Prefab revolution? Factory houses are the secret to green building

The Conversation

The building sector globally currently consumes more energy (34%) than the transport sector (27%) or the industry sector (28%). It is also the biggest polluter, with the biggest potential for significant cuts to greenhouse gas emissions compared to other sectors, at no cost.

Buildings offer an easily accessible and highly cost-effective opportunity to reach energy targets. A green building is one that minimises energy use during design, construction, operation and demolition.

The need to reduce energy use during the operation of buildings is now commonly accepted around the world. Changing behaviour could result in a 50% reduction in energy use by 2050.

Such savings are strongly influenced by the quality of buildings. Passive buildings are ultra-low energy buildings in which the need for mechanical cooling, heating or ventilation can be eliminated.

Modular or prefabricated green buildings, designed and constructed in factories using precision technologies, can help achieve these standards. These buildings are higher quality and more sustainable than buildings constructed on-site through manual labour. They are potentially twice as efficient compared to on-site building.

However, despite support for modular houses, there are a number of hurdles in the way of a prefab revolution.

How green can modular buildings be?

Factory production means modular green buildings are better sealed against draughts, which in conventional buildings can account for 15-25% of winter heat loss.

And factories also have better quality control systems, leading to improved insulation placement and better energy efficiency. Good insulation cuts energy bills by up to half compared to uninsulated buildings.

Because production in a factory setting is on-going, rather than based on individual on-site projects, there is more scope for R&D. This improves the performance of buildings, including making them more resilient to natural disasters.

For example, factory built houses in Japan have performed very well during earthquakes, with key manufacturers reporting that none of their houses were destroyed by the 1995 Hanshin Great Earthquake, as opposed to the destruction of many site-built houses.

Buildings constructed on site probably can’t achieve the same benefits as modular buildings. Case studies in the UK show savings of 10% to 15% in building costs and a 40% reduction in transport for factory compared to on-site production. Factories also don’t lose time due to bad weather and have better waste recycling systems.

Sorting waste at Sekisui House Ltd Recycling Centre Karen Manley

For instance, Sekisui House, a Japanese builder, has a system for all their construction sites where waste is sorted into 27 categories on-site and 80 categories in their recycling centre to get the best value from the resources.

On-site building is open to the weather. This prevents access to the precision technologies required to produce buildings to the highest environmental standards. These technologies include numerical controlled machinery, robotic assembly, building information models, rapid prototyping, assembly lines, test systems, fixing systems, lean construction and enterprise resource planning systems.

For example, numerical controlled machinery provides more precise machine cutting that can’t be matched by manual efforts. This, combined with modelling, fixing and testing systems helps ensure that factories produce more airtight buildings, compared to on-site production, reducing energy leakage.

High-Tech Factory, Shizuoka, Sekisui House Ltd. Karen Manley, Author provided

 

Australia is behind the curve

Less than 5% of new detached residential buildings in Australia are modular green buildings.

In leading countries such as Sweden the rate is 84%.

In Japan, 15% of all their residential buildings are modular green buildings produced in the world’s most technologically advanced factories.

Globally, there is a trend toward increased market penetration of green modular buildings. Yet their adoption in the Australian building sector has been slower than expected.

Constructing houses on site is less sustainable Grand Canyon National Park/Flickr, CC BY

 

However, we can still catch up. The latest evidence suggests that strengthening building codes and providing better enforcement is the most cost effective path towards more sustainable housing.

Australia doesn’t have a great record here. Our building codes could be better focused, stricter, and certainly our enforcement could be a lot better.

Building for the future

As the biggest polluter and a high energy user, the building sector urgently needs to reform for climate change mitigation.

There are serious legacy issues. Mistakes we made in the past endure throughout the life of buildings. Building decisions we make today can be very costly to reverse, and buildings last for decades! In Australia, a timber building is likely to last at least 58 years, and a brick building at least 88 years.

Currently, potential building owners are funnelled toward on-site construction processes, despite the clearly documented benefits of factory-based production. This is reflected in the low profile given to modular housing in the National Construction Code and a lack of aggressive and well enforced environmental standards. We clearly need better policy to support the modular green building industry.The Conversation

Source: The Conversation. Reproduced with permission.

Comments

8 responses to “Prefab revolution? Factory houses are the secret to green building”

  1. Gerberaman Avatar
    Gerberaman

    Never mind prefab, what about basic design? The average aussie house design is created with no thought to the climate, sun, wind, or storms. I am currently in the process of designing myself a new house, and have found it very difficult to find a draughtsman who will deviate from what they are used to. The same with builders. Anything different from what they’ve been doing for the last 50 years is regarded with suspicion, and attracts a large extra charge. Draughts are only a problem if the house is incorrectly designed in the first place.

    1. mick Avatar
      mick

      Michael moggs is a bloke who retrofitted his city house to be efficient and carbon neutral and wrote a book about it,i borrowed one from a library taught me heaps good luck

      1. Jonathan Prendergast Avatar
        Jonathan Prendergast

        *Mobbs

        1. mick Avatar
          mick

          yep just checked on Wikipedia depends on how far you want to go,for me the fridge ventilation is genius. he had to be firm about how he approached builders, architects etc if I ever go to Sydney again il chase it up

  2. Phil Shield Avatar
    Phil Shield

    The claims that modular construction is cheaper have proved false in Australian cities. The prefab revolution is not coming anytime soon. It can only compete with insitu construction in remote locations.
    I would also caution against generalising about construction in Australia based on experience in Europe and Japan where the climate is much different. Increased insulation generally cuts energy use in residential buildings, but not always in commercial buildings in temperate climates. Airtightness and insulation is good up to a certain level, but there is no point in reaching Passivhaus standards for most building types in most Australian climates. Invest in rooftop PV instead.
    It makes more sense to focus on building green using conventional construction techniques rather than wasting money on modular construction.

    1. Nick B Avatar
      Nick B

      Here here, show me modular housing in Australia that is cheaper than in-situ construction and I’m sure most would jump on board. Case studies of 10 to 15% cost reductions produced by the UK prefab association aren’t particularly convincing.

    2. Jonathan Prendergast Avatar
      Jonathan Prendergast

      I’ve seen where modular is cheaper than insitu. Particularly now we are in a housing construction boom so prices have gone up.

  3. Miles Harding Avatar
    Miles Harding

    I was involved in the conceptual design of one of these systems a few years ago. The proposal was to construct the building on-site, using Insulated, pre-wired and plumbed wall and floor sections, small enough to be lifted with a small (1 tonne) numerically controlled crane. Panels would arrive by truck and be lifted into position by the crane and workers, floor panels would be positioned and a small amount of concrete would be poured to connect the components together. No trimming or fitting waste.

    Not mentioned in the story was one of the big benefits – short on-site build times. The system should be able to erect a 4-floor building in approximately 4 weeks from the pour of the footings.

    The issue with these systems is the required scale, as with the Japanese example a substantial factory is required. The automation shown would suggest that a large number of identical components are being made for a common design. Not well suited to McMansions.

    Some benefit may be possible through modular components that simplify the on-site construction task.

Get up to 3 quotes from pre-vetted solar (and battery) installers.