Home Energy 101
Achieving Thermal Comfort
2000 years ago humans understood how to build houses that were appropriate to the local conditions. In the last 100 years we seem to have forgotten almost all of what we knew, even as building techniques and materials have improved in range and (generally) quality. Thankfully this knowledge has not been lost, merely overlooked, while we basked in the cleverness of our ability to burn huge quantities of fuel at relatively little cost. Yet energy guzzling homes tend to be less thermally comfortable than those which are in tune with their environments...
Thermally comfortable homes have considered four critical elements:
1) Where is the sun?
2) How much insulation?
3) How much thermal mass?
4) Is the local climate:
Figure A. Cool Temperate? (this is Dunedin's climate)
- In cool climates we need our homes to be very well insulated, have high levels of internal thermal mass and to capture as much of the suns’ energy as possible.
Figure B. Hot & Dry?
- In climates where there are hot days and nights we need our homes to be very well insulated with a strong connection to the mass of the earth and lots of shade so no sun can enter the home.
- Where the days are hot but the nights cold we need our homes to have low insulation, very high thermal mass and to ensure that very little sunlight enters the home directly.
Figure C. Hot & Wet?
- This is the most challenging environment where we need our homes to maximise shade and ventilation whilst minimising mass. Reflective insulation can help with shading.
The Sun - Truly Free Energy
There are many ways in which the suns’ energy is used in the average home – how many does your household make use of?
• Providing lighting within the house
• Providing space heating
• Drying, washing
• Growing food
• Heating water
• Generating electricity
How well a house is lit and heated by the sun depends greatly on its orientation and construction. In existing houses it is often not easy to change these things, however, it is important that people understand what good solar design looks like so they can make more informed decisions when renovating, buying, or building in the future.
In a nutshell Kiwi homes:
• Are poorly insulated - even the new ones. The current building code requires insulation at approximately one third of best practice levels.
• Have poorly performing hot water systems; for example hot water taking 2-3 mins to reach your tap, or the shower altering temperature every time somebody uses another tap.
• Use inappropriate lighting; for example the overuse of downlights which only provide unhelpful puddles of light whilst compromising the quality of your ceiling insulation.
Links to Helpful Solutions
The following sites provide lots of good, technically accurate information about home design and energy use:
- Smarter Homes - owned by the Building and Housing Group within the Ministry of Business, Innovation and Employment. It was created in a joint initiative by the Department of Building and Housing, the Ministry for the Environment, Consumer, Beacon Pathway Ltd and URS, with assistance from a number of other organisations interested in helping consumers access good quality, reliable and independent information about smart homes.
- The Design Navigator - built and operated by Albrecht Stoecklein who has worked as a researcher and consultant on energy and building matters for the past 15 years. He has a MSc in Physics from Heidelberg and Oldenburg Universities in Germany, and an Energy Management Diploma from the Central Institute of Technology. Previously he has worked at various overseas universities, at BRANZ and at Right House.
- Your Home - a joint initiative of the Australian Government and the design and construction industries
- NZ Home Energy - a joint project by the University of Otago and NERI
- Energywise - EECA's consumer programme that provides information and funding for householders so they can make the most of energy efficiency, energy conservation and renewable energy.
- RightLight - developed by the Electricity Commission with support by the Energy Efficiency Conservation Authority (EECA), Consumer New Zealand, New Zealand Green Building Council, Lighting Council NZ (LCNZ) and the Electrical Contractors Association of New Zealand (ECANZ). The RightLight campaign uses information provision and advertising to encourage consumers to find energy efficient lighting alternatives that serve their needs, across both residential and business. RightLight activities are funded through the energy efficiency component of the electricity levy. The RightLight campaign was started by the Electricity Commission, before its merger with EECA, and is now incorporated into EECA's work. Read more about lighting on the ENERGYWISE website.
- Little Greenie - EECA teamed up with the ex-Hikurangi Foundation, now Akina Foundation and Little Greenie Design and Build to produce a report on the 'Little Greenie' so that others could be inspired and learn from the 'Little Greenie' example. 'Little Greenie' is a great example of a home built with high energy performance in Golden Bay. It was built by owner/builder, Lawrence McIntyre, during 2008/2009 and is one of the most energy efficient houses in New Zealand, designed with five major principles in mind - energy efficiency, low maintenance and longevity, ease of construction and value for money.