Transcript Sustainable construction

Sustainable Construction
3A9
Construction Technology
Dr S Pavía
Dept of Civil Engineering
Trinity College Dublin
Sustainable Construction
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Sustainable development
Life Cycle Assessment
Sustainable building materials
Sustainable construction
Energy
Passive house
BER Certificate
Retrofit - Improving the energy efficiency of a house
Energy efficiency in historic buildings
Sustainable Development
• Meeting the needs of today, through the prudent use of natural
resources - not compromising the ability of future generations to
meet their own needs.
• Getting the balance right between the economy, social issues and
the environment
• A balance must be achieved between the rate of resource use and
the rate at which renewable materials can regenerate.
• A building designed and constructed in a sustainable
way minimizes the use of water, raw materials, energy,
land, waste and pollution over the whole life cycle of the
building from siting to design, construction, operation,
maintenance, renovation, and demolition.
• The building industry is in the midst of rapid change toward more
sustainable design and construction.
Reasons for Sustainable
Development
• Global warming, resource depletion etc.
• The built environment is responsible for 40% of global
CO2 emissions, 40% of solid waste generation and up to
40% energy use (Ki-moon et al. 2007).
• In 2008, construction and demolition waste in Ireland
totalled 16.8 million tonnes, which represents 54.8% of
the total waste generated.
• In Ireland in 2008, 26% of the primary energy demand
and 27% of CO2 emissions can be attributed to the
residential sector.
Building Life Cycle Assessment
technique to assess
the environmental
impact of a building
over the course of its
entire life
viewing it as an
operational building
plus considering its
life starting with the
extraction of raw
materials
tracing all operations
until its final disposal
as waste (cradle to
grave).
Energy
Embodied energy of a
building is the energy
used to extract, process
and refine all its building
materials
as buildings become
more energy efficient
in their operations, the
embodied energy can
approach half the
lifetime energy
consumption.
The operating energy of a
building is the amount of energy
that is consumed by a building
to satisfy the demand for
heating, cooling, ventilation,
lighting, equipment, and
appliances
Passive House
• very low energy buildings - require little energy for space
heating or cooling.
• built to the Passivhaus standard for energy efficiency.
• a comfortable interior climate is maintained without active heating
and cooling systems.
– heated from a combination of passive sources including solar gain, background
heat emissions from appliances and even the occupants.
• the U-values of the exterior building components range between
0.1 and 0.15 W/m²C and the total energy provided for space
heating does not exceed 15 kWh/m²/yr
• some of the key components of a passive house include southern
orientation, high levels of insulation, triple glazed windows, air
tightness, heat recovery ventilation, cold bridge elimination and
energy saving appliances.
• mostly applied to new building-can be suitable for refurbishments.
Passive House
• Advantages
– Very low (if any) operational energy requirement – cost efficient
– Increased interior comfort
– Beneficial to the environment
• Disadvantages
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Condensation on interior glazing
No traditional fireplaces
No noise from nature
Higher construction costs
Building materials may have high embodied energy
Sustainable Building Materials
• To minimise environmental impact of building materials:
– use reusable, recyclable, biodegradable materials that can
be removed/salvaged
– use renewable resources i.e sustainably harvested woods
– materials must not emit volatile organic compounds or
other toxic compounds
– must be maintained with non-toxic cleaning
materials/methods
– avoid high embodied energy materials
– minimize environmental impacts of raw material acquisition
(strip mining, dredging, etc.)
– minimize packaging and transport
– use durable materials-suitable for the intended application
Sustainable Building Materials
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Vernacular Building
Straw Bale Construction
Cob/Adobe/Rammed earth construction
Hemp Lime Construction
Sustainably harvested timber –timber frame construction
Building Limes
Recycled Material
Others including bamboo, cordwood, stone, wattle and
daub etc
Sustainable Construction
Vernacular architecture
• Built from locally sourced
materials –traditional design
and methods of construction
• Thatch roof
• Mud / stone walls
• Timber doors and windows
• Maintenance is key
• In Europe, some have
survived over 300 years
Lime Vs Cement
• One ton of ordinary Portland cement (PC) requires about 2.8
tons of raw materials such as limestone and coal, and
releases about 0.7 tons of CO2 to the atmospheredecarbonation of lime in the kiln
• The amount of annual emissions of greenhouse gases (GHS)
from the worldwide production of PC is around 1.35 billion
tons which corresponds to approximately 7% of the total GHS
emissions
• The use of lime-based mortars declined during the 20th
century due to changing market demands and the move
towards cement based products - speed of construction and
fast strength gain.
• Current revival in the use of lime-based mortars. Lime is
suitable for many applications that currently use cement
mortars.
Lime Vs Cement
• Lime also contributes to consumption of raw materials and
release of green house gases but
– reabsorbs a large proportion of CO2 released during
burning
– Lime is burnt at lower temperature and therefore requires
less fuel
– easier to reuse masonry units bonded by lime after
demolition
• Hydraulic limes and pozzolan can be used to speed up
setting and strength development.
The 27 members of the family of cements
• new products have emerged with a lower
environmental impact
• replacing a proportion of cement with waste
materials such as pulverised fly ash (PFA) or
ground granulated blast slag (GGBS)
• EN 197-1.
Recycled Materials
• In 2008, construction and demolition waste in Ireland totalled
16.8 million tonnes which represents 54.8% of the total waste
generated.
• 89% Recovery of stone and soil but the recovery rate for the
remainder (concrete, steel, wood, plastics, etc) was only 35.8%
• In order to reduce the waste generated, design for
deconstruction or demolition must be included in the project
planning
• The use of construction materials which can be recycled
should be maximized (e.g. recycled aggregate –tyres, crushed
ceramics/concrete).
• Need to consider energy required in processing, transportation
etc.
Recycled Materials
Some unconventional building
materials – wood pallets, tires and
scrap metal!
BER (Building Energy Rating) Certificate
• Designed to provide the purchaser or tenant with
information about the energy efficiency of a particular
building.
• Compulsory for all homes being sold or rented from the
1st of January 2009
• Valid for 10 years from the date of its being issued
• BER assessments are carried out by SEI registered BER
assessors
• An advisory report must accompany a BER certificate
– to advise owners of new buildings on how to use the features in
the building to maximise energy efficiency and
– to advise owners of existing buildings on the options for
upgrading of building to maximise its energy efficiency
BER Certificate
• It is a standard calculation of the energy performance of a building,
made using a computer software: DEAP software – Dwelling Energy
Assessment Procedure.
• The BER measures energy use per square meter (floor area) of the
dwelling per year.
• Similar to energy rating on appliances.
• BER scale (kWh/m2/yr) A1,A2,A3,B1,B2,B3 to G. Each band
equates to 75 (kWh/m2/yr - A dwelling built to the 2007/08 building
regulations should achieve a B or C rating
• CO2 emmision indicator (kg/m2/yr)
• The DEAP is a theoretical procedure whereby relevant details
describing the home are input into the program and an energy rating
is then computed.
• The assessor must carry out a building survey to record: insulation
levels; window types; ventilation features; air-tightness; details of
the building services systems (heating, hot water, lighting, etc.).
BER Certificate
• The DEAP (as well as most computer based simulations)
considers building features including insulation levels,
window performance, ventilation and efficiency of
heating and lighting systems. However, it does not
incorporate any factual measurements (field data).
• As a result, these theoretical values may not correspond
to reality.
• Also, it does not take into account the energy usage
behaviour of the occupants (the calculation methodology
makes certain assumptions about how the users of any
particular building would use hot water, heating, lighting,
etc).
BER Certificate
BER Certificates contain the
following information:
•The BER rating for the
dwelling/building ie B1
•The address of the building.
• The BER Number.
• The date of Issue
• The date the BER is valid
until.
• The BER Assessor Number.
• The Assessor Company
Number.
• The rating of the dwelling.
• A Carbon Dioxide (CO2)
Emissions Indicator.
Ireland’s Building Stock
• Estimated 1.46 million permanently occupied dwellings at
the end of 2006 of which 930,000 houses were built
before the building regulations were introduced in 1991
– 350,000 have no wall insulation
– 200,000 houses have no roof insulation
– 350,000 houses have single glazed windows.
• In 2006, the residential sector accounted for just under a
quarter of all energy used in Ireland and, after transport,
it was the second largest energy using sector.
• The sector was responsible for 25% (11,896 kt CO2) of
energy related CO2 emissions.
Retrofitting
• Retrofitting buildings to high energy standards offers the
cheapest, most readily available source of carbon and
energy savings in Ireland.
• constructing new buildings is generally more expensive than
retaining and re-using existing buildings.
• re-use of buildings is better for the environment.
• Upgrades can pay for themselves in energy cost reductions
• The retro-fit market is growing. SEAI approve on average
over 50,000 applications for grants per year.
• Grants available
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wall insulation
roof insulation,
high-efficiency gas- or oil-fired boiler
upgrade of heating controls or installation of a thermostat.
Retrofitting - Energy Loss
Retrofitting
Case study by Historic Scotland : two bedroom
cottage situated in the border region of Scotland.
Retrofitting
Retrofitting
Retrofitting
• Prior to undertaking any work
• A detailed survey of the building to be retrofitted is an
important basis for a good low-energy design.
• An inspection opening may be necessary to identify the
construction type.
• Data on energy consumption and comfort levels of
occupants should indicate the thermal performance of
the building
• Air Tightness Testing of Domestic dwellings (IS EN
13829:2000) will ascertain the level of airtightness and to
where cold air may infiltrate the building
• Infra-Red Thermography can also be locating weak
points in the thermal envelope
Retro-fitting
Thermal Imaging
•blue areas are
coldest and
therefore show the
lowest heat loss
•red and yellow
areas are those
with highest heat
lost
Retrofitting
• Insulation – walls, roof, floor
• Upgrade windows and doors to more thermally
efficient alternatives
• Improve airtightness
• Minimise thermal bridging
• Heating, Ventilation, Cooling, Hot Water and
Lighting Systems (not considered in this lecture)
• Pay-back periods - how long it takes to recoup
initial costs
Retrofitting - Insulation
• Thermal insulation provides thermal comfort for occupants, reduces
unwanted heat loss or gain and can decrease the energy demands
of heating and cooling systems
• Low U value material –see U value calculation
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durability and fire resistance
vermin and rodent resistance
settling resistance
processing and / or chemicals involved in their manufacture
• Types of wall insulation
– Internal Insulation
– External Insulation
– Cavity Insulation –see cavity wall construction lectures.
Retrofitting – Wall Insulation
Considerations for internal and external insulation
Internal Insulation
External Insulation
Room size reduced
Exterior appearance altered
Room heats up quickly
Heat energy is stored in the mass
of the wall
Redecoration and refitting of lights, Can’t be installed in poor weather
radiators etc
conditions
Thermal bridges ie at
external/internal-wall-junction
No thermal bridges
Risk of interstitial condensation
Improves air tightness
Retrofitting-Roof Insulation
• Insulate roof pitch or floor of attic
• Allow for ventilation
Insulation between and over
joists
Insulation above and between
rafters
Retrofitting - Floor insulation
• Floor constructions are difficult to upgrade because most
often the finished floor level cannot be changed
– 1. Suspended floors - insulating between the joist
– 2. Concrete floor slabs with a screed finish – take off
the screed and insulation and exchange the existing
insulation with a better performing insulation.
Construction of
SOLID GROUND
FLOORS
• Thermal insulation (above or
below concrete slab) is
introduced to reduce heat
loss into the ground.
• A damp proof membrane
needs to be located either
below the screed or below
the concrete slab, preferably
not lower than the ground
adjoining external wall- if
lower, vertical DPC required.
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– Bed of hardcore
– Concrete slab
– Cement and sand
screed
– Floor finish
– DPM
– Thermal insulation
I Seeley 1995
Ground
surface to
be
covered
with a
layer of
concrete
not less
than 100
mm thick
EN 5328,
or
Concrete
oversite
not less
than 50
mm thick
laid on
polyethyle
ne sheet
with the
joints
sealed.
Suspended timber joisted ground floors
Ventilated air space above the concrete surface
(not less than 150 mm).
 I Seeley 1995
Thermal insulation of
suspended timber floors
• Quilt insulation:
supported
between the
joists by drapping
polypropylene
netting or other
plastic mesh
across the joists
and stapling it to
joist sides.
Homebond 2005
• Rigid insulation batts (rigid slab materials):
supported on battens or fillets nailed to the sides of
joists.
• Avoid draughts at the junctions with walls.
Homebond 2005
JS Foster 1994
• Insulation products fall mainly into three classes:
– Mineral derived – mineral wool, glass wool,
vermiculite, cellular glass
– Oil-derived – rigid cellular plastic foam insulations polyurethane (PUR), polyisocyanurate (PIR),
phenolic, polystyrene
– Plant/animal derived – hemp, cellulose, cotton, flax,
sheep wool, cork.
• Consider- health and embodied energy
2012, Constructii Case Ecologice
Sheep wool 2013
Ecowise 2013
Retrofitting - Airtightness
• The airtightness of a dwelling, or its air permeability, is
defined as the flow of air through gaps and cracks in the
building fabric.
• Expressed in terms of air leakage in cubic metes per hour
per square metre of the dwelling’s area when the building is
subjected to a differential pressure of 50 Pascals
(m3/(h.m2)@50Pa).
• Uncontrolled air leakage increases the amount of heat loss
as warm air is displaced by colder air from outside.
• Air leakage of warm damp air through the building structure
can also lead to condensation within the fabric (interstitial
condensation), which reduces insulation performance and
causes fabric deterioration.
Retrofitting - Thermal Bridges (cold bridges)
Thermal bridges are points in the building envelope that
allow heat conduction to occur between the interior and
exterior of the building- thermal bridges contribute to
poor energy performance.
Thermal bridge are caused by the use of materials with a
higher thermal conductivity or non insulating materials
inserted in the fabric e.g. structural metal beams or
aluminum window frames without thermal break
Infratec. De 2008
Retrofitting – Thermal Bridge
Viking House 2013
Typical thermal
bridges are
caused by the
building structure:
• at the junction
of walls and
floors,
• at the junction
of walls and
roof,
• in the corners
or around
windows/doors
if they are not
properly installed.
Retrofitting - Vapour Barriers
• A vapour barrier is an impermeable membrane that
blocks the flow of air and water vapour through the
building envelope protecting the structure from
condensation damage.
• As water vapour from the inside of the building moves
outward through a wall on a cold day, it encounters
progressively lower temperatures.
• At the point in the wall where the temperature of the air
equals the dew point, the vapour starts to condense, and
it keeps condensing from that point outward
• Condensation damages the wall materials and reduces
the effectiveness of the insulation.
Timber frame construction elements
• Internal lining-gypsum
plasterboard
• Vapour barrier. Vapour barriers
• I Seeley 1995
must be installed on the warm side of
the insulation
• Structural timber frame of vertical
studs with sheathing board
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(plywood or other wood material
nailed to studwork) and breather
membrane attached.
Incombustible insulating quilt.
Breather membrane to keep
rain/draught out allowing wall to
breathe.
Cavity
External cladding
I Seeley 1995