House Energy Site

THERMAL MASS & HOuse Energy improvements

Some construction materials can store heat up to 10-12 hours, before beginning to release it - an ability that can be used in some space heating and cooling strategies.

What's Thermal Mass?

Materials like wood have a very low heat storage capacity; in other words: heat passes through them easily, without being stored. Wood is a low-mass material.

But that’s not the case of materials such as tiles, concrete, bricks or stone, which can store heat for hours, before releasing it slowly. These materials have high thermal masses.

Bottom line: construction materials have different thermal mass, and that's a factor to be taken into consideration, in some heating and cooling strategies.

High Thermal Mass and Low Thermal Mass Construction & Insulation

High thermal mass doesn't replace insulation. High mass materials store and re-radiate heat. They do not prevent heat from flowing into or out of the house (that's why masonry homes with low levels of insulation can be so uncomfortable). High thermal mass materials are not good insulators.

Unless you live in some hot climates, whatever the type of construction (low or high-thermal construction) you will also need proper levels of insulation over the envelpe of the house. That’s crucial for comfort and energy efficiency.

Low Thermal Mass Construction

Typical wood-frame homes are lightweight low-thermal mass.

And that's not necessarily a bad option.

Low thermal mass homes can be a good option for energy-efficient strategies.

See: High and Low Thermal Mass Strategies

High Thermal Mass Strategies

Thermal mass strategies range from the very simple to the sophisticated. Thermal Mass Strategies Passive Heating

Sophisticated strategies can use clerestory windows or trombe walls and sunrooms.

In their simplest form, thermal mass strategies use windows to capture solar heat that is stored for some hours in concrete floors or walls (image at right), before being released during nighttime (or removed with the help of breezes, in cooling strategies).

High and Low Thermal Mass Strategies
Thermal Mass Rules for Floors and Walls


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