Modeling the effect of reflective calf hutch covers on reducing heat loss.

This study determined if a reflective film could theoretically be useful in moderating the rate of heat loss from calves housed in polyethylene hutches during cold weather. An engineering approach was used in which rate of heat loss was modeled using 38-l steel drums filled with body temperature water and covered by fresh calf hide. The reflective film (cover) consisted of aluminized 0.0635 mm low-density olive color polyethylene. The non-reflective olive side was sprayed with flat black paint. Covers were 1.8 × 3 m with the aluminized side facing the hutch. Two of four hutches were either uncovered or had covers across the top and sides. During the night, (mean temperature ± SE -13.6 ± 0.29 °C), the rate of temperature loss was -0.21 °C per 5-min interval over 28 temperature readings in the covered and -0.25 °C in the uncovered (R (2) = 0.99). During the daytime (mean ± SE 14.3 ± 0.52 °C), rate of heat loss was -0.15 °C per 5-min interval over 33 temperature readings in the covered and -0.11 °C in the uncovered (R (2) = 0.99). Reflective film reduced the rate of heat loss during cold nights, but when the sun was shining on the hutches during midday, the uncovered hutches warmed up more and, hence, reduced the rate of heat loss when compared to the covered. Further research is needed on the orientation of hutches in relationship to the sun and with live calves because calves would be able to move into the sun during cold sunny days.

Effect of four different reflective barriers on black-globe temperatures in calf hutches.

Polyethylene hutches are a popular method of housing dairy calves from 0 to 60 or more days of age, although these hutches get hot when in full sun. This study characterized the relative differences in the ability of four different types of radiant barriers to reduce black-globe temperature within these hutches. Treatments included three different types of covers (two types of laminates (Cadpak P and Cadpak ESD) and an aluminized 3.0-mil white low-density polyethylene (LDPE)) and a reflective paint (LO/MIT-1). The reflective covers were 1.8 × 3 m finished size, and covered the top and sides of the hutch down to 0.15 m above the ground, leaving the front and back exposed. The LO/MIT-1 paint covered the entire sides and roof of the hutch. Two 24-h trials 1 week apart were conducted during relatively hot and clear days in early August. Black-globe temperatures were recorded in duplicate and averaged at 20-min intervals using blackened table tennis balls mounted 0.3 m above the floor in the center of each hutch. Ambient temperature (shade) during the hottest 2-h period for both trials averaged 39.9 °C while the uncovered control averaged 41.1 °C, and LO/MIT-1 averaged 39.9 °C; both of which were significantly higher (P < 0.01) than the Cadpak P (38.9 °C), Cadpak ESD (38.6 °C), and aluminized LDPE (38.7 °C). During periods of high solar radiation, the hutches with covers had lowest black-globe temperatures followed by hutches painted with reflective paint, while control hutches had the highest temperature.

Usefulness of an aluminized polyester film for reducing heat in polyethylene calf hutches.

This study determined the efficacy of a radiant barrier material used in the construction industry to moderate summer temperatures in polyethylene calf hutches. The cover consisted of a single layer of two-sided reflective aluminized polyester film with a center polyester scrim reinforcement (reflectivity = 95%). At each of two dairies, six hutches containing a young calf were either uncovered (control) or had reflective covers across the top and sides of the hutch, leaving the front, back, and 1.2 × 1.8-m attached outdoor wire pen exposed. Duplicate loggers mounted 20 cm above the flooring in the center of each hutch recorded interior temperature at 30-min intervals over 22 days during late August to early September. The mean daily interior peak temperatures in each of the hutches over 21 days of observation were significantly less (P < 0.001) in the hutches with reflective covers (37.48 ± 0.14 °C) than in the uncovered hutches (41.65 ± 0.45 °C) and did not differ (P = 0.77) between dairies. The mean daily interior peak temperatures in each of the hutches over the warmest 10 days of observation were significantly less (P < 0.001) in hutches with reflective covers (40.15 °C ± 0.16) than in the uncovered hutches (44.93 ± 0.47 °C). The mean interior ceiling temperatures in each of the hutches over 4 days of observation were significantly lower (P < 0.001) in the hutches with reflective covers (37.82 ± 0.36 °C) than in the uncovered hutches (46.89 ± 0.47 °C). The reflective cover used in this study moderated interior hutch temperatures but showed signs of delamination after 22 days and was relatively expensive, so more suitable material needs to be identified.