Cardiff University – Case study
Background
This property is occupied by a family of two adults and two young children, who are at home most of the day. The home has a total floor area of 72m2 and already had an efficient gas heating system that provided heating and hot water. The shower was powered by electricity. Previous to the retrofit, one resident said that the entire family were dealing with health issues as a result of the damp. Their son’s asthma, in particular, was getting worse “by the day”. They noted the “awful” smell of damp in their bedroom. There was a draught coming from around the door, which was making the home cold.
Measure(s)
Cardiff University’s Low Carbon Build Environment (LCBE) team worked with Wales and West Housing to complete the solid wall end-of-terrace retrofit in March 2018. Detailed surveys were undertaken in order to understand the home and identify strategies; these were then compared using computer modelling. This enabled the team to select a package of tailored solutions, taking into account location, orientation, shape and likely occupancy patterns.
In order to reduce the household’s energy demand, the following measures were installed: internal wall insulation (front elevation), external wall insulation (gable and rear walls) and loft insulation. The installation of a mechanical ventilation with heat recovery (MVHR) system decreased humidity, leading to improved air quality and reduced condensation and mould growth.
To provide the home with renewable energy at source, the team installed east- and west-facing PV solar panels, which allowed energy to be generated throughout the day, plus a Transpired Solar Collector (TSC) on the gable wall (which pre-heats the air used for the heating system with solar energy). In order to store this energy, a battery was put in place alongside various supportive electrical works. The TSC and MVRH work together to reduce the amount of energy needed to heat the home.
Impact
The residents reported considerable improvements to their respiratory health: the son’s health is “so much better”, with his cough completely gone. This has enabled him to go back to school. This is a result of the improved internal conditions and comfort of the home, whereby the MVRH supplies clean, warm air to living spaces. The average internal air temperature increased from 19.8°C to 20.5°C, while average relative humidity fell from 71% to 58%, reducing the risk of mould growth.
The home’s EPC rating improved from EPC E (47) to EPC B (89) as a result of the retrofit. Whilst before the house took a long time to warm up, they now only have to switch the heating on for 15 minutes before feeling the warmth. The house’s improved fabric, combined with the TSC and MVHR systems which reduce the need for energy consumption, resulted in a reduction in gas use, from 16,127 kWh to 11,074 kWh per year.
Not only was energy consumption reduced, but almost all consumption was able to be met by the solar panels and battery. Over the course of a year, the solar PV panels enabled electricity import from the grid to be reduced from 3,175 kWh to 776 kWh. During warmer and lighter spring, summer and autumn months, 2,853 kWh was exported back to the grid.