Post Retrofit Research Articles

Selection of moisture reference year for freeze-thaw damage assessment of historic masonry walls under future climate: A simulation-based approach

Today, there is an increased research effort on improving energy efficiency in heritage buildings through retrofit measures. Hygrothermal simulations tools are often used to assess the long-term performance of building envelopes and determine whether they are suitable for interior insulation. To reduce the high computation time and cost incurred with these simulations, a moisture reference year (MRY) is typically selected based on long-term annual climatic conditions. Simulation results obtained under MRYs are assumed to represent the long-term performance. However, when assessing the risk to freeze-thaw (FT) damage of historic masonry walls, methods selecting climate-based MRYs have failed to represent the actual performance – determined based on results from simulations over the 31 consecutive years. This paper attempts to find an alternative method to select MRYs, based on the hygrothermal simulations of specific constructions. First, a parametric analysis was proposed to identify the parameters that have the greatest influence on FT damage. Then, simulations are performed for a continuous 31-year period and for each single year. A comparison of their results suggests that there is no accumulative effect on the annual freeze-thaw cycles; and therefore, MRYs can be selected as the single year with the 93rd percentile FT damage severity or the worst year commonly found between masonry walls pre and post retrofit. The application of MRYs was then verified for different insulation types and thicknesses. Results showed that simulation-based MRYs are construction and orientation dependent; however, they are reliable to use for retrofitting design decision making.

Energy savings potential and life cycle costs of deep energy retrofits in buildings with and without habitable style loft attic conversions: A case study of Irelands residential sector

This paper evaluated the potential energy and life cycle cost (LCC) savings arising from the deep energy retrofit of residential buildings. The cost optimal model was determined for material upgrades and the addition of an air-to-water heat pump, where the household level of savings at 2023 energy prices will be dependent on the typical housing characteristics and weather conditions. LCC savings post retrofit for a detached dwelling insulated at the ceiling/rafter including installation of a heat pump amount to a €20,031-€21,370 for an uninsulated dwelling pre-retrofit, rising to €38,448 for dwellings with a habitable loft conversion. Partially insulated dwellings, pre-retrofit did not all incur favourable returns in investment, and in some cases were unviable. Although, the application of a 50% grant results in a viable return on investment for home owners. A sensitivity analysis found high discount rates, fuel prices and increasing capital costs can negate positive returns on investment. Finally, at a national level energy saving of 7.72 TWh by 2030 could be realised if the Irish Climate Action Plan 2023 retrofit targets are adhered to. In addition, total LCC savings could be valued at €1.4 billion. Where only material upgrade are pursued a loss occurs of €0.56 billion.

An energy performance baseline scenario for 19thC listed dwellings in the UK

PurposeThe inclusion of heritage dwellings in the UK decarbonization policies can contribute to cut operational carbon emissions from the building stock; this needs to be made a priority if net zero carbon targets are to be achieved. However, the energy and carbon savings potential of suitable retrofit interventions on this part of the stock is extremely variable and strictly intertwined with the range of baseline conditions of such dwellings. This study aims to propose a framework for interventions in traditional listed dwellings (TLDs) to improve their energy performance utilizing dynamic energy simulation (DES) of selected case studies (CSs) in the city of Brighton and Hove (South-East England).Design/methodology/approachTo achieve this aim, the study established a baseline scenario which provides a basis for the assessment of energy performance and thermo-hygrometric behaviour pre- and post-interventions and allows for comparison between different CSs under comparable conditions.FindingsPresenting a brief overview of the methodology adopted in this study, the paper describes the approach devised to generate such baseline scenario. The paper then compares the results obtained from simulation of normalized and baseline models with the status-quo energy consumption of the dwellings investigated (based on meter readings).Originality/valueThis analysis finally allows to highlight some key physical determinants of the baseline HEC which, in the following stage of research, proved to have a considerable effect also on the amount of energy and carbon savings achievable post retrofit interventions.

Energy, Environmental Impact and Indoor Environmental Quality of Add-Ons in Buildings

On a European scale, the existing building stock has poor energy performance and particularly vulnerable structures. Indeed, most of the existing buildings were built before the introduction of energy standards and under structural safety criteria different from those currently required. It is therefore necessary the intervention in existing buildings according to an integrated approach that contemplates both the structural safety and the energy efficiency of buildings. This study, consistently with the objectives of the European research project “Proactive synergy of integrated Efficient Technologies on buildings’ Envelopes (Pro-GET-OnE)”, proposes a retrofit intervention for a student dormitory of the National and Kapodistrian University of Athens. The scope of the evaluation is to understand how an integrated intervention, that implies a structural and energy retrofit, as well as a spatial redistribution, leads to an improvement of the Indoor Environmental Quality (IEQ). In detail, the structural retrofit was performed through exoskeleton that leads to the addition of new living spaces and to a remodeling of the building facades. The energy retrofit regarded all three levers of energy efficiency, and thus the building envelope, the microclimatic control systems, and the systems from renewable sources. The integrated intervention, in addition to a reduction of energy demand, has led to advantages in terms of IEQ. Thermal comfort, both during summer and winter, is improved and the hours of suitable CO2 concentration pass from 34% in the pre-retrofit stage up to 100% in the post retrofit stage.

The significance of occupancy profiles in determining post retrofit indoor thermal comfort, overheating risk and building energy performance

Recently, retrofit of tower blocks has gained momentum particularly in the UK social housing sector due to the increasing rate of fuel poverty coupled with deteriorating indoor living conditions. However, the process of making improvements to the thermal performance of building envelopes can significantly impact on occupants' thermal comfort, increasing overheating risks with the changing climate and associated heat waves. The first phase of the study evaluated the building energy performance of a 1960s social housing tower block prototype in London, pre-retrofit, where the building simulation model was created and calibrated with monitored indoor data and occupants' interviews. The second research phase, the subject of this paper, uses the model to further investigate the impact of improved thermal insulation of the building envelope, based on U-values prescribed by the UK Building Regulations (Part L1B), on the potential risk of overheating. The study investigates the impact of retrofitting on occupants’ thermal comfort and building energy performance in the current and future climate scenarios (2030, 2050 and 2080). Results confirm that improving the U-value of external walls will significantly reduce the heating energy use by 70% under future climate scenarios while the To increases by 15–17% with U-value of 0.5 W/m2K and 0.3 W/m2K in comparison to the base case. The overall results indicate that the different occupancy patterns adopted in the simulation model have a significant impact on the predicted duration of overheating which will, in turn, have an impact on determining appropriate retrofit strategies to reduce overheating risks.

A novel holistic EPC related retrofit approach for residential apartment building renovation in Norway

This paper presents a novel Energy Performance Certification (EPC) related holistic building retrofit approach for a Norwegian apartment block built in 1980s. Based on the pre-combination principles of “Fabric priority”, “Renewable in supplement”, “Avoid complicated installation”, 11 energy retrofit measures (ERMs) were defined and combined into 18 typical retrofit combination packages (COMBs). Targeted simulations with the aim to explore the interconnected and coupled impacts of selected ERMs are performed in a dynamic simulation tool IES Virtual Environment (VE). A novel Energy Limiting Difference (ELD) assessment factor has been defined, which only considers the difference between primary and renewable energy consumption in the extreme cold winter and hot summer months. The post retrofit EPC standard for each COMBs are then linked with these ELD assessment factors respectively. The relationship between ELD assessment factors and the relevant EPC grades for the 18 COMBs is plotted and verified against the obtained EPC results. Without performing the simulation for each month in conventional retrofit approaches, this approach leads to at least 78 % reduced simulation efforts. This ELD-EPC related approach could therefore be used as useful guidelines for similar apartment building retrofits incorporating renewable energy measures in high-density areas in the cold climate region.

A pre and post evaluation of indoor air quality, ventilation, and thermal comfort in retrofitted co-operative social housing

In comparison to building energy performance, assessment of the impact of energy upgrades on indoor air quality and occupant comfort has received little attention.Concentrations of indoor air pollutants in fifteen, three bed semi-detached co-operative social dwellings were monitored before and after an energy upgrade during the winter periods of 2015 and 2016. The fifteen dwellings consisted of seven cavity wall (CW) dwellings and eight hollow block (HB) wall dwellings. Concentrations of indoor air pollutants including CO, PM2.5, CO2, TVOCs, formaldehyde, BTEX, NO2 and thermal parameters including temperature and relative humidity, were measured in the main living area and main bedroom before and after the energy upgrade.Building air tightness decreased from pre retrofit values of 9.26–10.00m3/(h.m2) @ 50 Pato an average of 5.53 m3/(h.m2) @ 50 Pa and 8.61m3/(h.m2) @ 50 Pa post retrofit (CW group and HB group, respectively). Concentrations of CO2, TVOC, and PM2.5 significantly changed post-retrofit, increasing post retrofit in both dwelling groups (CW; p = 0.014; p = 0.009; p = 0.005) (HB; p = 0.003; p = 0.032; p = 0.008). Increases in pollutant concentrations were correlated with lower building air exchange rates post retrofit. This study suggests that the energy retrofit had a positive impact on occupant comfort and building temperature; however, concentrations of some pollutants were found to increase following the retrofit.The study highlights the importance of characterising indoor air quality post energy retrofits within the overall building energy performance to ensure improved health outcomes for building occupants post retrofit.

QUANTIFYING ENERGY SAVINGS FOR RETROFIT CENTRALIZED HVAC SYSTEMS AT SELANGOR STATE SECRETARY COMPLEX

Objective of this study is to estimate building energy saving at Bangunan Sultan Salahuddin Abdul Aziz Shah from a retrofit of Water Cooling Package Unit (WCPU) system. This research calculates energy savings as recommended by International Performance Measurement and Verification Protocol (IPMVP) using Option C-Whole Facility Measurement. In this study, the baseline period is defined from July 2012 to June 2013, the retrofit of WCPU was performed on July 2013 and the reporting period is from August 2013 to July 2014. The baseline energy use and the post retrofit energy use data are collected from utility bills. On the other hand, the energy governing factors other than the retrofit such as outdoor temperature or Cooling Degree Day (CDD), number of working days (NWD) and occupancy on the building are gathered corresponding to the pre-defined baseline and post-retrofit period. These non-retrofit energy governing factors are used to model adjusted baseline energy in calculating energy savings using regression analysis. Two types of energy saving analyses have been presented in the case study; 1) Single linear regression for each independent variable, 2) Multiple linear regression. Results show that number of occupancy has the highest coefficient regression, R2 followed by NWD and CDD. This indicates that occupancy has stronger correlation with the energy use in the building than NWD and CDD. Finding also shows that the R² for multiple linear regression model are higher than single linear regression model. This shows the fact that more than one component are affecting the energy use in the building.

Developing a pre-retrofit energy consumption metric to model post-retrofit energy savings: Phase one of a three-phase research initiative

• This research details the process and results from the first step of a three-step research process. • We look to identify the most predictive pre-retrofit metric of energy consumption. • The best pre-usage metric is the simplest, total energy consumption divided by total floor area. • The problem of endogeneity is alleviated by removing the year used to calculate the savings post-retrofit. • Two years prior to retrofit is the best year to utilize as the base year when evaluating savings as one year after retrofit vs. one year before retrofit. This paper details the process and results from the first step of a three-step research process. This first step looks to identify the most predictive pre-retrofit metric of energy consumption to utilize in a model to predict the energy savings post retrofit. The ultimate goal of this research is to predict candidacy for retrofit using only a combination of demographic and home-characteristics data that is available for the entirety of the U.S. residential housing stock. This is important, as utility data is almost always protected for privacy and thus unavailable to assist in targeting where energy efficiency retrofits will be successful. It is found that the best metric is the simplest, total energy consumption divided by total floor area. In addition to evaluating which pre-use metric is most indicative of post retrofit savings, the paper evaluates the endogenous component of pre-use to post use and a potential method to alleviate this endogeneity. The research finds that by removing the year that is used to calculate the savings as the baseline pre-use year removes a portion of the endogeneity. It is also found that one year before the savings base year is the best year to utilize as the base.

A Methodology for Introducing M&V Adjustments during an Energy Retrofit Impact Assessment

The assessment of an energy retrofit necessarily requires an energy measurement campaign before (base year energy consumption) and after (post retrofit energy consumption) the retrofit. Only in this way is it possible to reach a safe conclusion, on the true retrofit impact. In addition, a number of adjustments are necessary to secure that the retrofit impact on energy consumption is effectively isolated, i.e., which we report on the true retrofit impact and not, for example, on external variations, such as a more mild winter. This paper introduces a conceptual framework for taking account, in the retrofit impact assessment, of three external parameters: weather, indoor comfort and space occupancy. The broader strategy behind this work is to develop a comprehensive methodology that would allow a cost efficient, fast and accurate assessment of energy retrofits in buildings. This would allow insight, on the investor side, as to the prudence of his investment and, and in this way, could help the proliferation of the practice of energy retrofits. The adjustment methodology, introduced here, is a first step in this direction.

Use of Simplified System Models to Measure Retrofit Energy Savings

The retrofit of dual-duct constant volume systems (DDCV) with energy-efficient variable air volume systems (VAV) has become common in recent years. In general, the energy savings from such retrofits are estimated by developing a temperature-dependent regression model using whole building preretrofit energy consumption data. Model predictions are then compared with measured post retrofit consumption, to determine the savings. In cases where the preretrofit energy consumption is not available such a method cannot be implemented. This paper describes a method that can be used to calculate savings in such cases. The method is based on use of simplified calibrated system models. A VAV model was developed based on the ASHRAE TC 4.7 Simplified Energy Analysis Procedure (SEAP) (Knebel, 1983) and calibrated with the postretrofit energy consumption of a large engineering center in Central Texas. The loads from the calibrated VAV model were then used with the DDCV model to estimate the preretrofit energy use, also based on TC 4.7 SEAP, and apparent savings were determined as the difference between the DDCV predicted consumption and measured energy consumption for the postretrofit VAV system. The simulated hourly cooling energy consumption from the VAV model was within ±1GJ (±20 percent) of the measured consumption. The simulated daily consumption (the sum of 24 hours of consumption) compared better with the measured daily consumption (within ±7 percent). The apparent saving from the retrofit of the DDCV system with VAV was about 684 GJ in cooling energy and 324 GJ in heating energy for a three-week period June–July 1991.