“In hot conditions, cattle can become unproductive, overheat or die”.

Those words are from the opening line of a paper in the Journal of Agricultural Engineering Research published in 2000 by two colleagues – Rod McGovern and Jim Bruce. They had produced a model of the thermal balance for cattle in hot conditions and concluded that in hotter conditions, feed intake would be reduced, and production would fall.

Since then, we have also come to understand that there is an earlier negative impact of hotter conditions/heat stress. Namely, that is the reduction in fertility (RIDBA Journal 2021: Vol 22, Edition 1). Their thermal model included air temperature, humidity, wind speed and radiation, together with metabolic heat production from the animal.

Metabolic heat is lost from the body in a variety of ways. They include conduction from the body core to the skin, from the skin by convection, by long-wave heat transfer by radiation, and by latent heat loss via respiration and sweating.

Table 1 shows the results of instantaneous heat balance simulations at four different air temperatures.

Example	1	2	3	4
Air temperature oC	-10	15	30	40
Heat production W/m2	122	122	122	80
Respiratory heat W/m2	47	12	74	73
Stored heat  W/m2	0	0	0	83.5
Evaporation from skin W/m2	17	142	116 (max)	181 (max)
Convective heat loss W/m2	15	59	45	28
Heat flux through coat W/m2	102	11	-24	-75
Respiration rate, breaths per minute	12	12	59	86 (max)
Rise in body temperature oC	0	0	0	1.2

Solar radiation can be added to the model to give results for the expected impact of solar gain (or shading) delivered at stated angles, wind speed, cloud cover, latitude, albedo, the emissivity of the animal and the reflectance. Many of these terms will be familiar to building engineers, but what is the result?

In cold weather – example 1 in Table 1 – convective heat losses are reduced by vasoconstriction but losses through the hair coat are high. In example 3, respiration rate increases to dump more energy as moisture and in example 4 the body starts to acquire heat and body temperature rises. In reality these cattle will already have adapted but with resultant losses to fertility, then feed intake, and then milk production.  The impact of the summer which we’ve just experience in the UK on cattle was, and is, predictable.

The daily – or diurnal – pattern of air temperature can lead to a predictable pattern of heat stress in livestock, and a more recent study with young calves at Iowa State University (Appuhamy, et al. 2021 “The Effects of Diurnal Heat Stress in Dairy Heifer Calves”) describe further impacts.

The study shows that although feed intake increased at night to balance the reduced feed intake during the heat of the day, average daily liveweight gain and feed efficiency decreased significantly during periods of diurnal heat stress. They considered these effects are a likely consequence of nutrients being moved towards an activated immune system and away from productive processes. They also report that water intake per unit of feed consumed also increased significantly during diurnal heat stress.

We do need the science to inform us, and we don’t need the science to inform us. When it gets hot animals consume less food and drink more water and may have reduced immune competence. What a surprise! But heat and water are issues that have been tackled with different levels of precision around the world and this summer will have shaken UK livestock producers – hopefully into an acceptance that what is predictable can also be managed better. We have plenty of information on how to better manage heat and water in the UK’s livestock buildings, but we need to acknowledge the issues first, and work out what it costs to get it wrong.

A recent query involving a new build pig unit threw up the interesting detail that for the month of July 2022 the water consumption in the farrowing rooms increased by 20 litres per pig, per day, compared with the average of the previous three months. That is 37 m³ for the month on this particular site – from drinking water intake increasing to the smart pigs throwing water everywhere to keep cool. Of course, this also adds to slurry volumes. Dairy cows dramatically increase the volume of water intake in warm weather and pigs and poultry show clear preference for cooler drinking water in hot weather conditions. The main production and design questions for any farm – new or existing – are:

• Do we have the correct volumes and flow rates of decent water quality and temperature at the right height and with adequate space for expected competition?

That is no less than six design factors to get right… or wrong.

In food production processes, heat and moisture go hand in hand and the UK agricultural sector has plenty of potential to improve on the management of both factors. Potential gains have been mentioned before as something that need to go into any investment appraisal of our livestock systems. The example of poor fertility – the major reason for culling cows in the UK (NADIS 2022) – will be uppermost in UK dairy statistics this year of high air temperatures and low rainfall. The financial losses of poor fertility accrue from a range of variables (Table 2) and average £250 per cow in the UK herd.Â

Table 2. The cost of poor fertility.

• genetic gain
• ↓ milk production
• ↑veterinary costs
• ↑ number of heifers that need to be reared
• ↑ cost of AI (or the number of bulls needed)
• Disrupts the pattern of milk production

The chronic health issues linked in part to climate extremes are costing tens of thousands of pounds every year on individual UK livestock farms, which leads to significant potential benefits to offset investment in improved building design and higher specification materials.

And sell rainwater harvesting to the clients and the planners! It should be good business sense and will improve the sustainability image of our industry.

Jamie Robertson
RIDBA Livestock Consultant

The interaction of space and animal welfare has been mentioned before in this section, along with the suggestion that we need to recognise the value of the quality and quantity of space made available to animals.

In the early days of research into animal welfare and the development of animal systems, the defining physical attributes were space (m²) per animal, ambient temperature and not a lot more.

The optimum number of animals in a group (cows can ‘recognise’ up to 60 cohorts, not more) or the height of water troughs and feeders was evaluated (depends on age), and as the science improved the design of animal systems also included factors such as air changes per hour (based on CO₂ production) and the design of sleeping areas (lunge space; cubicle design).

Overall, there emerges an understanding that while we can easily define an equitable unit of space per animal, there is considerable value in the quality of that space, but the quality will often come at a cost. So, the question for the system designer is how much increased cost does the client value?

The UK cattle sector is the same as any other business in that it needs to invest to remain sustainable, and once the ear tags, fancy feed additives, power, water and all the other consumables have been paid for, there is a need to invest in buildings.

They represent a major, once-in-a-lifetime cost, but the aim is to bring in value to the business. The build design process needs to start with the number and size of animals to be housed, group size and feed system. Immediately there will be conflict, because the industry experience is ‘we can/cannot keep 10/15/20 cattle per bay’ and ‘we have always done it like this’ and ‘We tried one of those and it did/didn’t work’. It is not logical to make a once-in-a-lifetime series of technical decisions based on a string of opinions. Instead refer to the information provided by BS5502 and the RIDBA Farm Buildings Handbook or AHDB guidance material.

The Dairy Housing: A best practice guide (AHDB, 2012) outlines the space requirements in cubicle housing. The book has been freely available for more than ten years and yet producers and builders will still build cattle housing that does not fit industry guidance or – the usual favourite – only use the guidance information they want. The aim is to house a certain number of cattle at a cost and not at a value. We know that wider passageways, cubicles, feed and water spaces, cross-over passages and holes in the roof all increase the cost per cow, and we need to sell the value of these increased costs.Â

The benefits of good design outlined in the AHDB Dairy Housing booklet include:

• Longer lying times
• Better feet condition
• Reduced aggressive behaviours
• Reduced fouling
• Reduced risk of udder damage or disease
• Optimised feed and water intake
• Improved bedding conditions
• Reduced slurry pooling
• Reduced heat and cold stress

In addition to the above, improved fertility with adequate floor space and surface, lighting quality and impact of well-designed ventilation on the incidence and severity of respiratory diseases, also apply. The positive value of the cost of these design features on the lifetime of a building will run into the tens of thousands of pounds.

Provision of a large area building for single animal systems can be attractive as a means of restraining build costs per housed animal. Build costs per unit of space can be reduced as the total build space increases, up to a limit.

Builders need to be aware the engineering limits on a single build space are far higher than animal system limits on space. This has been mentioned previously whereby an increased number of animals in a single airspace increases the risk of the spread of disease. The poultry sector and, to a lesser extent the pig sector, manage this by designing buildings that match the throughput of animals to facilitate All IN, ALL OUT (AIAO) management of each room. 

The image below shows a beef new build on a top-class farm where there will need to be a significant change in health management before next year to avoid repeat health issues from this past season. The build design and quality is fine, but because the build area is so large that it contains stock of mixed ages, the space quality has been reduced compared with building two separate air spaces. Space cost versus space value.

Jamie Robertson
RIDBA Livestock Consultant

My intention for this article was to present an update from the various British Standards committees on which I represent the interests of the agricultural sector.

Then the Met Office issued a rare red weather warning and Storm Eunice arrived. Once again, the news was filled with fallen trees, displaced trampolines and cladding (roof and wall) ripped from modern buildings.

While the first two can be regarded as the expected norm when storms and gales hit our country, the sight of cladding sheets and panels flying around left me wondering whether the UK had just experienced the one in 50-year event that buildings are supposed to be designed for, or whether some buildings had not been designed properly.

With this in mind, this article revisits the issue of wind loading on buildings and explains how buildings can be designed to withstand the worst of our winter storms. In the next issue, I shall look specifically at some of the detailing issues that affect the storm resistance of buildings.

Wind forces on buildings

Let’s start with some basic aerodynamics. When the wind blows over or around a building, it is forced to change direction and either speed up or slow down depending on the shape and orientation of the obstruction.

Where the wind blows directly onto a surface, the local external pressure will increase. Where the wind blows parallel to a wall or over a roof, it speeds up causing a decrease in the external air pressure. Unless the building is completely airtight, the wind will also change the internal pressure, either increasing or decreasing it.

The combination of changes to the internal and external air pressure results in either a net positive pressure (on windward facing walls, and the windward slopes of steep roofs) or a net suction (on leeward facing walls, on walls parallel to the direction of the wind and on roofs generally).

From a building design point of view, it is important to understand that wind speed varies enormously with location and building geometry, meaning wind loading is site and building specific, so should be calculated for each and every building project.

Since the magnitude of the wind loading has a direct bearing on the design of the frame, column and rafter sizes for example, it follows that the design of every building is. It should come as no surprise that a building designed for a sheltered location in Oxfordshire may not be adequate if placed on a hilltop on the coast of Cornwall.

Importantly, the wind force on the building is proportional to the square of the wind speed, so doubling the wind speed will produce four times the wind loading on the building.

What are the factors that affect wind speed

1. Location

Some parts of the country tend to experience higher wind speeds than others and this needs to be taken into account when calculating the wind loading on a building.

To enable engineers without specialist meteorological expertise to judge the likely wind speed at a particular location, the available meteorological data has been analysed to produce a contoured wind map of the UK, which is published as part of the UK National Annex to BS EN 1991-1-4. The values shown on the map are magnitudes of the basic wind speed to which correction factors may be applied to take account of wind direction, altitude and exposure conditions.

2. Altitude

Wind speed increases with altitude and this is accounted for by a correction factor that is applied to the basic wind speed. This is especially important for agricultural buildings, since many are constructed at altitudes higher than 200m above sea level, where wind speeds are significantly higher than those in low-lying locations.

3. Distance to sea

The shorter the distance to the sea, the greater the wind speed because the wind loses energy and speed as it blows across land. The greatest reduction in wind speed occurs over the first few miles, meaning that locations on the coast experience much higher wind loading than sites only one or two miles inland. Cliff top sites that combine a coastal location with altitude, experience particularly high wind speeds.

4. Town or country

Agricultural buildings are generally built-in exposed locations that do not benefit from the shelter provided by a surrounding town or city. This results in wind speeds which would be higher than would be experienced by comparable buildings located on an urban site.   

5. Topography

Topographical features such as hills can increase wind speed as the air is forced over them. For this reason, it is important for the person calculating the wind loading to have some familiarity with the site and not simply rely on postcodes. Local obstructions can have a significant impact on the wind speed, by providing shelter, for example, but this effect may vary across the site or even across the building footprint.

6. Wind direction

In the UK, the strongest winds generally blow from the southwest, so a southwest facing coastal location is likely to experience stronger winds that one on the North Sea coast. As wind can – and does – blow from any direction, the factors listed above, in particular distance to the sea and distance into a town, need to be assessed for several points around the compass and the wind speed calculated for each direction.

7. Building height

Taller buildings are exposed to stronger winds and this needs to be reflected in the wind loading calculations. For single storey buildings it is common practice to calculate the wind speed for the ridge height. For a multi-storey building, especially high rises, it is possible to divide the building into zones over its height, so that only the very top of the building is designed for the maximum wind loading.

Design practice

The wind forces acting on a building should be calculated using a recognised code of practice, which in the UK is BS EN 1991-1-4. This is one of the structural Eurocodes and is applicable across Europe, although each country has its own National Annex containing nationally determined parameters and specific national recommendations.

The calculation method in BS EN 1991-1-4 is complex and requires specialist technical knowledge, so it is essential wind loading calculations are undertaken by a qualified structural or civil engineer.

By far the simplest approach is to use one of the many software tools currently available. These range from commercially available packages that take account of all of the factors noted above to free online tools that produce reasonable, but conservative, results with minimal input from the user.

Several steel purlin manufacturers include wind loading tools as part of their specification software which are free to customers. In many cases, the precise site location may be specified in the software by its postcode or grid reference. Alternatively, various online resources may be used to obtain the grid reference, altitude and other location data. Thanks to Google, even the local topography and surrounding terrain may be surveyed without leaving the office. 

The simpler the design approach, the more conservative (i.e., higher) the wind loading, so building designers face a trade-off between design effort and the cost of materials.

Taking a one size fits all approach and designing all buildings for the worst possible wind load will result in over-designed structures and is not recommended. On the other hand, calculating the wind pressures to the n^th degree for a standard industrial unit or agricultural building is an unnecessary expense that will probably give little or no saving in material costs compared to the standard design approaches.

The standard approach presented in BS EN 1991-1-4 and employed by many software tools is a pragmatic way of ensuring that buildings are safe and efficient without needing too much effort at the design stage.

While employing an engineer to calculate the wind loading may seem to be an unnecessary additional cost, the cost of not doing so is almost certain to be greater, either in additional steel or the cost of remedial measures when the building encounters its first storm.    

Dr Martin Heywood
RIDBA Technical Consultant

In the previous issue I wrote about the impact buildings have on greenhouse gas emissions and the potential impact of climate change on the design of buildings. We are all going to be hearing the phrase ‘net zero’ a lot more over the next few years as the UK attempts to balance its environmental books by ensuring the CO₂ we release does not exceed the CO₂ removed from the atmosphere.

To some, net zero means replacing a petrol or diesel car with an electric model and paying someone else to plant a tree. In reality achieving the government’s goal of going net zero by 2050 is going to require some significant changes to the way we approach many aspects of our lives, including how we construct and operate our buildings.

As noted in the previous issue, buildings contribute to the UK’s greenhouse gas emissions through their embodied carbon (that is the CO₂ associated with the building fabric and its construction) and their operational carbon (the CO₂ associated with the operation and use of the building). This article looks a little deeper at a few specific issues relating to a building’s operational carbon and considers the ways in which good building design can play a significant role in meeting the nation’s target of net zero by 2050.

Design strategy for net zero buildings

At the highest level, the overall strategy for achieving a net zero building is to minimise the energy required to operate the building and then to generate that energy from renewable sources (i.e., not fossil fuels). In implementing this strategy, there is a clear hierarchy:

1. Reduce demand for heating, lighting, mechanical ventilation, etc.
2. Deliver the heating, lighting, etc. as efficiently as possible.
3. Use the building to generate renewable energy.

While it may be tempting to think covering a roof with photovoltaic (PV) panels is a quick fix that ticks the sustainability boxes, there is little point generating renewable energy and then wasting it. Indeed, as pressure to eliminate fossil fuels increases, the demand on renewable energy sources will also increase and this scarce resource will need to be used wisely. Energy efficiency, therefore, needs to be at the heart of any building design strategy.

Depending on the use of the building, energy demand can be divided into the following categories:

• Heating
• Lighting
• Cooling/ventilation
• Processes relating to the use of the building (not usually the responsibility of the building designer)

Heating

From a building designer’s perspective, minimising heating demand is a matter of minimising heat loss through the building envelope. Of course, turning the thermostat down by one degree and closing the windows while the heating is on would also help, but that is out of our control. Thermal energy (heat) will always try to move from a relatively hotter location to a colder one and can do so by a combination of conduction, convection and radiation. In a heated building, the particular heat flow paths of concern are conduction through the walls, floor and roof, conduction through cold bridges and convection through gaps in the building envelope. To achieve an energy efficient building, all three of these issues need to be considered by the building designer. Installing 300 mm of insulation but forgetting about the joints around the doors, windows and service penetrations is of little use.

Of the three heat paths, the conduction through the roof, walls and floor is the easiest to tackle and a range of insulation products and insulated panel systems are widely available with plenty of technical literature and support to help building designers specify the product that best meets their needs. The thermal performance of a building element (i.e., an insulated wall or roof) is usually referred to as its ‘U value’ and is quoted in W/m²K, i.e., it is a measure of how much energy escapes per second (in Watts) for every square metre of roof or wall per degree of temperature difference (a temperature difference of 1 Kelvin (K) is the same as a difference of 1°c).

Thermal bridging is a trickier issue to deal with because the strongest materials best suited to load carrying are also the most conductive. Thermal bridging through fasteners is generally considered to be small and is accounted for in the U value for the roof or wall, but larger metal objects, such as steel support beams for balconies or rafters penetrating the building envelope (architects!) can be a major source of heat loss if they are not detailed correctly. Furthermore, the loss of heat will cool the beam or rafter on the inside of the building giving rise to a condensation risk. In some cases, for example balconies, special low conductivity connections have been developed and should be specified where possible. Building designers should seek specialist help if they encounter this situation.

The third source of heat loss, leaky joints, is best dealt with via good detailing, or – more likely – by someone with a tube of sealant. Most building envelope solutions used in industrial and similar commercial buildings are reasonably air-tight by design, especially if the installers follow the manufacturer’s guidance in terms of filler blocks and sealant. The issues tend to be at doors, windows and service penetrations, where gaps are often ignored or left for someone else to fill. This is one case where attention to detail can make a significant impact.

Lighting

The simplest way to limit the demand for artificial lighting is by ensuring there is sufficient natural daylight entering the building. For agricultural and industrial buildings, this is usually achieved by installing rooflights, although north lights are an alternative. The quantity and location of the rooflights is critical to the energy performance of the building. Too many rooflights could result in overheating in the summer (turning the building into a greenhouse) or excessive heat loss in the winter. Poorly positioned rooflights that illuminate the tops of racking storage rather than walkways are of little use, so the building designer needs to co-ordinate the design of the roof with that of the internal layout of the building. The National Association of Rooflight Manufacturers (NARM) has specialist guidance available. The internal layout and decoration of a building can enhance the effect of the natural daylight by reflecting the light and avoiding unwelcome shadows.

Of course, some artificial lighting will always be needed, and the building designer needs to ensure this is as energy efficient as possible. As with rooflights, the quantity and position of artificial lighting is critical to its performance and can be enhanced by a well-designed internal layout and decoration. Specifiers can choose from a wide range of low energy lighting solutions (i.e., LEDs) and should also consider sensor-operated controls to avoid lighting unoccupied rooms.

Cooling/ventilation

As global temperatures rise and rare heat waves become more common, building designers have to give serious consideration to the risk of overheating. To make matters worse, buildings are often filled with heat generating devices such as computers and, in the agricultural sector, livestock can be a significant source of heat. Related to the need to cool the building interior, is the need to supply fresh air for the health and welfare of the building occupants (human and livestock).

Both of these matters can and should be addressed as part of the building design process by ensuring a plentiful, controlled and well-directed flow of natural ventilation, noting that a well-ventilated building is not the same as a draughty one! The alternative is noisy, expensive and energy intensive air conditioning that does little for the welfare of the building occupants and only adds to the building’s carbon emissions.

Conclusions

The operation of our buildings account for a significant proportion of the UK’s greenhouse gas emissions. But reducing the energy demand by minimising heat loss, and through the careful design of the building, building envelope and building services, is within the control of the building designer. Small changes to the specification and attention to detail can often have a major impact on a building’s carbon emissions and improve the welfare of the people and animals who occupy it.Â

Dr Martin Heywood
RIDBA Technical Consultant   Â

The language of late 2021 has a focus on climate change, and how our leaders are going to commit to consumption and investment policies that will make a significant change for the better. The language is not new but is finding a wider usage; re-think, reduce, re-use, recycle. At the same time the global livestock industry is under substantial exposure.

A full-page advert in The Times on November 1, as COP26 started in Glasgow, states: “Our planet is in crisis. The issue of food and agriculture impact needs to form a central part of the discussion and world leaders need to be ready to bring about serious change” and, “global meat and dairy consumption must be greatly reduced”. With typical irony the newspaper also contains a full-page advert for British pork at point of sale for £2 per kilo for bone-in pork shoulder, and £3 per kilo for two other pork products. The CEO of the UK’s biggest poultry producer, along with others, has pointed out the inconsistency in our food market where the price to consumers of a whole chicken is very similar to a high street coffee and its discarded cup and lid.

Where does this leave the future of the UK livestock industry? Retrenchment and decimation? Regardless of the media stories in their many forms, meat and dairy will continue to be consumed and moved around the globe. If the volume of product was halved and the price doubled, there could be a lot of successful businesses out there, but how to get there?

The UK livestock sector and especially the cattle and sheep sectors are reasonable parallels of the relatively poor average UK productivity levels compared with our European counterparts. The UK livestock sector has world class nutrition, genetics, tech, management and personnel, but the average productivity is dragged down by a very long tail of below average productivity on other livestock farms. On those farms the business performance, however measured, is not sustainable.

A major impediment is lack of investment in infrastructure, and any cries of, “we don’t have the money” need to be directed towards those examples where money has been spent and made. On too many livestock farms the buildings and surrounding infrastructure are outdated and inefficient. Some farms look equivalent to a haulage business in 2021 trying to compete using a Ford Anglia van and a Bedford TK; if you don’t get the image, look them up on the internet and I will have made the point.

Appraisal of investment in buildings should be part of every dialogue on buying or selling a building. Why would a business invest in an asset if it did not improve the longevity and financial returns in that business? The current low efficiency, losses through mortality and morbidity, down grading of product, long hours and unattractiveness of some livestock operations is also an opportunity for an improved future. The suggestion is that we can move the opportunities of the livestock sector to the fore and present the livestock sector to the UK population, the buyers and the planners as a sustainable part of the UK future. But we need to use the correct language.

Investment in buildings and infrastructure will only proceed if the producer, the builder, the lender, and the planner line up the arguments and deliver a convincing plan for investment to go ahead. The building sector has a major role to play in getting the other parties invested in a more sustainable future, not least because many of the other parties do not have the required knowledge to set out a project plan that is convincing to detractors.

Presenting the future of investment in UK livestock

Food conversion efficiency (FCE): Animal feed in; human food out. This is a good place to start. A new build should always improve efficiency of FCE, whether a simple matter of food in, food out, or producing the same quantity of milk, meat or eggs from less cows, sows, ewes or chickens. A standard, measured improvement will be at least +5%, and where current systems are creaking, a lot more.

Carbon footprint: Energy efficiency

A lower feed requirement per kilo of output means less energy at every stage of production; ploughing the land, harvesting the crop, storing the crop, feeding the stock, removing the manure. Calculate the number of journeys per year and any impact from improved efficiencies, and if imported (to the farm) resources are used, number of HGV visits per year. Make sure the planners and any critics are aware of the facts. The meat and methane is only one part of the chain.

Biodiversity

Poor standards of production should not be protected, and that includes livestock. Intensive production and concentration of by-products and effluents are not acceptable today and will be less acceptable tomorrow. There is a substantial opportunity for the livestock sector to reduce diffuse pollution into the environment, but investment is required to achieve that aim.

The positive contribution that livestock and particularly grazing animals make to biodiversity varies dependant on system but will beat intensive plant production every day. There are between 100 and 150 invertebrates living in every cowpat; how many planners know that?

Soil health

Unless it is derived from the sea, all food we eat comes from the soil, some of it via livestock. The role of ruminant livestock in particular in sustaining the cycle of materials from and back to soils is casually ignored by too many critics of livestock production. There is no doubt that investment is needed to improve the storage and maintain the nutrient value of manures on many farms, and to reduce diffuse pollution, but UK soil health is not going to be maintained by annual spreading of inorganic fertilisers from foreign countries.

Social health: Rural communities, employment

Diversity of systems requires a diversity of skills, and allowing farms of any size to invest in the future is essential to keep people on farms. It is also useful to remind the planners and others of the number of UK jobs created up and downstream of the apparently ‘simple’ task of growing food.

Technological advancement: Robots, feed nutrients, vaccines

The customer may see the meat or eggs or milk or cheese on the shelf, but there is an extensive supply chain to produce that apparently simple result. Livestock systems support up and downstream development of buildings, technology, nutrition, vaccines and genetics that are important contributors to UK business health, UK jobs and UK food supply. No livestock, no chain.

Antibiotic use

Antibiotic use per unit of UK livestock production has tumbled in the last five to ten years, and investment in facilities has played an important part. There is still progress to be made, but it is not going to materialise by using buildings that are hard or impossible to clean, or where stress on animals is contributing to current losses. The UK does have a mostly effective quality assurance (QA) system for food production and is in the premier division of QA at a global level. Imports may often be cheaper, but it is important to remind the planners and others of the benefits of UK based production. It is important to remind our customers of the reasons that investment in our livestock systems is part of a sustainable UK future, that will be cleaner, that will be more efficient, and will be in the UK.

Jamie Robertson
RIDBA Livestock Consultant

With the COP26 summit beginning in Glasgow this month and the latest Intergovernmental Panel on Climate Change (IPCC) report published in August, climate change is back on the news agenda.

The IPCC report presented further evidence of rising global temperatures and the likely range of future temperature increases if little or no action is taken to limit greenhouse gas emissions.

Furthermore, for the first time it reported that we’re already seeing the impacts of climate change in the form of extreme weather events, such as flash flooding and wildfires.

With buildings accounting for 17% of the UK’s greenhouse gas emissions (2019 figures), reducing the energy demand of buildings is a priority for the UK government in its attempt to make the UK net zero by 2050.

With the IPCC predicting an increased frequency of extreme weather events, climate change is also on the agenda of those responsible for our codes and standards, as they strive to ensure buildings remain safe from stronger winds, higher temperatures and potentially deeper snow.

The role of buildings in greenhouse gas emissions

Buildings contribute to the UK’s greenhouse gas emissions in two ways:

• Embodied carbon: The CO2 associated with the building fabric and its construction
• Operational carbon: The CO2 associated with the operation and use of the building

The relative importance of embodied carbon and operational carbon depends on the use of the building and its design life.

For a heated building with a 50-year life, the embodied carbon will be small compared to the total operational carbon over the 50 years, whereas for an unheated building that is demolished after only ten years, the embodied carbon will be far more significant.

Changes to building regulations over the past couple of decades (e.g. improved insulation and airtightness and more efficient lighting) have significantly reduced the operational carbon of buildings, increasing the relative importance of the embodied carbon in the process.

The embodied carbon of a building, building element or construction material may be assessed by what is known as the life cycle assessment (LCA). This takes account of all of the processes and associated CO2 from when the raw materials are extracted from the ground through to their disposal or recycling at end of life.

It should include carbon emissions associated with the materials themselves (including waste materials that are not recycled), the manufacturing processes and transportation.

For many common materials, the embodied carbon values may be obtained from established databases. Many manufacturers declare the embodied carbon of their products as part of their environmental product declaration (EPD).

The operational carbon is due to the energy needed to operate the building and includes heating (and potentially cooling), ventilation and lighting. The energy performance of buildings is already highly regulated (e.g. Part L of the Building Regulations in England) and these rules are set to become more onerous as new buildings are pushed in the direction of net zero.

The operational energy of a building, and hence the mitigation measures required to reduce its carbon footprint, will depend on building use.

For commercial buildings, reducing heat loss through the building envelope has been a priority for the past 20 years and the regulations have pushed for lower U-values (a measure of how much heat conducts through the building envelope) and airtightness.

Such concerns are irrelevant for a semi-open sided livestock shed, but there is an energy demand associated with lighting and ventilation. While the use of more efficient lighting and ventilation in this instance will reduce the operational carbon of the building, an even greater benefit can be realised by good building design to maximise the use of natural daylight and ventilation (also better for the welfare of livestock).

Design for reduced CO2 emissions

As the impact of climate change becomes more apparent so the need to tackle it will become more urgent and efforts to reduce the carbon footprint of human activity will intensify.

This started in earnest in the UK at the start of the millennium with incremental changes to building regulations to reduce operational carbon and the greater use of environmental assessments, such as BREEAM, to grade buildings in terms of their overall environmental impact.

In parallel, documents such as the ‘Green Guide’ will gather and disseminate data on the environmental impact of building elements and EPDs for construction products have become the norm.

However, with the UK government now committed to net zero, it is safe to assume that an even greater emphasis will need to be placed on the environmental design of buildings in future.

Likely changes can be grouped into three categories:

• Improved energy efficiency to reduce operational carbon
• Better use of more sustainable materials to reduce embodied carbon
• Greater incorporation of renewable energy devices

Reductions in operational carbon are likely to be achieved by continuing recent trends aimed at minimising energy wastage from inefficient lighting, mechanical plant (heating, cooling and ventilation) and heat loss through the building envelope, but the emphasis of these reductions may change.

For example, as the thickness of roof and wall insulation has increased over recent years, emphasis switched from U-values to airtightness, since proportionately more heat was now being lost through leaky joints.

This change has resulted in modern houses that are theoretically very energy efficient, but uncomfortable for the occupants, who take matters into their own hands by opening the windows in the middle of winter while the heating is on. Needless to say, there is now a greater emphasis on human behaviour and control systems.

For unheated buildings, optimising lighting and ventilation are likely to be key, i.e., allowing as much daylight in as possible without too much solar gain leading to overheating.

As operational carbon is reduced, expect a greater emphasis to be placed on the embodied carbon of the building, with sustainable sourcing and the greater use of recycled materials becoming normal practice.

There could also be a move towards structural forms that minimise material weight at the expense of fabrication effort (e.g. lightweight trusses) and construction methods that reduce waste (e.g. offsite manufacturing – which is already standard practice for frame manufacturers).

Finally, as demand for renewable electricity increases to charge all of those electric cars that we will soon be driving, it is likely that the trend to cover building roofs with photovoltaic (PV) arrays will pick up again, if the financial incentives are right. However, PVs add weight to structures and can potentially increase wind loading, so there may be implications for the design of the structure.

There are also options to harness the power of the sun to meet local energy needs, for example cladding grain stores with transpired solar collectors (steel sheets with tiny perforations) to collect hot air to dry the grain.

The consequences of climate change on buildings

One of the most shocking aspects of the recent IPCC report is that the impact of climate change is already apparent. We’ve been warned it’s going to get worse even if we slash carbon emission over the next couple of decades.

Given that all buildings have to be designed for what the Eurocodes call “climatic actions” (wind, snow and sometimes ice and thermal expansion), it should not come as a surprise if climate change results in more onerous design conditions for our buildings.

CEN (Europe’s standards organisation) is already considering how best to factor climate change into the Eurocodes, with the option of applying a scaling factor to snow and wind loads being considered.

It is also likely that the maximum temperature values used for calculating steel expansion (very important for bridges and railway track) will increase. This rise in peak temperatures will also increase the risk of buildings overheating.

Another consequence of climate change is likely to be heavier rainfall, requiring the redesign of gutters and drainage systems.

Conclusions

Climate change has arrived as a physical reality in the form of heat waves and storms and as a political priority. In both senses it will have consequences for the way buildings are constructed and operated.

With buildings accounting for 17% of the UK’s greenhouse gas emissions, reducing the energy demand of buildings should be a priority for our sector as we seek to limit the impact of climate change and minimise the harm to our planet.

Dr Martin Heywood
RIDBA Technical Consultant

Although the subject of heat stress has been mentioned before, some of the predictable changes in cattle systems in the UK are beginning to bite on animal health and welfare.

The first change is that as cattle become more productive, they process more energy and need to dump more sensible heat to maintain energy balance. The second is that increased production requires increased moisture throughput, with a high yielding dairy cow consuming water in excess of 100 litres per day.

This means a building with 200 dairy cows will have a throughput of more than 20,000 litres of water per day, with at least 16,000 litres of that being excreted back into the system.

The final change is that our cows are increasingly likely to be housed all year round, so livestock building systems have to operate at ambient temperatures above 15c.

One question that has bounced around the livestock building sector for more than ten years is: ‘Is there a requirement for insulated roof sheeting and can the additional cost be justified?’. My response has been that, in terms of hard data, we don’t know.

Our understanding of physiology and relevant meteorology can provide an estimation of the risk from heat stress, in the same way location data and meteorology can give risk guidance for wind loading on structures. We need more data.

Just over 18 months on from the emergence of Covid-19, on farm meetings in the UK have begun again and it was a pleasure to be working in the south-west of England recently.

The focus was how to manage heat stress in dairy cows, and the sun duly shone providing air temperatures above 24c from mid-morning until mid-evening.

My contribution was on using building design to maximise wind driven ventilation without losing control of air speed in the winter months and ensuring there is no restriction of ventilation by stack effect.

The progressive information came from Mark Scott, of Cargill, which like the meeting sponsors Crediton Milling Company is an animal nutrition company, supplying the energy in aspect of our cattle systems.

The question of return on investment from adding costs to our cattle buildings is answered more easily if we know the costs of a system being out of balance. Mark and his colleagues at Cargil have installed temperature and humidity sensors on dairy units around the UK which provide constant monitoring of the thermal humidity index (THI).

This data is useful because there is a temptation to think that our UK air temperatures are seldom stressful, with air temperature data from overseas significantly higher than typical UK summer temperatures in cattle buildings.

In fact, it is more useful to adopt THI as a measure of thermal conditions experienced by cattle than air temperatures because, as air temperatures rise, cattle increasingly rely on dumping moisture from the body into the environment.

Moisture loss by respiration increases two-fold when air temperature increases from 12c to 24c.

This works well in hot, dry climates, but is not so easy in a maritime climate like the UK, with relatively high but normal air humidities. It is hard to dump energy as moisture in a damp atmosphere.

The data collected from 26 farms in the UK can be accessed at www.weatherdatauk.provimi.eu, with the primary observation that from south-west Scotland to south-west England, there are a significant number of days where cattle reproduction and performance is being limited by THI.

Managing heat stress on UK cattle units

Where the number of days per year of THI above 65 is very low, the opportunity for return on investment will also be low. However, the evidence that UK cows are becoming heat stressed is clear.

Managing heat stress can be done at the design stage of buildings and also retrospectively. For example:

• Drainage slopes prevent the accumulation of moisture.
• Sidewall cladding to provide wind driven air movement without losing control of winter air speeds.
• No restriction of the stack effect by the inlets and outlet areas.
• Roof material.
• Roof slopes.
• Water troughs.

The role of the wind is so important in managing ventilation and thereby energy and moisture management in a cattle building, that the location of individual buildings has a critical impact. It is tempting to think our weather is unpredictable, but the facts prove the opposite. It is useful to refer to local meteorological data for a level of predictability about the impact of weather on a building.

Even with drainage and natural ventilation optimised there will still be predictable benefits from helping cows stay cooler. Nutritionists have a role by providing products that change pathways of energy metabolism and can help to reduce body temperatures by 1-2c. Remember, access to clean and cool water helps too.

After that, our systems need more help. Mechanical ventilation is used extensively around the world to cool livestock by increasing air speed across their bodies and increasing the rate of heat loss. As long as the airborne heat and moisture entrained in the fan-driven air leaves the building and is not allowed to accumulate, cow health and welfare will benefit.

The Hot Cows Road Show in July included presentations from Robin Hibberd, of Hydor, on the requirements of and benefits from mechanical ventilation. The main requirement for managing heat stress is to provide large volumes of air across the backs of as many cattle in the building as possible. Some general rules are:

• Locate fans to move air in same direction as predominant wind direction, where possible.
• Locate fans in series to ensure the moving air column does not accumulate inside buildings.
• Locate fans so that air flow passes around the cattle, not above.
• Balance fan types and capacity to available power supply and running costs.
• Persuade the client that the cost of automatic control, probably for temperature and humidity, provides good value.

The addition of mechanical ventilation also provides the possibility of adding water to livestock systems and increasing the rate of energy from a body by evaporation. Spraying of water – or misting – may be particularly valuable in THI hot spots such as collecting yards, but never where ventilation is compromised.

So, I return to the original question: ‘Is there a requirement for insulated roof sheets?’. The current information on THI in UK cattle buildings strongly suggests there is a need, and that return on investment will depend on the scale of current losses.

Jamie Robertson
RIDBA Livestock Consultant

Introduction

I’m writing this article on the 4th anniversary of the Grenfell Tower tragedy, an event that shocked the entire nation and shone a much needed spotlight on the issue of fire safety in buildings. Of course there are several significant differences between a highrise residential block and a single storey agricultural building and many of the issues identified at Grenfell Tower do not apply to grain stores or animal housing. Nevertheless, fires do break out on farms, sometimes with tragic consequences, so it seemed timely to dedicate this article to the subject.

Regulations and fundamentals

As most readers will be aware, agricultural buildings that are not used as dwellings are exempt from the Building Regulations provided that they meet certain conditions. RIDBA members, however, also supply a wide range of non-agricultural buildings (e.g. buildings for industrial, retail or educational applications), so knowledge of the basic requirements of Approved Document B, the part of the Building Regulations in England and Wales dealing with fire, is important. Furthermore, farm buildings are sometimes built close to dwellings (e.g. a barn next to the farm house) or are converted for other uses (e.g. a riding school), so the Building Regulations exemptions don’t always apply. Fortunately, even when a single storey building falls within the scope of Approved Document B, the rules are far less onerous than they are for multi-storey buildings.

There are two fundamental issues that need to be considered when designing a building against the risk of fire:
• Saving the lives of occupants within the building
• Preventing the spread of fire to neighbouring buildings.

The former is usually critical for multi-storey buildings, where there is an emphasis on preventing the spread of fire within the building (compartmentalisation), providing escape routes, the installation of sprinklers and preventing collapse of the structure by protecting critical structural elements. By contrast for single storey buildings, the emphasis is very much on preventing the spread of fire to neighbouring buildings, in particular through the collapse of a burning building onto its neighbour.

Saving lives

The overriding priority of Approved Document B is saving the lives of building occupants in the event of a fire. This is achieved by a combination of minimising the time needed to egress from the building and maximising the time taken for the fire to spread. The former is enabled through the provision of escape routes leading to fire exits, while the latter is often achieved by the use of fire doors, fire-proof barriers, compartmentalisation and sprinklers. Since the majority of agricultural buildings are single storey, the simplest way of saving lives is to ensure that everyone within the building has easy access to an exit. For this reason, the exemption of agricultural buildings to the Building Regulations states that nowhere within the building may be further than 30m from an exit.

Preventing the spread of fire

Of greater concern for single storey buildings is the spread of fire to neighbouring buildings, especially where a neighbouring building is a dwelling. Preferably, agricultural buildings (i.e. those that are generally exempt from the Building Regulations) should be at least one and a half times their height from any building with sleeping accommodation. Where this is not possible, or for industrial or commercial buildings where there is no exemption from the regulations, it is necessary to design the building such that in the event of a fire. For braced frames, this could be achieved by protecting the external walls only (i.e. the columns and bracing), but this approach is inadequate for portal frames, because the columns and rafters act together as if they were a single structural element. For standard frames with nominally pinned bases, if the roof structure were to collapse in a fire, the walls would also collapse allowing the fire to spread. Of course, in theory, this problem could be overcome by applying fire protection to the entire portal frame.

However, applying fire protection to rafters is difficult and expensive so an alternative solution is needed. SCI publication Single Storey Steel Framed Buildings in Fire Boundary Conditions (SCI-P-313) presents an alternative method in which engineering principles are applied to the design of the columns and bases to demonstrate that the columns alone could withstand the overturning moment applied to them even if the entire roof structure were to collapse in a fire. In this method, the overturning moment at the point of rafter collapse is calculated for a special fire limit state case, in which the loading is less severe than that normally used to design the structure.

The column base strength and stiffness are estimated based on the actual base dimensions and thickness and the size and strength of the holding down bolts. Sprinklers are recognised to have a considerable beneficial impact on the intensity and spread of fire and a significant relaxation in the rules is permitted when they are used.

Fire protection

Where columns along external walls require fire protection, this should extend up to the underside of the haunch, or to the rafter where there is no haunch. The level of fire resistance of the protected columns should be the same as that of the wall. Values of fire resistance (i.e. duration in minutes) are given in Approved Document B. Building designers and frame manufacturers have several options when it comes to the means of fire protection. The most common are summarised (right).

• Boards – This is probably the simplest solution and is especially suitable for commercial and retail premises, where the boards provide the additional benefit of hiding the steelwork within a neat box. The boards are fitted as a dry trade after the completion of the structure, so do not interfere too much with the construction programme.
• Sprays – This solution is less common in the UK, but is sometimes used where complex shapes would be difficult to protect using boards. The end result, while effective as fire protection, is not aesthetically pleasing, so sprays are not used where appearance is important. Spays are messy to apply and no other construction work is possible during this operation.
• Blankets – This solution combines the advantages of boards and sprays. In common with boards, blankets are applied as a dry trade to the completed structure, but like sprays they are suitable for complex shapes. They are especially useful for protecting truss structures, since the blankets can be wrapped around the individual elements of the truss.
• Intumescent coatings – Unlike the first three options, which all offer passive fire protection, intumescent coating react to temperature, foaming up to provide fire protection in the event of a fire, but otherwise resembling a painted finish to the steel.

Intumescent coatings can either be thin or thick film and may be applied in the frame manufacturer’s workshop or on site. Off-site applied thin film intumescent coatings are probably the most appropriate for portal frame structures and have a significant market share in the UK.

Efficiently run livestock housing is key to productivity, health, welfare and, ultimately, the success of the industry. Proficiently balancing inputs and outputs places some businesses ahead of others and creates more resilience in navigating through the uncertainty of the future while we live through these unprecedented times.

In 2019, English pig producers were asked about their predicted investment into new buildings and technologies. Half of producers surveyed said they are likely to be capping investment into buildings at £50,000, mostly because of the known return in investment and the previously mentioned uncertainty of the industry. Producers do want to invest long term, with more than half keen to build a healthy and sustainable farm business to pass on to the next generation. For producers to have the confidence to invest and drive business improvement, they need reassurance that their investments will increase production efficiency, while also providing welfare and environmental improvements.

Making savings in running costs and inputs is not a new theory in business management plans, but is increasingly at the forefront of investment considerations, not only to streamline production and reduce running costs, but also to support the UK Government’s requirement to reduce all greenhouse gas emissions to net zero by 2050. GrowSave, a collaboration between AHDB and NFU Energy, is a knowledge exchange programme helping both farmers and growers save energy. Until recently, the programme has been focused solely on horticulture, but as energy saving
and management is clearly critical across wider AHDB sectors, the programme has now been expanded into the cereals, dairy, pork and potato sectors. To date, the programme has helped horticultural businesses save energy and reduce their environmental impact, which, due to the volatility of energy prices over the last five years, coupled with the increased demand for year-round produce, have been significant drivers for businesses to carefully manage their energy consumption. Pig producers have similar pressures to meet consumer needs, with running costs, in particular electricity, driving the need for overall efficiency improvements.

GrowSave has already helped businesses recognise areas in which energy savings can be made. A market review and gap analysis have identified current practices and highlighted where changes could be implemented, either now, or in the future, to improve business performance and energy efficiencies, while reducing carbon emissions.

Discussions with pig producers and industry representatives dominated by the themes of slurry treatment, including cooling, LED lighting, automation, and data acquisition. Other themes that people are thinking about include the use and improvement of heating systems or climate control techniques, and the application of renewable energy, such as heat pumps, solar photovoltaics, or anaerobic digestion.

The technique of cooling slurry before it leaves the pig shed brings two principal benefits: ammonia suppression (most producers achieve reductions of 30–50%), and heat recovery. Which of these has the upper hand depends on the individual system. Installation of this technology is most efficient in new buildings but can be retrofitted.

Other slurry treatments, such as plasma reactors producing ammonium nitrate liquid fertiliser, are under development.

Now that energy-efficient LED lighting is widespread, specialist products with tailored spectral output are emerging. One supplier of such lighting, Unilight UK, claims that Danish studies on pigs recorded growth increase of 3–5%, or about a week, under LED lighting. In addition, sow lactation improves, piglets grow quicker, and weaning weight increases.

Data is commonly used to benchmark farm operations and often energy consumption as well. When looking to improve energy efficiency, this data should not be limited to the obvious areas such as energy consumption, temperature, on/off times, etc. To get the best value from data, it should be gathered and reported against all sensible metrics, such as feed requirements, fertility, weight gains, mortality, etc. By doing so, the full impacts of the changes that are made can be assessed and the right decisions made to gain maximum efficiencies in all aspects of production, together with using predictive analytics.

To find out more about the successes of GrowSave so far, visit the AHDB website: ahdb.org.uk/growsave.