SuperHome Database

Southampton, Hilldown Road

House Summary

Adrian Pickering

House Type:
Detached, chalet style house (built ca 1937, extended in 1984 and 2009)

Carbon saving:
63% - Remote Assessed  

  • Southampton SuperHome
  • SuperHome 207 Southampton Solar Panel
  • SuperHome 207 Southampton Thermal solar panel
  • Rainwater harvesting tank
  • SuperHome 207 Southampton Boiler

Measures installed:

  • Cavity Wall Insulation
  • Condensing boiler
  • Double Glazing
  • External Wall Insulation
  • Floor Insulation
  • Loft Insulation
  • Low Energy Appliances
  • Low Energy Lighting
  • Roof Insulation
  • Solar PV Panels
  • Solar Water Heating
  • Water Saving Devices

Upcoming events

Early interest in Open Days encourages SuperHome owners to host more events. If you'd like to visit this property please contact the owner and let them know. SuperHomers are often happy to respond to questions about their refurbishment project by email between times. Please read ‘more on contacting this SuperHomer’ before you make contact.

What visitors are saying

"Some very interesting solutions to common problems. We especially liked the use of the water table and sun tunnels."

"Very impressed by the extent of the measures that Adrian has undertaken, and his knowledge of the necessary hi-tech and safe aspects."

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 background:

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. This added about 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’.

Key changes made:

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). As the sitting room floor and downstairs bathroom floors needed at least half the boards removed, the floors were replaced with insulation hung between the joists (100mm glass fibre on breather felt hammocks). The floor boards were reused in the attic suspended floor. The new rear extension walls and warm roof are insulated to 2009 Building Regulations (glass fibre bats and PIR respectively). In the Winter of 2015 I monitored the inside walls using a surface IR thermometer and I found failings in the blown fibre installation. These were eventually remedied under guarantee.

Double glazing and doors: The house was already partly double glazed when it was bought in 2006. Further windows were replaced in 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. The letterbox flap has brushes fitted to its edges.

A Clearview Pioneer wood-burning stove (5kW) was installed in the original, recovered sitting room fireplace. The house is in a smoke-controlled, urban area so the burner must be qualified to be smokeless. The previously shortened chimney was dismantled and rebuilt to its original height with a new stainless steel flue liner held in place with Lecca 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. 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 made every effort to reduce the drawing lengths and volumes. Having a dishwasher reduces the need for repeated, small amounts of hot water in the kitchen. (The dishwasher is of the type that recycles its rinse water.)

Central Heating: The Worcester Bosch mains gas boiler mentioned powers the CH. Together with the DHW zone, there are two independent heating zones, upstairs and downstairs, each controlled by a Horstmann AS1 mains, wired, programmable thermostat. All radiators, except the controlling ones, have TRVs fitted. The warm period target temperature is 18degC all year. The zone valve logic is arranged so that the boiler heat exchanger is cooled by dumping 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 charged from the ground water in a shallow well in the garden. The tank has passive, automatic mains water backup. I designed and built the simple filling controller which is now used in two other schemes. The well and tank levels are monitored using Kingspan ultrasonic sensors made for fuel oil tanks. There is also a roof rainwater collection system with storage in two, 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 inducing crossflow in the tanks to keep 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 supply pressure as some washing machine programs can stall if fills aren’t prompt enough. The tank level is monitored using a sight tube mounted where it can be seen from the washing machine. A small, fluorescent-coloured fishing float in the tube gives a clear indication. Both the water systems use widely-available, standard parts (except the controller) and 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 also provide 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 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). 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 electric jug kettle has a fully-opening lid so it can be easily filled with just the right amount of water. Much of the AV rig is only powered when in use i.e. it is not left 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 and oven are both gas-fired.

Photo Voltaic (PV) generation: 10 panels totalling 2.35kWp on the south-facing roof feeding into a Sunny Boy inverter with a BlueTooth energy monitor in the kitchen mounted near the kettle so it gets looked at often. I designed the panel layout to mitigate the effect of the chimney and neighbouring roof (winter) shading. I use the PV monitor with the weather forecast to decide when it might be opportune to use the dishwasher, do some laundry or fill the header tank. By the PV monitor I also have a house energy consumption monitor. In houses where there is ‘reverse energy demand’ you cannot just put the current clamp sensor on a meter tail alone. Such sensors are not able to distinguish between forward- and reverse energy demand and the monitor will read nonsense. So, I arranged that the PV circuit ‘live’ is also looped through the current clamp at the consumer unit and the monitor then reads true.

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, illuminating the wash basin. Even on cloudy days this provides perfectly adequate daylight into the whole room.  Indeed, it worked so well that in 2013 I fitted another over the stairwell. This has transformed what was a dark, redundant space into a light area suitable for hanging pictures. Both sun tunnels now have LEDs to provide safety lighting similar to low-level daylight. The LEDs are controlled by a roof photosensor and a timer.

Ventilation: Passive stack ventilation (PSV) was installed in both bathrooms complying with the 2009 Building Regulations guidance. 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 use of the shower or bath. The fans have a low cross-sectional blade area so as not to inhibit the PSV effect. They are mounted on a brick wall in the attic below the roof terminals with a length of acoustic duct before the fan. They are almost silent in operation. Through the building developments I paid attention to ensuring that the ground floor joists continued to have good cross ventilation.

I have avoided having a tumble drier so the laundry is ambient-air dried, usually outside on the washing lines on beam extensions to the wood store roof. The utility room DHW tank has a small (ca 50W) heat loss despite being very well insulated. With this unavoidable waste heat, together with a little extra cross-ventilation, it is an excellent place to finish drying the laundry.

Measures installed in detail:

  • 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)
Benefits of work carried out:

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 – low by current standards, particularly for a house with dominantly one occupant. Metered water use is 60 litres per day rising to 90 litres when there is another occupant (ca 45 to 60 lpppd). Southern Water’s published figure for a single-occupancy house is 250 litres per day. Industry consultations have shown that water companies are relaxed about the savings coming from both the substituted water AND the proportional sewerage charge. Indeed, the Water Industries Act mandates the sewerage charging regime for domestic consumers with enforced metering. So, at an energy cost of 4p (or less if PV is available), each header tank filling represents a saving of 30p. (Note that toilet-flushing is typically a third of house water consumption.)

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 maintenance of an installed 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 header tank is at low pressure. Thus guests and I can use the flush at night without worrying about disturbance. The bathroom ventilation is very effective (and silent) and the rooms are kept dry and sweet without any chemical assistance.

Communal water supplies have a very low carbon impact. The Centre for Alternative Technology (CAT) points this out and so, for them, water reuse no longer a strategic priority. 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 both significant, recurring carbon- and financial savings, as originally sought.

Contact this homeowner

Assessment types

SuperHomes Assessed

A home that has been visited and assessed by us and confirmed as reaching the SuperHome standard, which demonstrates a 60% carbon saving.

Homeowner Reported

Information has been provided by the homeowner about their home and energy use prior to the installation of measures and following their installation which demonstrates a carbon saving. This information has not been verified.

Remote Assessed

The homeowner has provided information on their home including what measures have been installed which has enables an assessor working on our behalf to assess their carbon savings. This home has not been visited to verify the measures installed.


This home has not been assessed, but the homeowner has reported what measures have been installed. It may be that this home is awaiting assessment.