Improving Energy Efficiency in Buildings

Introduction

Climate change is a major world issue, average temperatures have risen across the globe by 1^oC between 1906 and 2005 with a more rapid increase over the last 50 years (Conserve Energy Future, 2017], this rise has been attributed to global warming (McGrath, 2017). Emissions of gases such as carbon dioxide (CO₂) and Methane (CH₄) contribute to this global warming and are known as greenhouse gases (NASA, 2017), though the Environmental Protection Agency in the United States of America stated in 2017 that CO₂ was not a primary contributor to global climate change (McGrath, 2017).

Energy use is a major producer of these greenhouse gases, governments around the world have put in place measures to reduce the production of these gases by introducing rules to improve energy efficiency (Conserve Energy Future, 2017].

In the UK energy use, can be broken down into 4 main areas, Transport, Domestic, Industrial and Services Sector (Department for Business, Energy, and Industrial Strategy, 2016).

This report will look at energy usage of buildings and techniques that can be utilised to improve a buildings energy efficiency.

UK Energy Usage

The breakdown of the UK’s energy usage across the 4 main areas in 2015 was as follows (Department for Business, Energy, and Industrial Strategy, 2016): –

Transport 40%

Domestic 29%

Industry 17%

Services Sector 14%

The fuels used to provide this energy were a mixture of Gas, Electricity, Solid fuels, Petroleum and Bioenergy (Department for Business, Energy, and Industrial Strategy, 2016). Both industry and transport use large amounts of energy undertaking their processes be it production lines or the operation of various modes of transport such as trains or buses rather than the running of buildings (Department for Business, Energy, and Industrial Strategy, 2016).

Energy usage is fundamental to the operation of any building be it for lighting, heating, cooling, cooking or other services such as lifts (Wade, Pett and Ramsay, 2003), with most of this energy being provided by either gas or electricity (Department for Business, Energy, and Industrial Strategy, 2016). Thus, Improving the energy efficiency of a building can considerable reduce the amount of energy that is used.

Over the last 30 years there has been a considerable increase in energy usage by office blocks due to the rise in the use of technologies such as large computers and the increased use of air conditioning systems (Wade, Pett and Ramsay, 2003). In the service sector office buildings are second to retail units in the levels of energy that they consume, and these office buildings contribute to 1.1% of the UK CO₂ emissions each year (Pothitou, Connaughton and Torriti, 2015).

Figure 1: Energy Usage of a standard Office and Efficient Office, Source: – (Knissel, 1999)

To become more energy efficient a building needs to use less energy to undertake the same tasks or role (International Energy Agency, 2017), as figure 1 above shows, improvements from a standard office block to a super-efficient office block can reduce energy usage by 70% (Knissel, 1999)

Lighting

In a commercial office, the lighting uses up to 50% of all the electricity consumed (Irish Energy Centre, 1995) and 35% of the total the energy consumption of the building (Knissel, 1999). Lighting can be broken down into several types these being access lighting, task lighting, emergency lighting and effects lighting (Irish Energy Centre, 1995).

For a building to become more energy efficient attention needs to be paid to the lighting design to reduce the level of usage, technological advances mean that improvements in the efficiencies of lighting can be done in several ways (Energy Saving Trust, 2017), some of these can also be applied to existing office buildings without too much work having to be undertaken other methods need major alterations to incorporate into older buildings and are more suited to new buildings or buildings going through major refurbishment (The Renewable Energy Hub, 2016).

The simple replacement of existing lamps within light fittings can reduce energy usage, with more modern fluorescent tubes being 25% more energy efficient than older versions and compact fluorescent lamps using up to 75% less energy than an old tungsten lamps (Irish Energy Centre, 1995), these tungsten lamps having been invented over 100  years ago(Energy Saving Trust, 2017) Light Emitting Diodes lamps (LEDs) are also now available and are up to 80% more efficient than the tungsten lamps (Energy.gov, 2013), when invented in the 1960’s LEDs were no more efficient than tungsten lamps it has only been in the last ten years that great improvements in their efficiency has been achieved (Energy.gov, 2013).

This method of energy efficiency can be applied to existing buildings without too much trouble but does have a cost over and above normal maintenance costs of changing the lamps but by the energy saved the LED lamps can pay back their extra initial cost within 3 years. (Corkhill, 2014).

Another area where lighting can be made more efficient is insuring that it is only used when required and that lights are turned out when not in use (Open Technology, 2016). The use of sensors such as proximity or absence detection also means that the lights come on automatically when occupied and turn off after a period of non-occupancy (Open Technology, 2016), the dis-advantages of this can that someone sitting still at a desk may not activate the sensor and the light may go out while they are still there.

Office areas can also be divided into different lighting zones with different controls for each zone, lights then only need to be on in areas of the office that are occupied or being used (Knissel 1999) leading to further efficiency.  The use of daylight sensors to adjust the amounts of artificial light used when there is sufficient natural light helps reduce energy usage (Carbon Trust, 2017). This may be achieved by having lights that either switch off or dim depending on levels of natural light in an area and can be used alongside lighting zones so that the lights closest to the windows dim separately when the natural light levels increase (Open Technology, 2016).

Dimming controls and timers can also be utilised to minimise energy usage, it may be that less lamps operate at a lower light level at certain times of the day such as during the evenings or night while cleaning of the office is being undertaken (Open Technology, 2016).

The room layouts can also play a part in energy efficiency by positioning desks to make more use of natural light and by painting walls and ceilings light colours can maximise the effectiveness of the lights (Irish Energy Centre, 1995).

Thermal Comfort

All individuals working in an office want to feel comfortable and not to be either to hot or too cold no matter what time of the year it is (Seton, 2015). There are 6 factors which can affect the thermal comfort of people within an office environment, these can be broken down into environmental factors and personnel factors (HSE, 2016). The 4 environmental factors being Air Temperature, Air velocity, radiant temperature and relative humidity (Harish, 2017), the other 2 factors are personnel these being clothing and metabolic heat (HSE, 2016).

The Chartered Institute of Building Services Engineers (CIBSE) have identified several elements of a building that will affect the thermal environment these being items such as glazing, ventilation, air tightness, thermal mass, plant and equipment, waste heat along with working patterns, activities and workforce profile (Seton, 2015).

CIBSE also provide recommendations on the temperatures levels, air supply and illuminance to provide a comfort level that will be acceptable to 80% of the occupants (Woods, 2015), this does though mean that there will be 20% that do not find it comfortable (Woods, 2015). Due to personnel preferences, it is not possible to find settings that are acceptable to all occupants and the recommendations are levels deemed to be a healthy office environment (HSE, 2016)

Figure 2 – CIBSE Comfort recommendations for Offices
Conditions	Temperature (oC)	Air Supply per person (l/s/person)	Illuminance	Noise Rating (NR)
Summer (Light Clothing)	22-25	8	500	35
Winter (Warm Clothing	21-23	8	500	35
Source: – CIBSE Guide A: Environment Design 2015 (Woods, 2015)

Many office blocks have heating, ventilation and air conditioning systems (HVAC) to maintain these comfort levels (Carbon Trust, 2017), figure 1 earlier in this report shows that in a standard office these systems use up to 42% of the all the energy consumed by the office block (Knissel, 1999).   For the most efficient use of these HVACs systems it is important to design the buildings fabric to reduce the load imposed on these HVACs systems (Harish, 2017).  For example, radiant temperature can involve both heat gain and heat loss through the structure, this is especially so near large windows, in these instances the structure can be designed with solar shading such as brise soleil or reflective blinds on elevations facing the sun to reduce solar heat gain (Harish, 2017). The windows can also be designed with triple glazed glass along with blinds that have thermal insulating properties to help reduce heat loss during the cooler months of the year (Harish, 2017). These measure help reduce the amount of work that either the cooling system or heating systems must undertake (Knissel, 1999), the disadvantage that any shading or blinds have is that they reduce the amount of natural light entering the building leading to the extra usage of artificial lighting.

Heating in office buildings is usually provided by a central boiler (CIBO, 1997), the efficiency of the boiler can depend upon the fuel used, back in 1997 the typical energy efficiency for boilers based on fuel varied greatly as shown in figure 3.

Figure 3 – Typical Efficiency for New Boilers in 1997
Fuel	Full Load Efficiency %	Low Load Efficiency %
Coal	85	75
Oil	80	72
Gas	75	70
Biomass	70	60
Source: – (CIBO, 1997)

Improvement in technology has meant boiler efficiency has greatly improved since 1997, micro combined heat and power (mCHP) boilers are now available for offices and domestic properties, prior to 2006 these were only economically available on extremely large scales (The Renewable Energy Hub, 2016). CHP boilers simultaneously generate useful heat and electricity making better use of the fuel being used (Ecoliving, 2017).

Figure 4 – Micro Combined Heat and Power Boiler Schematic.

Source: – (The Renewable Energy Hub, 2016).

These combined heat and power boilers can be up to 98% efficient, with the electricity produced being either used by the building or returned to the main grid (The Renewable Energy Hub, 2016). A disadvantage of CHP is that it is only useful in a building that requires both hot water and electricity, if other methods are used for heating and hot water is only used for washing then a CHP is not practical (Dinneen, 2014).

As well as improved efficiency of boilers and air conditioning systems better controls also help reduce energy usage, for every 1^oC lower that the heating is run it reduces energy usage by up to 8% (Carbon Trust, 2017) so setting heating levels at the lower level of 21^oC set by CIBSE rather than the upper winter level of 23^oC can reduce the energy usage by up to 16%.

In open plan areas controls to both heating and cooling should also not be accessible to the occupants as there could be instances where one individual turns up the heating in their area and another turns down the air conditioning in their zone and the two systems then try to work against each other (Carbon Trust, 2017).

Some areas of a building such as computer hub rooms will require cooling all year due to the heat generated by the equipment within them (Wade, Pett and Ramsay, 2003), the use of a heat recovering system can be utilised to use this heat for other parts of the building reducing the load put on the heating systems and reducing the energy usage (Energytechs, 2017).

	These heats recovering units operate by using hot air from within the building to heat fresh cool air from the external environment (Energytechs, 2017) this warmed fresh air is then circulated around the building reducing the heating requirements (Wade, Pett and Ramsay, 2003)
Figure 5 – Heat Recovery Unit, Source: – Energytechs, 2017

Conclusion

Technology and energy efficiency of services for buildings is continually improving this can be seen by the advances in LED technology for lighting and the use of Combined Heat and Power boilers in smaller scale buildings that have advanced over the last 20 years (Wade, Pett and Ramsay, 2003). Buildings can only be built as energy efficient as the technology available at the time of construction, some energy efficiency measures can be installed later if the technology becomes available but this can be costly and disruptive (Wade, Pett and Ramsay, 2003)

It is though important when considering energy efficiency of buildings services to ensure that comfort levels for occupants are maintained for the tasks they are undertaking and are not compromised to achieve great energy efficiency (Irish Energy Centre, 1995)

Modern technology makes more use of automated controls to assist in improving energy efficiency within buildings, this helps to remove occupant’s interference with controls and the potentially unbalancing of the systems resulting in more energy usage. As already mentioned earlier in this report the guidance figures given by CIBSE will only be acceptable to 80% of the occupants (Woods, 2015) the other 20% will be looking to alter the settings to suit their requirements so good communication with the occupants on the reasons the strategy for control settings will help with the implementation of the energy efficiency measures (Irish Energy Centre, 1995).

References

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