BUILDING BRIEFING :

Energy Efficiency

- Part 1; conservation and benefits

Energy consumption is becoming more and more important in the modern world. Landlords are not exempt from these effects as tenants will start to choose more energy efficient properties. In this article we will discuss energy conservation strategies, the selection criteria, timing of improve-ments and look at the associated cost and benefits.By Adrian Birch, Senior Lecturer in the Faculty of the Built Environment, University of the West of England

Energy consumption

 The introduction of Energy Performance Certificates to residential lettings from October 2008, coupled with the significant rise in fuel costs, provides landlords with a timely opportunity to review the ways in which energy consumption can be reduced. This article describes approaches that have been adopted by the Energy Savings Trust.

Energy consumption and heat loss

In a typical poorly insulated Edwardian house, energy is used in the following proportions:

• Cooking                                   4%

• Space heating                         63%

• Water heating                         16%

• Lights and appliances              17%

For this type of house some 8 tonnes of CO₂ are emitted each year.

Heat lost through the fabric of such a building is typically in the following proportions:

• Roof                                       25%

• Walls                                      30%

• Windows                                 15%

• Floors                                     15%

• Air leakage                             15%

The average household could save about 2 tonnes of CO₂ a year by making their home energy efficient

A strategic approach to energy efficiency

The most effective strategy to be adopted is to reduce energy consumption at the same time as adopting measures to reduce heat loss. This can be broken down into:

• Fabric strategies: -provision of insulation, double or secondary glazing and draught proofing
• Services strategies: - improvements or renewal of heating systems and controls
• Lifestyle strategies: -low energy lighting and appliances, energy monitoring and targeting

Cost benefit analysis

It should be apparent from the above that in an ideal situation, insulation of roofs, walls and floors should be a priority as should provision of double or secondary glazing systems and draught proofing to prevent uncontrolled air leakage. However, the ideal situation does not often occur and the landlord has to factor in the cost and benefit of such measures together with the suitability of the works and potential disruption and nuisance to the occupiers or neighbours.

The Energy Savings Trust have produced a series of cost benefit tables in their document GPG 171 Domestic energy primer - an introduction to energy efficiency in existing homes, which can be downloaded free of charge from their website www.est.org.uk or can be ordered by phone on 0845 120 7799.

A summary of their recommendations is illustrated in the table below.

Measure	Annual saving (£)	Installed  cost (£)	Payback   (yr)
Cavity wall insulation	40-250	250-500	2-4
Solid wall insulation (external)	100-600	1,000-3,000	5-10
Solid wall insulation (internal)	100-550	£40-50/m2	4-8
Loft insulation (new)	250-340	250	1-2
Loft insulation (top up to 270mm)	60-70	250	3-5
Floor insulation	30-50	100-150 (DIY)	2-3
Replacement condensing boiler	50-160	200  (extra cost of grade A)	1-2*
Hot water tank insulation	20	10-20 (DIY)	1
Full heating control package	50-90	200	2-5
Draught stripping	10-20	75-100	4-8
Lighting (4x lamps)	15-20	15	1 Max

* assumes existing boiler is to be renewed. Cost of purchase and installation £4-5,000

Priority order

The timing of improvements also needs to be considered. Certain works can be undertaken whilst tenants are in occupation without causing major disruption whilst others should be deferred until such time as the property is vacant.

Some external works should be undertaken when access scaffold is available for another activity such as redecoration so as to economise on scaffold charges, or alternatively when other improvements are being considered.

Typical examples could be:

If an external wall requires re-rendering or re-pointing then it would be opportune to consider fitting external insulation, provided of course the wall remains weathertight and stable and the finish does not adversely affect the appearance of a property in say a conservation area where planning approval will be required.

If it is planned to renew kitchen and bathroom fittings then it would be appropriate to consider internally insulating the external walls before the new fittings are specified and fitted to the wall.

Ventilation strategies

‘Build tight ventilate right’

Whilst it is desirable to control heat losses and air leakage there is also the need to create a flow of air in buildings to prevent the build up of condensation and contaminated air. Trickle vents to windows are required by building regulations to permit a flow of air when the window is shut

for security reasons and provide good background ventilation. They can be retro fitted to existing timber casement windows.

Through the wall ventilation grilles are required for rooms containing multifuel fires and some gas appliances to provide replacement air, and should not be blocked by tenants.

Mechanical extractor fans are required by building regulations to extract warm moist air from kitchens and bathrooms, although passive stack ventilation is now an accepted alternative, which does not require fan assistance, thereby saving on fan operating costs.

Alternatively, simple plate heat exchangers can be fitted to fans or ducts to extract heat from exhaust air. A more sophisticated system is a ‘whole house ventilation system’ which passes heat extracted back to a ventilation system serving the whole house, in the roof or mounted in a unit above the cooker. These are quite expensive and have extensive ducting and a long payback time, but achieve high indoor air quality.

Heating strategies

There are three main types of heating:

• Wet central heating systems based on boilers and heat emitters - radiators and convectors

• Other central heating systems – ducted warm air convectors or electric storage heaters

• Individual room heaters - radiators and convectors

In addition to this there are seven possible fuel sources; gas, oil, wood pellets, chips and logs, solid fuels-coal and coke, liquified petroleum gas (LPG), electricity and solar.

There are three common types of ‘wet’ central heating system boilers utilising different fuel types:

• Conventional boilers providing hot water via a separate storage tank, powered by gas, oil or LPG)

• Combination boilers providing instant hot water at mains pressure (gas, oil, LPG)

• Thermal stores (gas, oil, LPG, electricity)

Conventional and combination boilers have operating efficiencies at about 75-85%. Condensing boilers and condensing combination boilers operate at about 90-95% efficiency.

The use of electricity as a heating medium is not generally recommended as electricity generation using fossil fuels is very inefficient and emits large quantities of CO₂ to the atmosphere. Operating costs are generally high. In some buildings such as high rise flats, gas may be prohibited in which case electricity may be the only option.

Building regulations require all new and replacement boilers to be of the condensing variety. These are more expensive than the equivalent conventional boiler and require regular maintenance and servicing by the manufacturer’s specialist staff. The lifespan of these boilers is thought to be 12-15 years, which is far less than the 25-30 years life expectancy of conventional boilers. It may be more cost effective to retain a conventional boiler until it reaches the end of its design life before replacing it with a condensing variety.

Nevertheless, there are significant operating cost savings to be made by upgrading boiler controls and introducing energy saving devices. Typical improvements are:

• Provision of a programmer capable of timing the space heating and hot water separately

• Provision of room and hot water cylinder thermostats

• Provision of motorised valves to provide independent control of heating and hot water

• Controls so that the boiler only operates when required

• Conversion to a fully pumped system

• Provision of thermostatic radiator valves to most radiators

There are few improvements that can be made to electric heating systems short of providing thermostatic controls and time clocks where none exist or renewing them with other more efficient ‘wet’ systems.

Hot water strategies

Hot water is likely to come from:

• A hot water cylinder indirectly heated by a boiler

• A hot water cylinder directly heated by an immersion heater

• A combination boiler or multipoint heater directly heating the hot water on demand

• Electric instantaneous heaters in shower units or under/over sink units

Not many economies can be achieved to combination boilers and instantaneous heaters apart from thermostatic control of temperature and regular servicing of burners, but economies can be achieved to water cylinders by increasing the insulation to 80mm thickness and ensuring there are no gaps around the cylinder.

If the cylinder is heated by an immersion heater only then provision of a second immersion heater to a suitable boss and connected to off peak supply would reduce operating costs.

Reducing the storage temperature to say 55 degrees C by means of thermostatic controls will also create energy savings. Further small savings can be made by ensuring primary hot pipes (between the boiler and cylinder) are properly insulated with neoprene insulation.

Lifestyle strategies

Lighting accounts for 15-20% of a typical electricity bill and is a key area for energy saving.

There are many different types of compact fluorescent lamps that are now available from supermarkets and electrical retailers that have a very low payback period due to the gradual reduction in unit cost.

A-rated domestic appliances have also come down in cost so that there is little difference in initial cost from less efficient models. Many appliances are fitted with ‘standby’ lights which remain lit even if the appliance is not operating. Significant savings can be made over a longer period if such fittings are switched off overnight or when the occupiers go on holiday.

Other lifestyle strategies are turning down radiator thermostats in uninhabitable rooms, or those only in use occasionally, boiling only enough water necessary for a cup of coffee or tea etc.

The use of showers instead of baths can also create savings provided the time taken in the shower is no more than 2-3 minutes! Power showers are not to be recommended if energy saving is required.

Part 2 of this article will discuss insulation and service improvements in greater detail.

References

Energy Saving Trust: www.est.org.uk

Department for Business Enterprise & Regulatory Reform (BERR): www.berr.gov.uk/energy/environment/efficiency/index.html