Thermal mass if used correctly can improve your homes energy efficiency by leaps and bounds.
Building elements such as bricks and concrete are considered to have high thermal mass. They are able collect heat and store it for long periods of time. For example when a brick wall is slowly heated up by the sun during the day, it is able to store that heat and release it slowly during the night. where buildings with low thermal mass heat up quickly and also cool down quickly.
In Australia most houses have been designed not to take advantage of the thermal mass. For example brick veneer houses, which are the most commonly built brick houses. Have the bricks on the outside of the home meaning the inside of the house has been insulated from the thermal mass, it’s totally back to front to what it should be.
Really the bricks need to be on the inside of the house insulated from the outside temperature. If the window layout is designed correctly allowing as much sun as possible to enter the house in winter to warm up the thermal mass during the day. so it can release the heat from the thermal mass of a night. In summer the window layout must allow little or no sun to enter during the day so the thermal mass stays nice and cool.
Some people now are building reverse brick veneer houses, which incorporates these principles. They are more expensive however. Usually the cost difference between a brick veneer house and a reverse brick veneer house will be the extra cost of the cladding for the out side. This cost could start from around $80m2 for the area of the external walls of the dwelling depending on what type of cladding you want to use. For an average size house it will probable be around $15000 – $20000.
I personally think that double brick is the way to go there is much less maintenance involved.
Here is some links http://www.sustainability.vic.gov.au/resources/documents/Thermal_mass.pdf