Wind loading – do we need to update our building regulations?

With gusts of 183km/hr (51m/s) and 10-minute mean wind speeds of 135km/hr (37.5m/s) measured at Mace Head in Galway during Storm éowyn last week, are our design wind loads for buildings and structures in our building regulations in Ireland adequate to keep us safe? The previous record for the highest wind gust ever recorded in Ireland went back to 1945, when a gust of 182km/h and 10-minure mean wind speeds of 131km/hr were recorded at Foynes in Co Limerick. In Ireland, we estimate wind loading on our buildings using the wind map contained in Part A of our building regulations which has the basic design wind speed varying from 90km/hr (25m/s) to 101km/hr (28m/s) (see map below). This map is used with the provisions in the European Design Code, Eurocode 1, to estimate design wind loading on buildings and structures. According to Eurocode 1, Clause 4.2 of EN 1991-1-4, “the fundamental value of the basic wind velocity is the characteristic 10 minutes mean wind velocity, irrespective of wind direction and time of year, at 10 m above ground level in open country terrain with low vegetation such as grass and isolated obstacles with separations of at least 20 obstacle heights”. The wind actions calculated are determined from the basic values of wind velocity or the velocity pressure. In accordance with Eurocode 0 (EN 1990) Clause 4.1.2 (7)P, the basic values are characteristic values having annual probabilities of exceedance of 2%, which is equivalent to a mean return period of 50 years. That's equivalent to an event happening only once in a 50-year period. But, within 80 years we have had two occurrences of 10-minute mean wind speeds of greater 130km/hr (36m/s) recorded on the West of Ireland – one last week and one in 1945. Even if we go back to the so-called "night of the big wind" in 1837, this is still within a 200-year period, so at least 3 events with winds in the order of magnitude of 130km/hr in a 200-year period compared to the current design value of 97 km/hr (27 m/s) for a 50-year return period.

According to RTE reports, renewable energy investor Greencoat Renewables said the highest average wind speed measured across its portfolio of 26 wind farms in Ireland during Storm éowyn was at Sliabh Bawn in Roscommon, where it recorded a 40.82m/s (147km.hr) average wind speed there over a 10-minute period (https://www.rte.ie/news/business/2025/0124/1492712-greencoat-renewables-storm-eowyn/). Killala in Co Mayo was a close second at 39.77m/s (143km/hr) and Cloosh Valley in Co Galway at 39.74m/s. The company said that as a safety measure, its turbines automatically cut out at around 25m/s (90km/hr) to protect themselves from excessive loads. It is notable that these measured wind speeds at those sites during Storm éowyn are substantially higher than the basic design wind speed at 10m above the ground for those sites, which correspond to a 1 in 475-year event, as given in Technical Guidance Document (TGD) Part A. These are 91.8 km/hr (25.5 m/s) for Sliabh Bawn (Roscommon), 97.2 km/hr (27 m/s) for Killala (Mayo) and 93.6 km/hr (26 m/s) for Cloosh Valley (Galway).

Below I have taken one of the weather stations in Ireland as an example (Mace Head) and looked at the historical maximum 10-minute wind speeds measured there over the last 11 years. We can see that there have been 4 storms in this period where the 10-minute wind speeds have been over the basic design wind speed of 101 km/h. If we go back another month in the data, we can find two additional instances where the wind speed exceeded this value! So, I do think there is a need to go back through historic data for each of our weather stations and update the wind design maps based on occurrences of maximum wind speeds over the last 50+ years.

It should be noted that to estimate the peak velocity pressure on our buildings and structures, we need to take into account an exposure factor, which increases with height and in more exposed areas such as at the sea. A taller building or structure (e.g. 100m high) could have an exposure factor up to 4 times that of a low building (e.g. less than 10m high). On the other hand, a two-storey building (8m high) at the sea could have, for example, an exposure factor of 33% higher for a similar building located in a city away from the sea. This difference arises primarily from the lower roughness of the terrain at the sea, which allows wind to flow with less resistance. However, it should be noted that if the structure is to be located close to another structure, that is at least twice as high as the average height of its neighbouring structures, then it could be exposed (dependent on the properties of the structure) to increased wind velocities for certain wind directions. Such cases should be taken into account in its design. We can also take into account altitude at which our building is located, where accounting for altitude reduces the wind speed due to lower air density.

So, can we put these damaging wind speeds down to climate change? Scientists and researchers haven't shown to date that climate change has led to, or might lead to, higher wind speeds in Ireland. Conversely, some scientific studies have predicted that maximum wind speeds in Ireland may reduce, rather than increase, due to climate change. In any case, we need to ensure that our buildings and structures are climate resilient taking account of robust science available on future weather patterns including wind, temperature and snow loading.