R Value and Thermal Mass
These two concepts are important to understand when designing a new home, as they will directly affect energy efficiency, and therefore power bills!
The ‘R-value’ of a wall, roof or floor indicates how well it keeps heat in (or out). The higher the number, the greater the insulation, and the less the building will need to be heated in winter, or cooled in summer.
Thermal mass is the concept that a material will absorb heat when the air around it is warm, and then release that heat when the air around it is cool. For example, a wall with a high thermal mass will absorb heat in a room that is being heated, and once the heating is turned off, it will release heat back into the room, slowing the rate at which the room cools.
Different materials have different properties, and the whole picture needs to be examined to get a feel for real environmental benefits. For example, timber offers carbon storage and low embodied energy (the energy needed to make the product) but has low thermal mass, while concrete is a more energy-intensive product but has high thermal mass, saving energy in the long term.
Glazing
Buildings can lose a significant amount of heat through windows – fortunately there are many options for improving the performance of glazing. Fraemohs buildings can be designed to accommodate these options, including:
- Double glazing: two sheets of glass with an air space in between
- Gas-filled double glazing: two sheets of glass with a heavy gas in between that further avoids heat loss
- Low-E coated glazing: Glass that has been coated to help reflect heat
- Triple glazing: Three sheets of glass, with space in between - this type of glazing greatly improves energy efficiency of a building.
An example of a NZ-based double glazing manufacturer is Eurovision.
Insulation
Insulation increases the R-value of a wall, roof or floor, keeping a building cosy. There are a few different types of insulation materials that can be used, all of which offer energy efficiency benefits:
- Glass fibre (batts): This is the most common type of insulation in New Zealand. It consists of blocks of spun glass fibres. Pink® Batts® is an example which is made primarily from recycled glass, and has gained Environmental Choice accreditation.
- Wool Insulation: This insulation is made from natural wool fibres, usually modified in some way to make the material easy to handle. It has good insulation properties, is made of renewable resources, has a low environmental impact and is fire resistant. Two manufacturers in the Canterbury region are Latitude Insulation and Terralana.
- Expanded Polystyrene (EPS): This material has a high R-value, is lightweight and is long-lasting. EPS is incorporated in Fraemohs StrongWall, and can be used in Fraemohs solid timber homes as well. It is especially suited to underfloor insulation. Perhaps the most prominent manufacturer in New Zealand is PolyCut.
Detailed R-values, indicative costs and further information on all types of insulation can be found at the University of Otago’s Energy Database.
Other Energy-Efficient Design Options
- Fraemohs solid timber double wall: For superior warmth in cold winters while retaining solid timber construction, consider solid timber double walls. The space between these walls can be filled with insulation to form a wall with a very high R-value.
- Extra thickness StrongWall: Fraemohs StrongWall can be made extra thick for enhanced strength and insulation.