Living with demand response: Insights from a field study of DSR using heat pumps

Demand response with domestic heat pumps has gained interest in recent years. It is seen as a possible solution to the need to balance electricity grids that are sourcing a higher proportion of their electricity from variable low-carbon electricity sources. Although many modelling studies suggest that demand response with heat pumps will be successful, we have little knowledge of their real-world impacts, including the impact on indoor conditions and the perception of these. This study compares what happened in three homes of early adopters of heat pumps with demand-side response (DSR). In the three households, the operation of the heat pump was constrained from 4pm to 7pm to provide demand response. Drawing on technical monitoring, we report on indoor conditions in the home and heat pump operation. Drawing on interviews and informed by social practice theory, we explore how comfort at home is experienced and achieved. The focus of the study is on the indoor conditions as the material background for daily practices, and on how these are sensed, interpreted, and created through comfort practices. The analysis of the results revealed that air and surface temperatures dropped during demand response (air temperature dropped 0.3-1.1 degrees in 3 hours). However, these changes were sensed and interpreted differently by different participants: (1) not perceived, (2) noticed but tolerated without affecting DSR or (3) not tolerated. Although material adjustments were common in (2) and (3), the nature of the adjustment depended on the know-how of the participants and the meaning associated with temperature changes; for example, (2) adopted new materials (e.g., clothes) while (3) changed the operation of the heat pump to produce more acceptable indoor conditions. The findings challenge conventional modelling assumptions that demand response is unnoticed by people if the indoor temperature remains within the limits of steady-state models of thermal comfort and reveal how demand response is negotiated and incorporated into daily practices

Open or Closed? Use of Windows and Doors at Home: Ventilation Rates in Occupied Dwellings

Ventilation in dwellings is likely to be impacted by configurations of windows and internal doors, but there is little empirical research investigating this in occupied homes. Closure of internal doors will affect noise, light, heat flow and how air moves into and through a building, as well as the volume of air in which pollutants are diluted. However, most ventilation measurements in homes have either conducted long-term averages in which the effect of use of windows and doors is not addressed, or small numbers of ‘snap-shot’ measurements in which the distribution of ventilation rates in particular configurations is not known; this reduces our understanding of environmental quality at home. This paper reports the detailed investigation of window and internal door use and their link to ventilation measurements in two occupied flats in the same building over six months. Doors and windows were monitored using event-logging contact sensors and CO2 was measured in all rooms. An algorithm for determining occupied periods was used and ventilation rates were estimated using the CO2 decay technique during unoccupied times. In one of the flats almost 70% of the ventilation measurements were less than 0.5 ach in the configuration in which the occupant spends 55% of their time while at home; in the other flat windows were open for 80% of the occupied time and 90% of the ventilation rates measured with windows open were above 0.5 ach. The dwellings were physically similar, equipped with the same ventilation equipment and subject to the same weather. These results highlight the importance of considering the extent to which conditions during measurement periods (or modelled conditions) reflect the conditions that occupants experience. Further research employing methods able to characterize ventilation in homes and distinguish between occupied and unoccupied times, contextualized by measuring configurations of doors and windows, will support greater understanding of ventilation in dwellings. This could provide insights into the real conditions in homes, supporting effecive modelling and design. Such detailed research would support developments in practice and policymaking, by helping to disentangle the related issues of ventilation rates, indoor pollution, personal exposure to pollutants and the effects of these on health outcomes

Moisture in walls before and after internal wall insulation: a long-term in-situ dataset

This work addresses the need for long-term, high-resolution, in-situ datasets by providing in-wall humidity and temperature data from three walls of in-use office buildings over three to four years, two of which were insulated during this period. Temperature and humidity sensors were inserted diagonally into three locations within the thick brick walls, and the holes were carefully packed with dry brick dust. Surface, ambient and interstitial measurements were also recorded, as were additional climatic data during 18 months at one wall, and in-wall moisture content using resistance pins for 18 months in another. This dataset is unique due to the combination of temporal length and resolution, spatial detail, as well as the availability of control data from both before and after insulation and the use of real climatic conditions on both sides of the walls. The experiment was designed to produce data to facilitate parameter estimation by inverse analysis. By using these estimated parameters, or by taking material property measurements, it would also be useful for validating and calibrating hygrothermal models, and by using plausible ranges for parameters it is useful for exploring model performance, such as through sensitivity analyses

Ventilation regulations and occupant practices: undetectable pollution and invisible extraction

This sociotechnical investigation examines the use of ventilation systems in homes in London, UK. These homes were built with ventilation systems as described by guidance in the UK Building Regulations Approved Document F. These systems are assumed to provide adequate ventilation rates. However, previous measurements in these homes show that ventilation rates are inadequate. Using social practice theory as a framework to analyse the qualitative data, the intended use of the ventilation systems is compared to participants’ actual practices of manipulating the indoor air, revealing discrepancies between the two. Occupants had limited knowledge of indoor pollutants but were highly motivated to control and interact with the smells and air in their homes. They primarily used technologies that were not part of the planned system, because the latter’s functioning was opaque to occupants and not well connected to their other practices. The highlighted discrepancies in four case study homes between planned and actual ventilation system operation help to identify how future systems could be improved to ensure adequate ventilation rates and good indoor air quality in airtight homes. Policy relevance This research investigates the extent to which the intended operation of domestic ventilation systems set out in Approved Document F to the UK Building Regulations is accomplished in practice. The findings show that ventilation equipment is not used as intended. The research suggests a need for future guidance to more actively consider routes by which occupants can learn how to use and maintain their ventilation systems, and how to identify and remove indoor air pollution. There is a risk of continuing underventilation in homes unless efforts are made to ensure the systems are easily interpretable and robust to a reasonable range of internal conditions and social contexts

Sensitivity and Uncertainty analyses on a DELPHIN model: the impact of material properties on moisture in a solid brick wall

This paper presents sensitivity and uncertainty analyses on a DELPHIN model, which is representative of a case study wall in real climatic conditions. Results of the Differential Sensitivity Analysis (DSA) show properties governing liquid water transported into, through and stored in the wall impact most on moisture accumulation, affecting relative humidity (RH) outputs by 10 – 35% at three different locations in the wall. Parameters affecting vapour transport into the room also influence RH outputs at the inner location, but less than rain amount and rain exchange coefficient. A probabilistic uncertainty study is then used to explore key material functions, parameterised as four sets of co-ordinates and varied randomly. The correlation between the parameter inputs and the resulting change in RH is assessed. There are some surprising divergences from the DSA, including the significance of moisture storage in the plaster layer in the presence of liquid. Low correlation coefficients suggest numbers of variables could be reduced to further clarify the effects of these parameters, and interesting questions are raised on the parameterisation of material functions to represent the uncertainty in the characterisation of real walls

Correction: Gori, V.; Biddulph, P.; Elwell, C.A. A Bayesian Dynamic Method to Estimate the Thermophysical Properties of Building Elements in All Seasons, Orientations and with Reduced Error. Energies 2018, 11, 802

The authors wish to make the following corrections to their paper [1]: [...