2. General thermal modification systems for housed livestock and poultry

vary greatly by region of the country. For all intensive purposes, HLPP buildings are considered

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Ventilation designs for HLPP systems range from complete natural ventilation (NV) to a combined hybrid natural/mechanical ventilation (NMV), to full mechanical ventilation (MV).

The NV building design (Figure 2) features controlled sidewall curtain and ridge vent openings. The sidewall and ridge vents are either manually or automatically controlled. The NV barn design has traditionally been used in broiler, turkey, beef, pig finishing, and dairy housing.

Orientation of building relative to historical summer winds is critical, as well as the percent calm periods during warm weather. For example, Figure 3a outlines the historical August wind rose pattern for Des Moines, Iowa, USA. For this region, the predominant summer winds are from the S-SE and a properly oriented NV building would have the ridge axis E-W or slightly tilted counter-clockwise to expose the sidewall curtains to the predominant summer winds. Deviation from predominant summer winds will significantly affect the potential freshair exchange rate in the building. Figure 3b outlines the predicted fresh air exchange rate (air changes per hour; ach) for a typical pig finishing facility designed to house 1000 pigs. The design maximum hot weather rate for this type of facility is 100–120 ach. For this example, both sidewall curtains are open 1.2 m. If the building is oriented completely E-W, with a

, 360o

, 270<sup>o</sup>

will sufficiently ventilate this building at and above design criteria. An orientation that deviates from the predominant wind direction significantly reduces ventilation potential. In theory,

although certainly some low-level exchange of fresh air will still take place. The NV building design is still a staple for many animal groups, especially dairy, beef, broilers, turkeys, and

Figure 2. Naturally ventilated (a) pig finishing building with (b) close-up of modern controlled ridge vents.

) wind, a 3 m s<sup>1</sup> and above wind speed

) will not ventilate the building at all,

) or northern (0o

thermally light, responding quickly to outside weather influences.

2.2. Ventilation design basis for the USA HLPP building system

2.2.1. The naturally ventilated HLPP system

perpendicular southern (180<sup>o</sup>

swine finishers.

a lateral (along the ridge line) wind direction (90o

In the USA, the raising of food animals in controlled climate facilities has progressed rapidly since the 1980s. It was not uncommon for livestock and poultry producers to rear food animals in outdoor lots or partially contained facilities with minimal modification to the thermal environment. This small-scale production practice has now given way, for the most part, to intensive housing systems where thousands of food production livestock and poultry are raised in tightly controlled climates, with sophisticated thermal modification techniques. The following sections outline some of the systems in use today. For a more complete historical perspective on the development of HLPP systems, see [1].

### 2.1. Structural design basis for the USA HLPP building system

The majority of HLPP buildings in the USA are composed of wood-frame construction supplemented with concrete stub walls, polyethylene or equivalent curtain sidewall openings, and light-gauge steel roofing and siding (Figure 1a, b). Waste products are handled in repositories below a slotted flooring system (pigs, beef; Figure 1b), within the flooring material (e.g., sawdust) itself (broiler, turkey, hens; Figure 1c) or outside below- or above-grade earthen, concrete, or steel containment systems (pigs, beef, dairy, hens; Figure 1d). Insulation levels

Figure 1. (a) A common Midwestern USA swine finisher with curtain sidewalls and (b) metal flat interior ceiling with concrete slatted flooring, (c) common broiler housing [2], and (d) common above-ground metal manure storage system [3].

vary greatly by region of the country. For all intensive purposes, HLPP buildings are considered thermally light, responding quickly to outside weather influences.

#### 2.2. Ventilation design basis for the USA HLPP building system

Ventilation designs for HLPP systems range from complete natural ventilation (NV) to a combined hybrid natural/mechanical ventilation (NMV), to full mechanical ventilation (MV).

#### 2.2.1. The naturally ventilated HLPP system

2. General thermal modification systems for housed livestock and poultry

In the USA, the raising of food animals in controlled climate facilities has progressed rapidly since the 1980s. It was not uncommon for livestock and poultry producers to rear food animals in outdoor lots or partially contained facilities with minimal modification to the thermal environment. This small-scale production practice has now given way, for the most part, to intensive housing systems where thousands of food production livestock and poultry are raised in tightly controlled climates, with sophisticated thermal modification techniques. The following sections outline some of the systems in use today. For a more complete historical

The majority of HLPP buildings in the USA are composed of wood-frame construction supplemented with concrete stub walls, polyethylene or equivalent curtain sidewall openings, and light-gauge steel roofing and siding (Figure 1a, b). Waste products are handled in repositories below a slotted flooring system (pigs, beef; Figure 1b), within the flooring material (e.g., sawdust) itself (broiler, turkey, hens; Figure 1c) or outside below- or above-grade earthen, concrete, or steel containment systems (pigs, beef, dairy, hens; Figure 1d). Insulation levels

Figure 1. (a) A common Midwestern USA swine finisher with curtain sidewalls and (b) metal flat interior ceiling with concrete slatted flooring, (c) common broiler housing [2], and (d) common above-ground metal manure storage system [3].

perspective on the development of HLPP systems, see [1].

2 HVAC System

2.1. Structural design basis for the USA HLPP building system

The NV building design (Figure 2) features controlled sidewall curtain and ridge vent openings. The sidewall and ridge vents are either manually or automatically controlled. The NV barn design has traditionally been used in broiler, turkey, beef, pig finishing, and dairy housing.

Orientation of building relative to historical summer winds is critical, as well as the percent calm periods during warm weather. For example, Figure 3a outlines the historical August wind rose pattern for Des Moines, Iowa, USA. For this region, the predominant summer winds are from the S-SE and a properly oriented NV building would have the ridge axis E-W or slightly tilted counter-clockwise to expose the sidewall curtains to the predominant summer winds. Deviation from predominant summer winds will significantly affect the potential freshair exchange rate in the building. Figure 3b outlines the predicted fresh air exchange rate (air changes per hour; ach) for a typical pig finishing facility designed to house 1000 pigs. The design maximum hot weather rate for this type of facility is 100–120 ach. For this example, both sidewall curtains are open 1.2 m. If the building is oriented completely E-W, with a perpendicular southern (180<sup>o</sup> ) or northern (0o , 360o ) wind, a 3 m s<sup>1</sup> and above wind speed will sufficiently ventilate this building at and above design criteria. An orientation that deviates from the predominant wind direction significantly reduces ventilation potential. In theory, a lateral (along the ridge line) wind direction (90o , 270<sup>o</sup> ) will not ventilate the building at all, although certainly some low-level exchange of fresh air will still take place. The NV building design is still a staple for many animal groups, especially dairy, beef, broilers, turkeys, and swine finishers.

Figure 2. Naturally ventilated (a) pig finishing building with (b) close-up of modern controlled ridge vents.

Figure 3. Typical (a) wind rose pattern evaluated when planning for a naturally ventilated building and (b) the influence of improper alignment relative to predominant summer winds.

3. Space and zone heating for housed livestock and poultry

as the ultimate diffuser opening control objective.

Space and/or zone heating are integral components of modern HLPP systems. Space heating has been traditionally accomplished with unvented forced air furnaces. Heated air distribution is handled primarily with a single diffuser attached to the heater outlet, providing minimal distribution and thus uniformity. Ducting of heated air to targeted locations is traditionally not employed in the HLPP systems. Zone heating has traditionally been handled with radiant spot (Figure 5a), radiant tube, or heat lamps (Figure 5b). In some of the colder regions of the USA (e.g., Minnesota), additional microclimate enclosures with heat lamps are provided for immature animals in the coldest weather (Figure 5b). Cold climate ventilation rates are designed to control moisture, gases, and temperature, with moisture control almost always governing the cold weather ventilation rates. Many HLPP ventilation control platforms available today allow the producer to control for building temperature, with relative humidity sensing as a backup for assessing moisture control. Gases such as ammonia, carbon dioxide, hydrogen sulfide, and methane can be an issue in many HLPP systems. In most cold weather situations, and during

Figure 5. (a) Radiant spot heater with shielded radiant sensor for feedback control and (b) microclimate with heat lamps.

Figure 4. Example ceiling fresh-air diffuser commonly used in HLPP systems. The cable shown passing through the diffuser is used to automatically control baffle opening in response to ventilation rate changes with static pressure control

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#### 2.2.2. The hybrid natural/mechanical HLPP system

The NV method of HLPP building ventilation, although once the predominant method of ventilating HLPP systems, has given way in many cases to NMV or MV approaches where tighter control of the thermal environment is desired. The NMV method uses exhaust fan ventilation in cold-to-mild conditions with sidewall curtains and wind potential handling warm weather ventilation (see Figure 1a). The NMV method was developed to replace the NV action during cold weather in an attempt to better control the thermal environment. Warm and hot weather ventilation is handled with sidewall curtain opening action and wind, requiring the same basic orientation requirements of an NV building. The NMV method does not require cold weather ridge vents and therefore in the NMV method a flat interior ceiling is often used (see Figure 1b) with a heavily insulated attic space.

#### 2.2.3. The mechanically ventilated HLPP system

The vast majority of modern intensive HLPP systems use a negative pressure MV system with exhaust fans connected in parallel and fresh inlet air drawn in through ceiling diffusers (Figure 4) in cold-to-mild conditions and sidewall and/or endwall curtains (Figure 1a, b) in warm-to-hot conditions. In modern HLPP systems, the ceiling diffusers are cable controlled to stage inlet action with fan staging, using static pressure differential as feedback. Typical operating static pressures range from 10 to 30 Pascals (Poutside-Pinside). The MV system will typically incorporate at least one sidewall 'drop' curtain opening for emergency power loss events. The negative pressure MV arrangement has become a popular choice, preventing moisture and gas-laden air from exfiltrating through uncontrolled locations where condensation and building deterioration could be an issue. Specialty-designed positive pressure systems are becoming more popular, which are discussed in a later section.

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Figure 4. Example ceiling fresh-air diffuser commonly used in HLPP systems. The cable shown passing through the diffuser is used to automatically control baffle opening in response to ventilation rate changes with static pressure control as the ultimate diffuser opening control objective.
