Architectural design

Modular construction

Different approaches in different countries

Modular construction is seen by the group as an opportunity to reduce the construction time, have a better control on the building process and reduce the construction cost.

There was the need to discuss this topic to face the challenge of building big amount of housing in little time and with less skilled workers on site

Some experiences have been shown at different TG meetings. A specific workshop was also arranged with external speakers and an interesting debate.

A first discussion on the topic was carried out in Brescia in October 2017, where three approaches where presented and then analyzed by the group.

Different approaches

  • Lindbäks: those are wooden construction modules prefabricated, that are constructed off-site and then assembled on site in different modalities (several modules are available). Modules comes to the building site already “finished”. The vantage of this system is the speed of construction (about 20 weeks from the beginning of design to the delivery) and the cost reduction.
  • Space models: it’s a German concept consisting in prefabricated concrete modules that are produced off site and assembled in the building site. The project is meant to reach a good architectural level with simple elements to be assembled.
  • Brix system: it’s a wooden based module for construction. It’s meant to be a quick system to build housing even by the occupants themselves. They are light weight elements, assembled with metal ware and can be insulated both on the inside or outside face. They can help reach a very high thermal performance since the wood helps to reduce thermal bridges.

The three systems above mentioned have been studied in a specific workshop. The outcomes are:

swedish approach

MODULAR CONSTRUCTION EXAMPLE 1 – SWEDISH APPROACH

POSITIVE ASPECTS:

  • Local material use
  • Low cost
  • Positive social impact (Work for people in the country side)
  • Possibility to configure different modules
  • Low embedded carbon
  • Actually being delivered on ground
  • Good energy performance
  • Purchase-deal very clean and simple
  • Speed of construction
  • Good for big buildings
  • High prefabrication level

CRITICAL POINTS:

  • Basic architectural quality: a cost/design optimization would be interesting
  • Durability
  • Transportation
  • Acoustic topic
  • Space required to stock components
  • Technical aspects of the modular construction are not very flexible
  • Critical where the wooden construction meets the plaster façade
  • “all inclusive”
  • what kind of debate with tenants?
  • How to connect the modules?
  • Seismic behaviour (there is not a resistant “core”)

REPLICABILITY IN YOUR COUNTRY:

  • Germany: problem with transportation, but positive inputs (wood, sustainable)
  • UK: need to use it in the single housing
  • F: fire codes could be an issue, but probably replicable
  • I: Possible if structural problems are solved

OVERALL SCORE (1 MINIMUM  TO 5 MAXIMUM): 3.6

german approach

MODULAR CONSTRUCTION EXAMPLE 2 – GERMAN APPROACH

POSITIVE ASPECTS:

  • Local Material
  • Replicability
  • Speed and cost
  • Possibility to configure modules and have different levels of prefabrication
  • Concrete gives a lot of possibilities
  • Supposed design flexibility
  • Possibility to add architectural quality
  • High mass of the envelope

CRITICAL POINTS:

  • Very important the architectural design and the cost/design optimization (risk to look bland)
  • Concrete is not well accepted
  • High potential for thermal bridging
  • High embedded carbon
  • Space required for storage
  • Still a lot of details to develop
  • Not easily dismountable
  • Seems costly
  • Seismic behaviour is not very clear
  • High weight can influence negatively the CO2 balance

REPLICABILITY IN YOUR COUNTRY:

  • UK: if possible to use it in single housing. Problem with the concrete
  • S: hard to say
  • I: Possible if structural problems are solved

OVERALL SCORE (1 MINIMUM  TO 5 MAXIMUM): 2.8

italian approach

MODULAR CONSTRUCTION EXAMPLE 2 – ITALIAN APPROACH

POSITIVE ASPECTS:

  • Quick and easy
  • Flexible
  • Fast
  • Cheap for simple standard
  • Very inspiring
  • Good thermal study and energy behaviour
  • Renewable material
  • Good for catastrophes and refugees
  • Dismountable
  • Good seismic behaviour

CRITICAL POINTS:

  • Complicate in case of higher expectations (thermally, constructional, financially)
  • Differs from local Italian tradition (wood)
  • Tightness of junctions
  • Contact to the ground
  • Still to develop details/technical solutions and to be tested in real building before to proceed with massive replication
  • Cost are still not well clear
  • Think about a massive production with carbon fibre
  • Not sure about long term behaviour, wood is a “living” material, could have some movements during the time
  • High level of manual work during construction could lead to high price

REPLICABILITY IN YOUR COUNTRY:

  • Germany: better for areas with environmental disasters, holiday homes. Maybe with other materials than wood
  • UK: quite possible, looks scalable from individual homes to large buildings
  • S: wood is a common building technique in Sweden so good possibilities
  • F: yes although wood is usually a “premium prize”
  • I: hopefully

OVERALL SCORE (1 MINIMUM  TO 5 MAXIMUM):  3.6

After the first round of discussion a big interest was raised and it was decided to go deeper into the topic. For this reason another meeting was organized in Västerås, inviting some big companies and experts for a lecture.

Construction sector and prefabrication

A lecture was held by Jerker Lessing (director R&D at BoKlok). Jerker said that productivity in construction sector has not been raising in the last 50 years, while the rest of industry grew 2.5 times. A reason of this phenomena is also the little competition in the constructing sector. Buildings today are more complicated, and there is still big potential of innovation. This means have the opportunity to make more profitable the construction.

The gap between construction sector and other sectors productivity could be filled thanks to industrialized construction.

What is industrialization? Industrialization doesn’t mean only to move the production from the site to a factory. It involves a series of different innovation such as:

  • Digitalization: it should be very connected with the construction itself
  • Standardized technology:
  • Automation
  • Building System: you can prepare platforms
  • Standardized processes
  • Prefabrication
  • Materials handling
  • Factory production
  • Assembly: building site should be more the “final assembly” in a longer production system

All those topics are not new, but all of them must to be put together in order to work together.

It’s also important the re-use of experience and measurements: you must learn from the previous experience.

eurhonet whitebook

We should take inspiration from other industries, for example the concepts of “Platform” and “modularization”. This takes a lot of time of course, but we can translate the approach also in the building sector. This means to divide the building into modules and components. Instead of “project unique design” using the “project configuration”: using some available components to assemble the product. In the end this brings to a faster and more detailed process.

We have two different platforms in a company: development of technical platform and development of process platform. Each project can take inputs and provide new inputs. It’s required a continuous flow of information. Thank to this approach you can improve and get to some “versions”, every time you improve by steps your platform.

There is a little “conflict” between flexibility and predictability: flexibility is maximized with low level of platform development, predictability increases with development of the platform. There is also a correlation in costs: more flexibility means higher costs. As property owner you can decide in which “level” you want to go for each building. This is not possible for the platform owner who has to decide about which level they want to stay.

For the homes owners it’s very important to know very well the customer segments. What customer are you aiming for? (what do they prioritize, what can they pay, demography, etc….).

We’d better to clearly identify the cost limits and find the balance with the right quality.

Once you’ve done that you can decide the level of flexibility and predictability you want to achieve and so you can choose the potential supplier.

The aim should be to establish relations beyond a singular project as doing so you can make it easier and refine the approach, so you can do it better from one time to the next.

Industrial Approach: Accord offsite manifacture

Industrial Approach: Accord offsite manifacture

eurhonet whitebook

There is an interesting experience in the Eurhonet group, that is the Accord Offsite manufacture that was presented by Chris Handy. The Accord group is settled in the middle of England, the area of industrial revolution. In this area there was a high unemployment rate so there was political pressure to provide jobs.

Accord was already used to work with offsite manufacture system since 12 years before. The supplier where then from Scandinavia.Accord decided to adapt the Scandinavian scheme to the UK market. In 2011 they opened their own factory, with the support of the Walsall Council. From that moment they started building 5000 new homes per year. An example of the homes they produced are the so called “Low Carbon Living”. They can produce 1.5 homes of this kind per day. It’s a panelized system, with a timber frame. The aim was to standardize it as much as it was possible. It is possible to vary the length, the height and the external finishing.

The whole process (design/manufacture/build) is done internally.

The prefabrication factory was also used for retrofitting purposes. They wrapped the existing buildings (energiesprong approach). The Accord group is now opening a new factory.

At the moment this kind of systems can arrive up to 3 floors but they are experimenting a new approach with a metal structure to get up to 5 stories. According to some calculations, the cost saving is about 50% compared to a traditional construction.

Industrial Approach: BoKloK

Industrial Approach: BoKloK

eurhonet whitebook

Another industrial approach was presented by Bengt Fardelius. The company is called BoKloK and was born thanks to an agreement between IKEA and SKANSKA. BoKloK is a housing company, they also do rental apartments. Nowadays IKEA uses 1% of world wood for furniture. Since 2010 they have been an independent company from Skanska, so could go out to the traditional construction system.

The initial target client was the single mum with children, so the idea was to produce a home that this kind of family could afford. To define the home design, it was asked to all clients in IKEA what they want in their homes and how much they could pay. Also for this reason they don’t build all over Sweden, but they select the areas where the prices are adequate. They have a standardized product, with low price, but they have anyway a high customer satisfaction.

In their approach there is a big attention to the community listening since they change the structure of the area where they are going to build.

BoKloK developed“Net Zero Energy Project”where the cost was reasonable.

The company does regularly some surveys to get inputs from the customers, the main outcome are:

  •   request of lots of natural daylight;
  •  high functionality (IKEA furniture)
  •  use of natural materials
  •  have a higher ceiling height

Now they also sell the houses, but there is the same product, with the same standard for both rental and selling market.

In 1996, when they started, they decided to stay in the “product family” level, so you could just select a variant. From 2010 they decided to develop a new platform, with more flexibility (Boklok flex). They can go up to 4 floors in Sweden. It’s the same module for every apartment.

The question is: how can the cost stay low? The solution it’s not only the prefabrication, the whole chain helps keeping the costs under control.

A very important aspect is the logistics: they can produce 37 modules a week and this means 15 trucks leaving the factory. If there are problems with the logistic it turns into a big issue.

Another aspect to consider is that a high volume is needed to get a little cost, consequently to have a high volume you cannot have so many choices.

In 2016 the Swedish association of local authorities did a procurement to provide houses for low cost and BoKloK is one of the four companies that can supply homes with that agreement. The price is fixed and it’s about 1800€/m2 living area (above the gravel bed).

Industrial Approach: Lindbacks

Industrial Approach: Linbacks

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Linbacks is a family home company, the 4th generation is working in the company at the moment (they have 100 years of history), they build houses in the northern part of Sweden, using local wood (about 60% of the production in the Stockholm region).

The company sell, produce and also own homes. Owning homes is a way to understand what are the costumer needs.

In one year they can produce about 1600 apartments. They can produce buildings up to 8 floors with wood frame. They built also 10 floors construction, but the firs two are made with concrete.

They work together with Scania, because car and trucks industry is a benchmarck for the industrialization.

Normal time for the construction is between 6 and 9 month, before there there is the engineering time.

A typical situation is building in an area with contrains,  so the construstion needs to fit the area . If the building has to be adapted is possible to repeat only a percentage of the houses and a part of them should be done unique. 75% of standard houses is the level they aim to reduce the engineering time and increase quality.

Nowadays the 80% of the construction process is inside the factory, only 20% is on site. The approach is: if you can do it in the factory you do it in the factory, even if you didn’t do it before and maybe could takes more time.

In the new factory there is an automatic system to move the modules, and they have PV panels on the roof, so they can cover the whole energy with those. New factory has a capacity of 16 volumes per day, it’s close to the harbour, so they have all the logistics options (boat, train and trucks).

They spend about 3% of the annual turnover for research with Lulea university.

At the end of the workshop a World Cafè was organized with the specific task to identify:

  • The barriers preventing a massive diffusion of the off site manufacturing;
  • The opportunities connected with this technology
  • The Life Cycle Cost of the prefabrication

Here are resumed the main workshop outcomes:

barriers

Table 1– barriers

The table discussed about the several barriers hampering a massive diffusion of prefabrication, off site manufacturing and modular construction.

Barriers have been divided in some main categories:

  • Market: there is still a low public acceptance of prefabricate homes idea. The group stated that it’s not necessary to “say” the technology that stay behind a home construction. What really matters is the final result. On the market side there is also the risk to have a monopoly if only few suppliers are present. On the other hand, what will happen to the market if there will be no more houses to be built in the future? A problem to reach an adequate market volume in some countries (Italy and Germany for example) is that there are many local regulations that changes some details, thus it’s not possible to fully standardize.
  • Political: there is the feeling of a certain pressure from traditional construction lobbies pushing against the new methodologies.
  • Internal housing company’s organization: to work with new technologies requires new skills, that are not always already present in the housing companies. This means that some training is required. Another internal problem is that the Housing Company management can make some resistance to the use of those techniques. A big issue is the “unabalnced power” when dealing with big suppliers that have a much bigger legal and economic power than a single housing company.
  • Procedure: in some countries there is a problem with the tendering procedure, that doesn’t allow to ask for a specific product. Another procedural problem is the need to go for early decisions in the design, that is not the usual way to operate for housing companies.
  • Technical problems: several technical details to take care about have been identified such as:
  1.  Acoustic: seems that in light weight construction there are some problems with the sound transmission
  2.  Seismic behaviour: in countries where earthquakes are frequent using modules to assembly can be a problem in terms of connections between the single modules.
  3.  Life time management costs: it is still not very clear the management costs in the long term.
  4.  Choice of the solution: many different systems are available now in the market, but there is not so much technical experience to define which solution is the best one for the specific case;
  5. Close system: for modular construction can be a problem to integrate the “smart home” systems present in the modules with the ones already owned by the companies.
  6. Workers training: in case of single component prefabrication there is a problem with the training of the final installation team.

life cycle costs

Table 2 – life cycle costs

It’s not possible to have a satisfactory analysis of a technology LCA during a short workshop. Anyway the group tried to identify which are the aspects in favor and which against the use of off site manufacturing under the LCA point of view.

PRO:

  • Better control on material quality + environmental friendly materials
  • Better documentation about construction
  • Reduction of defects
  • Maintenance easier in prefab construction
  • Smaller tolerances
  • Optimal environment for worksmanship
  • No visual difference in appearance of prefab and normal construction
  • Easier to find workforce due to better working conditions
  • Easier in dismantling + recycling + possible relocation / repurposing
  • Lower carbon footprint of wooden construction
  • Advantages of light construction
  • Effect on maintenance cost: unclear
  • Lifecycle cost should be lower

CONTRA:

  • Lack of flexibility in modular construction
  • Black swan risk [of large series]
  • Logistic and carbon footprint? (on the other hand small logistic and on site logistic in normal construction has also to be taken into account)
  • Poor architectural quality (on the other hand: can this be blamed on industrial production?)
  • Maintenance of over-engineered parts/HVACR
  • How does prefab buildings get old? What does Patina do to them?
  • How does maintenance of prefab bathrooms work? Do they have to be changed in total or can parts be repaired?
  • Availability of components in the future?
  • Cheap building but expensive after market

benefits

Table 3 – benefits

This table defined the reasons why it’s a good idea to use prefabrication in general, the main reasons are:

  • Construction of off-site products possible during some poor weather conditions such as continuous rain experienced in Sweden a few years ago
  • Digitalisation through robotics and automation is possible especially with the rapid expanse of technology, this could also make greater variety and diversity of products possible
  • Modular may well suit the life style change that is taking place especially with the younger generation moving to a more mobile nomadic future Helps rethink approaches to maintenance Huge potential on energy consumption reductions
  • With modular you get the finished product, sometime with traditional building quality on site and the integrity of materialises used can be compromised
  • They may be portability possibilities of moving a modular home elsewhere Capturing embodied energy especially with timber products
  • Potential to use recycled materials in the supply chain Very strong volume cost reduction relationship Housing companies could collaborate particularly within single countries to procure jointly at great scale or jointly to open production facility/factory
  • The products of modular may suit the adaptation to climate change issue well Reskilling the workforce was seen as a strong possibility
  • The available labour for services such as social care would be potentially great the greater the automation
  • There is potential to educate occupiers to ensure there was a reduction in the performance gap Export expertise to third world countries where modular is even more greatly needed
  • Better exploitation of natural and local raw materials, eg wood is used extensively in Scandinavia due to its abundance
  • There was an opportunity to use a combination of materials rather than the silo or purest approach of wood steel, concrete – hybridisation could be more widely possible
  • Better internal working conditions for the workforce since up to 80% of the work could be done inside the factory
  • Use of AI to develop better visualisations or end house for customers Opportunity for cross sector learning, ie from engineering and across Eurhonet members

Prefabrication for renovation

During the meeting in Manchester 2019, Ian Hutchcroft talks about Energiesprong, a Dutch developed approach for renewable homes, with a market developed team and European funding.

This approach is based on the idea that with an industrial approach things can be done better and better. That’s what happened with cars: nowadays you can buy a better car than 10 years ago, with the same amount of money. The same could happened to houses.

eurhonet whitebook

In an Energiesprong renovation all the pieces are made in a factory, the building site can end up in few days and the result is an nZEB house. The house has two guarantee, one for the energy performance and the other for the durability (40 years). Another benefit is that tenants don’t have to leave their homes during the works.

In renovation projects they put brackets outside the building and fix the panels above these; the roof is a single piece with solar panels and insulation system; windows are single pieces, fixed in the hole of the oldest ones.

They also construct new buildings, not only renovations.

Their first project in UK was in Nottingham, they spent 6 weeks of works for this terraced house.

Taking as an example the two houses in the image above, talking about energy:

  • Heating 18000 kWh/year before – 2000 kWh/year after works
  • Appliances 3500 kWh/year before – 2300 kWh/year after works
  • Generation 0 kWh/year before – 4300 kWh/year after works

They guarantee comfort and fixed monthly cost, guarantee temperature is 21°C.

Energiesprong creates a market for this renewable system. Now they are increasing the market, when the market will be bigger the costs can be reduced. More big will be the modular construction industry, cheaper will be the price.

Energiesprong aim to make house fit for 2050 targets.

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