Daniel Hadad - Institute of Soil, Water and Environmental Sciences, Agricultural Research Organization, Volcani Center, HaMaccabim Road, P.O.B 15159, Rishon LeZion 7528809, Israel; Institute of Plant Sciences and Genetics, The Robert H Smith Faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem, POB 12, Rehovot 76100, Israel. 
Victor Lukyanov - Institute of Soil, Water and Environmental Sciences, Agricultural Research Organization, Volcani Center, HaMaccabim Road, P.O.B 15159, Rishon LeZion 7528809, Israel.
Shabtai Cohen - Institute of Soil, Water and Environmental Sciences, Agricultural Research Organization, Volcani Center, HaMaccabim Road, P.O.B 15159, Rishon LeZion 7528809, Israel.
Ephraim Zipilevitz - “Zvi” Experimental Station, Jordan Valley R&D 91906, Israel.
Ziva Gilad - “Zvi” Experimental Station, Jordan Valley R&D 91906, Israel.
David Silverman - Agricultural Extension Service of Israel - Shaham, Ministry of Agriculture and Rural Development, Israel.
Josef Tanny - Institute of Soil, Water and Environmental Sciences, Agricultural Research Organization, Volcani Center, HaMaccabim Road, P.O.B 15159, Rishon LeZion 7528809, Israel; HIT - Holon Institute of Technology, POB 305, Holon. 5810201, Israel

This research studied microclimate and evapotranspiration (ET) of pepper in high tunnel screenhouses and greenhouses. A study was carried out during three consecutive seasons, 2015–2016 (Season I), 2016–2017 (Season II) and 2017–2018 (Season III), in two high-tunnels. One was covered by a plastic sheet (greenhouse) and the other by a porous screen (17 mesh insect net; screenhouse). Other than the covers, the structures were identical. In both houses, microclimate variables were measured simultaneously above the canopy. Evapotranspiration was estimated using six different variations of the Penman–Monteith model. Plant transpiration was measured by the heat pulse technique. Measured transpiration was compared with model estimates of ET to identify the model in best agreement with measurements. Linear regressions between internal and external climatic conditions resulted in R² values between 0.003 (greenhouse temperature) and 0.99 (greenhouse global radiation). Generally, higher R² values were obtained for the screenhouse because internal microclimate interacted with the outside more than in the greenhouse. Mean daily evapotranspiration estimated by the six Penman–Monteith models tested was 1.61–4.23 and 1.42–4.43 mm day⁻¹ for the greenhouse and screenhouse, respectively. Mean daily ratio between ET models and transpiration measurements varied between 0.81 and 2.01 with a mean value of 1.20 ± 0.34 (where ± is standard deviation). The comparison between transpiration measurements and the PM models showed that in most cases models based on internal climatic conditions were in better agreement with measurements than those based on the external conditions.