32. A Year's Worth of Energy

I can’t believe just how low my energy use has been for the first calendar year of living in the EcoBungalow. Perhaps I shouldn’t be quite so surprised. This project was meticulously prepared and executed, from buying the right sort of house through to getting a good architect on board and – most crucially – being constructed by a well-qualified builder with an eye for detail.

But, even so, just ….. WOW! I’m using so much less energy for a house that is always pleasant to live in: never too cold, never draughty, never damp, never stuffy.

So let’s crunch some numbers:

Final Quarter: February to May

I’ve been away from home quite a bit during this quarter. But, even taking this into account, the reduction in energy use is again spectacular. On average, the EcoBungalow has used just 16% of the energy for the same period pre-retrofit.

Costs are a much less meaningful comparison, given the volatility of energy prices. However, even though the EcoBungalow is now 100% electric, bills are lower than before for a much improved level of comfort.

Hand-in-hand with the reduction in energy use is a massive reduction in carbon emissions, down an average of 80% for the same Feb-May period.

The Whole Year: May to May

The summary table showing energy use (and the less helpful costs) for the year is extraordinary. I’m using about a fifth of the energy compared to my first year pre-retrofit and the house is WAY more comfortable to live in. Comparisons with 2022/23 are less helpful – like many people, I was trying to reduce my energy usage because the very high costs at this

time. The house was often cold, and yet I paid a lot for the privilege!

Of course, the reduction in carbon emissions is equally impressive – overall about 75% less than 2021/22.

The Viessmann Air Source Heat Pump (ASHP) has been working very efficiently to help give these very low energy use figures. The Coefficient of Performance (CoP) measures the ratio of energy in to thermal energy out. The average CoP for the year has been 5.66 – so for every 1kWh of energy that goes into the ASHP, I get 5.66kWh out. A good CoP is anything over 3.

The ASHP been able to work this efficiently because:

• the bungalow is so well insulated that there is little heat loss and, hence, a low demand for space heating. This means that the ASHP can operate at low (i.e. efficient) flow temperatures as we don't need a lot of heat;

• this bungalow is extremely airtight, so there is no loss of heat through draughts. The mechanical ventilation system warms incoming air during colder weather with the outgoing stale air, so very little heat is lost providing fresh air. This further reduces the demand for space heating;

• hot water is heated to a relatively low temperature of 45ºC, so minimising energy consumption; and

• it’s been expertly installed by local contractor Shane Leck Heating Ltd, and commissioned by Viessmann.

#EcoBungalow #Passivhaus #Passivehouse #EnerPHit #Retrofit #Deepretrofit #ASHP