Cost house roof



Photo Voltaics

Photo Voltaics have been installed to generate electricity to be used by the residents reducing their bills and CO2 emissions. Five Ulica Photo Voltaic 225 W Monocrystalline Panels have been installed giving a peak output of 1.125kWp. They are expected to produce 1020 kWh per annum. The pholtovoltaic installation is linked to the main distribution system via an inverter located within the loft space. This means that the electricity produced can be used by any electrical appliance within the house. The photovoltaic installation will generate income by means of the Feed-in-Tariff. This will generate around £421 per annum by means of the generation tariff and around £15 per annum by means of the export tariff. This income will be retained by Catalyst Housing Group. Energy Savings worth around £66 per annum will benefit the resident directly.


Solar Thermal Panel

A solar thermal panel has been installed; this will assist in producing hot water to the boiler, which is used to assist in heating water. Solar thermal energy can produce up to 60-70% of a domestic property’s annual output. All hot water outlets are provided with hot water from a twin-coil pressurised unvented hot water cylinder, located in a storage cupboard on the first floor landing. The lower coil is served by a 3 m² bank of Valliant auroTHERM VTK 570/2 evacuated borosilicate glass tube solar thermal collectors mounted on the west facing pitched roof. Collected solar energy is used to pre-heat the cold water supply, thus reducing the load on the boiler plant, and therefore saving gas. The upper coil is served by the gas-fired boiler. The expected output from the solar thermal panel is 800 kWh per annum.

Rainwater Harvesting

Rainwater harvesting (270KB) tanks that collect rain water run-off from the roofs have been installed. This water is then collected and used to flush the toilets within the properties. Rainwater is collected from the slate roofs and stored in an external plastic container. A filter is located in the rainwater pipe adjacent the connection to the store. This catches leaves etc, and also acts as an overflow. This filter is designed to be self-cleaning (with debris being washed down the overflow) but will require routine inspection. A stainless steel pump takes rainwater from a lower connection on the store and pumps it up to a loft mounted rainwater header tank. Automatic controls within the pump automatically sense a drop in water pressure in the pump discharge line when the float valve in the header tank drops, thus starting the pump. These controls also stop the pump when the float valve shuts and pressure rises, or if the rainwater runs out and there is no flow. The rainwater header tank has 2 float valves – the first is connected to the boosted rainwater supply as above. The second is connected to the cold water mains supply, such that if there is a lack of stored rainwater and the level in the tank drops below about halfway, mains cold water will be supplied instead.

Maximisation of Natural Light

The amount of natural light entering the property has been increased so as to reduce the need for artificial lighting and the energy to produce it within the property. It is also believed that the extra natural light will be conducive to the wellbeing of the residents. A Solar Tube by Solatube light adds light to the first floor hallway.

Roof Insulation

Loft spaces have been insulated with 325mm Black Mountain Natural Hemp (195KB) insulation achieving a u-value of 0.12 W/m²K. The product is manufactured from a blend of hemp and other natural fibre, incorporating a binder to ensure that the product retains its thickness. Hemp is said to have excellent insulation properties due to its low thermal conductivity and high thermal mass. It is a breathable material that is able to absorb, retain and release moisture whilst retaining its thermal properties. The product is treated with a simple compound to achieve Euroclass E fire performance. Where there are vaulted ceilings, 80mm thick GA4000 insulation has been fixed between the rafters, and 50mm thick Gyprock insulation board has been fixed to the internal side of the roof, to increase the level of insulation and reduce thermal cold bridging via the rafters. Here, a u-value of 0.17 W/m²K has been achieved.