We have chosen to build to passivhaus standard - a proven system of construction that originated in Germany and guarantees quality, comfort and energy efficiency. Beyond that there were two choices: whether to build a house that's thermally massive or thermally light - put simply, masonry or timber-frame. A thermally massive passivhaus absorbs heat from the sun during the warmer months and slowly gives that heat back during the cooler months - much like a storage heater. A thermally light passivhaus doesn't store up the heat it absorbs in the same way, but it takes much less time and energy to heat than a conventional house and won't lose that heat as quickly as a conventional house does.
Our first build, The Autonomous House, was of thermally massive construction and we were very happy with how it performed over the five years that we lived there. The internal temperature remained fairly even (around 21C) for much of the year, only dropping to 17C in the coldest winter months, from mid Jan to Feb. However, with no draughts and cold spots, the house was comfortable even at that temperature. We designed it using the Passivhaus Planning Package - complex software into which you enter all of the construction details, as well as data about the location's climate. It then calculates how much energy will be needed to heat the house (the details can then be altered if necessary to end up with the desired low figure).
We want to use the same method of construction for the new house - but this time we're going to apply for Passivhaus Certification. This adds an extra level of quality control - and initial cost, unfortunately - but means that we will have the satisfaction of knowing that the house qualifies as truly passivhaus - and we get a nice plaque for the wall...
The Portree Passivhaus will have a similar concrete core to The Autonomous House, with large triple-glazed windows, mainly on the south and west walls for solar gain - with summer shading designed into the window 'framing' to avoid overheating. Meticulous airtightness detailing, masses of insulation and an efficient mechanical ventilation system with heat recovery will all help to keep the house at a comfortable temperature throughout the year. Like The Autonomous House, this house will be 'upside-down', with bedrooms on the lower floor and the living areas upstairs. This works very well as it means the bedrooms stay cooler in the summer and the living areas are warmer in the winter.
All of the above was in our design brief to the architects, but the rest we left up to them. We chose local company Rural Design (based in Portree) as we like what we've seen of their work, which shows great imaginative, contemporary design flair, balanced with sensitivity to the surroundings. The designs they came back with were very impressive and after just a few tweaks, the introduction of more stonework and the addition of a curve or two, we were happy.
We chose to build a passivhaus because it's a proven system of .