Roof Insulation and Snow Load
Milking centers in cold climates require insulation to prevent heat loss and condensation on ceilings and exterior walls. The R-value of insulation indicates the material’s ability to impede heat flow with higher values indicating greater capacity for resistance. The MidWest Plan Service (MWPS-7, 2013) recommends a minimum of R=11 for exterior walls and R=19 for the ceiling of milking parlors with more insulation being desirable, if possible.
In freestall barns located in cold climates, proponents of roof insulation suggest that it maintains the internal barn temperature 1 to 2 °F (1.8 to 3.6 °C) higher than the outdoor temperature, which on certain days may be the difference between the manure alleys freezing or not. An insulated roof will also lead to less condensation on the under-side of the roof. In hot weather, the direct effect of radiant heat from the sun will be lessened, leading to cooler temperatures in the barn. MidWest Plan Service (MWPS-7, 2013) recommends roof insulation of R=5 or greater. Condensation problems should be solved not only with insulation but with proper ventilation of the barn as well.
Be sure to ask about any requirements for protecting the insulation material from birds as they can quickly damage some types of insulation materials, making the insulation less effective and unsightly.
A vapor retarder should be installed on the warm side of any insulated wall, ceiling, or roof. Vapor retarders prevent moisture from contacting the insulation and reducing the ability of the insulation to prevent heat loss. Ventilation will be required on the cold side of enclosed, insulated surfaces, such as parlor attics.
It is important to note that many types of plastic foam insulation products are highly flammable. Protective coverings should be used when insulating with plastic foam products.
Roof Insulation Check List
- An insulated roof keeps the inside of the barn warmer in the winter and cooler in the summer
- Minimum recommended R values are 5 for the barn roof, 19 for the ceiling of the parlor and 11 for the exterior walls of the parlor
- Include a vapor barrier and take steps to avoid bird damage
No matter if the roof is insulated or not, it is important to check the actual snow load on a building against the design snow load. The table below, by Curt Gooch of the Pro-Dairy Program at Cornell University, can be used to estimate the snow load on a pre-engineered barn only. Roof failure is not imminent if the actual load is less than the design load. Information regarding how to safely remove snow from the roof can be found here.
Snow Load Based on Accumulation Depth
| Snow Depth on Roof (ft) | “Dry Snow” (lbs/sq ft) | “In Between Snow” (lbs/sq ft) | “Wet Snow” (lbs/sq ft) |
|---|---|---|---|
| 1 | 3 | 12 | 21 |
| 2 | 6.5 | 24 | 42 |
| 3 | 9.5 | 36 | 62 |
| 4 | 12.5 | 48 | 83 |
| 5 | 15.5 | 60 | 104 |