Other measures: presently we spend an enormous amount of energy and money collecting and purifying fresh water to a high standard suitable for drinking. We then use this very inefficiently for purposes that do not require this level of purification. In this proposal, household and garden non-potable water requirements are met by collecting rainwater from the main roof via galvanized steel gutters and downpipes and storing it in water butts and a 3000 litre ‘Rainharvester’ underground storage tank. Water from underground storage is filtered and used for flushing toilets and the washing machine. The water butts are used for garden irrigation. Mains top-up water is available from the mains system, but due to the relatively high rainfall in Cumbria this has not been required. Efficient low water use dual flush toilets, with a maximum flush of 4 litres and aerated flow restricted taps and shower heads, have been installed.
Scatter rugs over reclaimed maple timber boarded floors, organic non-volatile solvent paints, avoidance of formaldehyde and other toxic equivalents, combined with natural materials along with summer natural ventilation and a winter heat recovery mechanical ventilation system has lead to a healthy internal air quality, which Tim and Sarah are very pleased with.
Kitchen waste and garden debris material is composted until dry and inert and then returned as a valuable non-toxic fertilizer to the food growing areas of the garden and conservatory greenhouse.
Development costs
The overall spend was £220K, which included for a 72m² one and a half story workshop/utility store and a 15m² conservatory greenhouse outside the thermal envelope of the 3 bedroom main house. So the actual spend on the Passivhaus thermal envelope was in the region of £1,370m², which is exceptionally good value for any one-off architect designed house never mind an eco house to the Passivhaus standard. Tim and Sarah will have minimal utility bills for life; in fact at the time of writing they have surplus income after paying bills due to the FIT and RHI tariff payments received.
The high quality, good value for money construction was achieved by Tim and Sarah acting as fully engaged active clients, employing two local Cumbrian builders; Sam Nelson and Jim Crawford on a labour only basis (Sam has done a lot of previous work with Eco Arc before; including building our office and private home, so he was highly trusted from the outset.) The timber frame element was sourced directly from MBC in Ireland at a good price. Sam opened direct trade accounts in the clients’ name with several local merchants and most materials were paid for direct to the merchant by Tim and Sarah at the end of each month, along with Sam and Jim’s labour costs, based on time sheets. Most other sub-contractor trades submitted competitive fixed price quotes which were agreed en-route through the build process. We have used this procurement route many times before, to avoid risk averse over pricing by main contractors who are not familiar with Passivhaus construction and tend to put up tender figures to a super inflated level to cover the un-known risks. Sam had never built a Passivhaus before, and learnt on the job with some gentle tuition from us. He finished this one on time and on budget without a cross word. Sam has now almost finished his second Passivhaus in Kendal and has agreed to go on and do a third house in Windermere on the same procurement basis, as it seems to be a winning formula for all parties.
Timber vs masonry
We have now finished 45 masonry Passive houses across five different sites in North England and are currently working on 18 individual timber frame Passive houses across a similar geographical region. Clearly there are pros and cons for both options, which vary from site to site and client to client, depending upon specific circumstances. Tim and Sarah’s house was a steep learning curve down the timber frame route but it was a success. We have now fine-tuned a timber I beam and cellulose system with a local Cumbria based timber frame fabricator, Trevor Lowis of Eden Insulation, and Cumbria based Ecological Building Services, which has allowed us to erect the whole timber frame thermal envelop consisting of all the pre-insulated walls and roof for a four bedroom house in one day, and follow on with installing the triple glazed windows with air tight seals over two further days and deliver consistent air tightness results in the region of 0.11 to 0.2 ARC at 50 Pascal’s.
