipework. By careful location of any temperature sensitive components this need not cause any major problems. An expansion vessel and ultimately a pressure relief valve provide protection against the increase in pressure. However it places a limit on the target solar fraction, since continual overheating can damage the heat transfer fluid.

A more robust approach that we apply as standard is to install a mechanism for dumping excess heat from the hot water storage vessel, preventing the solar collector from reaching stagnation temperatures. This can be achieved by circulating heat away from the storage through heat emitters or ideally to a useful heating load such as a swimming pool.

Yes. Any orientation between southeast and southwest is suitable. For more oblique orientations we may propose installation of a dual system with an east and west facing solar collector(s). Both systems get sun light for the part of the day and as both feed into the one heat storage cylinder the overall gain is similar to a south facing system. It does require more work during installation and also two collectors, but the extra cost is usually not a significant element in the overall installation.

If the collectors are not directly visible from a public highway, then they are considered to be a permitted development, which means you do not need to apply for planning permission, even in a conservation area. We find in practice that even if the proposed site is visible from the road, planning authorities are often prepared to accommodate a collector, but may work with you to try to identify a less obtrusive site such as an outbuilding or a garage.

Currently you are paid an export tariff (approximately 5.5p/kWh) for the elctricity you export to the grid, therefore if you are able to utilise more electricity on site then there is a financial benefit. The best way to do this is by using a solar switch. This device works by sensing when you are generating more electricity that you are using onsite and then it diverts electricity to a demand in the house such as switching on the immersion element in your hot water cylinder. This can provide a substantial amount of your domestic hot water in the non-heating season. Otherwise you could divert to an electric car charger or battery back-up system.

No, not necessarily, though it does mean that certain conditions may have to be met according to the guidelines laid out by your planning area. We have many clients in similar circumstances. In our experience, most situations can be accommodated by carefully considering the position of the solar panels such as placing out of direct line of sight, e.g. on a flat roof or in an inverted roof pitch, on an outbuilding or by ground mounting.

Your permitted development rights are exactly the same as for those living elsewhere. Restrictions on permitted development rights apply only to householders in listed buildings, designated conservation areas or World Heritage sites.

Yes. In some installations we recommend clients retain their existing boiler as a back up in order to provide an auxiliary means of ‘topping up’ the cylinder and meeting occasional ‘peak’ heat loads. When it's not being used there is no fuel cost for the existing system, so it is more often sensible to keep it available. The only draw back may be if you wish to claim any available govt grants. For example, the current Boiler Upgrade Scheme (BUS) is only available where the renewable technology completely replaces a fossil fuel boiler and hence the exisiting boiler must be removed in order to qualify for the grant.

It depends upon the model of wood stove but in principle, yes. It can be connected to a back boiler or a ‘collar’ around the flue to link to central heating or to supply domestic hot water. To provide a link-up with an existing gas- or oil-fired boiler we would typically install a thermal store, although sometimes a neutraliser may be used.

By charging an accumulator tank with heat from a log boiler, or even from a wood stove with a back boiler, hot water and heating will be available at the time it is needed. An accumulator tank ‘buffers’ heat so it can be delivered later.

The earlier the better. Where possible the technologies for ventilation, heating, cooling and power need to be incorporated into a building’s fabric, not just bolted on during the first fix stage. The best time to specify these elements is at the time of the as-designed SAP analysis. If you are considering a ground source heat pump then the ground collectors can be installed at the same time as the ground works are carried out.

No – all have their advantages but the optimal configuration for an individual household depends upon 4 key factors; the building’s fabric, its location, its occupancy, and the occupant’s lifestyle. Only by evaluating all four can the best solution be defined for a particular site. For some sites the constraints of planning policy will have an important role in determining which technology is most practicable to deploy.

We provide a consultancy service to evaluate the best suited technology or combination of technologies for any project. It is worth noting that we are not tied to certain manufacturers so we can give a completely unbiased opinion. Please contact us for more details.

Yes, currently the govt has a Boiler Upgrade Scheme (BUS) which offers a voucher for £5,000 for Air Source Heat Pumps and Biomass and £6,000 for Ground Source Heat Pumps. Your installer applies for the voucher on your behalf and if successful, it is paid to the installer to offset the balance on the final invoice.