IRELAND – A1 Net Zero Hyper nZEB – Case Study

This is a case study based on a real new build detached house in Dublin, Ireland. (it should be noted while this is a new build, we can make any retrofit meet or exceed this standard easily also)

The home was initially presented to us with a heat pump in the design. That makes sense, as you can only meet minimum nZEB regulations with either a HONE system or a Heat Pump (with some additional uplifts like extra insulation & Solar PV to get the heat pump over the line).

Of course, the big difference between the 2 options is that you have to buy 100% of your future energy for heating, hot water, electricity & car charging with a heat pump, which means lots of energy taxes for the Government, so they like this solution. However, with a HONE system, you make most or all that energy for free and keep your money and taxes in your own pocket.

The first thing to mention is the heat pump was giving the basic entry-level A2 nZEB result in the SEAI energy rating. The data you see below is for an A1 Net Zero Hyper nZEB result with the HONE system; this is two steps further than a basic A2 nZEB result.

Firstly, the costs, this is a 106 sqm detached 2 story home. The QS gap analysis below shows the difference in construction cost between the two options in this house. But PLEASE NOTE: the heat pump option is only a basic A2 nZEB where the HONE outcome is an outstanding A1 Net Zero Hyper nZEB that makes the same amount of energy from its own free renewable energy systems house will consume. (As it not possible to get the heat pump solution to meet an A1 Net Zero Hyper nZEB standard, we cannot work out an exact like for like cost comparison, but you can assume the Heat Pump building cost would have increased significantly).

So this house with HONE would be within the top 100 homes in the current BER energy rating list and would be significantly more valuable in the order of 20% based on the current market than a bog standard A2 nZEB.

It is significantly cheaper to build an A1 Net Zero Hyper nZEB using HONE, and the running costs will be 90% lower than the heat pump option. More importantly, your house will be worth 20% more in value, and you don’t have to be a rocket scientist to see which approach benefits you the most.

Download the QS GAP analysis below; it is designed to be easy to understand. 

QS-GAP-ANALYSIS-v3.0

Next, we will look at the DEAP calculations for that A1 Net Zero Hyper nZEB with HONE.

Let’s do a little test and see if you can work out the new annual heating bill and hot water bill with our help. This new house has a micro oil boiler, it could be gas, but you would have a monthly rental cost bigger than your gas bill. (both these options have the lowest CO2 emissions currently at the point of use, and only a third of the emissions of electricity, for example.

Let’s do the HEATING first.

Click on the SEAI DEAP dwelling report below; this is the construction detail of the home. (you can change the page at the bottom)

Go to page 12, and on the bottom right-hand corner of the page, you are looking for the Energy required for the main heating system [kWh/y].

That value is 1,914.67 kWh/year.

To convert that into cost, there are just over 10 kWhrs of heat in a litre of heating oil so let’s convert it into litres. 1914.67 kWhrs = 191.467 Litres of heating oil.

As heating oil is currently 60c/L, that makes your new annual heating bill €114.88. Yes, not a typo, ONE HUNDRED AND FOURTEEN EUROS (Do you still feel like spending thousands of euros installing a heat pump with annual electricity bills of €1,200 plus ??) in addition to having to pay for all your hot water, electricity and car charging?

HONE produces up to 90% of your annual hot water for free. Still, DEAP will report a shortfall so let’s see how much extra heating oil (or you could use the immersion with your own free electricity for that topup) but for this exercise, let’s assume heating oil as it has a third of the emissions of electricity and is cleaner and a lot cheaper than using the immersion from the grid.

Now go to page 13 and the top right-hand side of the page. You are looking for Energy req. for main water heater [kWh/y]

That value is 2,121.55 kWh/year.

To convert that into cost, there are just over 10 kWhrs of heat in a litre of heating oil so let’s convert it into litres. 2,121.55 kWhrs = 212.155 Litres of heating oil.

As heating oil is currently 60c/L, that makes your new annual hot water top-up bill €127.29. 

So your total heating oil consumption would be €242 for the year.

Here is the important part. Given a heat pump installation averages around €12,000 (SEAI Heat Pump Report Nov 2020), but we all know when you include Solar PV, extra Insulation, it’s actually bigger but let’s use the €12,000 for the installation cost in this case, that €12,000 would provide you with heating oil for 50 years.

The Total annual CO2 emmisions of the home with HONE is now 155.82 kg/CO2/year (1.55 Tonnes of CO2 every 10 years) and with the original heat pump would have been 1.2 Tonnes of CO2 every single year.