This study developed a numerical model of a standard farm building to quantify the bill of materials for two construction types - steel and timber. The model was based on Irish legislation and divided the building into nodes to calculate material quantities. Estimates of thermal transmittance and energy consumption were also determined. The quantities of structural steel, roof sheeting, timber frames and plywood were calculated. Future work will involve validating the model and performing a life cycle assessment of the materials to compare their environmental impacts.

1. APPLICATION OF LIFE CYCLE ASSESSMENT TO CONSTRUCTION
MATERIALS: A CASE STUDY OF FARM BUILDINGS
Rajat Nag and Nicholas M Holden
UCD School of Biosystems and Food Engineering, University College Dublin, Belfield, Dublin 4,
Ireland
Abstract
The materials used to construct farm buildings cause impacts to the environment. In this study a
numerical model of a farm building was developed to calculate the bill of materials required for Life
Cycle Assessment (LCA). LCA is widely used to evaluate emissions and consumptions and to find
out hotspots, yet many livestock system LCAs make a starting ‘exclusion assumption’ of not
including farm buildings. Few studies have evaluated this assumption. The influence of seasonal
changes, type of building material (steel and timber) is presented. This approach during the design
stage of a building will ensure compliance with the legislation and is the first step towards a net zero
building concept compatible with the exclusion assumption.
Introduction
According to the Department of Agriculture, Food and the Marine (DAFM) the agriculture and food
sector in Ireland contributes about €24 billion to the national economy and a farm building represent
about 30 to 45 % of the overall project cost for farm development. Worldwide, more than 40% of all
energy use is linked to buildings and they produce one third of greenhouse gas emissions during their
entire life cycle (Koesling et al. 2015). Despite this, many LCA studies of livestock systems omit farm
buildings from the system. The methodology of the overall study was based inter-linking IPPC
legislation, numerical modelling, thermal transmittance and model validation and finally the
application of LCA to quantity impacts (emissions and energy consumption). This paper focuses on
numerical modelling of the farm building.
A numerical model is a description of a system using mathematical concepts and language. Here
numerical models are used because the model may help to explain a system, to study the effects of
different components and to make predictions about behaviour. Experimentation with real farm
buildings is very costly and time-consuming. A numerical model can be used to quantify each of the
major materials to be used in construction of the building. Impact on heating and cooling, durability,
type of animal and the distance from the source to the construction site have a major influence when
selecting a specific type of building material. For example, timber is a good thermal insulator. Hence
during winter, we need to provide less amounts of heat inside the building compared to a building
made of metal and concrete. At the same time durability may be a concern for choice of materials,
because they all do not have a same life span when in contact with urine and faeces, containing the
aggressive ions Cl-
, SO4
2-
, Mg2+
, NH4
+
with high concentration of H2S, CO2 and NH3 (De Belie et al.
2000b). Monahan and Powell (2011) provided a system diagram for construction materials: Extraction
of raw material or recycled material > Transportation > Manufacturing of components and products >
Transportation to site > Construction > Occupation > Maintenance and renovation > Deconstruction >
Removal from site (Transport) > Disposal. LCA is a tool that can be used for assessing the global
emissions for the materials used in the building. Some material choices are made due to technology,
economy and purpose limitations such as concrete for slated floors in a farm building for cattle (De
Belie et al. 2000a). On the other hand, roof material can be flexible as it may be corrugated GI sheet,
glass fibre or wooden. This study considers IPPC legislations and the flexible areas for a material
choice.
The objective of this study was to model a farm building based on farm building legislation in
order to quantify the bill of materials and to select an equation for heating as well as cooling
which are key inputs for the subsequent LCA study.

2. Materials and Methods
IPPC legislation and dimensions
A simple steel frame (Figure 1) was assumed. This consisted of a framework of steel stanchions,
rafters, and bracing. It is used for most animal houses with feeding passages, and also for sloped-roof
‘single-sided’ houses. It can easily accommodate feed barriers, pens, and facilitate good ventilation,
and is therefore recommended for slatted or scraped floor houses for cattle, cows or sheep.
Bay
Width
Purlin
Slats
Sheeting
Rail
Ventilated Side
Cladding - 1.5m depth Roof
Pitch
Gap
Outside
Agitation Point
in Slab
SPAN
Stanchions
Overhang
Spaced
Sheeting
Angle
Braces
Ventilation
Outlet
Eaves
Height
Rafters
Roof
Cross
Bracing
Ventilation
Inlet
Figure 1: Single-sided simple steel frame (4 bay) house published by DAFM – S. 101: “Minimum
specifications for the structure of Agricultural Buildings”
This study focuses on rafters and purlins, columns / stanchions, roof sheeting, claddings, sliding
doors. Other components like foundations, mats, concrete floors, slurry tank, concrete apron, external
walls, cubicles & cubic beds, path, metal trough, feeding barriers, automatic scrapers, water trough
are not considered as they are common for scenarios whether steel or timber. The steel structure was
designed in accordance with IS EN 1993 and expected to serve 30 years with a steel corrosion rate of
200 µm thickness loss per year (De Belie et al. 2000c). Whereas for timber-design IS 444 was
adopted. All timber should have a minimum service life of 20 years (mostly pine or cedar) to satisfy
hazard class 4 requirements, as defined in IS EN 335-1:1992. Hence the LCA comparison requires 2
steel buildings and 3 wooden building to provide 60 years of service.
Table 1. Some features of the building according to legislation S. 101. (S) for steel, (T) for timber
Eve height 4m Roof slope 15 degrees
Bay width 4.8m (max for timber) Max purlin spacing 1.12 m
Cladding & roof (S) 0.5mm GI
(T) 12mm ply. (with PVC)
Sliding door (S) 1mm steel
(T) 12mm
plywood
Angle brace
(>1.5m length)
(S) UA 60x60x6
(T) 75x175
Over hanging rafter and
supporting member
(S) IPE 180
(T) 75x175
Stanchions
External column
Internal column
(S) UB 203x102x23
(T) 150x225 (10 nos.)
(T) 75x150 (10 nos.)
Main purlin (S) UA 50x50x6
(T) 50x75
Cross bracing and
main rafter
(S) UA 50x50x6
(T) 75x175
Supporting purlin (S) UA 25x25x3
(T) 50x75
Numerical modelling to quantify the bill of materials
The main elements of a numerical model are in the sequence of observation of the physical system >
numerical model > simulation > prediction. Using finite element methods, the model was split into n

3. (number of) nodes each with relevant properties. Modelling software (STAAD pro) was used to solve
differential equations to maintain equilibrium condition for each differential sub system.
Figure 2. Numerical model of the farm building: dimensioning and 3D view
Thermal transmittance and model validation
Mass balance of relative humidity, CO2 and heat balance can be estimated using equations:
mi
= (1.5 * Wa) / (Wi - Wo) (1)
mii = CO2a / (CO2i - CO2o) (2)
S = [(A * U + Mmin * C) * ∆T] - Hs (3)
Mmax = (Hs - A * U) * ∆T) / (C * ∆T) (4)
As a rule of thumb, Mmax should be limited to ten times of Mmin, CIGR (2002). All the abbreviations
are explained in Figure 3. Further work will validate the model and find ‘U’ for real conditions. With
a set of known data ‘U’ an unknown scenario can then be assessed. Furthermore, depending on the
supplement heating and maximum air flow rate the energy consumption can be calculated for
comparison in the LCA stage of the work.
Figure 3. Model for mass balance of HVAC system in an animal farm
Life Cycle Assessment
After quantification of materials, LCA models for both the scenarios will be built. The functional unit
of the study requires further consideration, but could be: per m2 of building, per m3 of building or per
animal housed, assuming a building 19m x 4.8m x 4.6m providing animal shelter.
mi
Ventilation rate based on relative humidity
Wo mii
Ventilation rate to control CO2
CO2o Hot air Wi Absolute humidity of inside air
Wo Absolute humidity of outside air
Wi Wa Moisture production rate by animals
Cold air CO2i CO2i CO2 content of inside air
CO2o CO2 content of outside air
S CO2a CO2 produced by animals
Animal Wa Mmin Minimum ventilation rate , minimum of mi
and mii
.
CO2a Mmax Maximum air flow rate to prevent heat stress in summer
Hs Hs Sensible heat from animals
A Area of building fabric
Animal farm building U Thermal transmittance
HVAC Heating Ventilation and Air Conditioning C Specific heat capacity of air
S Supplementary heat during winter ∆T Temperature difference (inside - outside)

4. Results and Discussion
The numerical analysis with STAAD pro indicated the major quantities for each structure (Table 2).
Table 2: Final quantity of materials obtained from numerical model
Scenarios Major component Quantity (ton) Remarks
Steel Structure
Structural steel 2.665 LCA to be performed for
these materials in
accordance with the energy
required to produce
supplementary heat
GI sheet 1.203
Timber Structure
Timber frame 2.429
12mm Plywood 1.403
Limitations and future work
The gusset plate quantity and nuts-bolts were not considered. Also, the architectural aspects (Fuentes
2010) of farm buildings were not considered in the initial stage of the study. A survey of farms in
Ireland will be undertaken to collect data for stepwise validation with SPSS statistical software. A set
of random variables that could influence ‘U’ will be defined for the analysis and the regression will be
used to eliminate variables and to establish a co-relation between the input variables and the
dependant variable, ‘U’. LCA for the two scenarios will be used to assess environmental impact.
Conclusions
This study successfully calculated the quantities for the bill of materials of the flexible portion of a
standard farm building for animal housing. This is the first step required to model the thermal
properties and to use LCA for comparing buidling materials from an environmetnal perspecticve. This
will provide a basis for eliminating materials prior to further design steps. This analysis will be the
first step towards the optimization of energy for a net zero building concept. Estimation of total
carbon balance may be possible after completion of an analysis with LCA.
References
CIGR (2002) Climatization of Animal Houses, Heat and moisture production at animal and house
levels. DK-8700 Horsens, Denmark: International Commission of Agricultural Engineering,
Section II.
De Belie, N., Lenehan, J. J., Braam, C. R., Svennerstedt, B., Richardson, M. and Sonck, B. (2000a)
'Durability of Building Materials and Components in the Agricultural Environment, Part III:
Concrete Structures', Journal of Agricultural Engineering Research, 76, 3-16.
De Belie, N., Richardson, M., Braam, C. R., Svennerstedt, B., Lenehan, J. J. and Sonck, B. (2000b)
'Durability of Building Materials and Components in the Agricultural Environment: Part I,
The agricultural environment and timber structures', Journal of Agricultural Engineering
Research, 75, 225-241.
De Belie, N., Sonck, B., Braam, C. R., Lenehan, J. J., Svennerstedt, B. and Richardson, M. (2000c)
'Durability of Building Materials and Components in the Agricultural Environment, Part II:
Metal Structures', Journal of Agricultural Engineering Research, 75, 333-347.
Department of Agriculture, Food and the Marine, (2015). S.101: Minimum specifications for the
structure of agricultural buildings.
Fuentes, J. M. (2010) 'Methodological bases for documenting and reusing vernacular farm
architecture', Journal of Cultural Heritage, 11(2), 119-129.
Koesling, M., Ruge, G., Fystro, G., Torp, T. and Hansen, S. (2015) 'Embodied and operational energy
in buildings on 20 Norwegian dairy farms – Introducing the building construction approach to
agriculture', Energy and Buildings, 108, 330-345.
Monahan, J. and Powell, J.C. (2011) 'An embodied carbon and energy analysis of modern methods of
construction in housing: A case study using a lifecycle assessment framework', Energy &
Buildings, 43(1), 179-188.