The drive to achieve to achieve zero carbon homes is a challenge for the
construction industry, but the advantages offered by timber construction will
play a central role in achieving these targets. James Walker, Technical
Consultant from the STA investigates.
According to the Committee on Climate Change (CCC), buildings account for
a third of the UK’s carbon dioxide emissions. The embodied energy associated
with the construction of buildings account for approximately 15% of the total
energy requirements, while heating and lighting through the life of the
building account for approximately 83% of the total energy requirements.
Timber is well suited to the construction of energy efficient buildings due to its inherent sustainability, low heat conductivity and high structural strength and boasts benefits such as:
- Low
embodied carbon
- A
choice of insulation
- Airtight
construction
- Proven
construction details with pre-calculated thermal bridging psi-values
- Minimal
waste
- Fast
construction
- A
supply chain choice
- Offsite
manufacture in a quality controlled environment
The STA is already leading the way to energy efficient timber construction using its Fabric First approach – this prioritises the insulation and airtightness of the external envelope to reduce the carbon emissions of the building before using more costly renewable energy or heating systems.
Improving the airtightness of a building involves sealing the complete
building envelope in an attempt to minimise draughts and air leakage, since
significant heat can be lost through the exchange of air between the inside and
outside of the building.
The insulation and airtightness strategy of any building must be combined
with a suitable ventilation strategy to ensure that fresh air is brought into
the building and humidity levels are controlled to avoid problems caused by
condensation. A high level of airtightness offers further opportunities for
energy savings by controlling the ventilation and transferring heat, through
the use of a mechanical ventilation and heat recovery (MVHR) unit, from the
stale air being exhausted from the building into the fresh air being brought
into the building.
Evidence suggests that it is also easier to achieve the predicted energy performance
when constructing with structural timber methods, due to the higher level of
offsite prefabrication inherent in this building method. This is particularly
the case for the performance of junctions, where work completed in the factory
allows for greater control of the building elements and ensures that the
junctions are considered during the design phase as a necessity.
It is not only easier to monitor quality in the factory environment, but allows
for the all-critical insulation to be positioned such that it is able to work
more effectively by minimising thermal bridges and thereby reducing the risk
posed by adverse environmental conditions.
Offsite construction ensures
quality that can be monitored at every stage, unlike other methods that are
reliant on a multitude of trades, with no interest in the next phase of the
build programme. Factory based activities allow better and safer working
conditions, while also protecting the workers from the changeable British
climate, which is more likely to lead to better quality work.
Joined-up Solutions
As well as the benefits of timber as a structural material and the offsite manufacturing processes available, the culture of the timber construction industry is already in a good position to provide zero carbon homes. The problem with the supply chain throughout the construction sector is that the build process can easily be deconstructed and fragmented in order to save costs, which means that the responsibility at each stage is passed on to a different person or trade without the correct knowledge of the material being used. Fundamentally, this problem comes down to a breakdown in communication.
A significant benefit of timber
construction is the fact that the timber industry already has a joined up
supply chain. Timber frame offers a high level of collaboration allowing a
totally integrated design, manufacture and erector supply chain, which provides
customers with a greater level of speed, efficiency and indeed quality every single
time. The big message here is that information flows between the client’s
design team and the timber system supplier ensuring that practical joined up
solutions evolve.
This also links with the adoption
of Building Information Modelling (BIM), which is something that will help to achieve
design continuity by monitoring and controlling changes during the construction
process through to handover; however BIM requires a significant amount of
upfront design and a high level of coordination which, for house building, may
not be a practical solution as yet.
While BIM is an ideal vehicle to
deliver efficiencies and compliments offsite construction, the timber supply
chain can work without BIM while it evolves. Joined up solutions are achieved
in the old way of communicating and taking responsibility for the envelope; if
the right people are engaged at the right time as part of the project team.
Education and Skills
The STA is committed to education and improving skills. We work with members to provide CITB backed tool box talks along with training for assembly teams, workshops on best practice, factory tours (designed to help educate the entire supply chain) and advice notes on design, technical and quality assurance.
In 2013, the STA recognised the
need to both up-skill and train more timber frame erectors – as a result, a
mentoring and training programme was developed to improve the skills of its
erector member companies. The STA
rightly identified that its erector members required a significant amount of up-skilling
to take advantage of the upturn in the construction market as well as the
increasing popularity of timber as a construction material. This proved to be very
successful and is something that continues to roll out further.
The STA offers a suite of advice notes that help members to understand
the basics of constructing energy efficient homes and meet the required
performance targets:
- STA Advice Note 6.1 Fabric first
approach to thermal performance.
- STA Advice Note 6.2 Information for
house builders addressing Part L 2013 updates for new dwellings.
- STA Advice Note 6.3 Structural timber
solutions to deliver advanced fabric energy efficiency (September 2015).
With the price of energy continuing
to rise and pressure being placed on ever shrinking family budgets, a
building’s operational performance will inevitably become something that
consumers will focus on more in the coming years. When people understand the
value of a truly efficient home and appreciate that they are getting a better
product, they will be prepared to pay for it and they will start to demand it.
For more information and technical information visit:
www.structuraltimber.co.uk
