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Southampton, Hilldown Road


House Summary

Owners: Adrian Pickering
House Type: Detached, chalet style house (built ca 1937, extended in 1984 and 2009)
Carbon Saving: 63%
Installed Measures:
  • Cavity wall insulation; 100mm blown fibre. 25mm celotex backing to further reduce waste heat to external walls.
  • Condensing boiler; CH fully remodelled in 2009 with new condensing boiler. 2 zones (downstairs, upstairs) with 1 controlling radiator per zone without TRV.  All the others have TRVs. Target zone temperature in programmed periods is 16degC. Master blender valve provides 48degC DHW to house
  • Double glazing throughout
  • Floor insulation; 100mm (joist depth in suspended wood floor) glass fibre in hammocks (but not kitchen yet). Extension has a solid floor on celotex, per modern standards
  • Loft insulation; 400mm glass fibre
  • Low energy appliances
  • Low energy lighting
  • PV; 2.45kWp, south aspect (on 52deg roof)
  • Roof insulation; 100mm glass fibre installed. Celotex used in 2009 extension to current standards.
  • Solar thermal panels; 2sqm aperture, south aspect (on 45deg roof)
  • Water saving devices; ground water used for toilet flushing (2off). Rainwater is used for clothes washing. Both sources are used for plant watering, in and out. (Local water is hard)
  • Wood burner (Clearview Pioneer)
Southampton SuperHome
  • Personal Story:

    I have been an academic electronic engineer all my life. Having retired from university service, I was concerned to make my reduced income go as far as it can. Since a child, I have always known that modern living using fossil fuels was unsustainable. Now I had the time and skills to ensure I exploited as little of these finite resources as possible.

    The ‘green’ systems were installed with the aim of permanently reducing the recurring costs of non-renewable energy supplies and water/sewerage. Each measure has a viable business case, though the payback can be 10-20 years. The measures also happen to permanently reduce my carbon impact on the environment.

  • Property:

    I bought the house in 2006 with the intention that it be my home for life. I am mostly the sole occupant but have one house guest fairly regularly. Primary issues with the original house were (a) no upstairs bathroom and (b) a failing lean-to utility room at the back. I sought architects’ advice which resulted in a 2-storey rear house extension built in 2009 adding 40% to the area of the house. It comprises a utility room and dining room downstairs and a double-bedroom upstairs, which is used as a study/workshop. The original downstairs bathroom was converted into a shower wetroom and an upstairs bedroom became the new bathroom, inheriting the old bath.

    While the house was a mobilised building site I took the opportunity to do the enabling work for ancillary water systems and solar thermal heating together with renewing the central heating and hot water systems. PV panels were installed in 2010 and the sitting room fireplace and chimney were rebuilt to install a small woodburning stove. Since, the solar thermal system and the water reuse schemes have been completed.

    The old house was built using traditional methods and materials. Any ventilation improvements needed to be sympathetic to the structure and air changes were reduced to the minimum necessary for each room consistent with allowing the building to ‘breath’.

  • Measures:

    Insulation: Original house – retrofit cavity wall insulation (blown mineral fibre) and attic insulation (>370mm glass fibre) under a new suspended floor. The older warm roof segments were insulated as part of the 1984 extension works (100mm glass fibre, maximum the cavity allows). During the 2009 works the sitting room floor and downstairs bathroom floors had half the boards removed, so the flooring was replaced adding insulation hung between the joists (100mm glass fibre on breather-felt hammocks). The floorboards were reused for the new attic suspended floor. The new rear extension walls and warm roof are insulated to 2009 Building Regulations (glass fibre bats and PIR respectively). In winter, I monitored the inside walls using a surface IR thermometer found failings in the blown fibre installation and one of the 1984 extension walls. The fibre fill was eventually remedied under guarantee. The south wall is the only exterior clay brick wall which has no waterproofing. Fortunately, it is sheltered from driving rain by the neighbouring house and there has not been any evidence of cavity damp-bridging. In 2016 the front face of the house was coated with ‘K-rend’ coloured render, which further improved its insulation performance. The faulty 1984 extension wall had a layer of 75mm PIR added and the tile cladding replaced over breather-felt.

    Double glazing and doors: The house was already partly double glazed when it was bought in 2006 and further windows were replaced the following year. During the 2009 works all the remaining windows were replaced, matching the new windows and doors. The recent units feature controllable trickle vents. The front door and frame were replaced with a well-sealing set and the letterbox flap edges fitted with brushes.

    A Clearview Pioneer wood-burning stove (5kW) was installed in the original, recovered sitting room fireplace in 2010. The house is in a smoke-controlled, urban area so the unit had to be DEFRA-listed as smokeless and care taken to ensure burning is >250degC. The previously shortened chimney was dismantled and rebuilt to its original height with a new stainless steel flue liner held in place with Lecca insulation pellets. To date all the wood fuel has been scavenged from neighbourhood tree operations. Some comes from the coppiced Hazels at the top of the rear bank of the garden.

    Solar thermal DHW: Two Ritter CPC6 vacuum-tube panels on the rear, south-facing roof with a Resol controller heating a 210 litre HeatraeSadia Megaflow twin coil mains pressure domestic hot water (DHW) tank. Auxiliary heating is from a 30kW Worcester Bosch gas-fired, condensing ‘system’ boiler, which also drives the central heating (CH) system. I command boiler backup if (a) I know there will be demand for hot water that night or the following morning (b) the upper store is <48degC and, preferably, when (c) the boiler is already warm. This can be remotely monitored and commanded. For biological safety the boiler holds the upper store at 60degC. On very sunny days the water in the tank can get to 95degC as the solar panels are cooled by over-heating the tank. To avoid the risk of scalding a thermostatic blending valve is fitted to limit the DHW supply to 48degC. When designing the revised plumbing, I endeavoured to minimise the drawing lengths and volumes. Having a dishwasher reduces the need for repeated, small amounts of hot water in the kitchen and it’s of a type that reuses its rinse water.

    Central Heating: The Worcester Bosch mains gas boiler mentioned powers the CH. Further to the DHW zone, there are two independent heating zones, upstairs and downstairs. Each is controlled by Nest programmable thermostat. All radiators have TRVs fitted except those that are zone-controlling. The warm period target temperature is 17degC all year. The zone valve logic is arranged to cool the boiler heat exchanger after a heating cycle by dumping its heat into the DHW tank.

    Water systems: The two toilets have 6 litre, dual flush cisterns fed from an attic header tank (100 litre) periodically filled with ground water from a shallow well in the garden. Mains backup into the tank is provided by a ball-valve set at ‘low’ level. I designed and built the simple filling controller, which is used in other homes. The tank level is monitored using a Kingspan ultrasonic sensor intended for fuel oil tanks. There is also a roof rainwater collection system with three, sheltered, black polythene 350 litre tanks sited at first floor level. The incoming rainwater is stilled in a sediment tower and then fed to the base of the levelled storage tanks. These overflow into a soakaway beneath, resulting in crossflow that keeps the water fresh. The naturally-soft rainwater is used for the washing machine and the garden-watering taps. A regenerative shower pump is used to boost the pressure as some washing machine programs can stall if filling takes too long. The tank level is monitored using a sight tube mounted where it can be seen from the washing machine. Both the water systems use widely-available, standard parts (except the controller). My plumber and I took care to make it be fully compliant with BS8515:2009 Rainwater Harvesting Systems Code of Practice and the Water Regulations. Anglian Water’s website also provided useful guidance.

    Also see: Rainwater Harvesting Q&A with Adrian Pickering Aug 2016

    Energy efficient lighting and appliances: All the interior lighting is LED except for some HF fluorescents in the bath- and utility rooms. The two most significant energy consumers are the fridge/freezer (A+ rated) and sitting room TV (A+ rated) and AV rig. Next are the washing machine and dishwasher, both of which use electricity to heat their water. Clothes washing is done at 30degC. Preference is given to running these when there is PV available. The header tank is automatically filled when required if there is sufficient PV. Much of the AV rig is only powered when in use i.e. most of the components are ‘off’ rather than in ‘standby’. The main computer in the house is a ‘lid down’ lap-top computer but with a large screen and keyboard etc. on the desk. It spends most of its time in ‘sleep’ mode. Auxiliary HiFi power amplifiers are ‘Class D’ types which have almost no quiescent current consumption. Cooking and reheating is largely done by microwave. The hob is induction and oven is gas-fired. A saucepan on the hob is used to heat the right amount of water for beverages.

    Photo Voltaic (PV) generation: 10 panels totalling 2.35kWp on the south-facing roof feeding a Sunny Boy inverter. A current clamp on its output drives a PV generation meter in the kitchen and the remote monitor. I designed the panel layout to mitigate the effect of the chimney- and neighbouring roof (winter) shading. The kitchen meter and weather forecast help decide when it might be good to use the dishwasher ordo some laundry. By the PV monitor I also have a house energy consumption monitor. An ordinary energy monitor current clamp doesn’t work with PV – it just reads nonsense when there is generation. The fix is to arrange that the PV circuit ‘live’ is also looped through the current clamp and then the monitor reads total house consumption.

    Sun tunnel lighting: The new upstairs bathroom could not be lit or purge-ventilated using a Velux window because of its proximity to the neighbour’s soil stack vent. Instead a Velux sun tunnel was used in the ceiling over the wash basin. Even on cloudy days this provides plenty of daylight. It worked so well that in 2013 I fitted another over the stairwell, which transformed what was a dark, redundant space into an area suitable for displaying pictures. Both sun tunnels also have LEDs fitted to provide low-level safety lighting at night, controlled by a roof photosensor.

    Ventilation: Passive stack ventilation (PSV) was installed in both bathrooms consistent with 2009 Building Regulations. The waste head from the PV inverter is ducted into the upstairs bathroom to assist driving its stack vent. To provide purge ventilation, each duct has a vertical axis fan triggered by humid activity. The fans have a low cross-sectional blade area so the PSV effect still works when not on. They are mounted on a brick wall in the attic below the roof terminals, with a length of acoustic duct before the fan giving almost silent operation. During the building developments I ensured that the ground floor joists continued to have good under-floor ventilation.

    All laundry is ambient-air dried, usually outside on the washing lines stretched between the wood store’s extended rafters. The utility room DHW tank has a 50W heat loss, despite being very well insulated. This, together with a little extra cross-ventilation, can be used to finish the drying.


    The PV and solar thermal FIT payments more than pay the house energy costs. Net annual consumption is 6.3GWhr for gas and 1.4GWhr for electricity – less than half of the average for a house of this type. Metered water use is about 60 lpppd (litres per person per day) whereas Southern Water’s published figure for a single-occupancy house is over 178 litres per day. The Water Industries Act mandates water-meter-based sewerage charging regime for domestic consumers with compulsory water metering. Taking advantage of this seems to be of little concern to the water companies. Toilet-flushing is typically a third of house water consumption and, for less than 4p electricity, each header tank filling represents a water and sewerage saving of 30p.

    Favourite Feature:

    The toilet water system is a regularly appreciated benefit. The water in Southampton is notoriously hard and it is difficult to keep toilets clean without repeated attention with chemicals or by having a water softener. Here, I can flush the toilets as many times as needed and I just need a good toilet brush to keep them clean. The cisterns fill almost silently as the supply from the low-pressure header tank. So, guests and I can use the flush at night without worrying about the noise. The bathrooms’ ventilation is silent and effective and they are kept dry and sweet without any chemical assistance.

    Communal water supplies have a very low carbon impact and water reuse is not a strategic priority. So, it is a pity that my favourite feature does not make much of a carbon saving, just a modest monetary one. However, the house energy savings are in a different league and have significant, recurring carbon- and financial savings.

    JAP 19/2/19

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