HEATING LIGHTING AND VENTILATION

Any new construction project, in order to be a useful and habitable environment, will require a level of heating, lighting and ventilation. The levels required will vary according to local regulations. For example there are minimum standards on ventilation, and for commercial premises, heat must be kept above 16 degrees Celsius during working hours.

In terms of green building these systems offer the chance to make huge savings on money and carbon emissions especially when considered at the start of a new build.

There are two main sub categories of heat, light and ventilation systems, termed passive and active systems.

Passive

Passive systems often give 'free' heat, light and ventilation. Active systems require some sort of energy boost. Each has their own advantages and disadvantages.

Passive lighting of a house is achieved through the planned use of the sun. When Passive solar design is used in a construction the most occupied rooms, such as living rooms, are placed onto the south side of a structure (in the Northern Hemisphere). This affords maximum exposure to sunlight allowing passive heating to take place. The large windows used to collect solar heat also allow a lot of light in reducing the need for artificial light.

To maximise this light it may be beneficial to plant trees and hedging in such a way as to provide privacy at ground level without blocking the sunlight's path to the structure. This will reduce the need for privacy measures such as net curtains that can reduce the amount of light and heat let into a room.

Sun pipes can also be used to channel light into dark rooms, usually those in basements or within structure. A sun pipe is a mirrored gathering framework which reflects sunlight down a mirrored pipe into the ceiling panel. Some have rotators or tilters to keep them aligned with the position of the sun during the day.

There is no one term for these passive devices. Sunpipe and Solatube are registered trademarks. They are also known as sun tunnels or tubes, light or daylight pipes, light tunnels, or tubular skylights.

Normal skylights are also called roof or attic windows and do not have the reflective channeling technology. Conservation skylights sit flush to the roof and are less ugly that normal skylights.

Active

Active lighting involves the creation of artificial light when natural light is unavailable (night time or heavily clouded days). There are many different types of light on the market all suited to various applications and each with its own energy efficiency rating. Traditional light bulbs consist of a filament in an inert gas such as argon, when electricity is applied the filament's resistance generates light and heat. These bulbs waste a lot of energy compared to other types.

Energy saving light bulbs take many forms but are commonly based around fluorescent technologies. Energy saving light bulbs are more expensive than traditional filament bulbs at around 3-7 GBP each (compared to 0.5 GBP and up for standard bulbs) however the cost is far outweighed by the energy they save over their lifetime. Depending on the lights usage a single 13 Watt energy saving bulb in place of a 60 Watt conventional bulb can save around 7 GBP a year as well as 26kgs of CO2 emissions. Replacing all the bulbs in a building can net savings running into hundreds of pounds annually.

Every make of low energy bulb contains up to 5mg of highly toxic Mercury, and should be recycled by sending back to the manufacturer. Also if more than five are broken at any one time, there is a risk of mercury poisoning, and the room should be vacated and ventilated. This is not normally an issue, and also applies to fluorescent strip lighting that has been used for decades with no panic. Compact fluorescent bulbs have even been reported to cause migraines.

While energy saving bulbs can be used in existing fittings they have a major drawback on systems that are fitted with dimmer switches. In these systems only a few energy saving bulbs such as the new DigiFlux from Varilight will work.

DigiFlux are more costly than normal energy saving bulbs. They also produce a warmer light. They have a continuous dimming ability, unlike some that are either off, half on, or on.

Energy saving bulbs are less popular than normal incandescent bulbs due to the cold quality of the light.

This is changing as new designs come on the market due to legislation requiring the use of energy saving bulbs.

Heating

The heating of a building is vital not just for the health of the occupants but also the safety of a building's structure. Too cold a building will cause excessive condensation, trapping moisture within the building leading to mould and rot.

Active heating systems normally require the combustion of a liquid or solid fuel. This process will inevitably release carbon dioxide into the atmosphere meaning that in green building using active heating systems requires that the amount of fuel used be reduced as much as possible.

A simple and effective upgrade to homes with a current gas central heating system is to replace inefficient boilers with an energy efficient condensing boiler. This type of boiler reduces the amount of waste heat sent up the flue. This is done by converting the water vapour created during the burning of the gas or oil fuel back into water, which releases latent heat then captured through a heat exchanger. This allows a condensing boiler to operate at over 90% efficiency (compared to around 75% for a modern non-condensing boiler).

Condensing boilers are now mandatory for new installations in the UK.

Although costing 50% more than a standard boiler, the saving of up to 40% in fuel usage allows this to be offset, with the extra cost being paid for in 2-3 years operation at UK gas prices.

Heating systems

Ground Source Heat Pumps (GSHP) use the earth's warmth to warm the house. In these systems water is pumped through tubing buried into the earth to extract its heat. These systems have the advantage of being low carbon and when other forms of electricity (such as PV solar panels) are used to power the pumps they can become a zero carbon and completely sustainable form of heating.

Initial costs particularly in adapting current buildings are high but running costs are similar to systems with a condensing boiler. Using a GSHP system can save 2-8 tonnes of CO2 annually, a saving of around £400 - £800; however this depends on the type of fuel being replaced. GSHP systems do require a lot of room to operate effectively making them ideal for rural areas, where mains gas is not available for heating systems. They are far better than oil which is the common choice in rural areas. Rural areas often do not have mains gas, which is the cheapest option (at present prices) for heating systems.

Other active heating systems that improve energy efficiency will require more to be done to existing structures. These include underfloor heating, which is more efficient than radiated heating systems. The use of different types of renewable fuel, for example wooden pellets, in boilers, although carbon neutral are expensive and not allowed in certain areas. For larger building projects, such as new housing estates, there is the option of generating heat centrally at a large boiler plant and pumping it out (some 200,000 homes in New York City are supplied this way).

Passive heating

Passive heating of a building relies predominately on solar power. There are various methods this can be achieved in both new and existing builds. When building a new structure it is imperative to design it such that the most occupied rooms face south, these rooms can then be glazed with large energy efficient windows (such as low-e triple glazing) trapping the heat in the building.

Passive heating can be built into the walls of structures either by design or purely relying on a buildings thermal mass. Thicker more dense materials will absorb the sun's heat during the day, releasing it at night. Constructing a southern facing wall in the Trombe style (where an insulating piece of glass is placed over a wall painted dark) will also cause significant heat build up. One way vents at the top edges of the wall allow heat to flow into a building, providing ideal space heating and ventilation.

Solar hot water systems can be added to existing central heating systems. These consist of panels which take the sun's heat and use it to warm water which allow boiler systems to act as a top up rather then providing all the heat. The saving a solar hot water system makes depends on the climate and the location of the building.

A typical system in the United Kingdom can save between £40-£80 a year and shave off 350kg of CO2 emissions. A domestic system will require about 2-4 square meters on a south-east to south west facing roof and a average domestic system can be installed for between £3,200 - £4,500 although grants may be available from the government to reduce the cost of installation.

A lesser used but still viable form of solar heating is Passive Solar Air Heating. This system is popular in Scandinavia and is useful for space heating. The system works by using external boxes designed to absorb the heat from the sun, this causes the hot air to rise, forcing cold air down. This warmer air can then be channelled into a building where, as an added bonus, it has a dehumidifying effect because the air has been dried by the heating process. These systems require no power to operate so the heating gained is completely free! See our chapters on solar power.

Ventilation

Ventilation is an essential part of building design. The changing of air is required to prevent rot and to prevent health problems such as 'sick building syndrome'.

Passive Stack Ventilation (PSV) systems use the heated air of a building to draw air through a building, as the hot air rises out of a building it pulls fresher air into it. This has the advantage of a completely silent ventilation system and also does not require any fans to operate reducing the energy requirement of the building.

Wind based Ventilation systems are more powerful the PSV systems. These are designed into a building so that the external air pressure on one side of the building is lower then the side facing the wind. Wind is then channelled through the building replacing old air and drawing it out into the lower pressure of the outside air on the non-wind facing (lee) side. Wind based systems are cheap to implement and effective but they do have the drawback that air quality is related to external conditions so they can draw in pollutants from outside a building such as industrial exhaust as well as being difficult to control precisely. Ideally wind and PSV systems are used together to create a full natural ventilation system that can work at any time of the day or night.

In contrast active ventilation systems require the use of power in order to move air around and some such as air conditioning systems are particularly wasteful and require harmful man made chemicals (old air conditioning systems are a major contributor to CFCs released into the atmosphere).

Mechanical systems have the advantage of being able to act as filters or dehumidifiers to the air being ventilated, as well as having the ability to recover some heat from the air about to be pumped into the outside world through the use of a heat exchanger. They can capture up to 80% of the exhaust vent's heat and distribute it back into the building. However the power required cancels out a lot of the energy efficiency gained from recovering the lost heat but does prevent fuel from being burnt. Solar power can be used to offset some of the energy usage of mechanical systems.

Both active and passive heating, lighting and ventilation systems have their uses for the green builder. When constructing a new build if careful consideration is given to all three the results can be staggering. Real-world examples of this include various buildings in the Middle East, which use solar energy to ventilate the hot desert air, as well as provide warm water. The German Passivhaus (passive house) style of building which incorporates passive solar design, mechanical and natural ventilation, efficient insulation and various forms of heating to create a house which consumes less than 15KWh/m2, compared to typically 55KWh/m2 in an average UK home, in heating yearly.

The reduction of fuel used by natural heating, lighting and ventilation systems reduces the need for fresh materials to be consumed, whilst achieving the same end result. This will increase the amount of time that finite reserves of oil and natural gas can be used, and will slow down the rate at which carbon dioxide is released into the atmosphere. While initial costs are high they can be subsidised with various grants and often (as is the case with condensing boilers and energy saving light bulbs) more energy efficient methods will pay for themselves.