With winter coming upon us, I thought I would post some R-values for different types of greenhouse materials. Its interesting to see what different types of material are rated and how they work with old man winter.

Glazing and insulation R values for energy conservation.

Many of the materials youÂll use in a greenhouse have different, noteworthy characteristics. This section might come in handy when you are working with retrofitting, or constructing greenhouses.

R values for energy conservation.

"R-value" is a commonly used term to measure a materialÂs energy conserving (or insulating) properties. It is a measure of resistance that a material has to the flow of heat. The below R-values reflect real world outdoor situations. Specific brand-name products may vary from these figures. It is always good to check on the stated R-value of a product as you evaluate a glazing. Also, consider other important attributes when evaluating glazings or insulation materials (see discussion in chapter 1).

The more energy conserving a material is, the higher its R-value.

Note: The term R-Value is a common measure of insulation (hr°Fsq.ft/BTU).

Polycarbonate 6mm quad wall R = 1.79

Polycarbonate 8mm quad wall R = 2.13

Polycarbonate 16mm triple wall R = 2.5

Polycarbonate 8mm triple wall R = 2.0-2.1

Polycarbonate 8mm double wall R = 1.6

Acrylic double wall R = 1.82

Glass double layer R = 1.5 Â 2.0

Glass double layer low-e R = 2.5

Glass triple layer 1 / 4 " ( 0.6 cm) air space R = 2.13

Fiberglass glazing- single layer R = .83

Polyethylene Double 5mil film R = 1.5

Polyethylene Double 6mil film R = 1.7

Polyethylene single film R = 0.87

6 inches (15 cm) of fiberglass bat insulation R = 19.0

Polystyrene (styrofoam) 1 inch (2.5 cm) thick R = 4.0

Note: You may also find products sold with a U-value instead of an R-value. A U-value is the inverse of an R-value. To convert a U-value to an R-value do the following: 1 divided by the U-value equals the R-value. For example: fiberglass has a U-value of 1.20 when it is divided into 1 it equals a .83 R-value.

Here is some excellant information about greenhouse basics for anyone wanting to refresh their knowledge. I think its always great to refresh every year as to whats really happening with out greenhouses.

http://pubs.caes.uga.edu/caespubs/pubs/PDF/B792.pdf

Now is the time to get these greenhouses ready for winter.