28 Jul 2015

What are the benefits of pre-manufactured homes?

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When looking to build your own house, effective cost and time are considered to be key components to a successful build. Each factor is minimised when a pre-manufactured structure is specified – just one reason why this method of construction is a popular choice for self-build projects.

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Over recent years, there has been a noticeable increase in the number of UK self-builders opting for a pre-manufactured house. Pre-manufactured provider Hanse Haus, based in Germany, is one company that has noticed this increase, now delivering a new home to the UK every 18 days.

Overrun costs minimised

Regardless of how well a self-build is thought-out, planned and budgeted for, many still face unforeseen and escalated build costs. One benefit of a pre-manufactured house is that costs are fixed from the start.

Although it always depends on the internal fit out and architectural design, the estimated cost of a pre-manufactured property starts at approximately £1300/m². This price can include all home elements, from floors and surfacing to electrical work, plumbing and heating. Once the initial contract is signed, and despite fluctuating exchange rates, many suppliers offer a guarantee that a house will be delivered, as promised, on budget.

Reduced build times

The cost and time frame of a conventional build often escalate. The scale and efficiency of engineering a house in a factory setting eliminates wasted time, as well as many of the headaches that are commonly associated with building on site. For example, the Hanse Haus headquarters in Germany manufactured 480 homes in 2014 – a highly efficient operation.

Although timings differ between companies, a typical pre-manufactured home-build project's timeframe usually follows the below structure:

When manufacturing begins, all components – such as the windows, doors, window sills and shutters – are assembled in the factory. All final measurements are then in-putted to enable precision-engineered machines to automatically build the walls. As soon as the walls are on the assembly line, all other products are added step-by-step. This takes, on average, just two days. The house is then delivered to site in the UK within just one week.

Once on site, it is possible – depending on the fit out – for a 200m² pre-manufactured property to be erected in just 10 weeks. The ceiling and roof elements are built with the outside membrane already installed, which ensures the roof is waterproof within a couple of days.

Bespoke elements

A pre-manufactured house provides the opportunity to create a bespoke property, allowing self-builders to easily create their ultimate dream home. The combination of versatile architects and state-of-the-art manufacturing technology means that pre-manufactured housing experts can offer flexible systems.

High levels of energy efficiency are a particular concern for many pre-manufactured homes. Unlike traditional builds, particular attention is paid to the building envelope – the shell – to make sure it’s airtight, ensuring that no heat can leak out through joints or gaps. This means that pre-manufactured homes often achieve outstanding thermal insulation and low space heating requirements. A standard brick built UK property presently consumes around 240 kW/m², whereas a pre-manufactured home ranges from 60 kW/m2 to just 15 kW/m² for passive house standard.

Energy efficient solution

Matt and Jo Warnes, along with their six-year-old daughter Lauren, now have a three-storey pre-manufactured home of their own in Putney, London. Pre-manufactured at the Hanse Haus factory in Germany and built onsite in January 2013, the house blends seamlessly with the neighbouring end of terrace property.

Matt explains: “Due to the limited plot of land on a London street and to the mainline railway right next to it, the planning and logistics of this project required a careful and thoughtful approach as well as a creative and skilled architect. Hanse Haus married the aesthetics we were after with great functionality. They also offered a quick build time on a very difficult site.

“Unlike many new builds, we don’t have a long list of renewable hardware – no solar panels, heat recovery or rainwater harvesting – but the airtight building envelope along with the insulation and triple-glazed windows has proved incredibly effective, meaning we really don’t need them. Bearing in mind we get our fair share of cold, wet and windy weather and that we’re right next to a busy railway line, the house feels consistently warm, without the need for much heating through the winter months. In fact, our total energy bill for the first year was £850 and to offer some comparison, my mum's traditionally built house right next door, which is marginally bigger in size, is costing a hefty £4000 a year to run. She has already asked if we want to swap homes!”

Sustainable ambitions

Hanse Haus built its first UK passive house in Somerset last year. Stephen Huber from the Scottish Passive House Centre, points out: “The super-insulated shell and windows, together with a highly efficient ‘Paul’ mechanical ventilation heat recovery system, take the annual heating consumption of this kind of passive design down to 13kWh/m².

“By using a modern heat pump and a solar thermal system, the primary energy demand for domestic hot water, heating and auxiliary electricity is cut down to 30kWh. This ensures very low running costs and the highest level of emission savings.”

Hanse Haus says that its passive houses only need heating on a few very cold days of the year, and this is provided by a micro heat pump, while solar collectors heat domestic water. The company’s Technical Director, Bruno Kleinheinz, comments: “For a 1800ft² passive house, the consumption cost for heating and hot water would be just £32 per month, on average.”

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