This publication presents the calculation results for the
life-cycle environmental impacts of a typical Finnish
wood framed house, called 'standard house'. The
calculation results are also presented for three
alternative log house, with extensive use of wood and log
products in structures. The log house cases vary only in
their external wall log thickness.
The results take into account the emissions from material
acquisition, production and transportations, as well the
emissions from construction phase. The lifetime emissions
are considered in terms of materials for repairs and
renovations, and emissions from operational energy use
over a life-cycle of 50 years. Also, the energy use for
demolition and removal of demolition waste from site is
included in the assessment.
The results for the material production show that the
greenhouse gas emissions of log houses are 40% lower than
those of the standard house. Total GHG emissions for
standard house are 25 tonnes (in terms of CO2-equ),
whereas the emissions for log house scenarios are 15
The structures of log house cases store 3.8 to 4.2 times
the carbon of the standard house in their structures. The
standard house stores some 14 tonnes of carbon dioxide,
whereas the figures for log houses are 53 to 58 tonnes.
According to the results, the energy content of the
structures of log house cases is 2.6 to 2.9 that of the
standard house. Energy content of standard house is 270
GJ, and the values for log houses vary from 720 GJ to 800
The mass of standard house is 88 tonnes, while the total
mass of log house cases varies from 70 to 74 tonnes.
When the total lifetime emissions from material-related
sources are considered, the results show that the
greenhouse gas emissions of log houses are some 33% lower
than those of the standard house. Total emissions for
standard house are 39 tonnes (in terms of CO2-equ
emissions), whereas the emissions for log house scenarios
are some 26 tonnes.
The total material need over the 50-year lifetime of
standard house is 106 tonnes, while the material need of
log house cases vary from 81 to 85 tonnes.
The operational energy use of the log house cases of this
publication is higher than that of the standard house,
due to differences in space-heating energy needs. This is
caused by differences in U-values of external walls. This
results in a 10 to 19% higher carbon footprint of log
houses, when no crediting for stored carbon or bio-energy
are made. If the carbon storage is credited in the
calculation of the carbon footprint, the differences
between standard house and log houses diminish to a level
of 0 to 10%.When both bioenergy and stored carbon are
considered, the carbon footprint for standard house is
167 tonnes and for log house 200, 168 tonnes (CO2-equ).
For log houses 243 and 270, the figures are 150 tonnes
(CO2-equ), and 139 tonnes (CO2-equ), respectively. The
results show that when both bio-energy of side-streams
and structures and carbon credits are taken into account,
the carbon footprint of log house 200 is at the same
level as the standard house. The carbon footprint of the
log houses 243 and 270 are 10 and 16% lower than that of
the standard house.
This publication also studies the so called total energy
consumption figures, as defined in Finnish building
regulations. The figure for standard house is 166 kWh/m2,
and for the log houses 184 to 194 kWh/m2, when
calculation is done as stated in regulations.
Two alternative calculations of theoretical nature are
also made. Firstly, the bio-energy related to wood-based
structures and their side-streams is taken into account
by assuming this bio energy could be used to replace
heating energy use in the building. This is done by
assigning the energy in wood-based structures an
energy-type factor of 0.5, as in the Finnish building
regulations. The results show that with these
assumptions, the total energy figure for standard house
is 164 kWh/m2. For log houses, the figures vary from 176
to 187 kWh/m2.
Secondly, bio-energy is taken into account by assuming it
to be completely emission free bio-energy, thus using a
value of zero for its energy type specific factor. The
results show that the total energy figure for the
standard house is 159 kWh/m2. For log houses, the figures
vary from 156 to 169 kWh/m2.
|Place of Publication
|VTT Technical Research Centre of Finland
|Number of pages
|Published - 2013
|MoE publication type
|D4 Published development or research report or study
- environmental impacts
- log house
- greenhouse gas emissions