How To Make An Outdoor Fireplace Draw

How to Make an Outdoor Fireplace Draw

An outdoor fireplace can be a beautiful and functional addition to any backyard. However, a poorly designed fireplace can lead to smoke and soot accumulating in the wrong places, making it unpleasant to use. A well-designed fireplace draws smoke upwards, creating a clean and efficient burn. This article will guide you through the steps of ensuring your outdoor fireplace draws properly.

Understanding the Principles of Fireplace Draw

The draw of an outdoor fireplace is determined by the natural tendency of warm air to rise and cool air to sink. The fireplace's design creates a convection current, drawing in cool air from the bottom and pushing out warm air through the top. This process is essential for a good draw.

Here are some of the key factors that influence fireplace draw:

Chimney Height: A taller chimney creates stronger draft due to the greater difference in temperature between the air inside and outside the chimney.
Chimney Diameter: A wider chimney can handle more smoke and create a stronger draw, but it must be properly sized to avoid excessive airflow.
Chimney Location: The chimney should be located in a position that minimizes wind interference.
Fireplace Design: The opening, throat, and damper of the fireplace should be properly sized and positioned to allow optimal airflow.

Optimizing Fireplace Design

When building or modifying an outdoor fireplace, several key design elements can be adjusted to improve its draw:

1. Chimney Height:

Aim for a chimney height of at least 10 feet above the fireplace opening.
Consider the surrounding structures and trees that may obstruct the airflow.
Avoid creating a chimney that's too tall, as it could lead to excessive draft and instability.

2. Chimney Diameter:

Choose a chimney diameter that corresponds to the size of the fireplace opening.
A good rule of thumb is to select a chimney diameter that is one-tenth the area of the fireplace opening. For example, a fireplace opening of 20 inches by 20 inches would have an area of 400 square inches, requiring a chimney diameter of approximately 4 inches.
Ensure the chimney is properly insulated to prevent heat loss and maintain a strong draft.

3. Chimney Location:

Position the chimney to minimize wind interference.
Place the chimney on the leeward side of the fireplace, facing away from prevailing winds.
Consider using a chimney cap to prevent rain and debris from entering the chimney.

4. Fireplace Opening and Throat:

The fireplace opening should be sized appropriately for the desired fire size and fuel type.
The throat, the space between the fireplace opening and the chimney, should be narrow enough to create a tight seal and prevent air leaks.
Adjust the size of the throat by using a damper or a fireback.

Troubleshooting Draw Problems

If your outdoor fireplace has poor draw, there are several things you can do to improve its performance:

1. Check for Obstructions:

Examine the chimney for any obstructions, such as bird nests, leaves, or debris.
Ensure the vent is open and not blocked by anything.
If any obstructions are found, remove them carefully.

2. Adjust the Damper:

If the damper is partially closed, it can restrict airflow and reduce draft.
Open the damper fully to allow for optimal air flow.
If the damper is too open, it could create excessive draft, leading to instability.

3. Consider a Chimney Extension:

If the chimney height is insufficient, consider adding an extension to improve draft.
Consult with a professional to determine the appropriate height for your specific fireplace.

4. Improve the Exterior Walls:

Ensure the exterior walls of the fireplace are sealed and insulated to prevent heat loss.
A well-insulated fireplace wall can create a more stable draft and improve the efficiency of the fire.

By carefully considering these design principles and troubleshooting steps, you can ensure your outdoor fireplace draws efficiently and provides a safe and enjoyable experience for all.