Building Advice: What heating system to pick for your home

One project can reduce your energy bills and your carbon footprint

An air to water heat pump by Nibe AB Sweden. Supplied in Ireland by Unipipe, unipipe.ie.

Hi Kieran. I am about to commence a renovation of my home that will include new insulation and a heating system. We are getting rid of the oil tank and boiler. I was considering a gas boiler for the central heating and hot water, but considering the rising prices of gas, I am having second thoughts. What are the alternatives to gas for a home heating system? Are some systems more difficult to install than others?

Thank you,

Peter, Cahir

Hello Peter. Thank you for your question. 

Renovating your home can certainly be an exciting and rewarding journey if carefully planned and executed. Of course, today, there are so many new factors to consider. Outside of growing environmental concerns there are the new NZeb building regulations which came into effect in late 2019.

CLIMATE & SUSTAINABILITY HUB

What this will mean to your renovation project is that if you renovate more than 25% of the external envelope (outer walls including windows/roof/ground floor) of your house, then you are required to bring the whole building up to a B2 energy rating to comply. This is quite a deep retrofit, and it should be borne in mind that there are now quite considerable grants available from the SEAI to assist with these works.

If you have the budget available, I would be for installing an air to water system. 

A Daiken air to water heat pump can fit in a cupboard.

There is a considerable upfront cost for sure, but with the grant aid available, this would be a one-time investment in very cost-effective energy bills into the future. This system would also cater for your hot water demand. 

For an air to water system to work effectively, you need a well insulated house with a good level of airtightness (e.g. seals around windows and floors and a hard coat at your external walls). You now would have an opportunity to greatly reduce heat loss through draughts, though it may well be worth considering fitting a demand control ventilation unit at this level of airtightness.

Air to water works best when you have a large surface area to heat, as it operates at a lower running temperature than a gas or oil-fired system, so the larger area compensates for this. What typically works best is an underfloor heating system on the ground floor. 

With air to water, it is generally not required to fit a screed in this instance, whereas it was always a requirement with gas or oil-fired systems in the past.

If you have a first floor, you could install aluminium radiators to this heating system. I generally find that the warm air from the ground floor rises upstairs anyway, and many people find they sleep better when it’s a bit cooler.

The only external energy input you will need for the air to water system is a low level of electricity, but make sure you inform the ESB (with the aid of your electrician) that you intend to fit this system as it may affect the voltage of their power line to your house.

Mitsubishi Ecodan 2177 air to water heat pump in an outdoor solution wall hung in a discreet position. The collector and pump are all in this one housing. A south facing position means warmer surrounding air and is therefore ideal. mitsubishielectric.co.uk

In the future you may even consider a photovoltaic system where solar panels are fitted to your roof and a battery storage facility is installed. This would allow you to generate electricity, and this could be used to power your air to water system, further reducing your energy bills and of course your carbon footprint.

Again, all this comes down to your budget, but there are many reasons I would advise carrying out all these works in one go. Firstly, it will be the most cost-effective approach, as you can get the best deal from the contractors involved rather than a piecemeal approach. Secondly, it will involve the least amount of disruption for you and your family. 

Thirdly, you can design all the measures to work together and take advantage of the grant monies available. And finally, all these systems have a payback time on your investment, so the sooner you fit them, the sooner you can begin to enjoy the comfort and value they add to your home.

• Civil engineer Kieran McCarthy is founder, and design and build director with KMC Homes. He is a co-presenter of the RTÉ show ‘Cheap Irish Houses’.