A Cottage Built with Structural Insulated Panels (SIPs) – with The Bears S.A. (Client Case Study)
The Bears S.A. shares his experience of building a house and explains why he decided to use structural insulated panels (SIPs).
Interview with Swift House Construction
Kingsley’s background as a plumber has given him plenty of opportunities to see houses losing heat and that’s why he was determined to build himself an energy efficient home. So, his goal was to create a small, flexible space with lots of natural light, that was easy to run and also cheap to heat. The new cottage would have a floor area of 125m2 and be built on a plot beside his existing property.
Despite Construction Experience, Kingsley Chose to be Just the Client!
Although Kingsley’s an experienced plumber he did not do any of the work himself, reasoning that it would not be a good idea to change the dynamic of a team that already works well together. He also hired a project manager because he believed that while he can work in a team, he did not have the necessary skills required to run a team and deal with the many things that can go wrong!
Hiring a Contract Administrator Made Dealings Simple
Kingsley took the advice of his project manager and hired a contract administrator. This effective third party acts as a membrane between client and builder, and provides some neutral ground should any problems arise. Kingsley says that it worked well for both parties.
Initially Kingsley Discussed The Outcomes He Wanted to Achieve with His Architect
Kingsley’s first step was to sit down with an architect and talk through what he wanted to achieve from the new house. Whereas his existing home was from 1884 and had lots of nooks and small rooms, in contrast he was keen to create a more contiguous living space.
The SIPs are Engineered to Suit the Design
Once a design was created and planning permission acquired, Kingsley had to decide on a build method. After researching structural insulated panels as an option and visiting houses that had been built with them, he chose this route. An engineer then reworked the SIPs method of construction to fit with the design. For example, where the timber panels were not suitable the engineer reinforced it with steel construction to achieve the required look. At no point did Kingsley have to compromise with the SIPs.
A Structural Insulated Panel is Like a Sandwich!
Kingsley talks about the structural insulated panels he used which consist of 2 layers of OSB with a core of PIR foam. [An additional 25mm insulation, TW55, was also added to these Kingspan Tek panels on the inside behind the plasterboard lining, which proved very cost effective.] Once machined these panels form part of a kit, which turns up labelled and numbered. There are rebates, grooves and fillers that lock all the panels together.
SIPs are Incredibly Quick to Put Up
With the hard work done in a factory, one key advantage of SIPs is that they can be assembled on site very quickly. In this case, the ground floor was done in the first week and the second floor was done in the second week.
The Precision of SIPs is Greater Than a Conventional Build
Having been in the trade for many years, Kingsley says the nature of block and breeze construction means you tend to work to the nearest inch. However, with SIPs you are working to about 3mm.
SIPs Allow You to Work on Two Faces at Once
Once the timber cell has been put up the services can be going on inside – pipework, electrics, etc. – while brick work or cladding can be underway on the exterior. Wet trades are not crossing paths with the services.
Kingsley Presented His Intentions to His Neighbours
Kingsley wanted his house to be a comfy fit for everyone in the area and so he negotiated with the people either side about the aspect, size of the building, etc. As someone who really values his neighbours, presenting his intentions at every stage of the project worked very well.
The Cladding Needs No Maintenance
Two thirds of the face work is in a cottage mix of bricks (three local bricks that are used randomly) and then one third has got a modern version of weatherboard, which is a concrete board, called Eternit board (made by Marley). It gives the impression of being wood but is good for minimising heat losses and also will never need to be painted.
The SIPs Hold up the Bricks!
Kingsley points out that the brickwork – the face work – is attached to the SIPs with brick ties in the conventional way, so it’s not just held there by gravity. It is secured in the same way that brick to breeze block is secured, but really the SIPs panels hold up the bricks, not the other way around.
Buying Windows From Abroad was Cheaper
Kingsley put a lot of effort into finding window frames. The triple-glazed ones he eventually bought were dramatically less than getting them locally. Kingsley does not understand why this is.
Put Your Money into the Fabric of the Building
After considering many options including Huf Haus, but trying to temper budgets and reality, Kingsley ended up concluding that the money is better spent making sure you don’t need energy than in having very fancy low cost energy. So he put a lot of effort and money into making sure he doesn’t lose heat in the first place (rather than having a cheap source of it).
Minimise Your Dependence on Technology
Kingsley did not invest in heat pumps or other renewables because he thought they were too expensive and he didn’t want to have the worry of maintaining them as he got older. The thought of claiming on warranties of companies in 10 years for £30,000 bits of kit somewhere in the ground was something he wanted to avoid.
The House is a Hermetically Sealed Box
Although the appearance may be conventional, the house is airtight and very well insulated. It uses an air management system (mechanical ventilation with heat recovery) to bring in new atomised air but without the heat losses. 80% of the heat of the expelled air is saved and there is a full air change in the house every hour and a half.
Installing Cabling for PV Means it Could be Easily Added Later
A modern high efficiency condensing gas boiler drives the underfloor heating and the hot water, etc. Plus there is a cylinder that will accept solar and cabling to allow for PV at a later stage. Kingsley has no plans to install renewable technology but if efficiencies continue to improve, he wants to make sure he can add them retrospectively (without having to change cylinders and knock holes in the walls to add wires, etc.).
Although Kingsley could get the gas and water companies to be pretty cooperative, he really struggled with UK Power Networks. Kingsley’s advice, for anybody doing a new build in the UK, would be to get that bit applied for at the same time as you get your planning permission. There is a 90 days notice period, even from when they say yes! And this does not necessarily mean they arrive on the 91st day. So, organising this is a priority because not having electricity reliably is going to be a problem. Kingsley says having a contract administrator really helped.
Life is Much Easier When All The Contractors Want the Same Outcome
Kingsley believes he was very fortunate to have a team that shared his vision and all clicked together. He gives the example how if his interior designer came up with a good idea for the kitchen, the person building the kitchen would readily help to achieve it. There were no hidden agendas.
Having Builders Who Got on With the Neighbours Helped
Kingsley was very pleased with his team and thought it was fantastic to have builders that put themselves out to get on with his neighbours. He says this set the flavour for the build and eased pressure points with parking, etc.
Download a transcript of the interview with Golden Bear Construction.
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Elrond Burrell on Home Style Green
Elrond Burrell is a guest on the Home Style Green podcast. He gave a really good explanation of the Passivhaus standard (the comfort standard). Check out episode 30: Is Passivhaus relevant to New Zealand?
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