Would heat recovery system help reduce our carbon footprint?

Our bungalow house was built circa 1984. In 2012, after I retired, we did some remedial work on our house which included increasing attic insulation, having outer walls pumped with bead insulation, and replacing our oil boiler.

I recently read an article about a system which recovers heat from ventilation units placed in various rooms in the building which would provide heat in the building. I was wondering if this system would help with the heating of our home and therefore help in reducing our carbon footprint?

There is an increasing drive towards energy efficiency or low-carbon footprints and rightly so as we have been profligate with the easy availability of cheap fossil fuels. These are rapidly coming to an end and it’s past time to really engage with energy efficiency, so congratulations on the steps you have taken so far.

The Government is also addressing this issue with revised building regulations coming into force in April next year for both energy efficiency and ventilation as part of the near-zero energy buildings (nZEB) initiative implemented by the European Union since 2010. You will also note that the Sustainable Energy Authority of Ireland (SEAI) is pushing hard on the uptake of grants for home improvements towards energy efficiency.

Why is one room always cold in our otherwise toasty dormer bungalow?

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Thermally efficient and airtight homes sound great but without adequate ventilation they can be very unhealthy. It is recommended that air in an occupied room needs to be changed at least three times every hour, that’s three sets of hard-garnered energy that will escape with that warm, stale air. This is a significant energy loss in an otherwise energy-efficient home but it’s essential for health reasons.

A number of companies have recognised the demand in this area and most of their systems claim up to 100 per cent efficiency. However, to be clear, that means that only half the energy can be recovered. Simply put, if your set temperature is 20 degrees and it’s zero outside then the system can save only 10 degrees, meaning the fresh air will come in at half the difference, eg 10 degrees. Typically it’s less, but this is still helpful because it’s better than the temperature outside.

I have noticed in a number of homes I have inspected that the units are turned off in winter because of the perception of a relatively cold draught leading to the potential of an unhealthy home, so it is very important to fully understand what such a system does and to operate it to the manufacturer’s instructions.

The new zeitgeist in this area – already popular in Scandinavia – is heat recovery ventilation with inbuilt heat pump in the exhaust air. These systems fully control energy movement because a small heat pump in the system moves required energy from the outgoing stale air to always maintain the set temperature in the incoming fresh air. They also recover spare energy to heat the hot water tank.

We are finding that year-round healthy, warm homes can be designed with such systems, which are less costly to install than traditional heating systems and are extremely efficient to run. Added benefits include their cooling effect during hot summers and ensuring that healthy, warm air is always maintained throughout the home.

I hope that the upcoming changes to the SEAI’s “dwelling energy assessment procedure” software for assessing energy ratings (BERs) recognises the benefit of these systems that don’t require large outside energy inputs, as already recognised in much colder countries; and, coupled with solar panels, they are a great way to reach nZEB standard.

I hope this helps you in researching a decision towards your zero-carbon future.

Fergus Merriman is a member of the Society of Chartered Surveyors Ireland, scsi.ie