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.
Coefficient of Heat Transmission (U)
The U-value, also known as the heat transfer coefficient, measures the rate at which heat transfers through a material or assembly of materials (like walls, windows, roofs, etc.). It is a critical factor in determining the thermal performance of building elements.
The U-value is expressed in units of watts per square meter per degree Celsius (W/m²°C) or in Imperial units, BTU per hour per square foot per degree Fahrenheit (BTU/h·ft²·°F). Essentially, it indicates how much heat energy passes through a specific material or assembly per unit area and per degree of temperature difference between the interior and exterior environments.
A lower U-value indicates better insulation properties because it means the material or assembly has lower heat conductivity and reduces heat transfer more effectively. Conversely, a higher U-value signifies higher heat transfer and poorer insulation properties.
U-values are used in building design and construction to ensure energy efficiency, as they help determine the insulation needs for various components like walls, windows, roofs, and doors. Lower U-values are desirable in colder climates to minimize heat loss from the interior, while in warmer climates, they can help reduce heat gain from the exterior.
| Construction Material Heat Transfer Coefficients (U) in W/(m2⋅°C) | |||||||||
|---|---|---|---|---|---|---|---|---|---|
| Roof Material | Floors | Windows | Walls | ||||||
| Aerated Concrete | 0.16 | Concrete | 1.35 | Metal Frame (single glaze) | 5.7 | Solid Brick | 2.1 | ||
| Clay Tiles | 1 | Pine | 0.13 | Metal Frame (double glaze) | 3.4 | Brick + Insulation | 0.28 | ||
| Felt / Bitumen | 0.3 | Steel | 5.0 | Wood Frame (single glaze) | 4.8 | Solid Stone | 2.25 | ||
| Concrete Tile | 1.5 | Hardwood | 0.18 | Wood Frame (double glaze) | 2.8 | Stone + Insulation | 0.32 | ||
| Shingles (asphalt) | 0.5 | Wood Frame (triple glaze) | 2.1 | Concrete | 3 | ||||
| Wood Shingles | 0.1 | Vinyl Frame (single glaze) | 4.8 | Concrete + Insulation | 0.31 | ||||
| Vinyl Frame (double glaze) | 2.7 | Hollow Wall (air gap) | 1.3 | ||||||
| Vinyl Frame (triple glaze) | 1.9 | Hardwoods | 0.18 | ||||||
| Doors | Pine | 0.14 | |||||||
| Solid Wood | 3.0 | Drywall | 0.16 | ||||||
A greenhouse, aka a glasshouse or a hothouse, is a building or complex in which plants are grown. A miniature greenhouse is known as a cold frame. Related to a greenhouse is a high-tunnel which is a greenhouse build over soil directly.
Greenhouse structures range in size from small sheds to industrial-sized buildings with different types of covering materials, such as a glass or plastic roof and frequently glass or plastic walls. 
A Greenhouse is designed to warm as incoming sunshine is absorbed inside the structure. Air warmed by the heat from warmed interior surfaces is retained in the building by the roof and walls. By using non-porous materials such as glass or plastic, the air that is warmed near the ground is prevented from rising indefinitely and flowing away.
Commercial glass greenhouses are often high-tech production facilities for vegetables or flowers. The glass greenhouses are filled with equipment like screening installations, heating, cooling, lighting and airflow systems and also may be automatically controlled by a computer to maximize potential growth.
vCalc's Greenhouse category (tag) contains equations and calculators pertaining to greenhouse calculations, metrics and other data.
Greenhouse and High-tunnel Calculators
- Volume of a Gabled Greenhouse: Enter the dimensions of a gabled building and compute the cubic feet volume.
- Volume of a Curved Dome 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 a Curved Dome 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.
- Bell-shaped Greenhouse Volume and Surface Area: Computes volume, surface area, floor space and height based on dimensions.
- 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.