All-electric houses will buy energy from each other in future

From March 31, 2019, if you are applying for planning permission, your house must comply with Nearly Zero Energy Building rules, says Kya deLongchamps.

All-electric houses will buy energy from each other in future

From March 31, 2019, if you are applying for planning permission, your house must comply with Nearly Zero Energy Building rules, says Kya deLongchamps.

Architect and passive designer, Wain Morehead, won a gold award from the The Irish Green Building Council for this passive, nZeb house.
Architect and passive designer, Wain Morehead, won a gold award from the The Irish Green Building Council for this passive, nZeb house.

WITH a fizzy acronym worthy of a Formula 1 car in competition colours, on December 21, 2020, Nearly Zero Energy Building residential legislation (nZEB) will easily surpass the carbon-crushing energy requirements of Part L (2011) of the Building Regulations. It’s basically a bound from a B1 BER to making A2 commonplace.

Transitioning? If you applying for planning from March 31, 2019, your home must be nZEB compliant. The future is a mechanically managed, all-electric building that potentially powers itself, and we have reached this halcyon moment on many progressive A1 estates.

I’ll admit to some lingering mistrust. Obligatory technologies? Is ‘nearly’ just passive-lite? Who is nurturing renaissance thinking in the mortgage meetings for retrofit? Can we sell our excess power? Lost in inflation, are we ultimately going to pay extra for this lean, green triumph in even higher new house prices?

Dr Marc Ó Riain, (FIDI) of RUA Architects ( and lecturer in the Department of Architecture, CIT, has completed a PhD in zero energy architecture, which involved the retrofit of Ireland’s first net-zero energy building on campus.

“nZEB (Part L 2017) is a standard introduced by the EU in 2010. We have been steadily improving building standards for energy conservation since 2005. Our new buildings and retrofits will now be 60% better than the 2005 equivalent.”

Part L targets our high reliance on fossil fuels with tightly constructed, generously insulated envelopes and managed ventilation. nZEB energy standards improve on what we have, perfected by dedicated software modelling at the earliest design stage.

What it delivers, in addition to solar panels and warmer walls, is a home that generates a large slice of the energy required to heat, cool, and power its daily round (or draws energy from a very local position).

Heat-pump technology (HP), the inclusion of mechanical ventilation with heat recovery (MVHR), and photovoltaic panels (PV) will become as commonplace as DPCs. Pilot projects and bespoke RIAI builds are already exceeding the proposed Irish nZEB finish line.

With heat pumps, in some cases, doubling an electricity bill, nZEB takes the next logical step. Power production is brought home and renewable energy ingredients will slash the heating demand from 15,000kWh to 1,500 kWh, or by 90%.

You may well find the architect handling your current self-build project is diligently reaching for nZEB methodology — put them on the spot. The Passive House Academy deems their quality and comfort assurance as perfectly married to the mandatory requirements for nZEB. Up to now, such lofty notions have only been mandated by the Dun Laoghaire Rathdown council.

Marc Ó Riain says: “The passive house standard, which has been around since 1988, informs the nZEB standard. Tomas O’Leary, who built Ireland’s first passive house, is always saying that a passive house could be heated with a hairdryer.” Actually, the heat from your hairdryer, in a MVHR managed nZEB home, will be ingested straight back into the house.

Marc says: “If you were planning a new house, or a retrofit, today, you should be using NZEB standards. I have to say, the regulations are very complex, but we have a lot of competent designers in Ireland, who know their stuff.”

Retrofit? “Yes, nZEB is included in the regulations, if you are retrofitting over 25% of the building’s external surface area. The standards are not as tough as new-build and not as good as passive house, but they are very welcome.”

Marc says that solar shading is not adequately covered in building design. Overheating as a problem in an Irish home? It’s hard to imagine, I know, but discuss this detailing with your architect.

The disappearance of grant aid for even natural gas-condensing boilers, in place of HPs, signals the seismic changes to come. Projected running costs for a small, 110msq, nZEB home have been tabled as low as €200-€270pa. Consumer ticks (are you comfy at 21c?) will have an impact. It’s a brave, new world, not without inherent challenges.

David Hughes is a specialist, low-energy architect, an award-winner in PH design and secretary of the Passive House Association of Ireland (PHAI). He says: “Most of the output of a PV panel is in the summer months, when there is the least demand for heat.

“However, hot water is a constant demand and, if anything, demand grows in summer, as we tend to shower more to ‘freshen up’.

A 35sq m PV array will be about 4kWp (kW peak), which is about the size of the element in a hot-water immersion unit. A PV array can provide all of the hot-water heating, run the MHRV fans, and provide power to the fridge, all of which are constantly on”.

What about selling power back to the grid from the surplus power we otherwise will just bleed away? “At present, it is not possible to sell any surplus (they will take it for free, of course). Many think this is unfair, but, actually, I agree with this.

“If the grid has large spikes of input and then lows when PV is not there — a cloud or bad weather — then a fossil-fuel power station has to be on standby all the time. This is much like a car following a cyclist, in case he runs out of breath.”

Marc says “the future is the all-electric house connected to other houses in its local community, buying and selling energy to each other, when or if they need it. We could cover all those flat roofs on commercial and public buildings with PV. They could use our house solar during the day, and we could use theirs in the evening.

“The building standards do not cover the stuff you plug in, like the fridge, washing machine, all those chargers and your electric car. These will use electricity. Theoretically, you could use Elon Musk’s solar electric roof tiles and his home battery to cover all this stuff. Otherwise, you’ll need to remain hooked up to the electricity grid.”

With up-skilling and more material innovations and expense in insulation, MVHR, PV, heat pumps, etc, are we looking at a spike in price for new housing, or will this be absorbed as standard inflation?

“With nZEB being a mandatory standard, ‘exotic’ systems, like MVHR and triple-glazing systems, will become the norm,” David says. “And, so, will support volume production by industry. If the building is well-designed, then it should not cost any more.

“The development in Enniscorthy, by Bennett’s, has shown a passive house can be sold on the market for €170,000. The cost argument has been put to bed, at this stage.’”

Marc chews on this, but ventures a 5% build-cost increase for nZEB. My gut says he’s right.

If new housing is cost-optimal, what about the 40% of our energy demands still leaching out of our old housing stock? Is the Government doing enough?

“If you had a bucket with a hole in it,” asks David, “would you buy a bigger tap or fix the hole in the bucket? I think the Government is wary of any intervention in up to one million homes that need a deep retrofit.

“This will have to change. The incentives to encourage people to have their homes retrofitted need to be increased substantially, possibly even offering a free retrofit, instead of paying hundreds of millions in fines to the EU.”

Marc says: “Only 1% of our building stock is replaced a year, and the 99% is where the real opportunity for emissions abatement is. We now need the Government to plough big money into the SEAI to really address the cost barriers to NZEB retrofit.”

- For amendments to Part L (2011) published in 2017 go to: (publications)

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