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Heat Retention

CoreAcryl Acrylic Tubs vs Cast Iron Tubs

All Classique and Hotel Line soaking tubs produced by Baths of Distinction are made from CoreAcryl. For a full description of what CoreAcryl is, please click here.

We are often asked which tubs retain heat better and why. The table below is a comparison test for heat loss between a CoreAcryl acrylic tub and a cast iron tub from a leading manufacturer.

We filled both tubs, almost identical in size, with the same amount of hot water direct from the hot water tank at 134 degrees Fahrenheit. The table below shows the heat loss over a 25 minute period.

Time in Minutes
Fill Water
0 mins
5 mins
10 mins
15 mins
20 mins
25 mins
Temp. CoreAcryl (F)
Temp. Cast Iron (F)

As can be seen from the test results, CoreAcryl maintains water temperature better than cast iron. Cast iron is an excellent conductor of heat, so large amounts of heat are transferred from the water to the cast iron as soon as the tub is filled. During the test, the cast iron became hot to the touch, reflecting this heat transfer. There was also a significantly smaller drop in the water temperature of the CoreAcryl tub, which remained cool to the touch on the outside. Over a period of 25 minutes, the cast iron tub lost another 22.4 degrees and the CoreAcryl lost a total of 20 degrees.

Please note that these temperature drops may be less prominent in a typical household bathroom as the temperature in the test room was only 65 degrees.

Manufacturing Cost

Contrary to popular belief, cast iron tubs cost no more to produce than good acrylic tubs. In fact, in most cases cast iron tubs would cost us less to purchase than our cost to manufacture CoreAcryl. We simply choose not to carry cast iron tubs as we cannot in confidence offer a 25-year warranty on them. They are also easily damaged during shipping and are very difficult to handle.

Installation Cost

Building contractors are constantly reminding us of the difficulties involved installing cast iron tubs. Some tell us that these costs can double between cast iron and relatively light weight acrylic or CoreAcryl. Generally, four people will be needed to place the tub in position, but often the highest costs are experienced with the need to reinforce the flooring beneath the tub.