Published: 18/11/2021The UK Government has pledged to reduce Carbon Emissions to Net Zero within the next 20 to 30 years. This is highly ambitious and will require every one of us to make a significant contribution if we are to succeed. Currently the UK residential sector contributes around 25% of all Carbon Dioxide (CO2) emissions, the remainder coming from industry (25%) and transport (50%).
So how do we become more sustainable in our homes and how do we reduce our carbon footprint in the Prime Residential Sector?
In the UK the average person produces 5 tonnes of CO2 a year. We’d need to plant one tree to absorb enough CO2 for each square foot of our property.
We’re all striving to be more sustainable but what does sustainability mean?
It has been said that “Sustainability is achieved when we are only using enough natural resources to ensure all future generations have the same opportunity to develop in the same way’’.
What do we need to do with the older prime housing stock?
We need to reduce the requirements of our homes’ heating, electrical and water systems by considering doing the following:
·Insulate wall and roofs
·Replace existing single glazing with double or triple glazing
·Install solar hot water panels on roofs or within gardens
·Reduce hot water demand by using low flow taps and shower heads
·Install mechanical ventilation with heat recovery to all rooms
·Install photovoltaic (PV) panels on the roof to generate electricity
·Reduce the use of dishwashers and washing machines.
Some of the above may require planning consent and, if the building is listed, may present further issues. The Government’s plans are for all properties but are largely unworkable for the older properties and mansion blocks, particularly listed buildings, which are found throughout Prime Central London.
What is the alternative to the gas or oil-fired boiler?
To complicate matters the Government is now also rapidly moving towards a future ban on the sale of all new fossil fuel boilers.
The future is the Heat Pump which can remove heat energy from the air or the ground and feed this into the house heating system. These are highly efficient in that for every 1Kw of electricity used to drive the compressors, up to 4Kw of heat can be produced to heat the dwelling. Another major advantage is that they can be used in reverse to cool the dwelling in the summer bearing in mind the anticipated Global Warming threat.
Air Source Heat Pumps are usually located externally but are noisy and unsightly and very difficult to retrofit into typical Prime residential properties. Furthermore, their efficiency drops off dramatically when the external temperature falls below 5°C, just when heating demand reaches its peak.
Ground Source Heat Pumps use coils or piles buried in the ground to extract geothermal energy. They are quieter and less obtrusive but may not be practical where buildings have no garden or basements beneath the garden.
The major drawback of all Heat Pumps is the relatively low heating flow temperature delivered to the heating system. A maximum is around 50°C. This is fine for modern underfloor heating systems but unsuitable for the more common radiator systems found in most older dwellings.
Fortunately, older dwellings have a heavyweight structure masonry which provides ‘thermal mass’ to the buildings causing them to heat up and cool down more slowly. This, coupled with taller ceilings, can help to significantly reduce the requirement for comfort cooling or air conditioning. Solar controlled glazing and external louvres and shades can also assist in reducing internal summertime temperatures.
All of us have a duty to be more sustainable. However the systems available to reduce our carbon footprint are simpler to install in modern developments than in older prime housing stock.
Getting energy efficiency measures wrong could harm the fabric of such buildings as well as their historic value and significance. A holistic approach is required necessitating an understanding of the design of the building fabric and of the mechanical and electrical services.
freddie g brown MCIBSE CEng Eur Ing
managing director, freddie brown associates ltd
building services and carbon consultants