Part 8: The Final Stages of Building a Passive House (Passivhaus)

7 September 2016 Paul Newman, Self Build Director
Image of SIPs show home open-plan living room
With the finish line in sight, Dr Paul Newman explains the key decisions behind the final touches to Potton’s Passivhaus and passes on his words of wisdom.

Constructing a new home involves many decisions, many of which (or the key ones at least) should be made before starting work on-site. This level of forward planning is essential when building a Passivhaus, and it’s a step that we have mostly been successful in.

However, lots of small decisions remained to be made and to keep things moving, they needed to be made quickly

Finish the Plasterboard

Before we could fix the plasterboard, we had another major decision to make — to skim, or tape and joint.

Finishing plasterboard with a skim coat of plaster takes longer and introduces a wet trade into the project. However, it arguably gives a better finish for decorating. On the other hand, taping and jointing plasterboard is quicker and suits a dry build system, but it is messier.

In the end, we decided to tape and joint as it’s what we’ve done in all our other show homes, and it’s also what we recommend our customers do. To do this quickly, we had multiple trades working alongside each other for the first time. The tiling, for instance, was followed by decorating the following week, while the kitchen installation was also taking place at the same time. By then, we had finished installing the plasterboard, using Gyproc Habito from British Gypsum.

Once the ceilings were finished, the second-fix electrics work began and we could also start thinking about installing the stairs. There was plenty going on!

Bring the Interior Scheme Together

Walnut staircase by David Smith stairs
Designing the interior of your own home is hard enough, but designing a show home that will be visited by several thousand people every year is even more daunting and something that needs careful thought and reflection.

So we opted to create, coordinate and curate the scheme using the skills of Terry Mahoney, a member of the Potton team. Terry retired many years ago as our national sales manager, but he continues to live and breathe self-build and now works as a consultant to the business.

The design he had pulled together is simple, stylish and sophisticated, with some fun twists thrown in for good measure. I think he managed to pull off something that is simultaneously timeless and contemporary. The interior design of the house is anchored by a few key feature elements, particularly the stairs and the central flexible “courtyard” space.

A decade ago, we offered our customers a limited choice of staircase designs. Things have moved on somewhat since then and both Potton and our long-term supply partners at David Smith St Ives are much more flexible and ambitious. The staircase in the show home will feature closed solid timber treads with glass balustrading and be constructed from American dark walnut. Walnut is more variable in figure and colour than oak or pine, and we believe that the completed assembly will provide a focal point for the rest of the interior design.

From a very early point in the design process, I told everyone who wanted to listen, and probably plenty who didn’t, that the central “courtyard” space under the large roof light is the most important part of the design. The finished space introduces great flexibility into how the ground floor of the house can be used and reconfigured on a daily basis — it can be used variously as a dining space and cleared of furniture for parties, but most importantly, kitted out with an Eames chair for me to relax in at the end of a long day with a book and a glass of wine.

Another of the key features is the large 3x8m feature window and door set supplied by Kloeber, which creates a strong link between the interior and exterior. We also strengthened this connection through our choice of materials. For instance, the external brick was used to create a feature wall inside the lounge area.

Building a Passivhaus Show Home

A complete step by step guide, we take you through the story of building our Passivhaus show home. From the design process, constructing the superstructure, achieving airtightness right through to the finishing touches.

Download the guide here.

Building a Passivhaus Download

Light In the Passivhaus

Kitchen in Potton's Elsworth show home
With the large feature window to the rear, the substantial roof light above the courtyard and the taller-than-average first-floor windows, our finished house gets plenty of daylight. Indeed, one of the challenges throughout the design process was to manage the shading, size and specification of the windows and doors to prevent excessive solar gain and subsequent overheating in this airtight home, but the PHPP (Passive House Planning Package) calculations enabled us to achieve this successfully.
However, we have been guilty in the past, as have many others, of forgetting the artificial lighting design scheme and leaving it as an afterthought to be agreed on-site between the electrician and project manager and/or customer. While these individuals invariably have many admirable qualities and experience, the ability to create a good lighting scheme design is not always one of them.

Clearly, there are specialist businesses that can design and install fabulous systems that will create a lighting mood appropriate to any occasion and setting, but these installations are frequently beyond the means and aspirations of many of our customers.

So what we wanted to achieve within the Passivhaus was a low-energy design that had been thought about properly before the building was constructed, rather than being forced into an overly simple design revolving around picking the number and location of downlights.

Specify Wall and Floor Finishes

Lounge area in Potton's Elsworth show home
Interestingly, Terry’s interior design called for large areas of ceramic tiled floor. There were a few reasons for this — beyond the aesthetic ones of following the general trend towards harder floor finishes — such as reflecting the contemporary external design of the property in the internal floor finish and maintaining the stylish appearance of the rest of the design.

From a technical perspective, the hard flooring maintains the thermal mass provided by the screed beneath, which can be helpful in a building envelope that is otherwise lightweight in nature (built, as it is, using structural insulated panels, or SIPs). Tiled floors are also durable, easy to clean and great for those who suffer from asthma.

Our partners at British Ceramic Tile supplied the products we had chosen — mostly from its HD Technology range. This company is the largest manufacturer of ceramic and glass tiles in the UK and has a state-of-the-art factory situated on the edge of Dartmoor in Devon.

The interior design scheme was pulled together with feature walls of stunning wallpaper from Mockbee & Co and paint finishes provided by Brewers. These independently owned UK businesses were extremely helpful in guiding our selections and then matching specific paint colours within those selections.

Anchoring the design around a small number of key elements and pieces was deliberate. The house has interesting spaces that we want visitors to recognise and appreciate and we also wanted to develop a design that wasn’t reliant on expensive technology and fittings. One key element of this is the simple audio and media installation, while another is the kitchen.

Kitchen and Bathroom Installation

Image_Show Home_Elsworth_15
Over the past few years, we have developed an increasingly strong partnership with Callerton (a kitchen system manufacturer based in the UK) and Cambridge Kitchens and Bathrooms (the retail partner closest to our Self-Build Show Centre).

For the Passivhaus showhome, our design brief required a simple kitchen, with stylish yet cost-effective materials. Callerton responded with a sleek handless design, which incorporated its Monza matt cabinetry, Blum’s award-winning Legrabox drawer systems, Dekton’s innovative XGloss worksurfaces, and the very latest Bosch appliances.

The kitchen is regularly described as the heart of the home, and while for many this is undoubtedly true, not everyone has the desire or inclination to spend an arguably disproportionate amount of their budget on the kitchen. Therefore, Callerton wanted to make a clear statement that great kitchens don’t have to be monstrously expensive. We also wanted to highlight that kitchen design should not be an afterthought and should instead be considered from an early stage of the design process to ensure that the finished article meets the requirements of the occupiers.

When designing a kitchen for a Passivhaus, early planning is also important as the interface between the mechanical ventilation heat recovery (MVHR) system in the house and the kitchen extract system is critical. Furthermore, the performance of the fittings impacts on the energy consumed by the house and, subsequently, the PHPP analysis.

I stressed earlier that the interior design for the house is intended to be simple, stylish and sophisticated. We carried this through into the kitchen design and the next challenge was to make sure that the three bathrooms followed suit. The Passivhaus has two en-suite bathrooms and a ground-floor family bathroom.

Each was designed by the team at Sottini (one of our partners) to showcase its latest products and complement the other elements of the interior design. Sottini believes that function dictates form and the best designs are those that are clean and simple. This was reflected in the brief we gave them and the designs the company created for us.

Sottini has been at the forefront of water-efficient technologies since the business started trading over 40 years ago and continuously strives to minimise waste and improve efficiency in its products, something that was key in the building of this Passivhaus.

There you have it, we’ve now discussed all eight parts of building a Passivhaus building in our step-by-step guide. It’s a complex build, but we are immensely proud of what we have achieved.

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