I NTERNATIONAL G REEN W ALL C ONFERENCE th September The Green Wall Centre, Staffordshire University, Stoke-on-Trent, UK Green Facades – How does plant choice affect wall cooling and wall insulation? Ross Cameron University of Sheffield, UK Jane Taylor, Martin Emmett

I NTERNATIONAL G REEN W ALL C ONFERENCE th September The Green Wall Centre, Staffordshire University, Stoke-on-Trent, UK The Context UK Victorian / Edwardian building stock Brick dominated Difficult to ‘retrofit’ Domestic properties – owned or rented Replicated real houses??? ‘Down-sized’ – replicated ‘mini-buildings’ and walls Controlled environment studies

I NTERNATIONAL G REEN W ALL C ONFERENCE th September The Green Wall Centre, Staffordshire University, Stoke-on-Trent, UK

3 Experimental protocols ‘Mini-city’ – cuboids ‘Stand-alone’ wall sections Controlled environment cabinets

I NTERNATIONAL G REEN W ALL C ONFERENCE th September The Green Wall Centre, Staffordshire University, Stoke-on-Trent, UK Designing the ‘mini-city’! 20 Brick cuboids 10 vegetated 10 blank Water tank in centre – Winter studies Temp sensors 5cm from cuboid wall surface (and behind vegetation)

I NTERNATIONAL G REEN W ALL C ONFERENCE th September The Green Wall Centre, Staffordshire University, Stoke-on-Trent, UK How do weather scenarios affect temperature profiles of air next to cuboids? (Mean data - Southern aspect)

I NTERNATIONAL G REEN W ALL C ONFERENCE th September The Green Wall Centre, Staffordshire University, Stoke-on-Trent, UK How do cooling profiles vary with diurnal cycle? Wall system Prunus v wet pot v blank wall Temp sensors for air adjacent to wall

I NTERNATIONAL G REEN W ALL C ONFERENCE th September The Green Wall Centre, Staffordshire University, Stoke-on-Trent, UK Mean hourly air temperature for walls flanked by Prunus (South = Δ; North = ▲ ), Pot+media (South = □; North = ■ ) or blank Control walls (South = ○; North = ●). Data restricted to days with ≥ 5 h irradiance > 120 Wm 2, August to September Bars = LSD (P = 0.05) blocked by date. Residual d.f. = 30 each time. Ambient temperature – dashed line. Prunus south aspect

I NTERNATIONAL G REEN W ALL C ONFERENCE th September The Green Wall Centre, Staffordshire University, Stoke-on-Trent, UK Wall surface temperatures At discrete times thermal images showed a 10 o C difference between vegetated walls and blanks E.g. Wall behind foliage = 24.0 o C, Control wall = 33.9 o C Pot+media wall = 33.2 o C; LSD = 0.81 (P = 0.05) d.f. = 12.

I NTERNATIONAL G REEN W ALL C ONFERENCE th September The Green Wall Centre, Staffordshire University, Stoke-on-Trent, UK What are the implications to the cavity space within a wall? Phaseolus vulgaris

I NTERNATIONAL G REEN W ALL C ONFERENCE th September The Green Wall Centre, Staffordshire University, Stoke-on-Trent, UK Air temp – at wall exterior

I NTERNATIONAL G REEN W ALL C ONFERENCE th September The Green Wall Centre, Staffordshire University, Stoke-on-Trent, UK Cavity Air temp.

I NTERNATIONAL G REEN W ALL C ONFERENCE th September The Green Wall Centre, Staffordshire University, Stoke-on-Trent, UK What types of plant are best at cooling? Wall Shrubs Climbers ‘Functional’ plants

I NTERNATIONAL G REEN W ALL C ONFERENCE th September The Green Wall Centre, Staffordshire University, Stoke-on-Trent, UK Fuchsia Stachys Jasminum Hedera Prunus Lonicera

I NTERNATIONAL G REEN W ALL C ONFERENCE th September The Green Wall Centre, Staffordshire University, Stoke-on-Trent, UK Controlled environment studies Vegetated v non-vegetated walls Warming programme with heater (300 W) within cabinet Air and wall surface temperatures Some programme runs with normal plants and some with leaves covered with poly (1-acetyloxiethylene) to block stomata - inhibited 96-98% of normal ET (shade temps) Some runs with wet media only (evaporation) Plant / pot temps stabilised at 18 o C before placement in cabinets Wall temps stabilised at 26.5 o C and monitored change as plants introduced. Plants etc. weighed before and after to determine water loss

I NTERNATIONAL G REEN W ALL C ONFERENCE th September The Green Wall Centre, Staffordshire University, Stoke-on-Trent, UK

Attained temp and water loss data for a = transpiring plant and media, b = non-transpiring plant and media c = media alone. This allowed calculation of the cooling effect on the wall ( o C) due to total cooling of – planted trough – plant evapo-transpiration – shade and – media evaporation Plants destructively harvested and data for: – leaf number, total leaf biomass (dry weight), mean leaf dry weight, mean specific leaf area, mean leaf thickness (individual leaf areas/leaf biomass) and total stem biomass (dry weight). Wall leaf area index (WLAI) was calculated as a ratio of total leaf area compared to exposed wall area and used to estimate the density of the foliage covering the wall.

I NTERNATIONAL G REEN W ALL C ONFERENCE th September The Green Wall Centre, Staffordshire University, Stoke-on-Trent, UK Temp. reduction on wall surface

I NTERNATIONAL G REEN W ALL C ONFERENCE th September The Green Wall Centre, Staffordshire University, Stoke-on-Trent, UK Temp reduction – per unit of leaf area

I NTERNATIONAL G REEN W ALL C ONFERENCE th September The Green Wall Centre, Staffordshire University, Stoke-on-Trent, UK Summer Cooling - Conclusions Vegetation can cool the air around a wall by 3-5 o C in UK context Wall surfaces as much as 10 o C different Reduces cavity temp by 5 o C in mid afternoon Different plant species have different cooling properties – Extent of cover – Depth of foliage – Some better at Shading – Some better at ETp cooling Water supply important in ensuring optimum performance Green facades appear a viable retrofit option - UK

I NTERNATIONAL G REEN W ALL C ONFERENCE th September The Green Wall Centre, Staffordshire University, Stoke-on-Trent, UK Shrubs and Climbers Their role in thermal performance of built structures in winter

I NTERNATIONAL G REEN W ALL C ONFERENCE th September The Green Wall Centre, Staffordshire University, Stoke-on-Trent, UK What about reducing energy consumption in winter – brick mini-building again? Replicated ‘mini-buildings’ with heated water tank within brick enclosure Water tank - Temp maintained at 16 o C throughout Energy use monitored over 2 consecutive winters

I NTERNATIONAL G REEN W ALL C ONFERENCE th September The Green Wall Centre, Staffordshire University, Stoke-on-Trent, UK Fig. 1. Energy use in Control (Blank) and Vegetated (Hedera) cuboids, during winter scenarios. Part-cover = foliage covering approx. 80%, and Full-cover = foliage covering 100% of cuboid. Bars = LSD values, df=79.

I NTERNATIONAL G REEN W ALL C ONFERENCE th September The Green Wall Centre, Staffordshire University, Stoke-on-Trent, UK

Results Mean winter energy reduction = 38% – varied between 17% and 45% saving per week, based on weather scenarios. At and am cuboid wall temperatures behind plants significantly warmer than ambient (mean 3.6 o C) – not the case for blank walls.

I NTERNATIONAL G REEN W ALL C ONFERENCE th September The Green Wall Centre, Staffordshire University, Stoke-on-Trent, UK How does species choice affect Winter insulation?

I NTERNATIONAL G REEN W ALL C ONFERENCE th September The Green Wall Centre, Staffordshire University, Stoke-on-Trent, UK Replicated ‘Cavity’ Walls ‘Dense’ Prunus v ‘Open’ Cotoneaster franchetti v Control (Blank) Late winter data Wall surface and cavity temperatures

I NTERNATIONAL G REEN W ALL C ONFERENCE th September The Green Wall Centre, Staffordshire University, Stoke-on-Trent, UK Fig. 4. Cold, Non-Snow scenarios. Mean air temperature recorded at wall exterior (blue) or in wall cavity (shaded), as affected by species. Bars = LSD values Left = comparisons for exterior temperature, df=154 and Right = comparisons for cavity temperatures, df=107.

I NTERNATIONAL G REEN W ALL C ONFERENCE th September The Green Wall Centre, Staffordshire University, Stoke-on-Trent, UK Results Both the Prunus and Cotoneaster warmed the walls at night - Interior and Exterior Denser Prunus was more effective at warming the exterior. During sunny periods, however, plants particularly the Prunus inhibited solar gain to the wall.

I NTERNATIONAL G REEN W ALL C ONFERENCE th September The Green Wall Centre, Staffordshire University, Stoke-on-Trent, UK Winter - Conclusions Plants can insulate walls and improve temperatures / energy conservation in winter. The benefits are greatest under colder / more adverse weather conditions. Overall - – Plant species choice needs more consideration when recommending wall screening plants. – Replicated ‘artificial’ buildings provided a high degree of statistical robustness – need to scale up. Thanks to Horticultural Trades Association, UK. for funding this research.

I NTERNATIONAL G REEN W ALL C ONFERENCE th September The Green Wall Centre, Staffordshire University, Stoke-on-Trent, UK Questions ? I NTERNATIONAL G REEN W ALL C ONFERENCE th September The Green Wall Centre, Staffordshire University, Stoke-on-Trent, UK