Building An Energy Efficient House

If you are thinking of building or buying a house it should really be an energy efficient house as this will probably be the largest purchase/investment that you'll make in your lifetime.

An energy efficient house is warm, comfortable, enjoys the benefits of lower running costs and is less damaging to the environment by reducing our impact on climate change.

When Should I Consider Energy Efficiency?

Really the best time to consider energy efficiency measures is at the beginning of the design stage. This way you can achieve the maximum benefits of an energy efficient house obtained through an integrated design, complementary to your needs (what you're happy with), from the 'get go', and for the least cost - as opposed to retro-fitting.

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Help - I Don't Know Where To Start?

Don't worry - below is a check list to guide you.

Get The Proper Team:

  • Choose an architect who understands low energy efficient house design
  • Be sure that builders are aware of the low energy aim of your house
  • Choose tradespeople that have both knowledge and experience in energy efficiency

Minimize Your Heat Loss:

  • Keep your house plan simple and compact
  • External walls should have high level insulation
  • Ensure there is good controlled ventilation and draught-proofing
  • Your architect can provide energy calculations of expected annual fuel bills

Maximize Your Solar Heat Gain:

  • Build along the East West axis
  • Houses in the northern hemisphere should locate most windows on the south side with reduced window size on the north side, and vice versa for houses in the southern hemisphere
  • Locate living rooms and main bedrooms on the sun facing side
  • In two storey houses consider having your bedrooms on the lower level (cooler for sleeping) and your living rooms on the upper level further reducing your heating requirements as upstairs gets warmer

Install Energy Efficient Heating And Hot Water System:

  • Renewable energy systems
  • Solar heaters
  • Use a condensing boiler if using gas or oil
  • Install easy to use controls

Additional Energy Saving Tips:

  • Ensure insulation overlap between elements, e.g, between the wall and loft/roof cavity
  • Ensure air gaps such as wall cavities are clear of debris that can bridge therefore compromising the insulating air gap
  • Make sure fibre insulating materials are not compressed (packed tightly) as this will undermine its ability to properly insulate
  • Make sure that all insulating materials are kept dry
  • Be sure to seal all holes where services such as water and gas pipes enter your home (this is called - Fire Stops)

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Using The Sun's Energy

An energy efficient house will capture the free energy from the sun to power and heat your home and hot water. Ideally where possible choose a site where your house can face the sun (external blinds can prevent overheating in the summer months) and be sheltered from prevailing winds.

  • Photovoltaic converting light directly from the sun into electricity without creating any air or water pollution
  • Wind Turbines can take full advantage of the sun's thermal wind power generation
  • Heat Pumps use the sun's thermal energy - all renewable energy systems are complementary to an energy efficient house design

Most windows should face the sun side to benefit from solar gains. However, some windows will have to be on the non sun side to enable good daylight in all the rooms in your home.

For example: Rooms which are going to be used a lot in houses in the northern hemisphere should be south facing (on the south side), and in houses in the southern hemisphere they should be north facing (on the north side) to take advantage of solar heat gain.

Kitchens and breakfast rooms are mostly used in the mornings, so for houses in the northern hemisphere a south-east orientation will take advantage of the morning sun. For houses in the southern hemisphere then a north-east orientation will take advantage of the morning sun.

Halls, stairs and bathrooms can be located on the side that doesn't get much sun as they are less frequently used.

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Using Thermal Mass

When thinking of an energy efficient house remember that the use of certain materials will also improve the 'thermal mass' of your house by their ability to slowly absorb solar heat during the daytime and then slowly release this free heat through the night.

The common materials used for thermal mass are:

  • Adobe bricks (mud or earth bricks)
  • Rocks and stones
  • Concrete (preferably concrete with stone)

This is because they have:

  • High specific heat - able to store a large amount of heat for a long period of time like the heat bricks in a sauna
  • High density - basically the weight (mass) of a material in relation to it's volume (it's size) - the greater the mass per unit volume the greater the density, e.g, iron will have less volume than water with equal mass - because the iron is smaller in size it's density is higher
  • Low thermal conductivity - slow absorption and slow release of heat

Note: Thermal mass is not insulation, it is the amount of specific heat that can be stored in a material (water has high thermal mass by being able to store a lot of heat). Insulation materials have a lower thermal conductivity to restrict the flow and absorption of heat.

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The percentage of heat loss from a house is approximately:

  • 42% Roof
  • 12% windows
  • 12% Unblocked chimneys and draughts around doors
  • 24% walls
  • 10% Floor

So when thinking of building an energy efficient house understand that installing insulation at the build stage is the easiest and cheapest way of improving your homes energy efficiency.

You can upgrade standard timber framed walls by using 140mm studs instead of 90mm studs - this will allow you more insulation. Masonry cavity walls can be improved by being filled with polystyrene insulating foam and by using lightweight thermal blocks. Either of these methods will give a U-value better than 0.30 W/m2K

The "U" Value is the amount of heat which will flow in 1 second through a particular piece of structure for every 1K (Kelvin degree) temperature difference. "U" = W/m2K. The lower the U-value the slower the heat loss

You should have at least 250mm of loft insulation, 100mm of insulation between the joists and 150mm of insulation laid across the top. Doing this will achieve a U-value of 0.16W/m2K. Loft conversions require careful attention especially if dormer windows are installed but a high standard of insulation can still be achieved.

Heat loss from the floor varies with different floor types. However, ground floor insulation is pretty easy. Generally a 125mm layer/sheet of polystyrene is used (this size will be increased if installing underfloor heating to minimize heat loss).

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House Design

When thinking about an energy efficient house design/layout, it is important to remember that a house with a simple 'Form' (one that is compact and without extensions) will have less heat loss due to the reduction in the external walls and roof area.

It is also good to know that single storey houses such as bungalows lose more heat through the roof than two or three storey houses where the rising heat is used throughout the levels before reaching the roof.

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Windows And Conservatories

You're always going to lose more heat through windows than through walls especially single pane windows. To minimize heat lost through windows 'Low-E' coated double glazing should be installed in all new houses.

Double glazing does not only reduce heat loss, it also offers some sound insulation. With double glazing the two panes are generally vacuum sealed. However, you can get argon-filled units (gas filled), and triple glazing which are well worth considering if you can afford them.

Conservatories can save you a little energy by acting as a buffer between the adjoining wall by trapping the heat from the sun, thereby reducing the heat loss from the room separated by the adjoining wall. To be effective, conservatories should be located on the sun facing side of the house and preferably not overshadowed by trees or other buildings.

Conservatories correctly placed should not require any permanent heating, but the doors that separate the house from the conservatory should be double glazed and shut when not in use.

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Efficient Home Heating

A well insulated house is a low energy consuming house meaning that energy efficient house heating requirements (needs) are lower than a similar sized house which is poorly insulated.

Your heating system should take into account:

  • Fuel source and availability
  • The time you will spend in your home - quick or slow response systems
  • Construction material - timber framed houses should have responsive heating such as radiators or air heat pumps, as they retain less heat than concrete, for example
  • If you want rapid space heating then underfloor heating systems (by itself) are not suited for houses built from lightweight construction materials like timber frame because of their slower heating response

You can however, have hydronic underfloor heating (wet - water based) systems combined with radiators. These are usually designed with the underfloor heating downstairs and radiators located upstairs.

Tiled solid screed floors work the best with underfloor heating. If you prefer a softer floor finish rather than tiles you should consider rugs rather than fitted carpets for better heat transference/output within the room.

Condensing boilers are much more efficient than conventional boilers - even in non-condensing mode.

Renewable energy systems like heat pumps and solar heating are perfectly suited for energy efficient house designs.

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Ventilation is an important aspect not to be overlooked as it provides both fresh air and removes stale air and moisture. Removing moisture prevents bacterial growth thus maintaining a healthy living environment.

Kitchens must have extractor fans or passive stack ventilation (PSV). PSV works using the principle of 'rising' warm air carrying stale air up and out.

Mechanical ventilation systems with heat recovery do offer filtered air and a reduction in noise intrusion as windows can be kept closed. However, unless you are using a renewable power system such as photovoltaic (PV) or wind turbines then the power required to run the fans rules it out as a feature for an energy efficient house.

Also, for a heat recovery system to work efficiently the house must be well sealed.

All rooms should have trickle ventilation - allowing air to come in at a trickle rate to provide required room air change rate per hour (ACH).

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Lighting and Appliances

Lighting and appliances should be low energy rated in a energy efficient house (low-wattage) because they will save you money in running cost and help the planet by reducing CO2 emissions.

Note: Recessed ceiling spot lights contribute to increased room heat loss, including those with heat retaining covers. Just be aware that the more holes you have in your ceiling, the more heat you will lose through it which is not conducive to an energy efficient house design.

Turning off appliances rather than leaving them on standby when not in use - even computers, will save you money (turning your lights down with dimmer switches will not).

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Architects And Designers

Most architects and designers today are familiar to some extent with energy efficient building principles. Many, however, don't go beyond minimum building standards and regulations - minimum isn't the most efficient.

When finding an architect/designer, consider the following:

  • Find one who has knowledge and experience on low energy energy efficient house design
  • Ask for references of previous builds incorporating low energy design
  • Find someone you feel is supportive and understands your reasons for wanting a low energy design
  • Ask him/her to provide projected fuel running costs
  • Ensure he/she understands how the house will be used

Useful links for Home Improvement:

3D Home Architect

  • 3D Home Architect provides full suite of software to design your home of your dreams. 3D Home Architect has what will make your home interior design,kitchen remodeling,room design, interior decorating.

Green Mortgages

  • Green, or “Energy efficient” mortgages, let you borrow extra money to pay for energy efficient upgrades to your current home or a new or old home that you plan to buy.

The Passive Solar House: The Complete Guide to Heating and Cooling Your Home with CDROM How to Heat Your Home with Less Fuel This Winter Renewable Energy

See also:

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