The Least Expensive Way to Heat an Insulated Sunroom

Add thermal mass to a sunroom to heat it passively.

The best way to heat a sunroom without cost is to capture the energy of the sun to heat the room. This requires two critical and primary components in place to use passive heating methods: south-facing glass and a thermal mass to absorb, store and release the heat during the cool of the evening. How this works is that during the day, when the sun is out, the thermal mass in the room absorbs the heat, releasing it at night for later use.

Things You'll Need

• Brick or tile
• Masonry block
• 55 gallon drums, painted black
• Insulated curtains
• Wood stove

Instructions

1. Ensure the sunroom faces south to admit the most solar energy into the room. Allow the south wall covered with windows to add heat to the room during the day by keeping curtains open.

2. Cover the floor with brick or tile to act as the thermal mass for the sun’s energy. Brick will work better as it will store more thermal energy than tile does.

3. Build a small masonry block or brick hearth at the back of the room where it will receive direct sunlight and absorb heat.

4. Place a wood stove on the brick hearth and use the wood stove during those days when the sun doesn't come out to add heat to the room.

5. Cover windows with insulated curtains during the night to prevent the loss of heat through the windows.

Tips & Warnings

• For maximum heating efficiency, do not cover thermal mass floors with carpeting, and keep the floor bare. Use 150 pounds of masonry for every square foot of south-facing glass for maximum heating efficiency.

• Using the thermal mass over a wider area is more efficient that a small amount of thermal mass in a concentrated area.

References

• Passive Solar Design: Passive Solar Heating
• Home Designer Software: Let the Sun Shine In!