Reducing the Energy Consumption of Affordable Housing in Shanghai – MSc Dissertation Results 怎么减少上海老住宅的能量用量 – 硕士论文的结果

I recently finished my dissertation and therefore completed my MSc in Sustainability and Adaptation in the Built Environment – hooray! This is why I didn’t update this blog for a long time while I concentrated on my studies, but I aim to get it going again now. So this post kick-starts the blog again with a summary of my dissertation:

The dissertation research investigated the most sustainable, locally available materials for use in retrofitting the building envelope (outside of the building) of ‘affordable housing’ in Shanghai. It tested whether the sustainable materials could compete with conventional retrofitting materials in passively reducing energy consumption for heating and cooling. This is an important area for research because 36-40% of total energy consumption in China is attributable to buildings and no other studies have focused on using sustainable materials for renovation in Shanghai or the surrounding region.

 ‘Affordable housing’ refers to typical 5-8 storey residential buildings built in very large numbers across China in the 1970s-1990s. Existing affordable housing in Shanghai is mostly uninsulated and built to poor standards for energy efficiency. Its residents generally rely on air-conditioning for both cooling and heating, contributing significantly to the rapidly growing CO₂ emissions of Shanghai’s residential sector, 57% of which are attributable to electricity use.

3 examples of affordable housing in Shanghai.

A 3D digital base model of a typical example of affordable housing was developed in Sketchup Pro 2017 and OpenStudio 2.7.0. EnergyPlus 9.0.1 was used to run simulations of the energy consumption of the model for heating and cooling with different retrofit options in order to find the most effective options.

The unconventional/sustainable materials tested were external insulation made of recycled PET (i.e. recycled plastic bottles) with a lime-cement render, recycled cotton/denim or hemp fibre external insulation with bamboo cladding in a rainscreen system, timber-framed windows and timber external doors. An optimised bamboo window shading system was also developed. The conventional materials tested were polyurethane, expanded polystyrene (EPS) and mineral wool external insulation with a cement mortar, uPVC and aluminium-framed windows and uPVC and steel external doors. There are cases where conventional materials have been used to retrofit affordable housing in China, providing hope that more of these buildings could be renovated in the future.

Screenshot of the base model of affordable housing.

An example of retrofitted affordable housing in the city of Jinan in Shandong Province,

using expanded polystyrene (EPS) as external insulation.

Modelling indicated that the best unconventional/sustainable materials (recycled PET insulation with a lime-cement mortar, timber-framed triple-glazed windows and timber external doors) could reduce annual energy use for heating and cooling by 74% in the present day. This is a comparable performance to the best conventional materials (polyurethane insulation with a cement mortar, uPVC-framed triple-glazed windows and uPVC external doors) which could induce energy savings of 75%. As Shanghai steadily warms under projections of future climate change, by 2080 both sets of materials would still result in energy savings of two thirds compared to the base model – that’s supposing these buildings are still standing by then!

Comparison of electricity consumption for heating and cooling in the present day before and after retrofitting (with CSWD weather data). Key: BM1: base model 1; BM2: base model 2 (with improved airtightness); USRM1: unconventional, sustainable retrofits model 1 (including improved airtightness); CRM1: conventional retrofits model 1 (including improved airtightness).

Comparison of total annual electricity consumption for heating and cooling between the present day and under future projections of climate change (with SWERA weather data). Key: BM1: base model 1; USRM2: unconventional, sustainable retrofits model 2; CRM2: conventional retrofits model 2.

The unconventional/sustainable materials have a lower environmental impact and require much less energy during their production processes than the best conventional materials. For example, using recycled PET would turn China’s growing plastic waste problems into an opportunity to reduce the energy consumption of buildings. Or using timber/bamboo/hemp renovation products would result in carbon being sequestered into the buildings, potentially making the renovations carbon negative.

Therefore the implications of this study are that subsidy policy in Shanghai and the surrounding region should focus on supporting the establishment and growth in use of sustainable materials to retrofit the existing affordable housing stock. This would sustainably reduce its energy use for heating and cooling in the present day and in the future under the influence of climate change.

A comparison of the energy used to produce 1m³ of each window frame material.

If you would like to read the full dissertation then please do not hesitate to email me at mikejoyce1988@gmail.com to request a PDF copy. Any comments, critique or feedback would be very welcome.

Thank you to all the staff and my classmates at the Centre for Alternative Technology (Wales) for the incredible experience I had while completing this masters degree. I wish you all well and please stay in touch! J