Energy Rating

A BER (Building Energy Rating) assessment is a legal requirement for all new homes. This assessment gives your house an energy rating similar to those seen on fridges, etc. Based on the characteristics of your home, its energy efficiency is determined using the DEAP (Dwelling Energy Assessment Procedure) software. With the latest revision (2007) of Part L of the building regulations, it is now necessary to use the DEAP software to check for compliance.

This takes many factors into consideration including:

  • Design including building shape, size & orientation
  • Insulation in floors, walls & roofs
  • Air-tightness of the building
  • Method of ventilation
  • Space heating system
  • Hot water heating system
  • Lighting efficiency
  • Control systems
  • Fuel efficiency

Design

While it can be relatively easy to achieve an 'A' rating in a small terraced or semi-detached house, it can be somewhat more difficult in a large one-off detached house. It is important to consider all the factors that will affect your homes BER right from the beginning - ideally at design stage.

At design stage, try to keep the size of the house sensible. A bigger house will obviously demand a lot more energy to heat. Try to keep the shape of the house as bulky and straight forward as possible. The lower the surface area to volume ratio, the better. For example a 'H' shaped building will have more surface area than an 'L' shaped of the same square footage and therefore more heat loss. Also consider the buildings orientation to get maximum solar gain from the sun. Keep living rooms and large windows to the southern side. Make sure some of your roof also faces south for installing a solar collector.

Construction

Consider how you will build your home. A timber frame building is much easier to insulate properly and make airtight than its masonry alternative. It is also much easier to minimise thermal bridging, i.e. heat loss at junctions, for example around windows or where a wall meets a ground floor.

The amount & type of insulation used and how it is installed will greatly affect the amount of heat loss from your building. The amount of heat lost through walls, floors, roofs, windows, etc is represented by its U-value. Put simply the lower the 'U' value of your floor, walls, roofs, etc, the less heat loss there will be and the less heat will required to heat your home. The air-tightness of your home will also be a big factor. If your home is not air-tight, warm air will leak out and cold air will leak in, again increasing the heat loss and hence the amount of heat that needs to be generated to compensate. Air-tightness is a key component of our system. Click here for more information on Air-tightness

Ventilation method

Ventilation is essential to the health of a home and its occupants. Most modern homes built in Ireland over the last 20 years use natural ventilation. Natural ventilation is usually installed using vents in the wall or trickle vents in the windows. This is a very poor way of ventilating a house. It is not energy efficient as heated air goes straight out these vents and cold air comes in. It is also hard to control and uncomfortable for the people living in the house.

MHRV (Mechanical Heat Recovery Ventilation) is a much better alternative. These systems supply fresh air to your home with minimal heat loss. An air-tight house is essential for a MHRV system to work effectively and likewise a MHRV system is essential to provide ventilation to an air-tight house.

Space heating system

Consider how you would like to provide space heating to your home. Underfloor heating is a good way to heat a house although it is not as responsive as traditional radiators. If you reduce your heat losses with good levels of insulation and air-tightness, you will need very little heating. In fact, in a 'passive' house there is so much insulation that you need only a supplementary backup heating system for use in the coldest few weeks of the year. Click here for more information on Passive Houses

Hot water heating system

A large amount of energy is used heating hot water for showers, baths, taps, etc. Solar panels are an essential feature to any new home and will provide a large proportion of the energy required for hot water use, even in winter. Solar panels should be as close to south facing as possible and ideally mounted on a roof of a 30 to 45 degree pitch.

Lighting efficiency

Using low energy lights such as CFL's or LED's will reduce the electricity consumed in lighting your home and improve its BER.

Control system

A good control system will contribute to the energy efficiency of a house. Heat should only be generated and supplied to a room if and when it is required. A good control system would consist of room thermostats with a time and temperature programmable controller.

Fuel efficiency

How you generate heat and from what fuel, will have a big effect on a BER. There are now a wide range of technologies available to generate heat from oil/gas boilers to heat pumps to wood pellet boilers. Some of this technology can be expensive and a full cost/benefit analysis should be undertaken before making such a large investment.

Remember that it makes much more sense to reduce your heat losses by investing in an extremely well insulated and air-tight house rather than spending big money on an expensive heat pump or wood pellet boiler.

If you would like any further advice on how to achieve a good BER for your home, talk to our in-house SEI registered BER assessor.