ECO ARC PROJECT INTRODUCTION
On paper it looked very difficult to achieve a passive house for Malcolm’s project. Existing planning restrictions meant that a bungalow was the
only viable design solution for a new house on this site. It was agreed to work towards a passive house standard but settle on the AECB Silver Standard as being an achievable goal given the planning restrictions and project budget.
Single detached bungalows are notoriously difficulty to make work as economically viable passive houses due to their poor form factor. Bungalows inherently have a large surface area (roof, walls & floors) relative to floor area. (TFA) To meet the passive house standard detached bungalows require extremely good or excessive fabric U values at high cost to compensate for the poor form factor.
The self build project is now complete and Malcom has collected 5 quarters of energy use data. Based on Malcolm’s information that 10% of the GSHP output has been used for hot water, & the remaining 90% has been for space heating.
The total GSHP energy use for one year (working back from the 5 quarters data) = 2451kWh/a. 90% of this total = 2206 kWh/a. Divide this by treated floor area (196 m2) we arrive at estimated specific space heat demand = 11.3kWh/m2/a, which is actually less than the Passive House requirement of 15kWh/m2/yr.
In reality the GSHP is also heating 10m2 porch + 35m2 workshop so the total floor area is 241m2 giving an estimated specific space heat demand = 9kWh/m2/a. which is well within the Passive House requirement of 15kWh/m2/yr. Although this is not an absolutely confirmed figure, it is good to make it clear that the house has been designed using PHPP to perform between Passivhaus and AECB Silver, and in terms of space heat demand, it appears to be performing as good as or better than a Passivhaus (due in large part to the design and also well-behaved occupants!).
What follows below is Malcom’s self build diary, recording his layman’s journey from inception through to completion building his Eco House. As architects we did not have a direct site role, Malcolm acted as client, project manager & self builder & should be congratulated for his conviction, tenacity and excellent achievement.
Andrew Yeats. Project Architect Eco Arc