BCD SPECIAL REPORT ON HISTORIC CHURCHES 32nd ANNUAL EDITION 25 Damage to decorative stonework and its new replacement at St Torney’s, North Hill: the predicted increase in wet/dry cycling is expected to lead to further rapid decay in the future. (All photos this page: Morwenna Slade) the south and west and beyond this the church is surrounded by the dispersed buildings of the village and farmland. The climate variables and assessments considered for St Torney’s were: mean temperatures; relative humidities; incident solar radiation; precipitation rates; wind speeds and direction; snowfall; internal temperature and relative humidity, including comparison with external conditions; flood risk review; geological, hydrogeological and geotechnical assessment; and hydrological river network – river gauging stations, historic flow and rainfall data. CLIMATE PROJECTIONS FOR THE SITE Over the next 50 years or so, average temperatures are predicted to increase across all seasons of the year, with increases of up to 6° C in summer and 3° C in winter. The mean January temperature would rise from 4.7° C temperatures internally tracked very well with external temperatures. Between December 2021 – May 2022, the internal temperatures in the north aisle corresponded well with external temperatures predicted by UKCP, though internal temperatures were generally 1–2° C warmer than external temperatures. Measurements show that internal relative humidities at the site frequently reach 100 per cent (saturation level) even in the summer months when external relative humidities are lower. Precipitation rates show a trend of significantly increasing in wintertime and slightly reduced in summertime. This site currently experiences high rainfall, particularly in comparison to the other sites in the study. The current average January rainfall in North Hill is 6 mm a day which is double that of Hamstead Marshall, Berkshire at 3 mm a day. North Hill’s winter average is projected to increase by nearly 50 per cent which underlines the need for a strategic approach to maintenance, rainwater goods and drainage to increase resilience. Existing rainwater goods include high-capacity hoppers and guttering on most of the church. Options for increasing capacity are limited due to the size of products on the market rather than impact on significance. Based on the projected increase in rainfall, overtopping of rainwater goods is expected and where adaptation wasn’t possible it was recommended that a strategic approach was taken to limit harm to fabric. Changes in wind direction and speed also have implications here as the projections highlighted a northward change in Timber decay at St Torney’s: rising temperatures and prolonged spells of warm weather favour the growth of dry-rot and other fungi, and will promote the activity of wood-boring beetle larvae to 7.4° C by 2080. In-line with higher temperatures, daily incident solar flux is predicted to increase year-round with the highest increase during summer months. External relative humidity in the area is high and this is projected to be relatively consistent in the winter, while summer relative humidities are expected to decrease by up to seven percentage points from present day levels. Even 2080 projections do not drop below 70 per cent, however. Internal relative humidities vary across the church but reach saturation levels in most spaces at least intermittently. The vestry experiences the highest levels of saturation, while the south aisle close to the Spoure monument has humidity levels that most closely resemble external conditions and least frequently achieve saturation. Recorded internal temperature and RH data was compared with UKCP weather predictions. In all spaces,
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