There are about 42 billion square meters of existing buildings in China. The energy efficiency of existing buildings directly relates to the energy consumption of the building sector. The retrofit of existing residential building began in the 1990s in Heilongjiang. The Sino-Canada demonstration project and Sino-France demonstration project of retrofitting existing residential buildings were carried out in 1997 and 2004, respectively. The retrofit method and energy conservation potential of the envelope and heating system of northern existing buildings are analyzed in this paper, combining the experiences of retrofitting existing residential buildings in Heilongjiang. The software was compiled to aid the design of the envelope retrofit in Heilongjiang and to analyze the working situation in existing residential building heating systems. The imbalance of the indoor temperature and the quantity of heating loss from opening the window in different retrofit projects are presented. The emphasis on energy efficiency retrofit of the envelope of existing residential buildings should be placed on the wall in northern region. It is possible to reduce about 50 percent of energy consumption of buildings by insulating the wall. The external insulation is suitable for retrofitting existing buildings, and the moisture transfer should be considered at the same time. To insure actual reduction in energy consumption, the heating system should be retrofitted when the envelope is insulated

Gao, G.

Li, L.

Xu, W.

Zhao, L.

English

Texas A&M University

ICEBO2006, Shenzhen, China           Building Commissioning for Energy Efficiency and Comfort, Vol. VI-5-5 
Retrofit of Existing Residential Building: a Case Study 
 
Lihua Zhao Wenfa Xu Li Li Ge Gao 
Associate Professor  Doctoral Candidate Doctoral Candidate 
South China 
University of 
Technology 
Architectural Society of 
China Building Thermal 
Dynamic Branch 
South China 
University of 
Technology 
Beijing Jiaotong 
University 
Guangzhou  
P. R. China 
Beijing  
P. R. China 
Guangzhou  
P. R. China 
Beijing  
P. R. China 
Zhao6874@vip.sina.com 
 
Abstract: There are about 42 billion square meters of 
existing buildings in China. The energy efficiency of 
existing buildings directly relates to the energy 
consumption of the building sector. The retrofit of 
existing residential building began in the 1990s in 
Heilongjiang. The Sino-Canada demonstration project 
and Sino-France demonstration project of retrofitting 
existing residential buildings were carried out in 1997 
and 2004, respectively. The retrofit method and energy 
conservation potential of the envelope and heating 
system of northern existing buildings are analyzed in 
this paper, combining the experiences of retrofitting 
existing residential buildings in Heilongjiang. The 
software was compiled to aid the design of the envelope 
retrofit in Heilongjiang and to analyze the working 
situation in existing residential building heating systems. 
The imbalance of the indoor temperature and the 
quantity of heating loss from opening the window in 
different retrofit projects are presented. The emphasis on 
energy efficiency retrofit of the envelope of existing 
residential buildings should be placed on the wall in 
northern region. It is possible to reduce about 50 percent 
of energy consumption of buildings by insulating the 
wall. The external insulation is suitable for retrofitting 
existing buildings, and the moisture transfer should be 
considered at the same time. To insure actual reduction 
in energy consumption, the heating system should be 
retrofitted when the envelope is insulated. 
Key words: existing building, energy efficiency retrofit, 
envelope, heating system 
1 INTRODUCTION 
The 420 billion square meters existing buildings 
in China are high energy consumption buildings. The 
retrofit of existing building directly relates the energy 
efficiency and sustainable development. Realizing the 
retrofit of existing buildings, avoiding energy and 
resource waste and improving the thermal comfort of 
buildings are important problems to be solved 
immediately in our country. As the energy efficiency 
of buildings booming, residence system’s innovating 
and the innovation proposal of heating system in 
north China begin to perform, the problem of existing 
buildings retrofit will become outstanding and great 
task. 
The retrofit of existing buildings in Heilongjiang 
province began in 1990. The scientific research 
project, the Energy efficient measures of external wall 
of existing building retrofit was the first 
demonstration project. The Sino-Canada 
demonstration project of existing residential building 
retrofit in Harbin were carried out in 1996~1999. The 
project of Heilongjiang province, Energy efficient 
retrofits of existing building in Daxing’anling were 
finished in 2003. The Sino-France demonstration 
project of retrofit existing residential building is 
carried out now. After yeas of practice and 
demonstration, the experience were accumulated in 
the existing buildings retrofit field, and the retrofit 
methods were maturing gradually. Because the 
retrofit of heating system was hard to be realized, in 
the accomplished projects, only the Sino-Canada 
project realized all-around existing heating system 
retrofit. Summarizing and using the experience of 
retrofit projects, the software which could analyses 
the retrofit proposal of envelops and the software 
ESL-IC-06-11-203 
Proceedings of the Sixth International Conference for Enhanced Building Operations, Shenzhen, China, November 6 - 9, 2006 
ICEBO2006, Shenzhen, China           Building Commissioning for Energy Efficiency and Comfort, Vol. VI-5-5 
which could analyses the condition of heating system 
after envelop retrofit were developed according to the 
national criterions and region standards. 
2 ENERGY EFFICIENT RETROFIT OF 
ENVELOPS 
In China, the envelopes almost wasn’t insulated 
before 1980 and the thermal properties of existing 
building’s envelop weren’t good enough. So 
insulation is an important method of retrofit. As usual, 
insulation of external wall and roof are preferential 
measures of such many measures that improving the 
thermal properties of envelops. 
The construction technology of external 
insulation is difficult. It should have the 
performances of quake-proofing, wind-proofing, fire 
protecting, waterproof, air permeability, and 
durability also. The external insulation wall should 
prevent condensation of moisture. Especially, the 
material of exterior finishing should not be affected 
by the climate. There are several types of external 
insulation wall systems nowadays. The EPS external 
insulation system is the most suitable system which 
can be applied in the envelop retrofit of existing 
building. 
 
2.1 Energy Efficient Measures of External Wall of 
Existing Building Retrofit  
From 1990 to 1992, the scientific research 
project that Energy efficient measures of external 
wall of existing building retrofit had done by the 
former Harbin University of Civil Engineering and 
Architecture. The project aimed at the energy 
efficient retrofit of the external wall of existing 
building with rock wool and developed steel fiber 
reinforced concrete board and its fixed technology 
on external wall. The aim of the project was saving 
heating energy consumption of 30% because the 
new building in heating region should fit the design 
standard of energy efficient 30% in 1990. 
The demonstration building located at the 
residential buildings region of Heilongjiang building 
design institute in Harbin. It was completed in 1979. 
The building was brick and concrete construction, 
five floors, southeast and the building area was 1723 
m2. Although the layout of building structure was 
reasonable, the construction quality was not good. 
The air leak from the circumference of window was 
serious and some inner surface of external walls 
formed condensation of moisture. 
Before retrofit, the annual heating energy 
consumption was 9.28×108kJ. The annual coal 
consumption for heating was 31.68 tons standard coal. 
After retrofit, the annual heat consumption was 
6.73×108kJ. The annual coal consumption for heating 
was 22.97 tons standard coal. With the 2.55×108kJ 
reduction of the annual heating energy consumption 
and 8.7 tons standard coal reduction of the annual 
coal consumption for heating, the energy efficient 
rate was 27.48%. From the reduction we could know 
that the energy efficient quantity of rock wool 
insulation board to the retrofit was considerable. 
 
2.2 The Sino-Canada Retrofit Demonstration Project 
of Existing Building in Harbin 
The energy efficient retrofit project of existing 
building of Harbin, i.e. the Sino-Canada 
demonstration project of energy efficiency 
cooperation was a sub-project of “the ninth five 
years” key scientific and technological project of the 
State Planning Commission. The project 
accomplished by Harbin Wall retrofit and Building 
Energy Efficiency Office, former Harbin University 
of Civil Engineering and Architecture and Harbin 
Institute of Coal Design and Research. An employee 
residential building of Harbin Institute of Coal 
Design and Research was selected as the 
demonstration building. According to the demand of 
the project and refer to the Energy conservation 
design standard for new heating residential building 
(JGJ26-95), the retrofit would realize 50% energy 
efficiency. The project not only accomplished the 
retrofit of envelop and heating system, but also do the 
research on the economic analysis, method and police 
of raise funds and etc. It was a synthetically retrofit 
project of existing building. 
The project was constructed in 1983, brick and 
concrete construction, 7 floors, 490mm bricks walls 
and inner cement, double wood windows, closed 
balcony and 120mm cement and perlite insulation 
roof. The area of building was 2442 m2. There were 2 
units and 42 apartments. 
ESL-IC-06-11-203 
Proceedings of the Sixth International Conference for Enhanced Building Operations, Shenzhen, China, November 6 - 9, 2006 
ICEBO2006, Shenzhen, China           Building Commissioning for Energy Efficiency and Comfort, Vol. VI-5-5 
 Firstly, combining test results and calculation 
analysis, the existing building energy consumption 
was analyzed. Secondly, the heat consumption of 
each envelop were decomposed and the 
corresponding energy efficient potential could be 
acquired. After the energy efficient objects were 
ascertained, the retrofit proposal could be decided. 
Finally, to retrofit the building under the proposals, 
analyze the energy consumption and the retrofit 
results from the view point of energy consumption, 
economy and technology. 
The demonstration project took measures as 
following to realize the energy efficient retrofit: 
. External wall: 50mm polystyrene board 
external insulation; 
. Roof: 100mm polystyrene board insulation 
and inverted roof; 
. Window: keep the original wood window; 
. Thermal bridge: to insulate the thermal 
bridge between the two layers of the double wood 
window; 
. Staircase: to add porch, change the door to 
double door and heating. 
The index of heat loss of building was 30.99 
W/m2 before retrofit, and it was 20.05 W/m2 after 
retrofit. The energy efficient rate was 35.3%. This 
retrofit already satisfied the demand of 50% energy 
efficiency. 
 
2.3 Energy Efficient Retrofits of Existing Building in 
Daxing’anling 
The retrofit project was located in Jiagedaqi in 
north Heilongjiang. The building area of the retrofit 
project was 2098m2, 7 floors, 2 units and 72 
apartments. The envelops were as followings: 
490mm brick external wall, cement mortar finishing; 
closed balcony; PVC window (double window in the 
north; Single-frame and Double-glazing Window in 
the south and northern window inside balcony) and 
150mm perlite insulation roof. The indoor 
temperature was low before retrofit and the inner 
surface of external wall were moldy and 
condensation. 
Restricted by the various conditions, the 
proposal was ascertained as followings: insulated 
with 100mm polystyrene board to external wall, 
30mm to the inter wall of staircases on the first floor 
and thermal bridges; added door at the entrance of the 
staircase; changed the metal-electronic intercom door 
to double door and added porch. 
Calculated the energy consumption, the index of 
heat loss of building was 40.59 W/m2 before retrofit 
and 24.77 W/m2 after retrofit. The energy efficient 
rate was 39.5% and the energy efficiency rate of 
external wall was 50%. 
 
2.4 Summarization and Analysis of the Three Retrofit 
Cases 
Summarizing the retrofit experience of the 
existing building in Heilongjiang province, according 
to the results of the energy consumption analysis, it 
could be shown that the energy consumption 
proportion of transfer heat losses of external walls, 
windows, roofs and staircases and heat losses of 
infiltration were bigger than the heat looses of others’. 
The windows retrofit should take the actual situation 
of the building into consideration and the proposal 
should be selected economically, practicably and 
reasonably, so the primary retrofit envelops of 
proposal should be put onto the external walls. The 
building energy efficient rate using external wall 
insulation could be more than 50%. The retrofit of 
external wall should employ external thermal system. 
To ascertain the retrofit measures of the wall, it 
should take energy efficient rate, heat transfer and 
moist transfer into account synthetically. Using 
external thermal system, the insulation thickness 
should be considered according as followings:  
. Satisfy the demand of energy-efficient ratio.  
Ⅱ. Solve the durability problem of sticking: The 
temperature of the sticking between the insulation 
and the base wall must be above freezing point. 
. The thickness of the insulation should be the 
bigger one of the above two calculation results. 
. Check the moisture-resistant to satisfy the 
thermal design demands of envelops. 
Basing on the practice of retrofit projects in the 
past 10 years, the Existing Building Energy-efficient 
Retrofit Proposal Analysis Software was developed 
and it could calculate energy losses and ascertain 
reasonable, economical, proper and applicable retrofit 
proposal which summarized from the existing 
ESL-IC-06-11-203 
Proceedings of the Sixth International Conference for Enhanced Building Operations, Shenzhen, China, November 6 - 9, 2006 
ICEBO2006, Shenzhen, China           Building Commissioning for Energy Efficiency and Comfort, Vol. VI-5-5 
experiences for different regions in Heilongjiang 
province whose climate conditions and index of 
building heat loss were different. In the retrofit 
project of DaXingAnLing, the energy consumption 
before and after retrofit and the insulation proposal of 
external wall were calculated applying this software. 
 
3. ENERGY EFFICIENT RETROFIT OF 
HEATING SYSTEM  
Because the retrofit of heating system was hard 
to be realized, only the Sino-Canada project realized 
all-around existing heating system retrofit in the 
accomplished project. 
In this project, a loop of original heating 
system was replaced by vertical single-pipe 
cross-over heating system. Two types were taken to 
adjust the indoor temperature, one was placing 
thermostat in the entrance of the radiator, and the 
other was placing regulating locking tee valve at the 
entrance of the radiator and placing constant 
temperature valve in the bottom room of each vertical 
pipe. To direct heating system design of the new 
building, another loop of the original heating system 
was replaced by double-pipe horizontal heating 
system.  
Two types were taken to control the indoor 
temperature. One was placing electromagnetic valve 
at the entrance of every group of radiator, and 
equipping an indoor temperature controller in every 
room. The other was placing an electromagnetic 
valve in every horizontal loop and an indoor 
temperature controller in every room which was 
equipped with electromagnetic valve, and setting a 
manual control valve in the entrance of every group 
of radiator. After retrofit, the two loops of heating 
system were all adjustable and measurable and the 
indoor temperature was uniform.  
Using the developed software Heating System 
Working Conditions Analysis Software for Exiting 
Buildings, the three projects mentioned above were 
calculated, and the indoor temperature of retrofitted 
envelop was simulated and analyzed. 
The reduction scales of the design heating load 
of each room were different after energy efficient 
retrofit. The effect factors were not only the 
insulation performance of envelops before and after 
retrofit but also the detail of the construction of 
envelop. The reduction scale of the design heating 
load in a room of the same floor was affected by the 
sum of external walls, and the reduction scale of the 
heating load in a room corresponding to a vertical 
pipe was affected by its position as bottom floor, 
middle floor or top floor. 
The distribution of indoor temperature of the 
retrofitted buildings was affected by the reduction 
ratio of the design heating load, the more reduce ratio 
was, the higher the indoor temperature was. So the 
average temperature in the room with two external 
walls was higher than in the room with one external 
wall. The indoor temperature in the top floor was 
higher than in the middle floor or bottom floor if 
insulation was realize in the roof. 
The dweller might open the windows to release 
heat if the indoor temperature was too high. At this 
time, the temperature in the room would fall and the 
thermal comfort would improve. But the quantity of 
the released heat was not allowed to ignore. This 
phenomenon was general in the Sino-Canada 
demonstration project, but was rare in the project 
Energy efficient measures of external wall of existing 
building retrofit. 
Although the indoor temperature was usually 
higher than 18, it was usual to convert the real heat 
consumption of the retrofitted envelop to the heat 
consumption which indoor temperature was 18 in 
order to calculate the energy efficiency ratio. Actually, 
the heat consumption of retrofitted building was 
higher than the calculated value and the excessive 
heat might be used to improve the indoor thermal 
comfort.  
The distribution of indoor temperature of each 
project were quiet different after retrofit, because 
each energy-efficient project had the different retrofit 
proposal of envelop and different insulation 
capability and seal conditions of original envelop. In 
the energy efficient retrofit of heating system we 
should take all actual facts into consideration instead 
of taking a same measure. If it was difficult to realize 
the temperature control retrofit to the building’s with 
vertical single-pipe system, different adjustment or 
retrofit proposal might be considered against the 
actually distribution of indoor temperature. 
ESL-IC-06-11-203 
Proceedings of the Sixth International Conference for Enhanced Building Operations, Shenzhen, China, November 6 - 9, 2006 
ICEBO2006, Shenzhen, China           Building Commissioning for Energy Efficiency and Comfort, Vol. VI-5-5 
4 CONCLUSIONS  
The energy efficiency of existing building is 
important to our country. It must develop from 
demonstration project to popularization. In the 
process of retrofit, the retrofit focus should be the 
external wall and the building energy efficient rate 
would be more than 50%. It should be noticed that 
the retrofit should be realized both to envelops and 
heating system together to fulfill the purpose of 
energy efficiency really. This is because that the 
heating quantity would not change as the heating 
system had no retrofit. Then the indoor temperature 
of buildings would rise. The residents’ behaviors of 
opening windows to release heat causes great heat 
waste. Further study on how to solve the above 
problems should be carried out. The energy efficient 
retrofit research method of Heilongjiang province and 
the soft wares in this thesis can be an assistant to 
retrofit in north China. 
REFERENCES 
[1] Lihua Zhao．The Research of Existing Residential 
Building Retrofit Demonstration for Energy 
Efficient——Building Envelopes Retrofit 
[D]． Harbin: Harbin Institute of Technology, 
1998(In Chinese) 
[2] Li Li．The Research and Development of the 
Existing Building Envelope Energy-efficient 
Retrofit Proposal Analysis Software[D]．Harbin: 
Harbin Institute of Technology, 2005(In Chinese) 
[3] Ge Gao．Development and Application of Heating 
System Working Conditions Analysis Software for 
Exiting Buildings[D]．Harbin: Harbin Institute of 
Technology, 2005(In Chinese)
 
ESL-IC-06-11-203 
Proceedings of the Sixth International Conference for Enhanced Building Operations, Shenzhen, China, November 6 - 9, 2006 


Retrofit of Existing Residential Building: a Case Study

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