1.6 Knowledge of modern construction techniques such as prefabrication. Flashcards
Can you tell me about some modern construction techniques that you are aware of?
Cross-laminated timber
The benefits of cross laminated timber are numerous –
from reduced loading on foundations and infrastructure
services (due to its high strength-to-weight ratio), to
impressive acoustic and airtightness performance. Most
importantly, a CLT construction solution provides cost
and programme certainty, and programme improvement.
CLT is manufactured offsite, allowing exceptional levels
of precision, thus ensuring minimal defects. Improved
construction and project delivery timescales lead to
reduced costs and maximised efficiency on all levels.
With cost and time certainty being a crucial factor in all
commercial projects, the use of cross laminated timber
significantly reduces risks, as it is manufactured in
controlled factory conditions.
Generally speaking, building in CLT costs around the
same as concrete (taking into account material and build
costs). However, cost savings are made up in areas like
logistics where the offsite construction methods mean that
considerably fewer deliveries are needed. Furthermore,
the reduced weight of CLT results in lower groundwork
costs, and the fact that it is weight saving (around 80%
lighter) means lightened foundations, and reduced
amounts of piling, allowing buildings to be built on what
would otherwise be considered poor ground conditions or
complex sites.
Modular construction and build-to-rent -
accelerating house building
Modular construction has been recognised for its ability
to help solve the problem of a lack of housing available
within the UK, designing and building high-quality pre-built
homes at a faster rate.
The construction industry often faces delays caused
by numerous factors, including lack of labour, or
weather conditions that halt or slow down construction
onsite. Modular housing provides a solution to those
problems. Building offsite within a controlled factory
environment minimises risk, resulting in a faster build
programme, assured quality control and enhanced
build performance standards.
From increased energy efficiency to reduced build time,
factory-built modular homes can be designed with both
occupants and the environment in mind, making modular
housing solutions increasingly popular.
But for modular housing to become a scale solution to
the housing crisis, a number of significant obstacles need
to be overcome. Noble Francis, Economic Director at the
Construction Products Association, says:
What Are SIPs?
Structural Insulated Panels are rigid panels of foam or polystyrene insulation, that have been sandwiched between Oriented Strand Board (OSB). They come as prefabricated boards that can simply be slotted together, to create the entire structure of your new home.
They can be used for both the walls and floors of the home, and are considered to be an excellent choice when it comes to insulation and acoustic barriers.
SIPs offer a structural element, due to the closed cell structure of the foam. They are highly rigid, and, therefore, can offer more flexibility when it comes to the design of the building.
There is less need for additional structure and beams when using this material. However the quality of the OSB is important in achieving the standards required in UK homes.
They have been used across the US for around 30-40 years, but have only become popular in the UK in the last 10 years, as the need for well insulated homes has become more apparent. They are usually clad on the outside the home with brick or sometimes render, to ensure that the insulation remain entirely dry.
What do we mean by sustainability in construction?
The practice of creating structures and using processes that are environmentally responsible and resource-efficient throughout a building’s life-cycle from siting to design, construction, operation, maintenance, renovation and deconstruction.
How can you affect sustainability whilst on-site?
Ensuring
Can you identify some sustainable heating options?
Insulation
Pros: Insulation will cut energy bills, but big investments such as high-quality windows, doors, or external-wall insulation will take many years to pay back – decades in some cases. If you can afford it, the added comfort is worth it in my view.
Cons: Apart from the upfront cost, the biggest obstacle is disruption and mess. One way of minimising this for internal-wall insulation is to do it room by room when decorating.
Smart controls
Pros: Smart heating controls will pay back fast (within 5 years).
Cons: Can’t think of any.
Ground-source heat pump extracts heat from the ground, so requires a garden for a trench. It is more expensive than an air-source heat pump, but also more efficient and quieter.
Electric radiators
These radiators use electricity to provide you with heat when you need it. They are cheap to buy and fit compared to the options above. They might cost less than a new gas-fired boiler. Many will be programmable and have smart controls.
Give examples of sustainability e.g. renewables
Example of sustainable materials are bamboo; wood; hemp; wool; linen; straw; clay, stone, sand; beeswax; and coconut.
What are Eco Homes Standards?
The Code for Sustainable Homes (the Code) was introduced in England in April 2007 as a voluntary national standard to improve the overall sustainability of new homes by setting a single framework within which the home building industry can design and construct homes to higher environmental standards. Where it is used the Code also gives new homebuyers information about the environmental impact of their new home and its potential running costs.
Energy and CO2 Emissions • Water • Materials • Surface Water Run-off • Waste • Pollution • Heath and Wellbeing • Management • Ecology
How does sustainability affect construction technology?
Encourages more creative solutions to meet targets. Such as Green roofs, ground heat pumps
What is BREEAM and how does it work?
BREEAM (Building Research Establishment Environmental Assessment Method)
Points System
BREEAM is an assessment undertaken by independent licensed assessors using scientifically-based sustainability metrics and indices which cover a range of environmental issues. Its categories evaluate energy and water use, health and wellbeing, pollution, transport, materials, waste, ecology and management processes. Buildings are rated and certified on a scale of ‘Pass’, ‘Good’, ‘Very Good’, ‘Excellent’ and ‘Outstanding’.
Give me some examples on how you would achieve sustainability in a building
BMS systems,
Insulation,
Carbon neutral materials, Cross-laminated timber
Green Roof
Do you know anything about environmental implications on dwelling projects?
The practice of creating structures and using processes that are environmentally responsible and resource-efficient throughout a building’s life-cycle from siting to design, construction, operation, maintenance, renovation and deconstruction.
What can you tell me about sustainable development?
The practice of creating structures and using processes that are environmentally responsible and resource-efficient throughout a building’s life-cycle from siting to design, construction, operation, maintenance, renovation and deconstruction.
In terms of sustainability give an example of a material that is a finite resource
Steel.
What are the different types of off-site construction methodology
Prefabrication
modular construction
What are the benefits and disadvantages with off-site construction
Advantages of modular homes:
Strong structure.
Modules that make up a building are more durable than those built traditionally. Prefabricated houses not only have to meet design requirements, but also withstand transport loads.
Shorter construction time.
A small modular house can be build in less than two months at the factory. The reason is automation, greater repeatability, greater teamwork. Assembly on the construction site is usually a few days.
Higher quality of the building.
The reason is much more detailed shop drawings of modular homes than in the case of traditional houses. Modular houses usually have every detail elaborated. Also a definitely higher health and safety level in the factory will increase quality of work.
The speed of implementation.
Shorter investment time means lower costs for any investor. There is no need to rent social rooms for employees at your site. If you you are renting a flat now, you will pay less for rent by moving into our home earlier.
Acoustics.
Acoustics of modular homes is much better than houses traditionally built. In traditional homes, sound propagates through the construction of walls and ceiling. That is why floating floors are often used to suppress noise. In prefabricated houses, each module is a separate construction. The modules connected together in the house are protected from transfering noise from one to the other.
Lower risk of damage.
Significantly lower risk of theft and damage caused by third parties. The theft most often occurs when the house is not yet adequately secured. Theft of building materials and equipment can be made by labourers working on your construction site. If you are building a house traditionally and wondering why you ran out of tiles, theft may be the cause.
Contractor’s benefits.
Modular homes also benefit your contractor and his employees. Employees who build a house in a factory do not have to waste time on long travels to construction area. They do not have to work in cold or in rain conditions. They have more comfortable working conditions in factory. They can also spend more time with family and friends. A satisfied employee is a good employee. If you want your home to be made by good professionals, the biggest chance for it is to choose modular technology.
Price.
Price is probably the most important advantage. Modular homes are not at all more expensive than traditional ones. I can not guarantee 100% that modular homes are always cheaper. It all depends on your design, material requirements, location, etc.
Disadvantages of prefabricated houses:
Lifespan.
The most common modular homes are timber frame constructed. It is a popular technology in Scandinavia and North America, but it is not widely used in central Europe. In Poland many people think, that brick houses are long-lasting and timber made houses not. Everything depends on the performance and manner of maintaining home, but the feelings are right.
Read my post about the lifespan of building materials. I did an analysis base om manufacturers’ recomendations. Most brick manufacturers declare durability of their products for over 100 years. Manufacturers of wooden frame walls declare 50–100 years. Of course, there are wooden buildings that are hundreds years old, but they are properly maintained and protected from fire.
Compare two abandoned houses — one wooden, the other brick. Which one will deteriorate quicker? The external walls of both houses could be protected by plaster and paints, and could be resistant to weather conditions. After a few years the windows in both houses were destroyed, and the roof would began to leak. After the next few years, in a brick house, water would destroy plaster. In a wooden house, water would not only destroy plaster, but also timber slab and walls would began to rot.
Shorten lifespan does not apply to concrete modular homes. In this case we can talk about identical lifespan as in brick houses.
Heat accumulation.
Timber houses are much lighter than masonry houses, so they do not keep warm and cool down quickly. This is a big drawback. Most central heating installations operate during the day and are switched off at night. In a modular timber house, we can’t afford it. In the event of any interruption in the heating operation, the house will get really cold.
Prefabricated houses with timber frame technology will not accumulate heat gains from the day.
If you plan to build a passive house, forget about building it in timber frame technology. Passive houses require high heat accumulation.
From the other hand concrete modular homes have high accumulation value, but concrete itself has very high conductivity. This means requires very thick insulation to avoid high heat losses.
Fire resistance.
The walls and ceilings of timber made modular houses have only 1 hour fire resistance. In brick houses, usually two hours. In addition, wood is a combustible material. Concrete and brick are non-flammable. The more we use non-flammable materials in the construction of our house, the lower the losses in the event of a fire.
Construction limitations of prefabricated houses.
This is not a big drawback, because you can, for example, combine several modules together to form one large room. Sometimes when you plan to have bigger / higher rooms, it may be more cost-effective to make prefabricated walls only.
How is living in modular homes?
Prefabricated modular houses have a lot in common with timber frame houses. Most reviews of prefabricated frame houses that I found on the internet are positive.
People exchange such advantages as delivery time, quality, reasonable price, less risk of theft.
I found a negative opinion of a person who thinks that modular homes lose value faster than brick houses … Considering lifespan of wooden houses compared to masonry, this is a good point.
In my opinion modular houses soon can become very popular, but first manufacturers should deal with all the shortcomings that these houses have.
The solution may be modular houses made of light weight concrete with very low thermal conductivity. This way modular house would have all positive parameters of house of brick, what is people really want.
Can you tell me about the advantages and disadvantages of SIP construction
Advantages Of SIPs
● Structural Insulated Panels are very strong, due to the way they are made. The composite nature of the foam core and outer OSB means that they are more rigid that each of these elements on their own. In fact, it is considered to be up to 6 times stronger than a simple timber frame.
● SIPs are flexible, as they can accommodate greater spans of walls than standard construction. For walls, a maximum height of three storeys is allowed, while floors that are 200mm thick can span 4 metres. Clearly this means that homes and rooms can be built larger and with more open space.
● Structural Insulated Panels can be manufactured off-site, and simply craned into place. This means that building a house with SIPs is less costly, and takes far less time overall than standard construction methods.
● SIPs are made from foam, and, therefore, are not prone to infestation from pests. They are also highly fire resistant, and have been tested to offer 73 minutes of resistance – this exceeds British Fire Safety Regulations.
● When it comes to thermal performance, Structural Insulated Panels are a good option. They have been tested to outperform fibre insulation, and offer a R-value of around 11 for a typical installation when installed correctly.
Disadvantages Of SIPs
● Homes built with SIPs require additional ventilation, due to the way that heat is trapped inside the house. This means vents and extractors must be used to prevent the buildup of condensation, and possibly mould that could actually damage the panels.
● Once you have decided on the design of your Structural Insulated Panels home, there is not much room for changes to be made. The panel will be prefabricated and sent to site – you may be able to change the internal layout, but the outside design will be set.
● SIPs are still relatively new in the UK, and, therefore, finding professional builders with experience can be tricky. In many cases, there are long waits for competent builders, or teams of builders must come from the EU.
● Services such as electricity can sometimes be added to the walls as they are constructed, but usually, they run between the SIPs, and the internal plasterboard, which must be added with an internal cavity. This is an additional layer that is not necessarily needed, and will add to the overall cost.
● If your Structural Insulated Panels become wet, they will start to degrade very quickly, and the outer wood can rot, causing the composition to de-laminate. This will destroy its ability to offer both structure and insulation to your home.
● The thermal ratings may look impressive, but it is important to take into account thermal bridging – ie the gaps that occur between the panels. The process of installation can never be perfect, and additional insulation is often used to ensure a tight seal.
● The fact that your home has a tight seal means that it needs to have additional airflow sources. If not, the internal walls can become damp, and even mouldy. This dampness can destroy the panels, causing them to breakdown, and require replacement.
● Structural Insulated Panels has a lifetime of around 60 years – although this is yet to be fully tested, as they have only been in use for 3 decades. This will significantly lower the lifetime of your home, and may mean that it will need to be rebuilt or adjusted in some way to remain liveable.
