New build - low-energy home
A Model for Low-energy Living
Alex Clifford has designed and built an award-winning family home, using the experience to encourage others to employ Passivhaus principles.
Story: Alex Clifford Photography: MBC Timber Frame
|Project||New build to passive house standard||Location||Surrey|
|Cost||Plot with bungalow £735k in 2007||Spent||£450k||Worth||Unknown|
We wanted to build a super-insulated low-energy house – the best we could afford rather than the biggest
I grew up just round the corner from where we are now, and my parents still live there. As a boy I had a paper round so I know the area well. It is on the edge of town, overlooking fields with easy access to the North Downs Way.
We moved back to Guildford from Battersea in 2007 when our eldest son was one and purchased a 1950s bungalow with the intention of extending it as a family home. Our plans evolved over the next nine years as we saved for the works. Eventually, though, we decided to replace it. The build was of a poor quality and we would have had to make too many compromises with both the layout and energy performance. We wanted to build a super-insulated, low-energy house – the best we could afford rather than the biggest – and one that would sit sympathetically in the landscape.
I decided to design and build it myself, and in the process I would write a blog, explaining the various aspects of the build and the benefits of a passive house with the aim of answering FAQs around low-energy housing and to promote my services to other selfbuilders in the South East.
We had a fairly modest budget as we didn’t want a huge debt
We had paid £735k for the bungalow in 2007, at the peak of the market, and our initial offer was well over the asking price but still unsuccessful. Several months later, however, the agent came back to us after the original buyer pulled out. By the time we came to demolish our bungalow in 2016 the property was valued at £950k.
The footprint for our new home was largely the same as the original bungalow for which we already had planning permission to add a side extension and a second floor. My design included a mainly open-plan ground floor with a separate soundproof living room snug.
The floorplan – the house has a largely open-plan ground floor comprising kitchen/utility, dining area and family area with a separate soundproof living room/snug. Upstairs there is the master suite with dressing room, a guest room with en suite and three similar-sized bedrooms plus a family bathroom.
Upstairs there were five double bedrooms, two with en suites, with the master and guest rooms larger than the other three, which were all the same size. One bedroom could double as an office, as I work full-time from home and Bronwyn, my wife, is occasionally home-based too. The existing garden office I had built could be used as a gym/kids hangout.
I wanted our new family home to be understated but beautifully detailed
I wanted our new family home to be understated but beautifully detailed – a mix of traditional roof forms and clay tiles with crisp modern detailing and deep-set windows – and clad in timber.
Having lived in the bungalow for nine years, we knew the views we wanted to maximise, and the various issues associated with living next to fields, such as the prevailing winds, and insects and pollen in the summer. Slot windows at high level were essential to view the sunrise over the distant hills, as were strategically placed windows to frame the views over the fields, along with large sections of glazing through which to enjoy garden views from the main living area.
The house needed to be environmentally sound too, with minimal energy costs. I believe that part of the ethos of a truly low-energy house is for it to be sized for your requirements rather than just building the biggest house you can afford.
We arranged our finance from Ecology Building Society as its fees were low and it offered good rates. I needed to demonstrate to them that my design would achieve a SAP rating of 100 or more. The lender would then offer a discounted rate for the remainder of the two-year mortgage. As I wanted the house to meet the Passivhaus standard, I had modelled it using Passive House Planning Package (PHPP) software.
Although the timber-clad facade looks plain and simple, careful attention has been paid to the detailing.
I had used timber frame and cladding before and liked the combination. This time, though, I really wanted to focus on the detailing. The house volumes were based on my already approved plans for the bungalow extensions and refurbishment.
Externally, the facade consists of two volumes, one slightly smaller than the other, and both with their own pitched roof. An architect friend had helped to resolve the roof shapes on my previous extension design as I had been overcomplicating matters. It proved to be a couple of hours well spent.
Our new application was passed by the planners despite objections from a number of neighbours who didn’t like the idea of a house being higher than the surrounding bungalows. I couldn’t see a problem as we are well spaced from most neighbours and two sides of the plot are fields. Fortunately the planners agreed. Their only stipulation was a 10 percent improvement over Building Regulations for energy consumption. We planned to far surpass this.
The kitchen island unit was sized to a full slab of granite, which was hand selected. Kitchen doors are a combination of painted and oak veneer stained to match the fumed oak cladding around the stairs and snug floor. The veneer is book matched and the grain from the same tree flows around sides of the island unit and across the doors under the sink. The open-plan living area has 2.4m-high doors, all made by Alex and cut from 8ft x 4ft fire door blanks and lipped.
I was the main contractor for the build, acting as labourer, trench digger, machine driver, and carpenter. MBC supplied and erected the timber frame to the watertight stage, leaving me to complete all the first-fix carpentry and most of the second fix too. I also installed the mechanical ventilation system, and fixed the external cladding – all 3km of it.
As well as supplying and erecting the timber frame, MBC was also responsible for the foundations and ensuring airtightness after window installation. This was essential if the house was to meet Passivhaus standards.
Good contractors tend to want to work with other good tradespeople and our build was no exception, with all the workers coming recommended. I also had a small network of low-energy selfbuilders in my area who were happy to share their experiences and contacts.
Once work started on site it was essential to live close by, so we rented locally. My daily routine started with opening the site every morning to receive deliveries before taking the kids to school. I had managed to design and plan the project around my other work as an interior designer during the two previous years but once construction started it became a full-time job which was to continue for the next two years.
I was pleased with MBC whose team worked really hard. My German tiler was amazing too – he pulled the plumber up on setting the bath 1.5mm too high as it messed up his setting out – and the electrician and plumber were both keen and interested in the build. The roofers and hard landscapers were more of a challenge.
When building something a little out of the ordinary it is important to use contractors with a ‘can do’ attitude who are interested in the project and enjoy problem solving rather than using it as something to moan about.
We had budgeted £425k, including fees, for the build at the outset, and a further £25k for landscaping. This would have been closer to £650k if I hadn’t been the main contractor and undertaken a lot of the site work myself. We financed the build with a combination of savings and a mortgage. Our lender let us draw down funding as and when we wanted rather than the usual stage payments. This made cash flow much easier to deal with.
In the end we came in pretty close to budget, and we are pleased with how it has all turned out. The house is excellent, both performance wise and as a family home. The house has a SAP rating of 101 and generates more electricity than it uses (5,500kWh annually).
For most of the year it can be heated by solar gain and incidental losses from cooking, showering, and electronics. The underfloor heating can function when there is a lot of solar gain by transferring heat around the slab. The boiler adds to this when there are prolonged cold periods with little sun. There is no heating upstairs apart from four 600W towel radiators, which come on for an hour a day over winter.
The windows have external venetian blinds that adjust automatically to track the sun and prevent the house overheating. When not in use they disappear behind the cladding. There is never condensation on the windows and clothes dry in a couple of hours as the MVHR does such a good job of changing the air and keeping moisture levels down.
Pollen from the surrounding trees and field, which sometimes has a crop of yellow rapeseed, is filtered to keep the air constantly fresh and reduce allergies.
A Loxone home automation system controls the external blinds, heating and lighting, opens the roof windows and monitors temperature and humidity. Rain sensors close the roof lights and an anemometer measures wind speeds so that external blinds are raised if there is a storm.
The open-plan living space on the ground floor and the open stairway can be ventilated out through the roof lights to night-purge any excess heat that may have built up during hot summer days. Opening a downstairs window creates a passive stack effect which quickly moves the air upwards and out through the roof windows.
Timber cladding has been applied to the stair balustrade and forms a wall under the stair with flush ‘secret’ doors. The solid oak handrail is lit by LEDs from underneath. Flush doors open to a storage area in hall.
The constant temperature makes a comfortable living environment and it is a great house for entertaining as there is lots of space. Three people can work in the kitchen (my kids like to cook) and talk to guests at the same time. And there are great views across the fields, hills and garden.
The icing on the cake for me was the project winning Best Individual House category in the 2020 Guildford Society Design Awards. I enjoyed the whole design and build process and learning more about low energy building. I can safely say I wouldn’t want to ever live in a standard house again.
- Passive raft foundation. 300mm EPS underneath and 200mm upsides to form a reinforced concrete slab with no thermal bridges. This was laid over a reduced dig with 350mm compacted stone chippings (no fines).
- Wet UFH pipework laid direct into the slab.
- Twin-wall timber frame supplied by MBC and constructed off-site with site-blown insulation.
- Clay tile roof to match arts and crafts vernacular. Machine made but hand finished to give a textured, slightly uneven appearance.
- Internorm triple-glazed windows and doors. All Passivhaus rated.
- Warmcell blown cellulose insulation (recycled newspaper and natural fire retardant). 300mm in walls and 450mm in roof. Rockwool insulation for sound transfer in internal walls and ground-floor ceiling.
- Habito plasterboard from British Gypsum (dense and heavy). Allows screw fixings for shelves and reduces sound transfer between rooms. Ground-floor ceiling has two layers of plasterboard and resilient bars to reduce sound transfer between floors.
- External cladding is ash Thermowood from UK forests.
- Though not a certified Passivhaus, the build is to Passivhaus standards using certified products for windows, doors and MVHR. House achieved airtightness (0.33ac/h @ 50Pa) and insulation levels (slab: 0.105W/m2K; walls: 0.12W/m2K; roof 0.10 W/m2K), well in excess of Passivhaus requirements.
The Final Word
What was the low point of the project?
Our window installers (not Internorm) subcontracted the work even though they insisted they wouldn’t. Once I threw them off site it took a long time to resolve issues and the damage they caused. Also, after the speed of the timber frame erection everything else always feels slow.
The high point?
Getting the timber frame up quickly is always exciting.
The most enjoyable part?
The whole design and build process. It wasn’t the first time I had done it so there were no nasty surprises. I also enjoyed learning more about low-energy (passive) building.
What would I do differently?
Maybe fit an air source heat pump instead of gas boiler, but it hardly gets used anyway.
The wow! factor?
The house is under-stated, though the views are great and the large living room has high ceilings, which is lovely.
Alex Clifford lives with his wife, Bronwyn, their two sons, aged 11 and 13, and their Hungarian Vizsla, Millie. With a background in commercial interior design, Alex now specialises in home interiors. He has also worked for a local builder/developer where he project managed the construction of six timber-framed, timber-clad eco flats.
This case study is from the February 2021 issue of SelfBuild & Design magazine.