Allan Curran Architects: Article 6 – Energy Watch Series Thinking Of Building: HEATING!?

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Traditionally, open fires were used to heat houses. This was because the only fuels available were coal, timber, or turf, and the open fire provided some heat while allowing smoke and other gases to pass out of the building where they dispersed into the atmosphere. Of course we know now that a lot of heat was lost up the chimney, and that burning fossil fuels is not good from an environmental point of view.

For the same reason, recently the trend has been to move away from oil, gas and electricity as a means for providing home heating, and towards modern technologies which rely much less on these costly fuels. Remember that electricity from the grid is neither cheap nor environmentally friendly as a heating source, because very often it is generated using fossil fuels. Only wind power and hydro power are clean in this country. On top of that the Building Regulations are pushing us ever closer to using renewable heating methods only in new building work. So what are the options if you are wondering about your heating and don’t want to use oil, gas or electricity?

Firstly, keep in mind the passive gains from the sun through south- facing windows, and from internal sources like cooking, lights and even the human body. In a well- insulated house, these heat gains will become a big part of the overall heating strategy. As an example, space heating needs in a Passive House are typically met through passive solar gains (40- 60%), internal heat gains (20- 30%) and the remainder (10- 40%) needs to be provided by a heating system.

Then, make sure that your hot water distribution pipes and hot water cylinder are well insulated.

Heat generation systems

Mechanical heat recovery ventilation
When we wrote our article about ventilation, we spoke about using a mechanical ventilation system that takes the heat from the stale air leaving the building, and uses it to heat the fresh air coming in. There isn’t any contamination of the incoming fresh air, as only the heat is taken from the exhaust air. Generally, a small backup system will also be needed. In general, the better the airtightness of your house, the more likely you are to need a mechanical ventilation system, to ensure that all rooms get enough fresh air. A small amount of electricity is needed to run the system.

Wood pellet/ wood log boiler
Wood pellets and wood logs can be burned in a simple stove, a stove with a back boiler to heat water, or a boiler to heat water only in a plant room. Stoves and boilers need an air supply for combustion and also a flue, but they are usually ‘closed’ so that home airtightness is not really affected. Most stoves are very efficient and if used with a back boiler can provide hot water to heat ventilation air, radiators and underfloor room heating, and hot tap water. This system can also be used in tandem with solar panels, but a stove that simply radiates heat into a single room can’t be used for whole house heating. Keep in mind that a stove with a back boiler doesn’t provide ‘free’ hot water as more fuel will be required to provide the same level of room heat as a simple stove.

Geothermal heat pump systems
These harness the free and renewable energy in the ground or the air to help heat your home and supply hot water at a low cost. They ‘pump up’ heat from a low- temperature source such as the ground or the air, and release it at a higher temperature into your heating system. This technology is becoming ever more common as a means of heating your home, and while the initial outlay is greater than say a standard oil- fired boiler, the savings will accumulate over a period of years to make this a very good medium- term investment. It does require underfloor heating pipes, as the technology has not yet developed far enough to run with traditional radiators. A small amount of electricity is needed to run the system.

Solar water heating (solar panels)
Solar water heating systems use free heat from the sun to warm domestic hot tap water. A conventional boiler or immersion heating system can be used to make the water hotter, or to provide hot water when solar energy is unavailable. Solar water heating systems use solar panels, called collectors, fixed to your roof. These collect heat from the sun and use it to heat up water which is stored in a hot water cylinder. Solar panels can be used to provide room heating as well as domestic hot water, but the amount of heat provided is usually quite small and not really worthwhile.

Heat distribution systems

In the recent past, radiator systems have been the common way of distributing heat around buildings. Lately, underfloor heating has become an option for new houses, although it remains very disruptive and expensive to install in existing buildings. Mechanical heat recovery systems use a network of ducts to move the fresh air in and exhaust air out of the house, and is suitable for both new and refurbishment projects.

Underfloor heating reduces the energy consumption required for home heating, because it uses low water temperatures to heat rooms from the bottom up. It’s not a new technology; it has been well tried and tested at this stage, and is fast becoming the standard means of heat distribution in a house. It can be used with most floor coverings such as wood, carpet and tile, and will work with heat sources such as geothermal heat pumps, oil fired boilers, gas fired boilers, and wood pellet/ wood log boilers. The big advantages of underfloor heating (versus radiators) are that it gives even temperatures throughout the room and house, unlike radiators, and will work with geothermal systems, unlike radiators. The heat convects upwards from the floor, creating an even comfort level.

Next time, we’ll look at the systems you might use to generate your own electricity. These are quite specialised and relatively untried, but worth examining at the same time. After that, we’ll look at putting all the various elements together in order to reduce your carbon footprint and as a result, keeping your home energy bills down.

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