Project planner: Eco updates explained

Michael Holmes looks at energy efficiency including Government incentives such as the Green Deal and Renewable Heat Incentive

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What do I need to consider when extending?

Energy performance relating to extensions is based on an elemental approach in which insulation and efficiency thresholds are set for individual parts of the walls, roof, floor, doors and windows and for the services.

There are requirements for standards to be achieved for ‘thermal elements’ (the walls, floors and roofs), ‘controlled fittings’ (windows, doors and similar fittings) and ‘controlled services’ (heating, hot water, ventilation systems and lighting).

In addition to setting minimum energy- efficiency standards for the building elements (as listed below), the regulations also require good practice in the building detail, in particular for the installation of insulation and ventilation.

 

Watts per m2

Element (1)

Kelvin (W/m2K)

Standards

 

1.

 Wall0.28 W/m2K (2)2.Pitched roof- insulation at ceiling level0.16 W/m2KPitched roof – insulation at rafter level0.18 W/m2KFlat roof or roof with integral insulation0.18 W/m2KFloors (3) (4)0.22 W/m2K

3.

4.Swimming pool basin0.25 W/m2K

Notes:

  • 1. Roof’includes dormers and ‘wall’ refers to wall parts cheeks) of domer windows 
  • 2.  Area-weighted values
  • 3.  A lesser provision may be appropriate where meeting a standard would result in a reduction of more than five per cent on the internal floor area of the room bounded by the wall.
  • 4.  A lesser provision may be appropriate where meeting a standard would create significant problems in relation to adjoining floor levels. The U-value (thermal performance) of an extension floor can be calculated using the exposed perimeter and floor area of the whole enlarged dwelling

What if I am converting existing space?

A garage, loft or cellar conversion involves a change of use of part of your home, and any building part that becomes a thermal element (separating an indoor heated space from an unheated outdoor space) must be made energy efficient. The elemental standards for this are now the same as for extensions (see table above). Windows, doors, new wiring, heating and ventilation must comply with the regulations.

 

What if I am only replacing some windows?

Windows and doors must comply with regulations for energy efficiency. Windows, roof windows and rooflights must have a manufacturer’s Window Energy Rating (WER) of at least B or C, or a U-value of 1.6 W/m2K or lower. Doors with more than 50 per cent of their internal face area glazed, and all other external doors, must have a U-value of 1.8W/m2K or lower.

What if I want to include lots of glass in my project?

When using the elemental method of compliance, there is a limit to the total area of glazed windows and doors that can be used: an area no greater than 25 per cent of the extension’s floor area plus the area of glazed doors and windows that are no longer exposed as a result of the extension project. Alternatively, the area of the windows, roof windows and doors across the whole property, including the extension, should not exceed 25 per cent of the total floor area. If your project cannot comply using the elemental method, for instance because you want to include a larger area of glass, or your replacement windows do not comply due to their thermal performance, you can compensate by improving energy efficiency elsewhere in the house, and use either the area-weighted U-value method, or the overall carbon index to demonstrate compliance. An energy consultant can assist in producing the necessary calculations.

What if I am repairing an existing building?

Where 25 per cent or more of an element’s surface area is to be renovated, the whole element should be thermally improved. This applies to roofs, walls and floors. Decoration or re-pointing brickwork does not count.

 

I live in a listed property – do I have to comply?

Special considerations can be applied to works on listed properties and those in Conservation Areas, national parks, Areas of Outstanding Natural Beauty and traditionally constructed buildings with permeable fabric that absorbs and allows the evaporation of moisture.

 

Can I use lower-performance replacement windows to match originals?

Where replacement windows don’t meet minimum standards as they’ve been chosen to match existing, they should meet a centre pane U-value of 1.2 W/m2K, or single glazing should be supplemented with low-emissivity secondary glazing.

 

Can I use lower-performance replacement windows to match originals?

Where replacement windows don’t meet minimum standards as they’ve been chosen to match existing, they should meet a centre pane U-value of 1.2 W/m2K, or single glazing should be supplemented with low-emissivity secondary glazing.

Can I use the Green Deal to improve energy efficiency?

You can arrange for a Green Deal assessor to explore the most cost-effective options to improve the energy efficiency of your home. You can then apply for a Green Deal loan, repayable through your electricity bill, to fund the improvements, ranging from a new boiler and controls to insulation, and to installation of renewable technology.

To ensure that the investment makes financial sense, the golden rule of the Green Deal is that the charge attached to the energy meter to pay for the improvements cannot be higher than the estimated savings for the package of measures in that property. For more details, visit Gov.uk/green-deal-energy-saving-measures.

Can I apply for the renewable heat incentive (RHI) for solar panels?

Eligibility for the latest Government-backed incentive for homeowners to fit renewable heat technology is dependent on getting the efficiency basics in place first to ensure that renewable heat is not wasted.

For similar reasons, receipt of the full rate of feed-in tariff payments (FITs) for building-wired solar photovoltaic installations is conditional on the building meeting an energy performance certificate (EPC) level D. For more information, visit Gov.uk/feed-in-tariffs, and for RHI, Gov.uk/household-energy.

What if I am rewiring?

For any new or replacement installation, you must fit energy-efficient light fittings. To comply, fittings must only take lamps with a luminous efficacy greater than 45 lumens per circuit Watt and a total output greater than 400 lamp lumens. Fittings with supplied power less than five circuit Watts are excluded from the overall count. The minimum required is: not less than one energy-efficient light fitting per 25 square metres of dwelling floor area, or part thereof, or one per four fixed light fittings.

 

What if I am updating my central heating system?

All new boiler installations (oil and gas) must be A-rated for energy efficiency, and all pipework and any tanks must be insulated. Replacing an old gas boiler with an A-rated condensing boiler and improving your heating controls will significantly cut your home’s carbon dioxide emissions and could save you as much as £305 per year. Areas of differing heating needs (living space, bedrooms) must have individual temperature zone control via room thermostats or thermostatic radiator valves. Space and hot water require separate timing controls (except for combination boilers that produce hot water on demand and solid-fuel appliances). You must also ensure that the system is commissioned with all parts working adequately

Does my local planning authority set other requirements?

Some local authorities will only grant planning permission for home-improvement projects if there is evidence of environmental benefits to justify the change. This can take the form of an EPC of the current building, and a predicted energy rating for the project. The two leading energy rating schemes are BREEAM*, and EcoHomes Standard.