Is A-rated too much in our changing climate?
For decades, the challenge in Irish homes has been straightforward: keep the heat in. We focused on better insulation, eliminating draughts, more efficient glazing, and reducing the amount of energy required to stay warm. After the hottest summer on record, many of us now find ourselves facing the opposite problem. We’re roasting.
I renovated my small cottage in 2020 and it has been cosy every winter since. It was brought from Ber exempt to a B2 and my gas bills are low. For 11 or so months of the year, everything is hunky dory. My one critical design mistake that has pummelled me this summer was a huge west-facing bedroom window. Combined with a well-insulated room, the effect was suffocating.
Diligent researcher that I am, I went deep down the rabbit hole of cooling solutions. The best advice was not to cool down the room, but to stop the heat getting in in the first place. I closed blinds and curtains, and turned off heat-producing appliances, as my hairdryer looked on forlornly at my expanding frizz. I cracked windows after sunset. On exceptionally hot nights, I rented a portable air conditioner and ran it for an hour before bed.
RM Block
I got through it, but as Ireland’s climate changes, do we need to rethink what an energy-efficient home means?
Pat Barry, architect and chief executive of the Irish Green Building Council, assured me that we should not abandon well-insulated A-rated homes. “Remember that insulation also keeps the heat out,” he says. A well-designed A-rated home should actually be more resilient against hot weather.
The problem is when other aspects of the design have not been considered carefully enough. South- and west-facing windows can admit substantial solar gain and, once the heat has passed through the glass it can get trapped. Internal blinds help, but Barry says external shading is preferable − awnings, external blinds, shutters, or planting work, although retrofitting can be costly.
Ciara Ahern of the Research Ireland Rinn Energy Centre, and a senior lecturer in building engineering at TU Dublin, also notes that sitting behind closed shutters all day is hardly appealing. Deciduous plants offer a neat compromise, advises Barry, shading in summer and allowing solar gain in winter.
Ventilation is also key. “Vents have to be designed so they can be securely left open at night, and ideally at opposite sides of the house, if the temperature is cool enough at night,” says Barry. Roof windows can create a stack effect, drawing cooler air upwards.
Barry and Ahern both identify single-aspect apartments as particularly vulnerable, because they are difficult to cross-ventilate. Barry believes current overheating guidance for houses could be better. To help, Ahern and her colleagues have developed the Dwelling Overheating Risk Metric, or Dorm, using factors including wall area and orientation to flag homes at risk. She says the team is due to demonstrate the tool to the Department of Housing.
Ahern agrees that the priority should be preventing overheating rather than mechanically cooling afterwards: “We shouldn’t need air conditioning in Ireland.” She also points to one delightfully low-tech solution that I had overlooked: ceiling fans, which are “very, very effective in terms of air movement and comfort.”
In my own home I wanted a more immediate solution, so I investigated reversible heat pumps. Paul O’Sullivan, a lecturer in sustainable energy engineering at Munster Technological University, and also a member of the Rinn Energy Network, says retrofitting cooling to an existing heat-only system “seems to be a non-runner”: the work can be expensive, with no guarantee of good performance.
Designed for cooling from the outset, however, an air-to-water heat pump can provide gentle radiant cooling through underfloor pipework and a floor slab. Radiators, common in retrofits, are less suitable and bring greater condensation risk. O’Sullivan describes the approach as supplementary cooling rather than a replacement for air conditioning, ideally run overnight with water at around 18 or 19 degrees, above the dew point, to cool the building fabric for the following day. He advises anyone buying one now to ask whether the heat pump, and the wider system, is “cooling ready”.
Heatwaves are only part of the climate resilience problem. Barry also points to the urban heat-island effect, where roads and hard surfaces absorb heat. He says French cities are removing paving and introducing planting to cool neighbourhoods. Permeable, planted surfaces also slow rainwater run-off rather than sending it rapidly into drains, helping to reduce the risk of climate-related flooding.
Storms and power cuts are changing how homeowners think about household energy too. Abhilash Borana, founder and chairman of Fáilte Solar, says homeowners increasingly consider the whole household energy ecosystem. “The moment you have a heat pump, you definitely need solar because heat pumps are very heavy on electricity.” He recommends solar paired with batteries to store surplus electricity.
Some modern backup systems can isolate a home from the grid during an outage and switch to battery power, while indicating how long the charge may last. Borana also points to bidirectional EV chargers, which can allow a car battery to supply the home. His advice is to think ahead: systems bought today should accommodate the addition of batteries, heat pumps, EVs or other products later.
Our climate may be changing, but we do not need to abandon the energy-efficiency progress of the past decade. We need to broaden the brief. A climate-resilient Irish home should allow accumulated heat to escape, keep warmth in during winter, unwanted heat out in summer, rainwater moving safely away, and essential systems functioning when weather puts pressure on the grid.
I, for one, will be starting with external shading.
