CTE-DB-SUA (Seguridad de utilización y accesibilidad)

It can be assumed that the temperature demanded within a home influences its energy use, however there are many factors (Wei et al, 2014) which can influence the temperature within homes, factors such as the type of building (Kane, 2011), the orientation of the building, levels of thermal insulation and the presence of eaves, as all of these affect the heat transfer of the dwelling (Bekkouche et al, 2011).

The fabric of the building itself impacts the energy efficiency of the building and therefore impact the energy used within it. A study by the Energy Saving Trust

39 (2006) found that insulation caused an increase of 0.57^oC in internal temperature.

The thermal performance of a building can also be dependent on factors which influence the heating load such as temperature variations between internal and external environments, different floors, adjacent rooms and distinctive heat losses expected for certain materials such as glass, walls, windows and roofs etc. (Raaij et al, 1983a).

To improve the fabric of a building and the physical performance of it, such that the energy efficiency of the building increases, various measures have been

implemented over the last decade. Stricter building regulations mean that new homes are built to a much higher specification than was expected 20 or 30 years ago. Improvements in technology and renewable energy sources mean that buildings are becoming more sustainable and reaching new efficiency levels.

Government schemes and grants have also been introduced to help persuade householders to take up different improvement measures and to begin retrofitting their homes.

Within the domestic sector, retrofit is used in the context of energy performance improvements, where a domestic property may have its energy performance improved by changing the building fabric or improving it through added insulation etc. It also includes changing the energy system within a property, changing any energy consuming appliances to more energy efficient ones or even changing the level of control over energy systems within the property. However one of the largest issues surrounding retrofitting the UK building stock is the sheer volume; the Department for Communities and Local Government state that roughly 22 million homes need to be improved by 2050 which they calculated to be around 1,600 homes per day (DCLG, 2012). Another issue challenging the completion of this task is the diversity of the current building stock within the UK meaning that it is almost impossible to roll out blanket solutions as different dwelling types and ages have different issues which need to be addressed. On top of these issues comes the fact

40 that the ease of retrofit will be influenced by the tenure. Within the UK, 70% of the residential building stock is owner-occupied with 12% being private rental and the remaining 18% being social housing (Chahal, 2012). The tenure impacts the ease of retrofit as owner-occupied have more say over deciding on retrofitting their

property which will be influenced by cost and level of disruption involved. Social housing is seen to be the easiest class of tenure to target for retrofit and various retrofit research studies have focused on them for this reason (Lowe et al, 2012, Chahal, 2012, Bates, 2012).

To help accelerate improving the housing stock through retrofit measures the government has previously introduced various schemes/initiatives to help people afford to improve their properties. The Energy Efficiency Commitment (EEC) required energy companies to reduce their customer’s energy consumption and emissions through funding various measures, however this was replaced in 2008 by the Carbon Emissions Reduction Target (CERT) which was a larger scheme aimed at improving the energy efficiency of the housing stock mainly through various

insulation measures. Alongside CERT the government also launched the Community Energy Saving Scheme (CESP) aimed at tackling community energy efficiency instead of just individual properties. The Warm Front scheme also helped provide

measures such as loft or cavity wall insulation or even new boilers for owner-occupied or privately rented properties on income related benefits to help reduce the fuel poverty issue within the UK. The Decent Homes Standard aimed to do a similar task but for those within social housing or particularly vulnerable owner occupied homes (Boardman, 2010). However it is worth noting that these schemes were designed for self-referrals from qualifying households therefore attracted the households where occupants were not only aware of these schemes but also understood about the disruption possible from installation of these measures and possible upheaval. The government announced a new scheme to help target more properties needing energy efficiency measures installed in the form of the Green Deal which was further supported with the Energy Company Obligation (ECO) scheme. The Green Deal had many barriers to overcome to ensure that it was

41 successful (Dowson, 2012). The financial structure of repayments through energy savings was seen to be weak due to the energy savings being reliant on estimates from modelled assumptions which could be impacted by poorly installed measures and occupants increasing their energy use. The complicated process of gaining grants towards any retrofit measures also did not help and therefore there was not a great uptake after initial assessments were carried out on properties.

The issue of comparing energy use after improvements is slowly becoming an issue that is needed to be studied in more detail within the domestic sector and example has been taken from non-domestic building sector to introduce post-occupancy evaluation. Currently there is no UK policy which requires post-occupancy

evaluations to be carried out on domestic properties and in fact little real feedback exists, therefore it is extremely difficult to assess whether an improvement has made an impact on a buildings energy consumption/emissions in reality (Stevenson

& Leaman, 2010). Vale (2010) points out that it is not simply enough to ask questions on building performance as part of a post-occupancy evaluation but, to have a real impact, real data are required on that individual household to give a better basis for comparison pre and post improvement. Vale also points out that a roll out of smart meters, such as the UK government has committed itself to, may not be the only action required. Showing occupants’ information about their energy use may not be the trigger to encourage people to reduce their

consumption. In fact Vale suggests it will be more effective to set real system limits for people to compare against, like how a car speedometer helps us towards

reducing speed but only when people take into consideration the speed limit set.

Aside from physical building properties affecting the thermal performance of a building, it is also related to the efficiency of the heating system present within the building with regards to type of boiler and type of fuel required (Yohanis, 2012).

This links to the second influence on the energy consumption within a home, the heating system present.

42 2.2.2 The system

Methods of providing heat and warmth within domestic properties have advanced from the open fires within communal rooms of the early 1900s. The introduction of central heating systems into UK homes from the early 1970s has changed the use of heating in homes significantly over the past half a century. At the time of the last national census, 2011, 97% of the 23 million homes in England and Wales had central heating, 83% being gas fired (ONS, 2011). Central heating systems within homes are typically one of three types, ‘wet’ systems, warm air systems or systems involving storage heaters.

Storage heat systems typically have both electric storage heating and direct electric heating present within the property. Storage heaters are located in the main rooms of the dwelling and charged at night when electricity is at a relatively low cost (EST, n.d, a). The heaters are programmed to release this heat during the next day at the time set by the occupants. However some only have input and output level controls on the system so occupants are unable to set times for when the heat should be released. Storage heaters are often unable to meet peak evening heat loads and so are supplemented by direct electric heaters. Warm air systems are not as common in the UK as other countries but essentially air is heated by a central boiler and this warm air is then circulated round the home via ducts. These systems typically run on natural gas to warm the air being circulated, however these are seen to be not as efficient or comfortable as wet systems.

Wet heating systems can be described as those which have a boiler which heats and circulates hot water through the home via a circuit of pipes leading to radiators.

Boilers commonly run on mains gas, however there are wet systems which can run on oil, liquid petroleum gas (LPG), coal or wood. Boilers can either be conventional boilers or combination boilers (combi) (APHC, 2013). A conventional boiler also heats the water stored in an insulated cylinder (hot water tank), which supplies the

43 hot water taps in the dwelling. A combi-boiler directly heats the hot water supplied to taps when a tap is turned on, so no cylinder is needed as part of the system.

The heating controls, which influence the inter-room temperature variations, are the same for either boiler type. The variety in heating controls available is further described in Section 2.3.3. When the heating controls signal to turn the system on, the gas boiler fires and the circulating pump runs and within a few minutes, hot water is delivered to the radiators (APHC, 2013). The temperature of the supply water can often be controlled by a dial on the boiler; although most homeowners are unlikely to use this facility. The pump runs continually until the thermostat senses that the set-point temperature has been reached. This is the temperature set by the occupants. When the set-point temperature is reached, an interlock will turn the boiler off. The boiler and pump cycles on and off to try and maintain the set-point temperature.

Individual rooms within the dwelling are heated by panel radiators supplied by hot water from the boiler. These are traditionally fitted with manually operated radiator valves, but increasingly these valves have been replaced by thermostatic radiator valves (TRVs). TRVs allow occupants to control the environment in each individual room to suit their needs and preferences.

Since 2002 UK Building Regulations state that the basic central heating system configuration within new homes (or if existing heating systems are being replaced) require that the system must have a timer, central thermostat, boiler interlock and TRVs on all but one radiator (typically where the room where the thermostat is located) (ODPM, 2002, EST, 2001). Since Oct. 1^st 2010, the UK Building Regulations (HM Government, 2013) have required that the ground and upper floors of new homes over 150m² must be controlled independently, each with their own wall thermostat. Very few homes built before this time have such a system and

44 retrofitting to such a configuration can be difficult and expensive. The Energy Follow-Up Survey (BRE, 2013a) reported that 90% of the homes researched had central heating systems with 98% of those having the primary central heating system controls (therefore at least one form of control from either a boiler on/off switch, boiler thermostat or a central timer to control the heating). Only 49% of the homes met with the Building Regulations of 2002 where a full set of controls were present within the home (TRVs, central timer and room thermostat) (Consumer Focus, 2012). This will be due to many occupants not upgrading their heating controls until the existing boiler needs replaced.

Many homes with central heating also have secondary heat sources (EST, n.d, a), commonly a gas or electric ‘fire’ which is typically located in the main living room where there would traditionally have been an open fire. Thus living rooms can be heated even when the main central heating system is switched off. This could increase the temperature variation between the living room and other rooms in the home. Often households also have small portable oil filled radiators which can then be moved from room to room depending on where the additional heat is required.

Electric fan heaters can also be used where the air is warmed within the appliance and then blown into the room.