Energy Efficient Homes

Step 1

Creating an Energy Efficient home

Building an energy efficient home is a question of doing a few things very well.

• Build it tight
• Insulate it right
• Orientate it for sunlight
• Correctly install efficient equipment

Always remember that energy efficiency comes before renewables – Don’t design in problems, design in energy efficiency. Improvements in structural and build quality will generally have a greater benefit than good appliances.

 

If you are planning to build a house try and choose a sheltered location so that you can reduce heatloss from exposure to wind. If that isn’t possible plan to plant trees or shrubs to act as shelter. A compact build form is more energy efficient with a lower surface to volume ratio. Try and avoid dormer and bay windows as they are difficult to insulate effectively. Pitched roofs should have one slope oriented south or at least south east to south west for optimum performance of solar panels.

 

When you have a design completed and a specification outlined have a Building Energy Rating Assessor work out the BER for the house and then if necessary refine either the design or the specification of the energy products.

Step 2

Build it tight

A well sealed building is the perfect start to an energy efficient house. Minimise penetration of pipe work and cabling through the insulated shell. Consider building a draught lobby. By using a smart vapour barrier, a near airtight envelope can be built. This can then be measured by use of a blow-door test. Air tight houses will require good indoor air quality which can be provided by a whole house mechanical ventilation system with high efficient heat recovery. Open fires should have an independent air supply.

Step 3

Insulate it right

Increased levels of insulation above the building regulations are obviously important and economically justified but what is crucial is that the improved level of insulation is installed to a high standard. That means no voids or gaps, no compression of the insulation. Avoid thermal bridging or “short circuits” across insulation at lintels, jambs and sills of doors and windows and at junctions where floors and ceilings meet external walls.

Step 4

Orientate it for sunlight

Try and orientate the house to capture a lot of sun in the winter. Concentrate the glazing and living spaces on the southern façade. That way exposure to the low altitude winter sun can allow passive solar heating and day lighting. Thermal mass within south facing rooms e.g. masonry walls or concrete floors can absorb and store solar energy during the day and release it at night. A well designed sunspace or conservatory on the south side of a house can reduce the heating requirements by acting as a buffer against heat loss. Sunspaces should not be heated.

Step 5

Correctly install efficient equipment

Energy efficient houses need smaller heating systems than conventional houses. Select high efficient equipment and controls that are installed correctly. Use “A” rated condensing boilers with high efficient radiators or under-floor heating, factory insulated cylinders, zone and separate time and temperature controls. Install solar water heating to provide up to 60% of a houses hot water needs. Install energy efficient lamps and appliances. Glazing should be “low emissivity” double glazing or consider argon filled triple glazing.

Step 6

(DEAP) in compliance with EPBD

DEAP includes the energy requirement for space heating, ventilation, water heating and lighting less savings from energy generation technologies. It calculates the annual values or delivered energy consumption, primary energy consumption, carbon dioxide emissions and cost, both total and per square metre of total floor area of the dwelling.

Principal components

 

U values – walls, floors and roofs
All the calculations are based on the actual construction details. For an A rated house the insulation would need to be between 40% and ^0% above the present building regulations requirements (see TGL Part L). An important part of the overall insulation question is related to thermal bridging or linear thermal transmittance this is basically short circuits through the insulation product through the likes or wooden joists and mechanical fixings. Installation of insulation would have to comply with the recommendations of the Home Bond “Right on Site” information brochure with regard to robust detailing around windows, door jambs and at junctions between elements. DEAP also uses the total floor area and the dwelling volume in the calculation with the main living space as the most important measurement.

 

Windows
Window U-values and g-values (total solar energy transmittance) are needed. For an A rated houses low U-values will be necessary with emphasis on the glazed area, the direction all the windows are facing so that solar gain can be accounted for.

 

Internal heat capacity
Internal heat capacity is estimated by the DEAP program based on the a number of criteria included the thermal mass of the structure, the average internal temperature, the annual space heating demand while allowing for solar and internal heat gains. This is also based on the how big the main living space is in relation to the total floor area.

 

Boiler efficiency
Efficiency rates for boilers is available online on the HARP data base. High efficiency condensing boilers are necessary. Important to have good quality and effective heating control system to included time and temperature zone controls. The type of fuel used is also important.

Standing loss can be overcome by using highly insulated and factory insulated cylinders.

 

Air leakage
Pressure testing of new building is now mandatory in the new building regulations. Use of a correctly installed air tight membrane will greatly improve a blow door airtightness test but will require a mechanical ventilation system with heat recovery to give the correct whole house ventilation necessary.

 

Solar Collectors
Solar hot water heating systems are probably the most cost effective way of complying with the requirements for approx 20% of the energy needs of a new build house to come from renewable energy sources. The systems with include the collectors, pump station and cylinders.

Specific fan power
Values from the manufacturer of the mechanical ventilation system.

 

Light
Annual energy use for lighting. Install low energy lighting.

 

DEAP Results
Annual delivered energy, primary energy, CO2 emissions, cost, comparison with reference dwelling, compliance check with Building Regulations L2.