`HL = "A" * "tV" * "U" `

Enter a value for all fields

The Conductive Heat Loss calculator computes the heat loss (HL) based on the surface area (A), temperature variance (vT) and the U factor of the surface material of a greenhouse.

INSTRUCTIONS:  Choose units and enter the following:

• (A)  Surface Area
• (vT)  Maximum Temperature Variance (indoor to outdoor)
• (U)  Insulating Coefficient.

Conductive Heat Loss (HL): The calculator returns the heat loss in BTUs per hour.  However this can be automatic converted to compatible units via the pull-down menu.

The Math / Science

Conductive heat loss is the transfer of heat through a membrane.  For application in spaces such as greenhouses, the transfer of concern is typically warmth from within the greenhouse that is lost through the skin of the greenhouse into the outside environment. The equation for the conductive heat loss is relatively simple:

                CHL=A⋅vT⋅U  

Where:

• CHL is Conductive Heat Loss (default in BTUs per hour)
• A is the surface area
• vT is the maximum temperature variance (indoor to outdoor)
• U is the insulating coefficient.

Insulating Coefficient

The U value is published for many material.  Consult your product supplier for the actual U value of the material planned to be used.  However, some common U values are as follows:

• 0.15 for high performance triple pained glass
• 0.3 to 0.5 for good double pained glass
• 0.7 double layered plastic
• 1.22 for single paned glazed glass

Note: U factor is the reciprocal of R factor which is used to rate insulation materials (e.g. fiberglass batting)

Consider the extreme cases in your area for the maximum temperature variance.  For example, if your plants require a minimum of 57^oF, and the possible low temperature outside is -14^oF, the variance is 71^oF.

The result of the equation is BTU/hour required to compensate for the conductive heat loss.

Greenhouses and high tunnels come in different shapes.  The following diagrams shows several of the common shapes.

The following calculators help compute the surface area needed when computing Conductive Heat Loss (CHL).

Greenhouse or High-tunnel Calculators

• Volume of a Gabled Greenhouse: Enter the dimensions of a gabled building and compute the cubic feet volume.
• Volume of an Arched Roofed Greenhouse: Enter the dimensions of an arched roofed building (see diagram) and compute the cubic feet volume.
• Volume of a Quonset Hut Greenhouse: Enter the dimensions of the Quonset Hut and compute the cubic feet volume.
• Surface Area of a Gabled Greenhouse: Enter the dimensions of a normal gabled building and compute the square feet surface area.
• Surface Area of an Arched Roof Greenhouse: Enter the dimensions of an arched roof building and compute the square feet surface area.
• Surface Area of a Quonset Hut Greenhouse: Enter the dimensions of a Quonset Hut and compute the square feet surface area.
• Greenhouse Air Flow: Computes the air flow volume at the fan, middle and end of the greenhouse and the Evaporative Cooling Efficiency
• Conductive Heat Loss:  Enter the surface area, the heat loss coefficient for the surface material and the maximum heat range, and the calculator will compute the BTUs per hour needed to heat the inside.