HHP has two completely separate autonomous rainwater systems – potable and non-potable. Since the completion of the houses in 1998, water from both systems has been tested regularly.
Our latest results (September 2011) indicate that our drinking water is perhaps cleaner than most branded bottled water! Could it really be that our filtered rainwater can be just as clean as the commercial products that line our supermarket shelves?
Broadly speaking there are two general categories of analysis; metals and bacteriological. In our case, the former remained consistently low with the exception of aluminium. Although previous years’ test results showed zero aluminium, September 2011 sample showed levels of 0.109mg/l. This figure is acceptable within the limits for small water systems (0.2 per mg/l) but larger water treatment plants are limited to 0.1 mg/l. Whatever limit we choose, we still feel this is unaccountably high – can anyone shed any light on this contaminant?
The bacteriological analysis proved to be both interesting and reassuring. Of all these, the Total Viable Count result (TVC) was of most interest. The test estimates the total amount of living organisms in a set volume of water at two separate temperatures; 22ºC (TVC 22C) and 37ºC (TVC 37C). The samples are left at that those temperatures for a period of 2 days and 3 days respectively, allowing any organisms present to populate the sample. These tests have been carried out on bottled waters with levels ranging between 42/ml and 32,659/ml for TVC 22C and between 3/ml to 1,950/ml for TVC 37C. Our drinking water, by comparison, showed 0/ml and 20/ml respectively. Even our aquaculture lake, which is full of fish, and receives liquid effluent from the reed bed, still manages to produce low results at TVC 22C 166/ml!
The irony is that even though we residents at Hockerton Housing Project consume approximately 2000 litres each per year of our harvested rainwater, we still have to provide paying visitors with bottled water! This is because, to comply with current health and safety guidelines, we would have to test our water on a monthly basis, currently around £1200 per year. Compare this with our visitors’ consumption of around 50 bottles of branded water per year, around £50 – the figures speak for themselves! (People on our tours also appreciate the tea, coffee and some wonderful local apple juice we supply for free!)
The generally recommeded level of loft insulation, and that provided in most new build houses today, is 250-300mm. The houses already had about 250mm of insulation in the loft, but we have topped that up to between 600-700mm. In addition, we have then sealed the loft hatch so that occupants cannot then compact the insulation by storing lots of belongings on top of it; if loft insulation is compacted, a lot of the benefit of the insulation is lost – it restricts heat transfer because of the air pockets within the fibres.
Significant levels of insulation in the loft
Although there is no access to the loft, the houses now additional storage areas in the sun space and porch.
Insulated thermal store
The hot water in the houses is provided by a super-insulated thermal store heated with an electric immersion heater. A thermal store is like a traditional hot water cylinder, but the key difference is that the hot water in the cylinder is not the hot water used, instead it simply acts as a heat storage mechanism, hence the term thermal store. The hot water delivered to taps and showers, is actually cold water directly from the mains supply, which is then passed through a large copper coil (heat exchanger) within the thermal store, and in doing so extracts energy from the hot water in the store to heat it. As the water in the cylinder is not being used directly, it does not need to be heated to 60 degrees to kill legionella bacteria; instead it can be kept at aorund 45 degrees, significantly reducing energy consumption. The hot water delivered is around 40 degrees, more than adequate for washing and showering.
Super insulated thermal store - it is in there, honest!
On Tuesday 16th May, Francesca (age 11 and resident of HHP) appeared on BBC2’s new early morning children’s programme, Level Up, explaining how the homes at HHP collect, use and treat water. This was compared with two other children and how they collect and use water, particularly in relation to toilets.
On Thursday 18th May, one of the other Project children, Naomi Tilley (age 10) will appear on the same programme with her Dad, using a tandem to get to school.
The successful completion of the houses is a result of five years planning, building and development. The launch day was an opportunity to celebrate our achievement and say thank you to all those who have been involved in the project.
It also marks the move towards the next phase of the project, the demonstration of sustainable living in practice. The focus for the project will now be to develop the trading company (HHP Trading Ltd), thereby providing an income for company members which is based on sustainability.