Victorian Solar House

This Red Brick 1850’s Victorian house was renovated using low tech Passive Solar principles without affecting its character.
The following alterations were undertaken;

• The house was re-roofed using natural slate and a breather membrane was installed.


• 100m2 of Under floor heating pipe was fitted between the breather membrane and the slates, to collect the equivalent of 20m2 of Solar Panels. Our calculations show that less than 25% of the solar energy that shines on the roof will heat the house for the winter, so we will have more than enough to allow for losses.

• The roof was insulated to Passive Standard with 300mm of Cellulose pumped at a density of 65kg/m3 and lined on the inside with OSB board with the joints taped with Siga tape, making it airtight and wind-tight, triple glazed Facro roof lights were fitted with a 0.97 were also fitted.

• Low enough U-value windows were unavailable so we made our own new triple glazed Krypton filled up and down sash windows using 0.6 U-value glazing, we estimate a U-value of 0.9 for the windows and frames. They were sealed to the wall with Siga air tightness tape to achieve a high level of air tightness, the sash boxes are lined with polystyrene, a layer of foam was installed between the frames and the brick to reduce cold bridging and the brick reveals were pointed with lime plaster.

• Chimney balloons were fitted to some of the chimneys and others were sealed up completely to improve the air tightness levels.


• A 300m2 thermal ground store was created under the house to store the heat collected from the roof pipes for use in the winter, the heat from the roof pipes is delivered using a home made heat exchanger to a point two metres below the centre of the house. Heat moves through the ground at a speed of 1metre per month, insulating above the store and diverting rain will reduce the heat movement to 1metre in 2 months. The soil beneath the house is expected to reach 25-30 degrees towards the end of the 3rd summer. Using a heat pump to exploit the heat store and a low temperature (30 degree) FiWi radiator to deliver heat we can achieve a COP of between 12 and 15.

• North, West and South facing PV panels on the chimney will run 3 separate low energy motors which will pump water through the East roof in the morning, the South roof at midday and the West roof in the evening. The pumps will start running when the water temperature in the roof reaches 25 degrees.


• A layer of under-floor heating pipe was laid on top of the thermal store to pre heat the hot water before it reaches the combi gas boiler, a sensor on this pipe will check the temperature lift.

• We placed a 2m deep temperature sensor beside the heat store and a 1m temperature deep sensor beside the external wall of the house.

• The floor was insulated with 300mm of Polystyrene covering the Thermal Heat Store. Under floor heating pipes were installed between the joists.

• 1000kgs of sand and 250kgs of lime were mixed in a dry mix to cover the under floor heating pipes, water was sprinkled on top to set the mix. Polystyrene can breathe and the sand/lime can breathe, preventing moisture being driven up the walls. The sand will keep the timbers dry and healthy by wicking away moisture similar to old church floors I saw in Sweden.

• Future modifications to this house will include, putting glass slates on the 40m2 south facing roof to increase the solar collection capacity, putting solar collection pipes under the tarmac on the street in front of the house to collect extra low grade heat.


• Using the 100m2 garden as a further Underground Thermal Energy Store by placing 100mm of EPS just beneath the topsoil. In future when gas or oil becomes unavailable we need to learn how to exploit sources of low grade heat. Here are some examples of houses with glass slates.