Property Clinic: What is the best solution for heating and hot water for a storey and a half house?

Your property questions answered

 Today we expect to maintain a warm home environment at around 20 to 21 degrees

Today we expect to maintain a warm home environment at around 20 to 21 degrees


On reading a recent answer to a query, I noted that the response stated in summary “air source heat pumps are less efficient and can be noisy”. My question is this: currently what is the best solution for heating and hot water for a storey and a half house? I am researching air to water but also the traditional oil and increased insulation with solar panels solution. It is very confusing, with some people complaining about high ESB bills whereas my architect is praising it and calling it planning for the future. Any advice much appreciated.

The key to understanding how we arrive at a comfortable environment in our homes is thinking about energy itself. Traditionally we started with fire and “burning stuff” as a way to keep warm. Gradually, better ways to burn stuff and keep the energy produced inside the home were invented.

Today we expect to maintain a warm home environment at around 20 to 21 degrees. At the same time building regulations ensure that we use less energy to create that environment by adding insulation; so much so that the current requirement for investment in insulation has almost reached the point where investment in burning stuff to create energy has become questionable. Why spend a considerable sum on a system that is rarely useful and indeed requires a constant supply of increasingly expensive “stuff” to produce energy that’s no longer squandered?

Of course that question is challenged by the professions and trades that formerly profited from these investments on the basis of their loss of income, so for now, misinformation abounds.

An air to water heat pump uses electricity to extract energy from the outside air at a ratio of around one unit of electricity to four times useful energy produced as hot water to heat the home. This is good, but the efficiency falls as the outside air temperature falls. These efficiencies can be greater than four and are much better than burning oil or gas which have energy efficiencies less than one but they rely on the efficiency of the electricity generators and distributors which still need to burn stuff at efficiencies of way less than one.

Your architect is right that we need to think about a future where energy is contained in our warm envelope. To maintain a healthy environment requires not just warmth, but fresh air too. In a typical home the entire volume of air should be exchanged at least three times every hour, with that air exchange goes our “free” energy too.

If you have invested in good insulation in an air-tight home then you can start to avail of the paradigm change of NZEB or near zero energy building that is occurring as we begin to stop burning stuff to keep warm and begin to concentrate on healthy air systems with energy exchange built in. Better units have small heat pumps inside that take energy in the outgoing stale air and return it into the incoming fresh air at extremely high efficiency rates; together with living and occasional sunlight this increases the internal energy available so the unit uses that to create almost free hot water too and that’s what I meant by my “less efficient” comment in the previous answer and the addition of the PV panels you mention.

These systems are also beneficial to the building itself by relieving stress in the structure, reducing condensation by removing damp air, hence propensity for mould and altogether make for a healthier home. The answer is: invest in insulation, air quality and a small amount of PV. While the energy providers might not like it, you can stop burning stuff and join the new energy revolution.

Fergus Merriman is a Chartered Building Surveyor and member of the Society of Chartered Surveyors Ireland,