tuapannguanut, 3911 sisimiut...tuapannguanut, 3911 sisimiut report sisimiut 10.7.2015. 1 foreword...
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Indoor Air Quality Renovation Tuapannguanut, 3911 Sisimiut
Report Sisimiut 10.7.2015
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Foreword
Winters in the Arctic are very cold and long. When the temperatures are so low, the occupants of
Arctic dwellings stop opening windows to avoid cold draught. Any natural vents get typically sealed
for the same reason. This, together with the lack of mechanical ventilation results in insufficient air
change in majority of the dwellings. Consequently the indoor air quality (IAQ) becomes rather poor
which has a negative effect on the occupants’ health and may also damage the construction due to
mold growth. In this project a state of the art ventilation unit was installed in an old house to study
its performance and any changes of the IAQ. The measurements have shown that the IAQ had
improved significantly. Also the occupants have reported significant increase in their comfort. The
initial costs of the installation would pay off in approximately 14 years thanks to the heat recovery.
All in all the installation of the mechanical ventilation had proved to be an efficient yet economical
solution to an actual indoor air quality problem in Greenland.
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1. Introduction
The climate in the Arctic is cold which means that living inside the heated space requires quite some
energy. To avoid large heat losses and cold discomfort, building envelopes are often sealed, which
reduces natural infiltration. Results of previous studies in Sisimiut [1,2] showed, that ventilation
equipment is rare, and when present, it is limited to an exhaust fan in the bathroom (only installed in
63% of households) and wall mounted fresh air valves. Fresh air valves are source of cold draft and
often get sealed by the occupants in order to avoid discomfort. Range hoods are not always installed
(missing in 18% of the households). Limited air change together with a tradition of long lasting
cooking, drying laundry inside and need to bring wet outdoor clothing inside to dry it often leads to
elevated concentrations of moisture. Too high humidity makes a good environment for dust mites to
grow and may also lead to mold growth. Poorly ventilated spaces also experience high concentrations
of other indoor pollutants such as tobacco smoke (34% of respondents to the survey smoke inside),
pollen, carbon monoxide, carbon dioxide or volatile organic compounds.
With respect to the amount of time people spend inside their homes the effect of poor indoor climate
(IC) on occupants’ health and comfort is considerable.
A recent study [2] showed that both existing and new buildings in Greenland suffer from insufficient
ventilation. In fact, the problem is growing with new dwellings as improving building techniques allow
tighter envelopes and properly designed ventilation equipment has not been introduced yet. Therefore
the problem of poor indoor climate is relevant for both existing and new buildings.
Possible solution for improving the indoor climate of a home in energy efficient way is installation of
ventilation unit with heat exchanger. This solution saves energy by reusing heat from the exhaust air
to preheat the fresh supply air. The fresh air is then supplied to rooms at temperature high enough to
avoid draught discomfort.
In the past there have been a lot of negative experiences with these systems as they were mainly
designed for milder climates and were not able to cope with the extreme cold. However, some of the
new modern ventilation units are capable of continuous operation even at very low temperatures in
the Arctic. They can also regulate the air change according to the actual demands of the users which
further reduces the energy consumption.
In December 2014 a Greenlandic housing administration company INI A/S in collaboration with Center
for Arctic Technology at Technical University of Denmark ARTEK installed a state of the art ventilation
unit into one of the city owned apartments in Sisimiut, Greenland. The aim was to study the
functionality of the system under Greenlandic conditions and to introduce the technology to the
community.
The results showed a significant improvement of the indoor climate which was not only measured by
instruments, but also confirmed by the inhabitants of the home. Moreover the system was capable of
operation during the coldest winter with temperatures below -25 °C without breakdowns.
This report describes the system in details and brings results of the experiment.
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1.1. Introduction of the home
The home which was a subject of this study is a type row house in Tuapannguanut – Sisimiut built in
80’s (shown in Figure 1). It consists of two floors. In a ground floor there is an entrance, laundry, living
room and kitchen. In the second floor there are two bedrooms and a bathroom (see the floor plans in
Figure 2). The floor area of the home is approximately 70 m2. The house is occupied by a family of 7
people (2 adults and 5 children).
Figure 1. Tuapannguanut home
Currently the ventilation consists of fresh air valves in bedrooms and living room, range hood with
exhaust towards outside and two vertical ventilation shafts from bathroom and laundry room (see
Figure 2). The fresh air valves were closed and taped by the occupants (to avoid cold draught).
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Figure 2. Tuapannguanut floor plans
1.2. Indoor climate
1.1.1 Carbon dioxide (CO2)
In previous studies it was found that exposures to moderately elevated concentrations of CO2 have
negative effect on human performance, perception of poor IAQ or prevalence of certain health
symptoms (such as irritation of mucous membranes, headaches or tiredness) [3-9]. It is however
believed that these symptoms are caused by various other pollutants whose concentrations rise along
with the CO2 concentration as a result of insufficient ventilation. CO2 is therefore often used as an
indicator of IAQ. Nevertheless a recent study on effects of CO2 on human performance [10] found
correlation between elevated CO2 concentration (above 1000 ppm) and decreased decision-making
performance in controlled environment free of other pollutants.
According to European standard EN 15251 [11] new buildings should have the CO2 concentration
lower than 500 ppm above outdoors for most of the time and existing buildings lower than 800 ppm.
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The international ASTM Standard D6245 (based on past studies) suggests indoor CO2 concentrations
lower than 650 ppm above outdoors so at least 80% of the unadapted persons will find the level of
body odor acceptable. The American standard ASHRAE 62.1 [12] recommends 700 ppm above
outdoors as an upper limit for CO2 concentration inside a living space.
With the average outdoor CO2 concentration in Sisimiut 400 ppm, the recommended indoor
concentration according to ASTM Standard D6245 is 1050 ppm, according to ASHRAE 62.1 [12] 1100
ppm and according to EN 15251 [11] 900 ppm for new and 1200 ppm for existing buildings.
1.1.2 Humidity
In numerous studies it has been found that increased levels of indoor humidity may have negative
effects on human health and comfort as they increase the risk of mold growth and concentration of
house-dust mites (HDM) [13-15]. Sundell [13] for example in his study in 30 homes in Stockholm area
found that elevated concentrations of HDM allergen in bedrooms were in correlation with additional
moisture. As well as too high humidity also too low humidity may cause problems. A Finnish study
[16] on the effects of humidification on the office workers had shown that office workers have
reported fewer symptoms (skin irritation, mucous membranes irritation, dryness sensation) when
exposed to environment with air at 30% to 40% relative humidity (RH) than when exposed to air RH
below 30%.
Generally, to minimize as many adverse health effects as possible, the indoor RH should be kept
between 30% and 50% [11].
1.1.3 Temperature
The European standard EN ISO 7730 [18] recommends 20 °C to 24 °C as a winter design temperature
and 23 °C to 26 °C as a summer design temperature in order to keep the amount of dissatisfied
occupants below 10%.
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2. Current indoor climate
Before the ventilation unit was installed, the indoor climate was monitored for two days for the
reference.
2.1. Carbon dioxide (CO2)
The measurements showed an overall average CO2 concentration of 2198 ppm in the bedrooms.
During the nights the average CO2 concentration was as high as 3124 ppm in master bedroom and
2977 ppm in a children’s bedroom. Such elevated concentrations of CO2 itself may cause tiredness and
concentration disorders [10]. Moreover, the elevated concentrations of CO2 also confirm that the
ventilation of the space is insufficient and hence concentrations of other pollutants may also be
elevated. Some of these pollutants may even be harmful to human beings (Volatile Organic
Compounds) or cause allergies and asthma (dust mites).
Figure 3. CO2 concentration in the two bedrooms before the installation of ventilation unit
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2.2. Relative Humidity
From the results it can be seen that the RH in bedrooms was between 30% - 50% for most of the
time (72% of the monitored period). For the rest of the time the RH was below the recommended
levels.
Figure 4. Cumulative percentage distribution of RH in bedrooms and bathroom before installation of the ventilation unit
The bathroom relative humidity was generally within the reasonable range except for the shower
period where it increased rapidly. After the spike it took 2 hours for the RH to decrease below 50%.
Figure 5. Bathroom RH
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2.3. Temperature
As seen from the Figure 6, the temperatures were within the recommended range for winter comfort
(20 °C to 24 °C) for the entire test period. The overall average temperature was 21.2 °C.
Figure 6. Cumulative temperatures in bedrooms and bathroom before installation of the ventilation unit
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3. Installation of the ventilation unit
As ventilation aggregate a SWEGON CASA R80 was chosen. The unit has a rotary heat exchanger
which allows a continuous operation down to -30 °C and heat exchange efficiency of up to 86%. The
unit is equipped with an electric after heater. The heater ensures that the air supplied to the rooms is
always at a comfortable temperature (above 18 °C) even during the coldest periods. It was decided to
install the ventilation unit in the laundry room where it would take the least space from the
occupants. See Figure 7 and Figure 8 for the laundry room before and after the installation.
Figure 7. Laundry before the installation
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Figure 8. Installed ventilation unit
For the air distribution in the house a Lindab InDomo system was used. The ducts are of small
diameter and go directly from the distribution box in the laundry room (see Figure 9) to each room
without further branching. This system allows easy installation and maintenance (cleaning).
Figure 9. Distribution boxes and ducts to each room
The layout of the ventilation system can be seen in Figure 10. The fresh air is supplied into the two
bedrooms in a first floor and to the living room. The exhausts are placed in a kitchen, bathroom and
laundry. The range hood remained connected directly to outside and was not part of the installation.
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Figure 10. Ventilation system layout
The supply air terminals were selected to eliminate noise and to supply the air to the rooms in optimal
direction to avoid any draught discomfort or short circuiting. The supply air terminal and its
connection to the duct are shown in Figure 11 and Figure 12.
Figure 11. Supply air terminal device
Figure 12. Air terminal device connection in a closet
The terminals on the façade have been selected to eliminate the intake of snow and insects (Figure
13). The existing fresh air valves were sealed with mineral wool and polyurethane (see Figure 14) to
avoid cold bridges and moisture damage of the construction.
Figure 13. Fresh air intake
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Figure 14. Mineral wool and polyurethane sealing of the fresh air valve
In Figure 15 the thermographic pictures of a fresh air valve are shown before and after insulation. One
can see that the lowest temperature of the valve before sealing was 8.6 °C (outside temperature -12
°C) whereas after the sealing it was above 21.2 °C.
Figure 15. Fresh air valve before (left) and after (right) sealing
The unit is equipped with a controller (Figure 16) which allows the occupants to choose between
three operation modes (see Table 1)
Table 1. Ventilation unit modes
Mode Speed [%] Air flow [m3/h] Air change [h-1]
Away 25 36 0.19
Home 55 120 0.63
Boost 80 180 0.95
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The occupants do not have an option of turning the ventilation system completely off at any time.
However, if the users turn the unit into “Away” mode its operation is almost unnoticeable yet there is
still an air change of 0.19 h-1 in the house. In addition to the controller there is a hygrostat (Figure 16)
in the bathroom which turns on the “Boost” mode in case of increased humidity (above 60%) in
bathroom automatically (during showers for example).
Figure 16. Ventilation unit controller (left) and hygrostat
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4. Indoor climate after the installation
After installation of the ventilation unit the indoor climate was monitored for four months to see any
possible changes. A period of two days was selected and compared with the state before installation.
4.1. Carbon dioxide
It can be seen from Figure 17 and Figure 18 that the CO2 concentration has decreased significantly after the installation of the ventilation unit. The night time average concentration decreased from 3124 ppm to 1420 ppm in a master bedroom and from 2977 ppm to 1520 ppm in a children’s bedroom. Although the CO2 concentration is still higher than the recommended value, the difference is marginal when compared to the original state and can be mitigated by adjusting the ventilation unit to supply more air into the bedrooms.
Figure 17. CO2 concentration in master bedroom before and after installation of the ventilation unit
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Figure 18. CO2 concentration in children’s bedroom before and after installation of the ventilation unit
4.2. Relative Humidity
The average relative humidity has (as expected) decreased after the installation. However, as it can be
seen from the Figure 19 the amount of time when the RH is within the recommended range had
actually increased from 72% to 77%. That is due to moisture recovery effect of the rotary heat
exchanger.
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Figure 19. Relative humidity in bedrooms after installation of the ventilation system
RH in the bathroom has also decreased. Additionally the time the RH was above 50% during and after
shower was significantly shortened (from 1 hour 55 minutes to 27 minutes) thanks to the boost
function of the ventilation unit (see Figure 20).
Figure 20. Relative humidity in Bathroom during shower before and after installation of the ventilation system
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4.3. Temperature
Although the temperature of the outside air was below -20 °C, the temperature of the air supplied to
the rooms was above 18 °C all the time.
Figure 21. Temperature of the outside and supply air
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5. Economy
The costs of the unit including installation were approximately 62,000 DKK. The average power
consumption of the unit was 80 W which yields the annual electricity consumption of 700 kWh (1,150
DKK). Additionally the annual heat loss related to ventilation is about 1260 kWh (1,010 DKK)
It is difficult to estimate the annual savings as the home was not properly ventilated before the
installation.
However, assuming a proper ventilation of the home the annual costs related to natural ventilation
without heat recovery would be approximately 6,700 DKK. With ventilation unit installed these costs
are 2,160 DKK (1,010 DKK for heat and 1,150 DKK for electricity). The ventilation unit will hence save
around 4,540 DKK per year which gives a simple return of investment of less than 14 years.
6. Conclusion
The experiment showed that the poor indoor climate of the house can be significantly improved in an
energy efficient way. The investment into the system would pay back in less than 14 years. Because
the system helps to reduce high humidity it can also be looked at as prevention against mold.
Consequently there are also savings related to mold renovation which were not included in the
calculations.
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References
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[13] J Sundell, M Wickman, G Pershagen, SL Nordvall. Ventilation in Homes Infested by House-Dust Mites, Allergy. 50 (1995) 106-112.
[14] I Pirhonen, A Nevalainen, T Husman, J Pekkanen. Home dampness, moulds and their influence on respiratory infections and symptoms in adults in Finland, Eur.Resp.J. 9 (1996) 2618-2622.
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