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Thermal Resistance, Thermal Mass And Thermal Insulation For Residential Housing

ReGen Building Solutions supplies thermally efficient building products.  It is important to educate the market on important elements of a building and how this can assist a homeowner. The walls, floors and roof are typically referred to as the building envelope. The selection of materials used  and the construction is vital for the thermal performance of the building envelope. There are three key element that impact the performance of a building envelope, Thermal Resistance, Thermal Mass and Thermal Insulation. The inter-relationship of these factors in the building envelope are the key elements that will determine the R Value of a house.

IMPORTANT :  Using building materials with higher R Values will reduce the amount of power required to heat and cool your house, which means less costs to the homeowner.

Thermal Resistance, Thermal Mass and Thermal Insulation are difficult topics creating significant confusion for those who are trying to understand how to achieve a thermally efficient house.

What is Thermal Resistance?

Thermal Resistance is the ability of a building material to resist heat flow. The greater the Thermal Resistance of the material the less it will transfer heat and cold. The thicker the material, the less the conductivity it will have in allowing heat transfer. Thermal Resistance is measured in R Values and is calculated using the equation R=L/k. L relates to the thickness of the product and k (which is a constant) relates to its thermal conductivity. The higher the R rating, the greater the insulation capacity.

Putting this into context. High density products, like bricks and concrete, are considered poor insulators as these have high thermal conductivity. Expanded Polystyrene (EPS) is considered a good insulator with low conductivity. The R Value for concrete (based on 2400kg/m3) @ 75mm thick is R 0.052. The R Value for EPS M Grade (based on 16kg/m3) @ 75mm thick is R 1.83 and is significantly higher. Remember, materials with higher R Values provide better Thermal Resistance.

Given that a standard house wall requires a minimum R 2.8,  the thermal resistance and thickness of  materials are both critical in achieving this. Note: There are R Value variations for houses that are in certain climate zones.

What is Thermal Mass?

Often, the terms Thermal Resistance and Thermal Mass can cause confusion in respect to housing. Thermal Mass refers to the ability of a building material to store solar energy during the day and then release that energy at night when it is cooler. It is suggested that a Diurnal Range of 10° C provides the best range for Thermal Mass to have a real benefit.  http://www.yourhome.gov.au/passive-design/thermal-mass.

If a house is in a climate that is hot during the day and cold at night and it has a concrete or brick or wall, the concrete or brick will store the energy during the day and release the energy at night. This will reduce the need to have heating and cooling at night. Conversely, a poorly designed house in these conditions will significantly exacerbate the worst extremes of the climate. Therefore causing increased cost in power consumption to maintain thermal comfort. Thermal Mass in the wrong area can radiate heat all night for those attempting to sleep during a summer heatwave or absorb all the heat produced on a winter night. Thermal Mass requires a balance of shading, ventilation, appropriate glazing and Thermal Mass in the appropriate locations of the house.

Most importantly Thermal Mass is NOT a replacement for insulation. Thermal mass stores and re-releases heat and cold; whereas insulation stops heat or cold flowing into or out of the building. As noted under Thermal Resistance above, concrete is not a good insulator but is excellent for Thermal Mass in storing and releasing heat or cold.

What is Thermal Insulation?

Insulation acts to limit heat and cooling loss in winter and summer buy acting as a barrier to heat and cold flow in the building envelope. A well insulated house reduces the cost of heating and cooling. Estimates of heating and cooling costs of a house are approximately 40% of the total energy costs http://www.yourhome.gov.au/energy/heating-and-cooling.

IMPORTANT : Imagine the financial benefit  to you if your power bills could be reduced  by 40%. Imagine the savings of that 40% over a 10 – 15 year period. When considered in this perspective, the importance of insulation becomes a lot more significant.

How do these three concepts work together?

Whether working with a builder or building the house yourself, firstly identify the products or materials used to construct the building envelope. Ensure that the products used as cladding have good Thermal Resistance. It is also important to consider window glazing. For example consider using double glaze glass.

If you live in climatic zones that have high fluctuations in day/night temperatures, seek architectural advice on appropriate Thermal Mass to your construction. Houses built by volume builders using their off-the-shelf plans will be built to their specifications. Often there is little understanding if the building plan and selection of building materials meets the optimum Thermal requirements for that house at that location.

Thermal Insulation is one of the most important building elements of your house. Inadequate insulation can cause significant living discomfort and high power costs. Therefore it is important to consider building design with appropriate insulation materials.

For a good insulating product for your home consider StructaClad Lite; The thermal wrap for your home

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