House insulation — a look at the trends


With the recent announcement from the Minister of Building Issues for higher house insulation requirements ringing in our ears, it is timely to look at current and future house insulation products.

The New Zealand Building Code requires buildings to meet a “whole building performance index”, not a specific R-Value for a wall, floor or ceiling, as most of us are led to believe.
Since calculating the “whole building performance index” requires the use of a computer modelling program, a simplified calculation method has been developed for ease of calculating minimum performance requirements, which uses R-Values for all the components used in a wall, roof or floor.

R-Values are used universally for calculating the effective insulation of a building. It is a best estimate and, because it is easy to use, is a popular method.
The difficulty of using the calculation method to estimate a building’s effective insulation is that the R-Value for each external wall, roof, window, door and floor component must be known, and many new products are not known.

To find out the R-Value of a wall, window or roofing system, one must have the system measured using a sophisticated apparatus called a guarded hot box.
This apparatus measures the flow of heat through all the components of the system and, therefore, measures the overall thermal resistance of the wall, window, roof or floor system.

To date, many building systems have been measured but many have not. EECA is now commissioning BRANZ to measure as many new building products as they can in order that there is a large database of information available for calculating a building’s effective insulation.

Soon EECA will be commissioning contractors to carry out assessments of the overall energy efficiency by measuring the effective insulation using R-Values.
This will lead to a building or house being given an Energy Star Rating to provide information to home owners about the energy use for their house.

The focus on thermal efficiency for building products is clearly going to increase dramatically as this new service begins to become more popular.
In New Zealand the most popular form of in-wall insulation has been fibreglass batts, followed by polyester-fibre batts and, of course, wool-fibre batts.

There are also loose fill materials such as mineral fibre and fire-resistant cellulose fluff.
In recent years houses have incorporated insulation sheets as part of their external cladding, known as External Insulation Finishing Systems (EIFS).

There are many variations of this using Expanded Polystyrene, HEBEL (aerated autoclaved concrete), Compolcrete (a mix of recycled EPS and concrete) and, more recently, High Density Extruded Polystyrene.

Each of these products can be used in wall, floor and roofing systems to provide the desired level of effective insulation.
In addition, new materials are being imported from Asia such as MGO board, which also offers insulation but is more of a fibre cement-type product.

The future of insulation is clearly going to be one that all will follow with interest as the standards and requirements continually improve, and add cost to the construction.
On the other hand, it will be fascinating to watch how new products and systems are introduced, and how they will affect energy costs and comfort in buildings and homes.

What’s New?

Building Element Assessment Laboratory (BEAL) has been looking at the need to measure the insulation properties of new building materials, and is looking at providing insulation measuring and calculating services in conjunction with other facilities.

The demand for such services seems to be growing rapidly, and is useful for product manufacturers to know what the R-Value for their product is. Watch this space for further developments.

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