Mallusk-headquartered company Brett Martin has developed roofing sheets for livestock sheds that are made from translucent plastic.

The corrugated plastic, marketed as Marlon CST Heatguard, contains tiny aluminium flakes which allow light to pass through, but heat from sunlight is reflected.

According to Dr Tom Chamberlain, sheds fitted with the product are brighter and cooler than buildings roofed with traditional fibre cement or metal sheets.

The veterinary scientist was commissioned by Brett Martin to conduct trials on Heatguard and his research found the product can help reduce heat stress in dairy cows.

Speaking to reporters on Tuesday, he described heat stress as a “growing problem globally” because average temperatures are rising, and cows become more susceptible as milk yields increase.


“The modern dairy cow is a highly productive animal. There are very high levels of energy flux going through them and, to a varying extent, they also radiate heat.

“We used to think heat stress was only a problem outside at grass, but we now know it is also a problem when cows are housed,” he said.

During his presentation, Chamberlain presented results from a trial carried out on George Bingham’s 900-cow dairy unit near Templepatrick.

The trial, which ran for a three-month period last summer, monitored temperature and humidity in a cubicle shed covered with Heatguard, as well as in a fibre cement roofed shed.

“All the way through from July to September, the fibre cement clad shed was hotter than the Heatguard shed. The temperature difference between the two sheds was running at 1.5 to 2 degrees,” Chamberlain said.

Previous research suggests cows come under heat stress when temperatures reach 23°C, but there were only two periods last summer when this happened on the Bingham farm.

“It’s fair to say that in NI most of the time, cows aren’t under that much heat stress,” Chamberlain acknowledged.

Milk yield loss

However, he maintained that “predicted milk yield loss” due to heat stress was still significant, especially during a week-long spell of warm weather in early September.

His calculations suggest milk yield losses due to heat stress over the entire trial period totalled 15.2 litres per cow in the fibre cement shed, compared to 4.5 litres in the Heatguard shed.

Chamberlain also pointed out that severe heat stress can lead to more problems than just reduced milk yield, such as acidosis and fertility issues.

“Some farmers report lameness as well because the first thing a cow does when she is too hot is stand up to let any breeze blow around her,” he said.

Costs and fitting Heatguard sheeting

Chris Chambers from Brett Martin said Marlon CST Heatguard costs around £12 per metre, which is more than fibre cement or metal roofing options.

However, he said the product is much lighter than conventional roofing, so significant savings can be made with materials for the rest of the shed roof structure.

He gave the example of George Bingham’s shed which was initially designed to hold up 19t of fibre cement sheeting.

“We put 7t of [Heatguard] material on the roof, so he was able to reduce his purlin size. The roof cost him an extra £6,000, but he saved £20,000 on purlins,” Chambers said.

Speaking in Mallusk on Tuesday, Chambers explained that Heatguard sheets usually need to be washed every few years, although frequency of washing varies across different sites.

He said a crawl board that spans between purlins should be used if maintenance is required on Heatguard roofs because the material is not suitable for walking on.

Robin Black from Brett Martin said the material can be fitted by anyone with knowledge of roofing and no specialist equipment is required.

However, he pointed out the Heatguard material expands more than traditional roofing materials when it heats up, so the way it is fitted is “slightly different”.

“Any contractors who are currently roofing sheds will be able to fit the material and we can provide a full technical guide on how to do that,” he said.