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Consider installing localised air conditioners with local on and off controls such as split systems or variable refrigerant flow systems for intermittently occupied spaces. 

During nights and periodical diurnal absence the thermostat can be set to a setback temperature, which saves energy. In spaces that require to be conditioned during unconditioned periods for reasons of frost or optimized start up etc. the space temperature can be set to a lower or higher temperature called setback temperature. For example, the setback temperature can be set to 32 °C from a comfort temperature of 24 °C during unoccupied hours. 

Use geothermal cooling or district cooling which uses naturally available heat sinks. Integrating air conditioners and heat pumps with these technologies saves considerable amount of energy.

The chilled water pipes in case of central chillers and refrigerant pipes in case of VRV/VRF should be thoroughly insulated to minimize cooling losses during transmission. Where possible they should be located within the building’s thermal envelope. Additionally, all the junctions and accessory fitting in the pipelines work should be thoroughly insulated.

Choose a system with high COP value and which uses refrigerants with no green house gas emissions and ozone depleting potential.

Programmable thermostats allow for complex functions like cooling the space just before occupancy and shifting the temperature to setback limits or turning off the system during standby or prolonged unoccupied periods. PT can be set for different modes such as manual on and auto off etc. and can also have a temporary override or hold function to manually control it when necessary. However, care needs to be taken that the user is in full control and fully aware of the functions of the programmable thermostats. US Environmental Protection Agency reports that homeowners can save about $ 180 (€ 140) a year by properly setting their programmable thermostats and maintaining those settings  (Energy star) It is noticed that by reducing the room temperature by 1%, 6% of heating energy is saved  (ABB). The most advanced ones work with multi purpose remote controls and via Internet Protocol through smartphones and laptops. 

Cooling systems with split evaporator and condenser should ensure that the condenser is located in a relatively cooler, shaded and ventilated area. The difference between the temperature in the evaporator unit and the condenser is crucial in determining the efficiency of the system and the energy consumption. The minimum the temperature differential the better it is.

Areas with both ceiling fans and air conditioning operating at the same time can operate at higher set point temperatures. Air movement induces feeling of comfort and make higher temperatures tolerable.

Cooling systems should not be overdesigned. It is a general tendency among the HVAC designers to design for peak load conditions with high factors of safety. Since peaks occur only for a brief period of time annually, it results in the system being oversized most of the time.

In spite of selecting high COP systems, most of the times the systems are not optimally designed for the climate, occupancy and usage patterns. The design and selection of system should be optimized to provide comfort at the least possible energy consumption. Cooling systems should be holistically planned. Both the cooling system and the cooling distribution to the spaces should be designed based on the above mentioned parameters.

The efficiency of the system depends on the difference between the cold end and hot end of the system. The lower the difference, the more efficiently the system operates. Considerable energy savings can be made by maintaining a constant difference between the cold end and hot end, above a certain threshold temperature, instead of maintaining a fixed set point temperature. Though this could result in fluctuating indoor temperature which changes by few degrees, this is often not perceivable. Additionally, control systems optimize energy consumption by responding to occupancy by modulating between setback temperature and set point temperature system schedules and local controls.

Heat rejection units (cooling towers in the case of water cooled chillers and Outdoor units/Rooftop units in the case of VRV Outdoor units/air cooled chillers) should be located in shaded cool areas to avoid unnecessary heat gains as much as possible. Although, they should not be enclosed and free air movement should be ensured all around. 

Use heat pump cooling systems with Variable Refrigerant Volume/Flow (VRV/VRF) technology. This enables the compressor motor to respond to the load and increase or decrease the speed of the compressor accordingly and thus saves energy compared to a motor operating at a constant speed. High efficiency VRV systems have a COP of 4.4-4.6 and save approximately 10-25% energy compared to regular VAV and chiller systems.

Chilled water pipes embedded in floor or ceiling or in specially made false ceiling or beams cool the space through radiation. This technology is very effective in buildings with tightly sealed envelopes and with constant cooling loads. An outdoor air system is required to provide treated fresh air in to the space. This however is not suitable in leaky buildings and spaces with continuously fluctuating cooling loads. In case of high latent gains due to humidity usage of special purpose dehumidifier is recommended to avoid condensation in the space.

If both Combined Heating, Cooling and Power (CHCP) and renewable systems are not feasible priority should be given to using the most efficient cooling systems available. Values for the EER of 5 or higher are recommended (Cooling efficiency is measured in Energy Efficiency Ratio (EER) (kW_th/kW_el)).

Cooling control systems employ a series of sensors and actuators, which are, controlled either locally or centrally. They take into consideration the occupancy patterns and user behaviour and optimize the cooling system accordingly by turning on and off the systems or adjust the temperature set point based on pre-set schedules and occupants in the space. This minimizes the wastage of cooling energy to a significant level, which otherwise goes unnoticed.

The distance between the chilled water pipes in case of central chillers and refrigerant pipes in case of VRV/VRF systems should be kept at minimum possible distance to prevent cooling losses during transmission.

Room terminal unit like split-indoor units, Fan Coil Units (FCUs) supply the cooling inside the building. These indoor room terminal systems complement the remote cooling outdoor system. They are capable to respond to space load conditions and communicate the changes to the outdoor system.

(CHP = combined heat and power) and CHCP (CHCP= combined heating, cooling and power) systems have the advantage of locally producing heat, power and cold simultaneously which can be used for generating electricity, hot water and space cooling using thermal cooling systems. They also minimize the transmission losses compared to conventional grid systems.

Replace existing thermostat with a thermostat that has a separate setting for cooling and a separate setting for heating or use one thermostat to control heating and one thermostat to control cooling. Reset thermostats to correct settings. Adjusted thermostats to 68ºF in heating season and to 78ºF during cooling season.

Preheat cold water entering the boiler with reclaimed waste heat. Higher entering water temperature makes the boiler operate more efficiently.

Most high temperature direct-fired combustion boilers operate at 10% to 20% excess air to fuel ratio to prevent the formation of dangerous carbon monoxide and soot deposits. However, heat is lost in the form of residual flue gas which can be saved by optimizing combustion air to fuel ratio. One of the simple ways to effectively monitor this is to install a combustion flue gas analyser and an oxygen trim control. This ensures periodic checking and resetting of air-fuel ratios for burners.  This can provide energy savings of up to 5% with a payback period of two years (Carbon Trust, 2013).

It has to be ensured that the hot water pipes are laid to a minimum possible distance from the heat generation source. The greater the distance, the greater is the heat loss.

In gas and oil fired boilers combustion air moves into the combustion chamber where it is mixed with fuel and is burned. A mix of flue gases moves out of the chamber through the heat exchanger and flows out through the flue pipe. This creates a draft in the ventilation stack. Too much draft results in heat loss where as too little causes the incomplete combustion and clogging. The amount of draft also depends on the wind conditions outside. Therefore, a barometric draft control device which consists of dampers is installed between the heating equipment and the exterior vent to monitor and maintain a constant draft across the ventilation stack. 

Waste heat from the exhaust air stream (and elsewhere) can be effectively used for preheating combustion air. Since exhaust air stream contains harmful and corrosive gases, care should be taken while selecting the heat exchangers. The efficiency of hot water combustion boilers typically improves by 1% for approximately every 4.5 °C (=40 °F?) increase in intake combustion air. 

Radiators, as the name indicates, transfer heat through radiation to the space and are considered as efficient means of heating in closed airtight buildings. They are typically hung on the wall above floor level and below window level. Ensure the radiators are of the highest efficiency available. Don’t cover radiators by curtains or other barriers. Hot water pipes embedded in floor heat the space through radiation. Radiant heating systems guarantee less difference in return temperatures, a prerequisite for the efficient use of electric heat pumps or solar heating and also favourable for condensing boiler and stratified heat storage tanks. This however is not suitable in leaky buildings and spaces with continuously fluctuation heating loads. 

Stratified hot water storage maintains clear stratification of hot water at the top at higher temperatures and cold water at the bottom at lower temperatures. This prevents the mixing of water which otherwise gets diluted to a mean temperature between the stratified layers. Since hot water is used from the tank periodically this stratification helps maintaining the heat of the water for longer time.

Boiler feed water should be chemically treated to reduce the risk of building up of scale or corrosion of the internal parts of heat exchangers. Various methods such as phosphate treatment, alkaline level maintenance etc. can be chosen depending on the type of boiler and heat exchanger. 

Insulate the hot water storage tank thoroughly to minimize the rate of heat loss.

Locate all the pipe work for hot water pipes within the buildings thermal envelope. Thoroughly insulate any exposed pipe work. Additionally, all the junctions and accessory fittings in the pipelines should be thoroughly insulated.

Radiators, as the name indicates, transfer heat through radiation to the space and are considered as efficient means of heating in closed airtight buildings. Ensure the radiators are of the highest efficiency available. Don’t cover radiators with curtains or other barriers. Radiant panel heating systems guarantee low return temperatures, a prerequisite for the efficient use of electric heat pumps or solar heating and also favourable for condensing boiler and stratified heat storage tanks.

Use heat pump systems with VRV/VRF technology. This enables the compressor motor to respond to the load and increase and decrease the speed of the compressor accordingly and thus saving energy compared to a motor operating at a constant speed.  

Check the temperature of the pipe on the downstream side of steam traps. If it is excessively hot, the trap probably is passing steam. This can be caused by dirt in the trap, a valve off the stem, excessive steam pressure, or worn trap parts (especially valves and seats). If the pipe is moderately hot (as hot as a hot water pipe), it probably is passing condensate, which it should do. If it’s cold, the trap is not working at all, and should be replaced or repaired. Initiate a steam trap maintenance program.

When multiple boilers are being used, an optimization control ensures correct sequencing of the boilers based on heating load. Boiler efficiency data based on the efficiency curves, fuel input vs. steam output can be used to determine the most efficient boiler to meet the heating load.

The efficiency of the system depends on the difference between the cold end and hot end of the system. The lower the difference, the more efficient the system operates. Considerable energy savings can be made by maintaining a constant difference between the cold end and hot end, above a certain threshold temperature, instead of maintaining a fixed set point temperature. Though this could result in fluctuating indoor temperature which changes by few degrees, this is often not perceivable. Additionally, control systems optimize energy consumption by responding to occupancy by modulating between setback temperature and set point temperature system schedules and local controls.

Use solar thermal collector systems like flat plate collectors, evacuated tube collectors or more advanced parabolic collectors for heating water, for space heating as well as for service water heating.

Locate the hot water storage tank within the insulated thermal envelope instead of outdoors or cold garages, which increases the rate of heat loss from the tank.

Use heat pump cooling systems with Variable Refrigerant Volume/Flow (VRV/VRF) technology. This enables the compressor motor to respond to the load and increase or decrease the speed of the compressor accordingly and thus saves energy compared to a motor operating at a constant speed. High efficiency VRV systems have a COP of 4.4-4.6 and save approximately 10-25% energy compared to regular VAV and chiller systems.

CHP (CHP = combined heat and power) and CHCP (CHCP= combined heating, cooling and power) systems have the advantage of locally producing heat, power and cold simultaneously which can be used for generating electricity, hot water and space cooling/heating using thermal cooling systems. They also minimize the transmission losses compared to conventional grid systems. Depending on the configuration and individual efficiency of the component systems, CHCP can potentially save anywhere between 5-40% of total energy consumption in a building. 

Size the radiators based on the space requirement. Oversizing the radiators results in both energy wastage as well as discomfort and undersizing results in discomfort.

In spite of selecting high COP heating systems, most of the times the systems are not optimally designed for the climate, occupancy and usage patterns. The design and selection of system should be optimized to provide comfort at the least possible energy consumption. Heating systems should be holistically planned. Both the heating system and the heating distribution to the spaces should be designed based on the above-mentioned parameters.

Heat pumps provide space heating and cooling, and hot water in buildings. By integrating a heat pump into a water heating system, EnergyStar estimates savings of 2,662 kWh/year or 55% of water heating costs. Heat pumps have an efficiency rating of approximately 2.2, while high efficiency electrical storage heaters are rated 0.95.

Boilers and other plant equipment for traditional heating systems are often dimensioned 80% too large. The sizing of the heating system depends on various factors like occupancy, comfort levels, rate of heat loss, internal heat gains, air tightness of the building and the combination of heat generation, supply and distribution. All factors must be carefully considered and optimized before sizing the system. Oversizing the system often leads to energy wastage and is one major cause of energy wastage in general.

Size the radiators based on the space requirement. Oversizing the radiators results in both energy wastage as well as discomfort and under sizing results in discomfort. 

Preheat boiler feed water using waste heat from the exhaust gases. The boiler works more efficiently when the temperature difference between boiler entering and leaving water, the more is kept at minimum possible.  

Use individual zone controller to effectively monitor local heating demand at various zones in the building. Reduction in heating demand in individual zones can lower overall heating demand on the central heating system.

The efficiency of the system depends on the difference between the cold end and hot end of the system. The lower the difference the more efficient the system operates. Considerable energy savings can be made by maintaining a constant difference between the cold end and hot end, above a certain threshold temperature, instead of maintaining a fixed set point temperature. Though this could result in fluctuating indoor temperature which changes by few degrees, this is often not perceivable. Additionally, control systems optimize energy consumption by responding to occupancy by modulating between setback temperature and set point temperature system schedules and local controls.

Use solar hot water to supplement for space heating. Use geothermal heating or district heating which uses naturally available cool sinks. Integrating heat pumps with these technologies saves considerable amount of energy.

If both CHCP system and renewable systems are not feasible, priority should be given to using the efficient heating systems available.

Instead of maintaining a fixed hot water supply temperature, an OAT reset function enables a hot water boiler to reset the hot water supply temperature as a function of ambient outside air temperature or as a function of reduction in heating demand. This function can be further enhanced by setting a heating lockout feature which turns of the boilers and pumps when the outside air temperature increases above a certain set point, say 15 °C. 

CHCP system produces power, heating and cooling locally. The primary use of such a system would be for producing electricity and waste heat generated in the process is used for space heating or domestic water heating and also for cooling if thermal cooling system is in place. Since the power and energy are locally produced and transmitted it is much more efficient compared to state electricity grid. 

Use renewable energy sources for heating if active heating systems are not avoidable. Choose a system with high COP value and which uses fuels with no green house gas emissions. 

HVAC systems tend to reject considerable amount of heating or cooling energy, which is vented out of the building in the form of stale/return air during the process of ventilation. By using Energy Recovery Ventilators the heat from the return air can be exchanged with the fresh air that is drawn in into the system and thus, reducing the heating and cooling load on the ventilation system.  Care needs to be taken when using such systems that the building has a high air tight level.

Variable Air Volume (VAV) systems adjust the volume of the air as per the demand in the space. VAV systems when connected to appropriate sensors such as temperature and CO₂ sensors and enables with control devices such as variable frequency drive, save considerable energy compared to Constant Air Volume systems (CAV).

Factors such as airflow cross sectional, length and bends and turns, relative roughness of the duct surface in the inside impacts the resistance offered to the flow. Therefore, care should be taken to ensure that duct resistance is minimized to the extent possible.

Systems are generally designed and at times malfunction, resulting in the intake of excess amounts of fresh air than required by the code. Since fresh air often adds to the buildings' cooling or heating load it is advised to maintain only the required amount of fresh air into the building. Also, CO₂ sensors could be installed in spaces to maintain precisely the required fresh air levels. During unoccupied hours fresh air dampers could be closed entirely to only recirculate the air to meet the set back temperature.

Use night flushing in summer when the diurnal temperature difference is high enough to remove the warm air from the building interior during the cooler night. This will significantly reduce the start up load on the cooling system. 

When the ambient temperature of air is less than the required supply air temperature the cooling system can be turned off and the ambient air after filtration can directly be used for space cooling and vice-versa for heating. Night purge ventilation can be effectively achieved using this control.

The sensor in the hood senses the amount of smoke; heat and steam released and thereby varies the speed of the fan in the hood. Unlike the constant volume fans that work at the same speed through out, variable volume fans work only when needed only in required quantity and thus reduce energy consumption.

The use of sensors, controls and actuators will reduce the energy wastage by taking appropriate action depending on the occupancy of the space and the demand for air exchange on the system. It also helps in maintaining appreciable comfort levels and indoor air quality while minimising airflow and the associated energy use for ventilation. Variable speed drive controls will maximize energy savings available from using sensors.

Make sure that air intake volume is not excessive. Reduce outdoor air quantity to the minimum allowed by codes by adjusting outdoor air dampers during hours of occupancy. Outdoor air intake dampers open when the building is unoccupied. Close outdoor air dampers when building is unoccupied. Be sure dampers have proper seals and adjust to ensure complete closure.

In buildings with balanced ventilation make sure to use heat recovery systems. 

Locating supply and return air diffusers within close proximity will reduce the efficiency of the system while compromising on space comfort and indoor air quality levels.

In spite of selecting high COP cooling and heating systems, most of the times the distribution and ventilation systems are not optimally designed for the climate, occupancy and usage patterns.  The design and selection of systems should be optimized to provide comfort at the least possible energy consumption. Ventilation systems should be holistically planned. Both the cooling system and the cooling distribution (both all air systems and air-water systems) to the spaces should be designed based on the above mentioned parameters. 

If exhaust air-ventilation is used in a building this should be controlled by humidity sensors. Here humidity can be used as a good sensor whether the rooms are occupied or not. Studies have shown that up to 40% of the energy consumption for heating and ventilation can be saved using such systems. (Source: IED 2009)

Fans form the core of any ventilation system. Every fan is rated based on its flow volume Vs its rated power. The efficient fan will have the maximum flow per given wattage in the fans of that class.

Where setting up a conventional air-to-air heat recovery unit is not feasible due to supply and exhaust air ducts not being adjacent to each other, a custom run around heat recovery loop can be designed to transfer heat. A run around loop contains multi row finned tube coils charged with water or glycol as heat transfer medium. Their application is limited based on the distance between the two ends of the system and they are typically 40-50% efficient. 

Lower thermostat or controller set point from 45 ºC to 40 ºC for general purposes. Consult appropriate codes and regulations for permissible water temperatures for sanitation, health and medical purposes.

Gas storage boilers with improved insulation, effective heat traps, less burner wastage and efficient combustion of fuel save much energy compared to poorly insulated electric storage boilers using inefficient heating techniques.

In wastewater heat recovery systems, drain water flows through a spiral tube and the intake water in the heater is preheated by exchanging heat with this wastewater tube. In non-storage systems the heat from the wastewater tube is directly exchanged with the water heater intake or fixture intake, such as a shower. A maximum of 60% of wastewater heat can be recovered by using various techniques.

Heat pumps provide space heating and cooling, and hot water in buildings. By integrating a heat pump into a water heating system, EnergyStar estimates savings of 2,662 kWh/year or 55% of water heating costs. Heat pumps have an efficiency rating of approximately 2.2, while high efficiency electrical storage heaters are rated 0.95.

Low water flow faucets, faucets with flow restrictors and auto off faucets minimize the flow of hot water and in turn reduce the heating energy required.

·       Use Local Booster or Point-of-Use Heaters

·       Install instant DHW heaters

·       Decentralize hot water heating

Flow-based power modulation technology in tank-less hot water heaters makes them more energy efficient than full on/full off water heaters. Typical less efficient boilers turn-on on full power regardless of the temperature and flow rate. On the other hand, more sophisticated water heaters measure the flow rate of water and will modulate overall power output to compensate for the flow rate change so as to maintain more precise temperature level.

Booster/point of use water heaters do not have storage tanks and only produces hot water on demand. Lack of tank also eliminates heat loss otherwise incurred in storage tanks. Instant hot water heaters produces hot water at about two to five gallons per minute. However, hot water demand of a facility should be studied properly before choosing either a tank less system or one with a storage tank. 

Wherever possible locate the hot water piping within the insulated building envelope. Insulate hot water pipes with good insulating material at all critical junctions and exposed places.

Solar hot water systems in temperate to hot climates use abundance of available solar energy to generate hot water. The efficiency of the system depends on the system technology, available solar radiation and the usage patterns.

Make sure that windows are not blocked or overshadowed with new additions such as balconies during refurbishment. Windows should be kept free from obstructions such as landscape elements, trees signage etc. on the outside which potentially limit the amount of daylight into the space.

Provide occupancy sensors in remote or seldom used areas where there will be brief occupancy periods.

Care should be taken that windows have high light transmittance. Windows which are too dark or tinted can increase the use of artificial lighting. 

Locate workstations requiring high illumination adjacent to windows. Avoid locating individual cabins along the periphery which potentially block daylight in the space further. Transitions spaces such as corridors etc. also should be avoided in the building periphery, as they do not need high illumination. 

All incandescent lamps can be replaced by compact fluorescent lamps (CFLs) or Light emitting diodes (LEDs). CFLs and LEDs save about three quarters to four fifths of the energy used compared to incandescent lamps and provide the equivalent lighting quality.

By using lighting that is designed for specific tasks, energy consumption for lighting can be greatly reduced. This includes such measures as using desk lighting for the required lighting levels at the work surface rather than using these light levels throughout the work area.

Use Light-Coloured Interior Wall Finishes when repainting or recovering. Use coatings or coverings with good reflectance.

Light emitting diodes (LEDs) can also replace any incandescent lamp but are especially adapted to replace halogen or incandescent spotlights, since they also provide a small and directed light source. This enables 80 to 85 % of energy savings in spotlighting.

With energy-efficient lamps and luminaires, households can save 80 to 90 % of their lighting energy use compared to the conventional light bulb with the same or better quality lighting. An energy consumption of 2 kWh/m²/year should be enough for good residential lighting. At a non-subsidised energy price, households will then also have lower overall costs.

Shading and lighting must be planned holistically so that optimum balance between lighting and cooling is met. Too much shading would result in higher energy consumption for lighting; too little shading would result in higher energy consumption for cooling. A balance between these both should be found in the planning to keep the total energy consumption to a minimum.

Light coloured interiors can help to reflect daylight to building interiors. This helps to improve the light quality in the building interiors. 

Windows should be placed high in the room for day lighting. Windows should however also be placed to let in the appropriate at working level and let occupants look out. Windows which are placed too low in the room will only improve the lighting at the window. 

Painting the jambs and sills in light colours can help to improve day lighting in the interior. 

Luminaires should be adapted to the light radiation characteristics of the lamp and should let most of the light transmit to the rooms rather than shade away or “swallow” most of the light.

By carefully studying vernacular architecture, information can be gathered for the best passive building strategies. Vernacular architecture must function without or very little active technologies, here lessons learned through experience have arrived at the best solutions for the local climatic conditions.

Programmable lighting controls can be used to automatically turn on or off lighting in an area as needed. 

Care should be taken when replacing windows that the new insulation on the building façade nor the window frame doesn't reduce the day lighting to the interior.

In large rooms and spaces were the room/space is too deep for natural day lighting through the façades, skylights are a recommended solution for reducing the dependence on artificial lighting. Care must however be taken, as skylights allow up to 2.5 more solar insolation into the building than windows in the façades. Skylights are also a potential source for heat loss in cold and temperate climates, as they face the heat sink of the night sky directly, here adequate windows with a low U-Value are needed.

Improving linear fluorescent lamp efficiency with electronic ballasts and efficient T8 or T5 technology is usually cost-effective and can save between 15 and 50 % of energy.

Occupancy sensors, also called motion sensors detect the presence of people in the space and turns off or on the lights accordingly. Occupancy sensors can potentially save 24% of lighting energy. 

Eliminate unnecessary lighting except for emergencies. By reducing outdoor lighting to the necessary minimum, energy consumption can be reduced. This includes turning off lighting for ornamentation etc. 

Minimize façade and exterior lighting as far as possible. Use highly efficient LED light fixtures for bollards, light poles and other non-high power lighting requirements. 

Always use the most energy efficient lamps possible to save energy.

In order to keep the optimum day lighting in rooms, windows should be not less than 15 to 20 % of the room floor area at typical room depths of ca. 7m. This reduces the necessity for artificial lighting to maintain the necessary lighting levels. In buildings which have deeper floor plans the windows will need to be appropriately bigger.

 There is no way to compensate through passive methods for poor daylight planning other than through active lighting systems.

Install light sensors and dimming equipment which automatically compensate for varying natural lighting conditions.

Building form, orientation and size of the windows determine the amount of daylight entering into the space. These factors should be optimised for maximization of daylight in the space. This means that rooms should have adequate access to daylight through appropriately dimensioned windows. Lack of adequate windows can only be compensated through artificial lighting. Light colours for internal walls, floors and ceilings will maximize internally reflected light, increasing potential use of daylight. Day lighting should be at least 300 lux for normal work, whereby 500 lux are recommended. 100 lux should be the minimum for floors and stairwells.

Besides low energy fixtures, other measures that could be implemented are installing occupancy sensors, daylight sensors and integrating lighting with the Building Energy Management System. 

Domestic hot water demand in buildings can be met by installing solar hot water systems on the roofs of the buildings. In cold and temperate climates the excess hot water production can be diverted to use for space heating as well.

Efficient biomass gasifiers should be used wherever there is an abundance of waste biomass available/generated. It can be used primarily for power generation or be used as a Combined Heating Cooling and Power (CHCP) system for an individual or a group of dwelling units.

‘Zero Energy Building’ and the ‘Plus Energy Building’ concepts include on-site power or heat / cold generation from renewable energy sources or from combined heat and power (CHP). Supplemented with on-site or building integrated renewable electricity generation systems, those buildings can transform from energy consumers to (net) zero energy and/or energy producers.

Any energy used in a building should be preferably from renewable systems.
This will nearly eliminate the carbon footprint during use and, if possible, convert the premises from an energy consumer to a net energy producer. In achieving this it is important that all energy be from renewable energy sources to eliminate the carbon footprint.

Solar photovoltaic panels have the capability to harvest available sunlight and convert it to electricity. Photovoltaic panels can be mounted on the roof or walls of building or can be installed in surrounding least or non-shaded open space. The energy generated can either be stored in batteries for later usage or be fed into the grid.

Small-scale wind turbines with advanced helical structures capable of harnessing wind energy from all directions can be easily mounted on the roofs and facades of the buildings. Most of the new wind turbine technologies are efficient in production and silent in operation.

The form of the building plays a significant role in the operational efficiency of the completed structure. Part of the heat transfer between the outside and internal spaces takes place through the building’s shell or surface (transmission), the other parts through ventilation and infiltration. The larger the building surface compared to the internal space (surface to volume ratio), the greater the heat loss or gain through heat transfer. In buildings that are actively heated or cooled, the preferred form would be a square form, where the surface-to-volume ratio would be ideal in the sense that any heat transfer between the inside and outside spaces is reduced. The least amount of energy would be ‘wasted’ through the building’s envelope (Olgyay 1992).

Orientation plays a significant role in determining the solar heat gains received. Buildings in cold climate should be oriented in such a way that they face sun. Generally speaking, the incidental solar radiation can be best controlled on the equator facing façade in the temperate zones and the north and south facing facades in the tropics. The high altitude midday sun can either be admitted to the space through glazed areas for heating or easily blocked by external shading elements or overhangs that also keep the walls cool where required.

Cold winds in cold and temperate climates add to the rapid heat loss from buildings due to chilling effect. Designing windbreak elements such as evergreen trees could minimize this. In addition, the buildings should be planned in such a way that they do not block the sun but block the cold winds during peak periods from the predominant wind direction. In Cold climates due to a decrease in wind speed, the ambient temperatures behind the windbreak can be up to 3.3 °K higher than in an open field and thus, reduce the heating load (Robinette 1983) and create improved thermal comfort conditions in winter. Using a well-designed windbreak cand reduce energy consumption by 15% to 20% because cooling of the building envelope is reduced (Source: Heywood 2012).

Cold winds in cold and cold temperature climates add to the rapid heat loss from buildings due to chilling effect. In temperate and cool climates evergreen vegetation can be effectively used to protect buildings from cold breezes. In cold climates due to a decrease in wind speed, the ambient temperatures behind the windbreak can be up to 3.3 °C higher than in an open field and thus reduce the heating load (Robinette 1983) and create improved thermal comfort conditions in winter.

Buildings should be sited in such a way that exposure to the sun is maximized. In cold and temperate regions this will save the amount of active heating required through the heat gained from solar insolation during the day. Avoid shaded sites on the pole side of objects such as hills.

Rooms which require more warmth for thermal comfort such living rooms should be placed on the facade facing the equator so as to receive solar insolation. This approach offers great potential for saving energy.

Buildings built higher on slopes, especially in cool and temperate climates, are more exposed to cooling effects of breezes especially on windward slopes thus increasing heating consumption in winter.

Building depth should be limited to 14m in depth to reduce energy consumption due to artificial lighting as well as mechanical ventilation

Valleys and lower north facing slopes should be avoided in temperate and cool climates due to the cold air pockets and downslope wind. This is due to the cold air sinking especially at night and the cold air currents that form in such areas.

In areas with cold winters, the bottom of an equator-facing slope is preferable. In areas with mild winters, east- and north-facing slopes can be used. West slopes should be avoided in all cases. Eastern orientation is beneficial because of the large daily ambient temperature range.

For buildings with complex programmes parametric studies can be done on various combinations of window wall ratio and building forms to arrive at an appropriate form that suits both the design brief and transfer minimum possible heat through the building envelope.

Dark Surfaces, with their low effective albedo and high thermal mass, such as roofs and facades of the buildings, roads and pavements absorb significant amount of heat during the day and heat up the surroundings. The absorbed heat is reradiated to the night sky and it affects the night-time temperatures as well. This can lead to a heat island effect where big urban areas are warmer than the surrounding suburban and rural areas. In regions with hot climatic spells, this can lead to a further increase in thermal discomfort as well as energy consumption for cooling. The difference in temperature for urban heat islands is generally between 1°K and 4.5°K, but larger ranges of up to 10°K have been observed (Santamouris, 2001). This can be mitigated by the reducing the hard paved surfaces, use of light coloured paving, cool roof techniques such as green roofs, roofs painted by high albedo materials etc.

Use building simulation tools to arrive at optimum orientation when dealing with buildings with irregular forms. The ideal orientation should maximize heat gains and at the same time should provide good daylight conditions in the space.

Build so that natural features, such as hill or forest, as well as man-made features, such as other buildings, act as a windbreak against cold winds. Care should be taken that these features do not block solar exposure.

The building form plays a significant role in determining the solar heat gains received. Generally speaking, the incidental solar radiation can be best controlled on the equator facing façade in the temperate zones and the north and south facing facades in the tropics. Reduced lengths in the East and West façades and larger South/North facades therefore result in slightly elongated shapes along the East-West axis.

Zoning of different conditioned rooms can act as a buffer and help to improve the energy efficiency of buildings. Rooms and zones which are not occupied for most the time such as stairwells, toilets, storage areas, airlocks and any other buffer areas should be located preferably on the pole facing direction. This helps in minimizing heat transfer between the interior spaces and outside and offers great potential for saving energy. Passive solar gains into the spaces from the equator facing direction can be hindered if these spaces are to be located in that direction

Increasing the vegetative cover can reduce air temperatures in urban areas through evapotranspiration, which has a cooling effect. In addition, the surfaces shaded by vegetation will be cooler than the surrounding surfaces due to the shading effect of the vegetation, both helping to reduce the heat island effect.

Office buildings have varied occupancy patterns and varied work and allied areas. Extended work areas should preferably be separated from regularly occupied to avoid unnecessary space conditioning.  Isolate these spaces (including related support services such as restrooms and break areas) from the portion of the building having fewer operating hours.

Energy consumption can be greatly reduced by allowing different temperatures according to the use of the room. Rooms that are seldom used can have temperatures at the edge or slightly outside of the thermal comfort without any negative effects. Stairwells are an example of such rooms.

The setback temperature is a temperature a few degrees above or below the normal (space set point) temperature within a room or building. By adjusting the thermostat to a setback temperature during nights and diurnal absence the energy consumption can be significantly reduced. In addition, the room temperature can be adjusted to a normal (set point) temperature more easily from a setback temperature than by turning off the system completely. Turning off and on often involves higher energy consumption for system start-up and operation at peak loads to meet rapid conditioning of the space. Reducing the thermostat in cooler climates by 5°C – 8°C for 8 hours a day (e.g. at night) can result in savings of up to 15%

Air movement will influence thermal comfort. The higher the air speed the greater the cooling effect. Without reducing air speed higher temperatures, and thus higher energy consumption, are needed to compensate this effect. High air speeds can be perceived as a draft and can be seen as uncomfortable.

Allowing indoor temperatures to fluctuate (within the thermal comfort zone) throughout a building can greatly help to reduce energy consumption. Adjusting the set-point temperature that varies according to the external temperature will reduce the thermal conditioning demand of a building.

Users should wear clothing appropriate to their climate and time of year. Clothing can act as an insulator. When occupants are able to adjust their clothing to suit lower temperatures, satisfaction with the indoor environment is greatly increased.  Wearing a jacket or pullover can offset the comfort zone allowing for lower temperatures in a room. In Europe (temperate climate) reducing the indoor temperature by 1 °C can for example save up to 10% of the energy cost.

Allowing users to control the indoor environment (within reason) contributes to occupant satisfaction and an ability to experience greater thermal variation without discomfort. This in turn can help to reduce energy consumption.

Climate responsive design should be a prime factor when designing buildings and selecting the construction materials. This is especially relevant in passive buildings with no active systems to aid thermal comfort. The lesser the reliance on active technologies for comfort the greater the energy savings.

Reducing the thermostat temperature in cold and temperate climates can result in significant energy savings. Occupants should identify the most optimum thermostat temperature that they are comfortable with instead of maintaining a fixed set point temperature whether comfortable or uncomfortable. In Europe (temperate climate) reducing the indoor temperature by 1°K can for example save up to 10% of the energy cost.

The entrances to the building should be through airlock spaces. The airlocks act as buffer spaces between indoor and outdoor and minimize the heat transfer due to infiltration and uncontrolled air exchange. Care should be taken that the doors to an airlock are kept closed and that no two doors are open at any time.

Doors and Windows located on the exterior facades of the building could result in unwanted draughts. This should be eliminated by using draught seals around door and window frames and also under the doors and floor insulation.

The entrances to the building should be through airlock spaces. The airlocks act as buffer spaces between indoor and outdoor and minimize the heat transfer due to infiltration and uncontrolled air exchange. Care should be taken that the doors to an airlock be kept closed and that no two doors be open at any time.

Unlike walls, windows have both optical and thermal properties. Visual Light Transmission (VLT) is an optical property that determines the amount of daylight in the space. Ideal windows should have high VLT values and SHGC values and low U-Values. In temperate and cool climates, solar heat gain is welcome during the cooler seasons as well as high levels of daylight. Because low U-values slightly decrease the scope for solar heat gain, a balance needs to be struck between solar heat gain potential and heat losses at night.

An air tight building caps the benefits obtained from insulating the building envelope all around and significantly reduces cooling/heating load due to infiltration. Once all the envelope retrofit is completed, conduct blower door pressure test to identify any air leakages and seal them properly. Blower door tests should be carried out to identify and reduce infiltration in building and to measure the air tightness of a building. Here a frame with a film and a ventilator fan is placed in a door or window. The building is pressurized or de-pressurized and air change rate per hour (ACH/hr) is determined at various pressure points. Buildings should be constructed air tight with air tightness values of 1.0h or less to minimize infiltration.

Leaks typically appear in and around the junctions, joinery details and around envelope penetrations for services. They cause much heating/cooling loss in the form of infiltration. Retrofitting the building envelope to high levels of insulation and air tightness can significantly reduce the heating or cooling demand and subsequently the old system might become oversized and could be replaced with a small, modern and efficient system.

Leaks typically appear in and around the junctions, joinery details and around envelope penetrations for services. They cause much heating/cooling loss in the form of infiltration. Retrofitting the building envelope to high levels of insulation and air tightness can significantly reduce the heating or cooling demand and subsequently the old system might become oversized and could be replaced with a small, modern and efficient system.

Insulated window shutters, which are closed at night can help to improve the thermal insulation properties of windows. On single glazed windows, for example, these can improve the insulation properties to near that of a double-glazed windows. It must however be noted that the windows will still have the lower insulation value when open. 

Since glazing offers more potential for heat loss than the opaque wall, pole-facing glazing should be minimized. However, more advanced glazing systems offer better U-Values than conventional. The amount of glazing should be decided based on the required daylight values in the space and the optical and thermal properties of the glazing system.

A well-insulated thermal envelope, without thermal bridges, is the most fundamental method to achieve a low energy building. Care needs to be taken to insulate the thermal mass as well as the slab edges to reduce thermal bridging.

Buildings using active conditioning should be well insulated to minimize the heat loss and gains due to conduction. A well-insulated thermal envelope, without thermal bridges, is the most fundamental method to achieve energy-efficent buildings for “closed systems” as well as improved thermal comfort. Improving the performance of the building envelope through insulation is generally a very effective, low cost method for increasing energy efficiency in new buildings. Building insulation on the internal sides of walls can bring problems and should be used only were absolutely necessary.

In reaching low energy levels it is necessary that the building envelope uses advanced insulation techniques. This includes highly insulated façades with a recommended U-value of 0.3 W/m²K or better.

Both mass and heat transfer takes place through building envelope. Insulation materials resist heat transfer. However, moisture seepage through insulation reduces its effectiveness significantly. Care should be taken in refurbishment that any insulation added should be protected from water, moisture and condensation as this reduces the insulating properties of the insulation. This is especially relevant with insulation, which can absorb water. The insulation needs to be covered by using a special vapour barrier on both sides to protect them from moisture due to condensation.

Special care must be taken to make sure that no thermal bridges occur at the point where the floor penetrates the wall to the outer envelope or where there is a ring beam.

In reaching low energy levels it is necessary that the building envelope uses advanced insulation techniques. This includes highly insulated roof with a recommended U-value of 0.25 W/m²K or better.

Over insulating the façade where it meets the foundation can help to reduce thermal bridges

Where the yearly average ground temperature is near to or within the thermal comfort zone, ground insulation is not necessarily needed. Instead, ground floor can be thermally coupled with the surface beneath, so that temperature swing is possible. Here the yearly average temperature in the ground of 19°C, for example,  can be used to heat the building in winter or cool the building in summer.

In cold and temperate climates, when combined with passive solar gains, thermal mass can be used as heat storage to aid heating as well as to dampen temperature fluctuations in the building interior. Passive heat gains during the day can be stored and transferred to the interior of the building during the night due to time lag. During the night the reverse action also could be mitigated due to the same high thermal mass which provides enough time lag till next cycle of passive solar gains. 

A balance must be reached in the use of solar heat gain to reduce active conditioning of the building interior. This should be done by maximising heat gain in winter and minimising heat gain in summer.

Install a switch on overhead doors that prevents activation of heating and cooling units when doors are open.

• Installing Movable Insulation
• Multilayer reflective roller shade device
• Operable insulating slats
• Quilted insulating draperies
• Assure that automatic door closers function properly

An easy and zero or low cost way to reduce cooling requirements is to use light-coloured rather than dark-coloured walls and roofing materials. It is a well-known fact that light colours reflect solar radiation and dark colours absorb it. Studies in California and Florida have shown that raising the albedo by 0.4 a reduction of cooling energy by 20 % can be achieved

Shading devices can play a major role in the energy efficiency of a building as they determine the load of the building whether from lighting or external radiation. In temperate and cold climate conditions it is advisable to design shades in such a way that they block the sun in summer and prevent overheating. In winter where solar gains can help to reduce the thermal heat load of a building care should be taken not to block solar insolation. This can be done by intelligently designing the shades or with movable shades etc.

Heat transfer through the glazing of the building is significant. This can lead to unwanted heat gains. Shading devices on all facades should be optimised depending on their orientation and daylight requirements in the building.

Plants offer shade to surfaces and buildings and modulate their temperature. Trees absorb most of the solar radiation falling on their leaves, just like dark coloured surfaces, and reradiate back only a small portion of it. In winter deciduous trees shed all the leaves allowing sunlight to reach the building envelope. By strategically locating deciduous trees on equator facing, east and west facades of a building can be shaded in summer without obstruction passive solar gains in winter. Strategic planting of trees and shrubs next to buildings can reduce summer air-conditioning costs by 15-35% and even up to 50% in specific situations (Santamouris 2001) yet allow up to 70% of solar insolation to reach the building facade in winter (Heywood 2012).

The sun altitude in the sky is low in mornings and evenings on the Eat and West facades. The shading on these façades should preferably include vertical shading devices such as fixed shades or louvers whose angle of tilt should be designed based on the azimuth angle of the sun.

External shading should be the preferred method of shading. Internal shading will help to reduce the solar insolation into the interior however the solar insolation that has already penetrated to the building interior and the reflected long wave radiation are blocked from exiting through the glass. This solar heat gain will then account for higher cooling demand. 

In urban areas, elements like roads, sidewalks, building facades and roofs and other hard paved areas absorb heat during the day and release it during the nights and contribute significantly to what is known as the urban heat island effect. Light coloured surfaces mitigate this effect to an extent, by reflecting the most radiation into the atmosphere.

Adjustable shading devices can be more effective for optimized energy use as they can be adjusted to the conditions. This is especially relevant in temperate and cold climates where shading in late hot summers and early autumns as well as the benefits of solar gain in late spring might still be needed. Fixed shading which can only be sized for a certain period does not account for this.

The sun altitude in the sky is high as the day progresses on the North and South facades. The shading on these façades should preferably include horizontal shading devices such as fixed shades or louvers whose angle of tilt should be designed based on the altitude of the sun.

Sun path diagrams give the position of the Sun with respect to the angle of azimuth and altitude in the sky at any given point of time. Simple and preliminary shading analysis could be done using these diagrams. More sophisticated way of designing shades is by using shading mask projections on facades and fenestrations. Shading masks provide information regarding the exposure facades and windows to direct solar radiation at any time. This helps in designing optimum shading devices based on the geographical location, local climate and daylight requirements.

Chose interior shading devices to reduce night heat loss in winter, and to reduce solar heat gain during the summer.

Daylight in the space is a very important parameter. Care needs to be taken that the shading design does not hamper the daylight quality in the space making it dull and dingy. An optimum balance should be struck between meeting the daylight requirements of the space and at the same time shading the space from harsh sun.

Air can be pre-cooled or pre-warmed by using the temperature of the earth, which at ca. 2 meters depth is the yearly average temperature. This can be combined with the stack effect for good passive ventilation strategies.

The temperature of the soil at a depth of about 4m can be low enough to serve as a cooling source during summer and a heating source in winter. Ventilation air can be drawn through pipes that are laid in the gorund, either by way of an array of small pipes or one large pipe of 100-300mm diameter and at a lenght of about 12-60m. By drawing the air through underground pipes, the temperature can drop by up to 10°C (Santamouris, 2001).

The building layout needs to be flexible, responding to both winter and summer conditions. During the heating season, the building must be compact, very well insulated without thermal bridges and airtight.

Design shaded areas with colonnades and canopies, patios with gardens as open daytime activity areas. These also serve the function of reducing the solar insolation on building walls and thus help to reduce the cooling load.

Outdoor shaded areas such as verandas can be used as living areas open to the cooling effects of breezes. In addition they shade the façades of the buildings helping to reduce the cooling loads.

Care should be taken to allow full solar access to a building in winter. Here passive solar heat gains can represent a major reduction in energy heating consumption. Care should be taken that no solar insolation is blocked and that the solar insolation of low winter sun can penetrate deep into the building warming as much as thermal mass as possible.

A handbook for building use, especially for energy efficiency, is recommended for users. This allows the user to reference information on building use, technologies and behaviour and their effect on energy and cost savings.

Typical user behaviour and cultural behaviour should be taken into account when planning a building and its systems. This can help to reduce energy consumption as the building can be optimised for these factors. One such technique is a “smart” energy management system that learns from the user behaviour to supply the energy needs when needed (such as hot water) instead of constantly keeping water at the required temperature.

User Behaviour can greatly affect the energy consumption of a building. The occupants should be made aware of all building systems as well as the use of a building including optimal implementation of passive measures. This will help to keep the energy consumption to a necessary minimum. User behaviour modulation is critical as it takes time to adapt to varying temperature with different choices of clothing and other habitual actions.

Studies have shown that real time consumption feedback can influence user behaviour positively enabling energy saving as this guarantees consumption transparency.

At the bottom line, comfort is a matter of individual preference. The occupants should be made aware of the benefits of having and using programmable thermostats. User behaviour modulation is critical as it takes time to adapt to varying temperature with different choices of clothing and other habitual actions.

Controls enable users to set and maintain comfort conditions in the space. The control should be largely image-based with easy and understandable user interface.
Heating, cooling and ventilation systems, lighting, domestic hot water and even appliances can be controlled using different mechanisms. In home automation ergonomics and ease of use are of particular importance.

Lighting controls like occupancy sensors turn lamps on, when somebody enters a room, or turns off, when nobody has been present for some time. They can be controlled locally or can be scheduled to operate suit usage patterns of the occupants. Lighting controls keep a check on unintentional and negligent behavior and avoid unwanted energy usage.

Modern appliances are equipped with ‘smart’ technology that will include sophisticated communication protocols embedded in the appliance and makes it easy to communicate and control them remotely. In residential buildings this would be able to control appliances like washing machines, ovens, dishwashers, coffee machines etc.

By using local heat meters at the radiators or by sub metering heating/cooling usage enables the study of heating/cooling patterns and energy consumption due to space heating/cooling. This helps in identifying spots of heating/cooling energy wastage and rectifying the same.

Intelligent programmable thermostats can perform more advanced functions than merely turning on/off the cooling or heating system. Complex functions which are critical to saving energy such as falling back to a setback temperature during night and unoccupied periods, varying internal temperature as a function of external temperature, responding to seasonal variations and multi room control can be performed using programmable thermostats. Though few of these functions can be achieved by using a manual adjustable thermostat, a digital programmable thermostat eliminates the chances of energy wastage due to human error and negligence.

Minimum levels of ventilation are required in space for fresh air, both for breathing and to maintain optimum humidity levels. However, ventilation also adds significantly to heating and cooling loads. Ventilation in the building can be optimized effectively through a strategy known as demand control. This strategy calculates the amount of required ventilation by sensing the amount of carbon dioxide and humidity in the space. Thereby it avoids excess ventilation and corresponding energy costs.

Advanced Metering Infrastructure (AMI) or smart meters with communication technology with home appliances, plug loads, energy and lighting systems known as Home Area Network (HAN) provides real time hourly data to the homeowner on the energy consumption. HAN is a network within the home that enables communication between “smart” devices including HVAC, security, lighting, and appliances. This provides the home user with ability to remotely control devices within the HAN (such as adjusting a thermostat or turning off lights). This helps consumers to better manage consumption and cost, utilities and to better manage supply and demand, and to react quickly during emergencies.

Flow-based power modulation technology in tank-less hot water heaters makes them more energy efficient than full on/full off water heaters storage. Typical less efficient boilers are turned on full power regardless of the temperature and flow rate. On the other hand more sophisticated water heaters measure the flow rate of water and will modulate overall power output to compensate for the flow rate change so as to maintain more precise temperature level.

Schedules describe the typical user occupancy pattern in the building. The usage of all other systems such as HVAC, lighting, hot water and appliances is a function of the building occupancy patterns. The controls need to be scheduled and automated to ensure comfort while reducing energy wastage.

Building automation, control and energy management systems play an important role in optimizing building energy performance and at the same time ensures increased occupant comfort. Energy efficient building systems and equipment integrated with optimized controls for cooling and heating equipment, ventilation, domestic hot water and lighting and to an extent appliances could result in approximately 60% energy savings especially in closed buildings.

Modern day equipment is fitted with sensors and transmits data wirelessly, making it a less hassle for homeowners. By using control strategies and smart meters, the energy consumption data is collected and presented with a graphic user interface on TVs, computers and smartphones. The energy usage data for various end uses can be compared to various parameters like external weather conditions; user behaviour, occupancy patterns etc. and the potential pockets of energy wastage can be identified and rectified accordingly. This analysis will help identify flaws in any of the systems and the same can be rectified. In some cases the whole system can be optimized by just recalibrating the system and adjusting the controls to suit updated user behaviour patterns.