Heating & Plumbing: Heat Sources

Mark Brinkley explains the options when choosing a heating system.

Boilers

Boilers, fired by either gas or oil, are the standard heat sources for all housing in Britain. Mains gas is the most convenient (and cheapest) energy supply but it’s only available to around 85% of households, and many rural plots will be off mains. Oil used to be the preferred alternative, but it’s become much more expensive relative to mains gas and is now challenged by LPG (liquid petroleum gas), biofuels and electric heat pumps. Generally speaking, the lowcarbon technologies cost more to install but promise lower running costs.

Boiler technology has evolved over the years and condensing (or energy-efficient) boilers are now standard under Building Regulations. You can also now choose modulating boilers that run in two modes: trickle output designed for space heating and boost mode for domestic hot water.

Hot-Water Storage

Allied to your choice of heat source, you also have to consider how you want to store your domestic hot water. The choices are:

• Instant hot-water boilers (or combis): Best suited to smaller homes or flats where water demand will probably be low. The boilers are a little more expensive but you do away with the need for any cylinder in the airing cupboard. Combi boilers tend to have trouble delivering a good flow of hot water and the hotter you want the water, the lower the flow rate.

• Gravity-fed systems: Traditional water storage systems involve keeping a tank of cold water up in the loft and using this to feed into a hot-water cylinder. It’s relatively cheap to install, but has largely been replaced by pressurised hot-water systems which promise much better flow rates.

• Mains pressure tanks: These are cylinders which store water under pressure and don’t require any further tanks. The big plus for these systems is that they deliver hot water at mains pressure, giving a much better shower.

• Thermal stores These work in a similar fashion to mains pressure cylinders but they are marginally better at storing heat from additional power sources such as solar panels and wood stoves.

Do You Need Heating?

There has been a lot interest recently in Passive Houses, which don’t require heating systems. The Passive House idea stems from Germany and it involves building in hitherto undreamt of levels of insulation, triple glazing and airtightness, so much so that the house loses so little heat that you can do away with a conventional heating system. There are a number of self-builders who have gone down this route using innovative building systems like SIPs (structural insulated panels) or ICFs (insulated concrete forms). It’s worth pointing out that whilst they can successfully do without radiators or underfloor heating, they still need a method of heating hot water, and they all rely on woodburning stoves and an air-handling system to distribute the heat. Heated towel rails in bathrooms also feature. So whilst massive insulation makes it possible to make some savings on your heating system, it is probably unhelpful to call them ‘No Heat Homes’.

ABOVE: This ‘No Heat Home’ in an East Yorkshire village is built out of SIPs, is highly airtight and has a mechanical ventilation heat-recovery system. The concept was born out of necessity: the village had no mains gas and there was no room for an oil tank in the garden. Read more about this project.
BELOW: For off-mains homes, a common fuel option is generally to have an LPG supply, which is regularly topped up in a tank. Companies such as Calor Gas can be contracted to do this.

A Standard Home Heating System

Pumped systems are by far the most common type of heating system. The water is heated by the boiler and sent round the pipework via a pump. The water is then routed to the radiator circuit and/or the hot-water cylinder by means of a motorised valve. The same water recirculates round the system. There is a ‘feed and expansion’ cistern (usually in the loft) which keeps the system topped up when water is lost by evaporation or leakage. Above the cistern a vent pipe relieves excess pressure.